SPECIATION AND TOTAL DETERMINATION OF ARSENIC, CHROMIUM
AND SELENIUM IN FRESHWATER BODIES SEDIMENT
NAZARATUL ASHIFA BINTI ABDULLAH SALIM
A thesis submitted in fulfillment of the
requirements for the award of the degree of
Master of Science (Chemistry)
Faculty of Science
Universiti Teknologi Malaysia
NOVEMBER 2009
iii
To my beloved husband and parent whose endless love and support
helped me get through all the obstacles.
Little Sufi and Faris;
always remind mama to work hard and achieve high.
iv
ACKNOWLEDGEMENTS
All commendations to Almighty Allah, who imparted me resoluteness and
fortitude for accomplishment of this work successfully.
I would like to express my deep gratitude to my supervisor, Prof Alias Mohd
Yusof for all his thought, guidance, encouragement and invaluable help given to me
during my graduate research.
I am also very thankful to my supervisory committee members in Nuclear
Malaysia Agency, Dr. Abdul Khalik Hj. Wood, Dr. Mohd Suhaimi Hamzah, Puan
Shamsiah Abdul Rahman and Md Suhaimi Elias for providing me with support and
feedback throughout my studies.
I also appreciate the help from Puan Mek Zum, En Hanan Basri, En. Ariffin
Talib, Puan Pirmala Devi, Mr. Lim Ching Choah, Puan Jamaliah Mat Yatim, Puan
Eeewiat, Cik Ezwiza Sanuri, Puan Zaleha Hashim and En. Burhanuddin Ahmad in
chemicals purchasing, samples collection and preparation, chemical analysis,
counting processes and discussion of my ideas in the research process.
The financial support for this project from the Universiti Teknologi Malaysia
in-cooperation with Malaysian Nuclear Agency under Reactor Interest Group Fund
and Master scholarship from Malaysian Nuclear Agency are greatly acknowledged.
I am indebted to my family members whose endless prayers and continuous
moral support enabled me to get through the period of my academic journey.
v
ABSTRACT
Arsenic (As) is generally known for its toxicity while chromium (Cr) and
selenium (Se) at the appropriate amount are essential elements to man and becomes
quite toxic in excessive amount. Anthropogenic activities such as industrialization,
agricultural and urbanization have led to the contamination of toxic elements into
aquatic that finally end up in the sediment system. Environmental process such as
diagenetic process causes the toxic elements to migrate from the bedrock materials
into the sediment surface and lastly into the water column. This process has been
recognized to be the factor of As contamination in well water in several countries
such as Bangladesh, Taiwan, USA and Canada. A number of samples of freshwater
sediments from identified rivers and lakes in Johor Bharu area had been analyzed to
determine the concentration level of As, Cr and Se using neutron activation analysis
(NAA) technique. Certified reference material (CRM) namely IAEA Soil-7, Marine
Sediment Reference Material BCSS-1 and PACS -2 were applied to provide good
quality assurance control during analysis. The results obtained show that the
concentrations of As in the rivers and lakes sediment fall between 10 to 34 g g-1 and
18 to 62 g g-1, respectively. The concentrations of Cr in the rivers ranged between
27 g g-1 to 125 g g-1, while in the lake sediments the concentrations ranged
between 173 g g-1 to 301 g g-1. The river sediment showed the Se concentration
ranged between 0.56 g g-1 to 1.91 g g-1 and in lake sediment the concentration
ranged between 0.31 g g-1 to 1.08 µg g-1. The results of the As, Cr and Se
concentrations were then compared to the ‘background value’ proposed by National
Oceanic and Atmospheric Administration (NOAA), USA and several sediment
quality guidelines. The As, Cr and Se concentrations were also correlated and
normalized to iron content in order to evaluate and estimate the degree of
contaminant enrichment in sediments. For speciation study, the inorganic species of
As(III), As(V), Se(IV) and Se(VI) were studied by extracting the sediments using the
microwave at the optimized time and power setting in the mild concentration of acid
media. The As(III) and As(V) were preconcentrated and separated by ammonium
pyrolidinedithiocarbamate (APDTC) into methyl isobuthyl ketone (MIBK) while the
Se(IV) and Se(VI) were separated after co-precipitation of sodium
dibenzyldithiocarbamate (Na-DBDTC) with phenolphthalein. The efficiencies of all
extraction procedures were determined using standard solutions and several CRM.
The results showed that As(V) and Se(VI) were the dominant species in the river and
lake sediments.
vi
ABSTRAK
Arsenik (As) telah diketahui umum akan ketoksikannya sementara kromium
(Cr) dan selenium (Se) pada amaun yang berpatutan merupakan unsur keperluan
kepada manusia dan menjadi toksik pada amaun yang berlebihan. Aktiviti
pencemaran seperti perindustrian, pertanian, perbandaran telah mendorong kepada
pencemaran unsur toksik ke dalam akuatik yang akhirnya terkumpul dalam sistem
enapan. Proses sekitaran seperti proses diagenetik menyebabkan unsur toksik
bergerak dari bahan dasar ke dalam permukaan enapan dan akhirnya ke dalam turus
air. Proses ini dikenalpasti sebagai faktor pencemaran As di dalam air telaga di
beberapa negara seperti Bangladesh, Taiwan, Amerika dan Kanada. Beberapa sampel
enapan sekitaran air tawar dari beberapa sungai dan tasik yang dikenalpasti di
kawasan Johor Bharu telah dianalisis untuk menentukan kepekatan As, Cr dan Se
menggunakan teknik analisis pengaktifan neutron. Bahan rujukan piawai antaranya,
IAEA Soil-7, Marine Sediment Reference Material BCSS-1 dan PACS -2 telah
digunakan untuk memberi kawalan kualiti jaminan yang baik semasa analisis.
Keputusan yang diperolehi menunjukkan kepekatan As di sungai dan tasik masingmasing ialah 10 hingga 34 g g-1 dan 18 hingga 62 g g-1. Kepekatan Cr di sungai
berjulat antara 27 g g-1 hingga 125 g g-1 manakala kepekatannya di dalam enapan
tasik berjulat antara 173 g g-1 hingga 301 g g-1. Kepekatan Se di dalam enapan
sungai berjulat antara 0.56 g g-1 hingga 1.91 g g-1 dan kepekatannya di dalam
enapan tasik antara 0.31 g g-1 hingga 1.08 g g-1. Kemudian keputusan kepekatan
As, Cr dan Se dibandingkan dengan ‘nilai latar’ yang dicadangkan oleh National
Oceanic and Atmospheric Administration (NOAA), Amerika dan beberapa panduan
kualiti sedimen. Korelasi dan normalasi kepekatan As, Cr dan Se kepada kandungan
besi dijalankan untuk menilai dan menganggar pengkayaan bahan cemar di dalam
enapan. Bagi kajian penspesiesan, spesies bukan organik As(III), As(V), Se(IV) dan
Se(VI) ditentukan dengan mengekstrak enapan menggunakan gelombang mikro
pada aras kecekapan masa dan kuasa yang telah ditetapkan di dalam media asid
berkepekatan rendah. Pra-pemekatan dan pemisahan As(III) dan As(V) dijalankan
dengan mengunakan ammonium pirolidineditiokarbamat (APDTC) di dalam metil
isobutil keton (MIBK). Sementara Se(IV) dan Se(VI) dipisahkan selepas kopemendakan natrium dibenzilditiokarbamat (Na-DBDTC) dengan fenolftalein.
Kecekapan semua prosedur pengekstrakan telah ditentukan dengan menggunakan
larutan piawai dan beberapa bahan rujukan piawai. Keputusan menunjukkan As(V)
dan Se(VI) adalah spesies yang dominan di dalam enapan sungai dan tasik.
vii
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
THESIS STATUS DECLARATION
SUPERVISOR’S DECLARATION
TITLE PAGE
i
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
xii
LIST OF FIGURES
xv
LIST OF APPENDICES
1
xviii
LIST OF SYMBOLS AND ABBREVIATIONS
xx
INTRODUCTION
1
1.0 Research Background
1
1.1 Problem Statement
5
1.2 Research Objectives
6
1.3 Scope of Research
7
1.4 Man, Environment and Toxic Elements
7
1.5 Arsenic
8
1.5.1
Geochemistry of Arsenic
10
1.5.2
The Toxicology of Arsenic
15
viii
1.6 Selenium
2
17
1.6.1
Geochemistry of Selenium
20
1.6.2
The Toxicology of Selenium
22
1.7 Chromium
23
1.7.1
Geochemistry of Chromium
25
1.7.2
The toxicology of Chromium
27
LITERATURE REVIEW
29
2.0 Sediment and Its Role in Freshwater Ecosystem
29
2.0.1
Sediment Contamination
2.0.2
Sediment Quality Issue and
Assessment
2.1
32
Analytical Technique for Elemental Analysis
34
2.1.1
Neutron Activation Analysis
35
2.1.2
Principles of Instrumental Neutron
2.1.3
Activation Analysis
35
Nuclear Reactor
39
2.2 Elemental Speciation
40
2.3 Speciation Technique for Sediment Analysis
42
2.3.1
Extraction Technique
2.3.2
Usage of Microwave in Sample
Digestion Prior to Extraction
2.3.3
2.3.4
3
30
43
46
Preconcentration and Separation
Technique
48
Detection Technique
51
2.4 NAA in Speciation Study
56
MATERIALS AND METHODOLOGY
62
3.0 Introduction
62
3.1 Study Area
62
3.1.1
River
64
3.1.2
Lake
66
ix
3.2 Sediment Characteristic
68
3.3 Sampling Methodology
68
3.4 Chemicals and Reagents
69
3.5 Labware
70
3.6 Laboratory Apparatus
70
3.7 Sample Processing Equipment
71
3.8 Sample Preparation
72
3.9 Standard Solutions
72
3.9.1
Standard Solutions for As, Cr, Se and
72
Fe
3.9.2
Standard Solution for Arsenic (III)
and Arsenic (V)
3.9.3
73
Standard Solution for Selenium (IV)
and Selenium (VI)
3.10 Certified Reference Material (CRM)
74
74
3.11 Preparation of Sediment Sample For Total
75
As, Cr, Se and Fe
76
3.12 Arsenic Species
3.12.1
Microwave extraction
76
3.12.2
Preconcentration and Separation
77
3.12.2.1
Effect of pH
79
3.12.2.2
Repeatability
79
79
3.13 Selenium Species
3.13.1
Microwave extraction
80
3.13.2
Preconcentration and Separation
80
3.13.2.1
Effect of pH
81
3.13.2.2
Repeatability
82
3.14 Analysis Using Neutron Activation Analysis
Technique
83
3.14.1 Limit of Detection
86
x
4
RESULTS AND DISCUSSION
87
4.0
Introduction
87
4.1
Water Quality of The Water Bodies
88
4.2
Data Quality
93
4.3
Total Concentration of Elements
95
4.4
Concentration of Arsenic, Chromium and
Selenium in Rivers
4.5
Concentration of Arsenic, Chromium and
Selenium in Lakes
4.6
96
101
Comparison in Elements Concentration to the
Guideline Recommendation for Freshwater
Sediments
4.7
107
Association of Arsenic, Chromium and
Selenium to Iron Concentration
110
4.8 Evaluating Contaminant Impact
117
4.8.1
Enrichment Factor (EF)
118
4.8.2
Geoaccumulation Index (Igeo)
120
4.9 Speciation of Arsenic and Selenium in
Sediment
4.9.1
4.9.2
122
Optimization of Arsenic Speciation
Study
123
4.9.1.1 Microwave Extraction
124
4.9.1.2 Effect of pH and Repeatability
125
Optimization of Selenium Speciation
Study
127
4.9.2.1 Microwave Extraction
127
4.9.2.2 Effect of pH and Repeatability
129
4.10 Concentration of Arsenic and Selenium Species
in River and Lake
130
xi
5
CONCLUSIONS AND SUGGESTIONS
136
5.0
Conclusions
136
5.1
Suggestions
139
REFERENCES
Appendices A - I
141
157 - 181
xii
LIST OF TABLES
TABLE NO.
1.1
TITLE
PAGE
Naturally occurring inorganic and organic arsenic
species
11
1.2
Inorganic arsenic species in the environment
13
2.1
Major contaminants in sediments
31
2.2
Summary of analytical arsenic and selenium speciation
in environmental samples
53
2.3
Speciation study using NAA method determination
60
3.1
Date of sampling carried out in the rivers and lakes
63
3.2
The coordinates and description of the river sampling
site
66
3.3
Sampling coordinates at the lakes
67
3.4
Standard solutions of original concentration supplied
3.5
by Merck
73
The specification of the CANBERRA HPGe detector
84
xiii
4.1
Overall average of the water physico-chemical
parameters in the rivers and lakes
89
4.2
Analytical results for As, Cr, Se and Fe in CRMs.
94
4.3
LOD for As, Cr, Se and Fe
94
4.4
Result of average concentration of arsenic, chromium
and selenium in sediment of each sampling sites at
river
4.5
Result of previous studies from several literatures for
As and Cr in river sediment
4.6
96
98
Result of average concentration of arsenic, chromium
and selenium in sediment of each sampling sites at
lake
4.7
Result of previous studies from several literatures for
As, Cr and Se in lake sediment
4.8
105
Several guidelines value for arsenic, chromium and
selenium
4.9
102
108
Selenium guideline value derived from the Guidelines
for Interpretation of the Biological Effects of Selected
Constituents in Biota, Water and Sediment
4.10
109
Enrichment factors (EF) and Index of
Geoaccumulation (Igeo) in sediment of rivers and lakes
117
xiv
4.11
The Igeo scale
4.12
Results of arsenic species under various microwave
121
condition and H3PO4 concentration (expressed as
µg g-1 dry mass)
4.13
125
Results of selenium species under various microwave
condition and HCl concentration (expressed as µg g-1
dry mass)
128
4.14
Arsenic speciation analysis in river and lake sediment
132
4.15
Selenium speciation analysis in river and lake
sediment
134
xv
LIST OF FIGURES
FIGURE NO.
1.1
TITLE
Structures of naturally occurring inorganic and organic
arsenic species
1.2
31
Schematic diagram illustrating the sequence of events
for a typical (n, ) reaction
2.3
26
Principal sources, fates and effect of sediment
contamination in aquatic ecosystem
2.2
21
The Eh-pH diagram of chromium in water at 25C and
one atmosphere
2.1
15
The Eh-pH diagram of selenium in water at 25C and
one atmosphere
1.5
14
Simplified transformation pathway of inorganic
arsenic in the environment
1.4
12
The Eh-pH diagram of arsenic in water at 25C and
one atmosphere
1.3
PAGE
37
Schematic set-up of gamma ray spectrometer for use
in INAA
38
xvi
2.4
Processes for speciation study in different samples
43
3.1
Sampling locations for river
65
3.2
Sampling locations for lake at University Teknologi
Malaysia
3.3
Flow chart of the preconcentration and separation of
As (III) and As (V) in APDTC – MIBK system
3.4
67
78
Flow chart separation-extraction procedure of Se (IV)
and Se (IV) by co-precipitation of Na-DBDTC with
phenolphthalein
4.1
82
Water Quality Status for River Basin of Peninsular
Malaysia in 2006 with highlight of Sungai Skudai,
Sungai Tebrau and Sungai Buluh (Kaw. Pasir
Gudang)
4.2
Average concentration of arsenic in sediment of river
sampling sites
4.3
100
Average concentration of arsenic in sediment of lake
sampling sites
4.6
100
Average concentration of selenium in sediment of
river sampling sites
4.5
99
Average concentration of chromium in sediment of
river sampling sites
4.4
92
103
Average concentration of chromium in sediment of
lake sampling sites
103
xvii
4.7
Average concentration of selenium in sediment of lake
sampling sites
4.8
Concentrations of As, Cr and Se plotted against
concentrations of Fe in river sediments
4.9
116
Extraction recovery of As (III, V) by APDTC-MIBK
at different pH
4.13
115
Ratios of concentration of As, Cr and Se to
concentrations of Fe in lake sediments
4.12
113
Ratios of concentration of As, Cr and Se to
concentrations of Fe in river sediments
4.11
112
Concentrations of As, Cr and Se plotted against
concentrations of Fe in lake sediments
4.10
104
126
Extraction recovery of Se (IV, VI) by co-precipitation
technique at different pH
130
xviii
LIST OF APPENDICES
APPENDIX
A
TITLE
The range of the water physico-chemical
parameters
B
PAGE
157
National Water Quality Standard for Malaysia
(NWQS)
158
C
Certified Reference Material
160
D
Results of As, Cr, Se and Fe concentration in
sediments
E
Details on the international guideline for
freshwater sediment
F
G
167
169
Statistic evaluation of As, Cr and Se correlation
to Fe in sediments
174
a)
The stability study of As species
175
b)
The extraction efficiency of As (III) and As
(V) to pH function
c)
175
The repeatability of the extraction by
APDTC-MIBK
176
xix
H
a)
The stability study of Se species
b)
The extraction efficiency of 1 g mL-1 Se
(IV) and Se (VI) to pH function
c)
a)
179
ANOVA : Analysis of arsenic species in
river and lake
c)
178
Results of As and Se inorganic species in
river and lake sediments.
b)
177
The repeatability of the co-precipitation
technique by DBDTC-Pp
I
177
181
ANOVA : Analysis of selenium species in
river and lake
181
xx
LIST OF SYMBOLS AND ABBREVIATIONS
%
-
percent
C
-
degree Celcius
-
microgram per gram
-
microgram per mililiter
g L
-
microgram per liter
mg kg-1
-
milligram per kilogram
mg L-1
-
milligram per liter
g kg-1
-
gram per koligram
ng m-3
-
nanogram per meter cubic
-3
-
pikogram per meter cubic
m
-
micrometer
mm
-
millimeter
min
-
minute
km
-
kilometer
kPa
-
kilopascal
M
-
mol
W
-
watt
APDTC
-
ammonium pyrolidinedithiocarbamate
AAS
-
atomic absorption spectrometry
AFS
-
atomic fluorescence spectrometry
BOD
-
biological oxygen demand
COD
-
chemical oxygen demand
CRM
-
certified reference material
DIBK
-
diethyl isobutyl ketone
DO
-
dissolved oxygen
DOE
-
Department of Environmental
g g-1
g mL
-1
-1
pg m
xxi
EPA
-
Environmental Protection Agency
ETAAS
-
electro thermal atomic absorption spectrometry
GFAAS
-
graphite furnace atomic absorption spectrometry
HPLC
-
high performance liquid chromatography
HCl
-
hydrochloric acid
HClO4
-
perchloric acid
HF
-
fluoric acid
HNO3
-
nitric acid
H2O2
-
hydrogen peroxide
H3PO4
-
ortho phosphoric acid
H2S
-
hydrogen sulfate
H2SO4
-
sulfuric acid
IAEA
-
International Atomic Energy Agency
ICPMS
-
inductively coupled plasma mass spectrometer
MIBK
-
methyl isobutyl ketone
NAA
-
neutron activation analysis
Na-DBDTC
-
sodium diethyldithiocarbamate
NOAA
-
National Oceanic and Atmospheric Administration
NWQS
-
National Water Quality Standard
RSD
-
relative standard deviation
UV
-
ultra violet
WHO
-
World Health Organization
CHAPTER 1
INTRODUCTION
1.0
Research Background
Development in industrial and agricultural sectors as well as rapid increase of
population and mining activities have adversely affected the quality of aquatic
system. Industrial, domestic and municipal wastes that contain toxic contaminants
including hazardous chemicals and pesticide residues may enter the aquatic
environment and affect the natural system. Toxic contaminants such as heavy metals
that are introduced into the aquatic system may also associate themselves with
sediment components and can contribute to toxicity up to some extent.
The Department of Environment (DOE) had, in 2006, monitored about 146
river basins in Malaysia. Out of those 146 river basins, 69 river basins had been
reported and categorized as polluted based on water quality parameter assessment
of biochemical oxygen demand and ammoniacal-nitrogen (NH3-N). The untreated
and partially treated sewage and discharges from agro-based and manufacturing
industries were the principal contributors to the major pollution in river system.
Meanwhile, 42 rivers were recorded to be heavily polluted by earthwork and land
clearing activities.
In the aquatic system, the sediment acts as a sink to a major number of
contaminants. It also serves as an important medium for the transformation and
migration of toxicants. Beyond this environmental system, the chemistry of some
chemicals may have changed due to environmental, biological and physical
2
processes. Some chemicals are not biodegradable but may be biotransformed through
food chain that reaches human beings where they ultimately result in chronic and
acute ailments and illnesses.
Förstner and Wittmann (1983) grouped the existence of metals in water into
two groups; inorganic and organic. Some of them might be soluble and others in
particulate form. The metals in soluble state are present as ions, complex ions,
chelate ions or molecule forms. The particulate metal form may occur as colloidal,
precipitate or adsorbed to other constituents in the aquatic environment.
In natural waters, both inorganic and organic metals may undergo oxidationreduction, precipitation-dissolution, adsorption-desorption or biochemical
methylation reactions. All of these reactions control deposition, accumulation and
mobilization of metals in the aquatic environment. These reactions do not only take
place in the aqueous phase but also interact at the solid phase such as sediment, soil
and geologic materials. Several metals can go through transformation and
translocation by soil microbes and higher plants via their uptake mechanism.
According to Förstner (1983), aquatic solids are composed of a mixture of
material inputs from various sources, including eroded rocks and soils, sewage and
solid waste particles, atmospheric fallout and other formation in the aquatic system
such as inorganic precipitates, biogenic matter, adsorbates on particles from solution,
complexed and colloidal matter. During periods of reduced flow rates, suspended
materials settle to the bed of the river, lake and sea, becoming partly incorporated
into the bottom sediment.
3
Sediment analysis is particularly useful in detecting pollution sources and in
the selection of critical sites for routine water sampling for contaminants that, on
discharge to surface water, do not remain solubilized but are rapidly adsorbed by
particulate matter (Simpson et al., 2005). Local sources of pollution can be
determined and evaluated with the lateral distribution analysis. Vertical sediment
profiles are also useful, since they often uniquely preserve the historical sequence of
pollution intensities and at the same time enable a reasonable estimation of
background levels and the variation input of a pollutant over an extended period of
time.
Since three decades ago, research aspect into sediment has become apparent
from the fact that the sediments with their contaminants are in a constant
interrelation with the liquid phases and organisms which means that the sediments
themselves represent another environmental contaminant. Several problem areas
with regard to the presence of contaminated sediment in the environment including
the potential availability of the contaminants in the sediments for aquatic life, the
behaviour of contaminants in soil and sediment with respect to potential pollution of
groundwater and uptake of contaminants by plants from polluted sediments on
agricultural land have been highlighted, studied and discussed extensively by
scholars (Kubota, 1983; Thornton, 1983).
One of the well-known aquatic environmental studies ever conducted was
conducted at The Great Lakes situated in United State and also in Canada region.
The Great Lakes contain 20 % of the world's surface fresh water which cover more
than 244,000 square kilometers of water (http://epa.gov/greatlakes/index.html).
Contaminants are washed into the lakes via rivers and streams, or through pipes and
discharge outlets. The lakes are also exposed to contaminants via atmospheric
depositions. Contaminated sediments, primarily in harbors and industrialized
segments of rivers and estuaries, contain pollutants that have been entering the lakes
for decades. The sediment assessment study for metals, acid volatile sulfides,
methylmercury, tributyltin, pesticides, polychlorinated biphenyls (PCBs),
polynuclear aromatic hydrocarbons (PAHs) and dioxins were conducted to evaluate
the nature and extent of bottom sediment contamination of The Great Lakes
4
(Schumacher, 1994). Studies conducted on sediment from this area have
demonstrated that contaminated sediments are of great concern to humans and wild
life that live in the Great Lake Basin. EPA’s Great Lakes National Program Office
has reported that polluted sediments are the largest major sources of contaminants in
Great Lakes rivers and harbors which could eventually enter the food chain (EPA,
2004).
The introduction of elemental contaminants into the aquatic system has
various sources. The source of contaminants could be originated from two origins;
direct and indirect sources. The direct sources could be coming from natural
processes like weathering and volcanic activity that contributes to the redistribution
of metals from bedrock into the surface environment. Through the water system runoff and leaching process, the metals in solution form are introduced into lakes, rivers,
groundwater and sea. The elements enrichment can be attributed to human activities
such as industrial processing of ores and metals, agricultural, industrial and domestic
wastes. The serious effects of mine, industrial and domestic effluents on water
quality in river and lakes, as well as on the organism, have been known and studied
for many years.
The indirect sources of contaminants could be originated from geochemical
processes occuring in a particular system. The diagenesis process is a natural aquatic
environmental process that contributes to the enrichment of toxic chemical in the
sediment. This process may induce the vertical migration of multi oxidation state of
element such as As from bottom of anoxic sediment to surface that can act as input
of the toxic chemical to the water column. The diagenesis process may have
developed in sediments of anoxic condition of the aquatic system occurring as a
result of exhausted oxygen due to excessive utilization for degradation of
biodegradable material such as municipal wastes. The diagenesis process usually
occurs in marine, river, lake and ground water ecosystem which are highly
contaminated by biodegradable materials such as sewage. Arsenic contamination in
Bangladesh and North East India, are example of serious consequence of migration
of multi oxidation state toxic element into water column in the anoxic sedimentary
condition (McArthur et al., 2004).
5
1.1
Problem Statement
In early civilizations, human culture and development were closely related to
freshwater utilization in many aspects of life. Rivers and lakes were utilized for
agriculture, transportation, daily usage and food resources. After the Industrial
Revolution in early 19th century, rapid development in urbanization and
industrialization took place including at some strategic areas close to the river or
lake. Without proper planning, enforcement in environmental controlling,
environmental education and awareness, man has allowed contaminants to enter the
river and lake ecosystem. In Malaysia, most rivers and lakes are still providing raw
water for daily consumption. But on the other hand, the contaminants entering the
freshwater system are not deniable.
Health issue concerning freshwater especially for drinking purpose has
always been a top priority in the nation. Rapid development in industrial and
agricultural sectors as well as rapid increase of population has affected the quality of
aquatic system adversely. Toxic contaminants such as arsenic, chromium and
selenium introduced into aquatic system may also associate with sediments
components as well and contribute to some extent of toxicity.
In the contaminated sediment, the chemistry of some contaminants may have
changed due to environmental, biological and physical processes. Some
contaminants are not biodegradable but may be biotransfromed through food chain,
thereby reaching human beings where they produce chronic and acute ailments.
While, some other toxic contaminants released from the sediment bound enter the
water column when the changes of the aquatic system environment occur such as
decline in dissolved oxygen or pH.
6
1.2
Research Objectives
Sediment contamination issue is highly important in environmental concern.
The sediment represents the largest reservoir for toxic contaminants within the
aquatic system such as marine, river, lake and pond. The freshwater bodies such as
river, lake and pond have great potential to be contaminated with toxic contaminant
as they are situated inland closely to human settlement. Contamination of freshwater
from anthropogenic activities or natural weathering may give hazardous impact
toward drinking water consumption. The study and investigation of contaminants
conducted at those stressful freshwater areas especially in sediments provides
significant information regarding the possible sources of contaminant, mobility, and
transportation behavioral, potential environmental and health risk particularly for
some contaminants that have bioaccumulation capability.
The research objectives can be outlined as follows:
a) To determine and quantify the total concentration of arsenic,
selenium,chromium and iron in river and lake sediments using neutron
activation analysis (NAA) technique.
b) To compare the quality of sediments particularly of arsenic, selenium and
chromium concentration with several international Sediment Quality
Guidelines.
c) To develop a suitable analytical method for inorganic speciation of As (III),
As (V), Se (IV), and Se (VI) in sediment samples using neutron activation
analysis (NAA) as a principal detection technique.
d) To depict and compare the availability of arsenic, selenium, chromium,
inorganic arsenic and selenium of the river and lake system used in this study.
7
1.3
Scope of Research
The main scope of research include sediment sampling at identified rivers
and lake and collection of water parameter data such as pH, temperature and DO,
analysis of sediment for the total concentration of arsenic, selenium, chromium and
iron using nuclear analytical technique namely NAA and correlation study between
the analysis results of arsenic, selenium and chromium to iron content.
The data of total arsenic, selenium and chromium concentration obtained
were compared to several International Sediment Quality Guidelines. An effort to
apply Enrichment Factor and Geoaccumulation Index for the purpose of evaluating
and estimating the contamination impact in sediment has been taken and completed.
In addition, a speciation preparation method using microwave and
preconcentration technique of inorganic arsenic and selenium species has been
developed and arsenic, selenium, their respective species as well as chromium
occurrence in two different environmental systems; river and lake, using statistical
technique has been undertaken.
1.4
Man, Environment and Toxic Elements
The introduction of elemental contaminants into the aquatic system has
various sources where the main point sources originate from anthropological
activities and geochemical processes. Anthropogenic activities in industrial,
agricultural, mining and transportation have led to many pathways of toxic elements
into aquatic system and significantly contribute to the increase in contaminations of
aquatic system. Some activities may include smelting process and fuel combustion
via atmospheric fallout, pollution from leak, effluents, and land application of
8
sewage materials and leaching of garbage (Förstner and Whitman, 1983; MacDonald
et al., 2003). Several elements may also originate from the natural weathering
process of underlying mineralized rock or associated overburden.
In water bodies, elemental contaminants are associated with the sediment
underneath whereby sediments are often the ultimate repositories of contaminants
leased to the environment. Toxic elements such as arsenic, cadmium, chromium,
copper, mercury, selenium and other species tend to accumulate at the bottom of the
sediment. The presence and addition of certain metals to sediments at such a level
that would have harmful effects on organisms can be considered to constitute metal
pollution. The compositions, quantities and the modes of these elemental inputs vary
widely from one sediment to another and thus influence the contaminants behavior in
affected sediments.
Aquatic organisms such as fishes, clams and mussels are among the species
closely associated with sediment. Under polluted water conditions, these organisms
can take up and accumulate metals present in the polluted sediment. Toxic elements
are then able to enter aquatic biota through the food chain and this provides a great
concern in human health perspective. Therefore, uptake of the contaminants by
aquatic organisms has become a subject of interest by several researchers in which
several organisms have been used as bio-indicators for assessing water pollution
(Yusof et al., 2004; Zanaton, 1994).
1.5
Arsenic
Arsenic is a metalloid that is widely distributed in the earth’s crust at an
average concentration of 2 µg g-1 (Merian, 1985). It ranks as the twentieth element in
crustal abundance and has been listed to be contained in at least 23 most commonly
naturally occurring minerals where the arsenargentite (Ag3As) was first described
back in 1795, (Azcue and Nriagu, 1994). Arsenic occurs mostly in rocks, soil, water
and air.
9
WHO, in the Environmental Health Criteria 224 for Arsenic and Arsenic
Compunds (2001), reported that the mean As concentrations in air from remote and
rural areas range from 0.02 to 4 ng m-3. The mean total As concentrations in urban
areas range from 3 to about 200 ng m-3 and much higher concentrations (> 1000 ng
m-3) have been measured in the vicinity of industrial sources. Arsenic is widely
distributed in surface freshwaters, and concentrations in rivers and lakes are
generally below 10 µg L-1, although the individual samples may range up to 5 mg L-1
near anthropogenic sources. Arsenic levels in groundwater average about 1–2 µg L-1
except in areas with volcanic rock and sulfide mineral deposits where As levels can
be up to 3 mg L-1. Concentrations of As in open ocean seawater are typically around
1–2 µg L-1.
In sediments, the As concentration may range from 3 µg g-1 to 4000 µg g-1
with the higher levels occurring in areas of contamination or pollution (Mandal and
Susuki, 2002). Background concentrations in soil range from 1 to 40 µg g-1, with
mean values often around 5 µg g-1 (Burguera and Burguera, 1997; Chu, 1994).
Arsenic concentration is considerably higher in sediment or soil than in earth crust,
because of its accumulation during weathering and tranlocation in colloid fractions.
Elemental As is a member of Group 15 of the periodic table that includes
nitrogen, phosphorus, antimony and bismuth. It has an atomic number of 33 and an
atomic mass of 74.91. Arsenic can exist in four valency states: –3, 0, +3 and +5.
Arsines and methylarsines are characteristic of As in the -3 oxidation state.
Elemental As, As0 is formed by the reduction of arsenic oxide. Arsenic trioxide
(As+3) is a product of smelting operations and is the material used in synthesizing
most arsenicals. It is oxidized catalytically or by bacteria to arsenic pentoxide (As+5)
or orthoarsenic acid (H3AsO4) (Eisler, 2000). Arsenic and its compounds occur in
crystalline, powder, amorphous or vitreous forms.
Arsenic accumulation in soils and sediments may be due to the use of
arsenical pesticides, application of fertilizers, irrigation, oxidation of volatile arsines
in air, dust from the burning of fossil fuels and disposal of industrial, municipal and
animal wastes (Prohaska and Stingeder, 2005; Skonieczny and Hahn, 1978).
10
Historically, the use of arsenic-containing pesticides has left large tracts of
agricultural land contaminated. Furthermore, soil treated with pesticides shows
higher As concentration when compared to soil treated with herbicides, which are
usually applied at lower rates (Prohaska and Stingeder, 2005).
In the industry, elemental As is used as an additive in special alloys. Arsine is
used in microelectronics and semiconductor industry. Some arsenic trioxide is used
in the glass and ceramics industry as a decolorizing agent. Coal combustion and fuel
burning contribute to As emission in the atmosphere. The degree of industrialization
is also reflected in the amount of As in sewage sludge.
The presence of As ions in the environment particularly in drinking water is
regulated by environmental and public health agencies or authorities. In Malaysia,
according to Ministry of Health, the maximum permitted level of As in drinking
water is 0.05 mg L-1 (Food Act 1983 (Act 281) and Regulations 2, 2000). Whereas,
the provisional guideline value established for As according to Guidelines for
Drinking-water Quality by WHO is 0.01 mg L-1 (WHO, 2004).
1.5.1 Geochemistry of Arsenic
The toxicity and mobility of As in the environment are dependent on the
chemical form or species in which it exists. There are many As compounds of
environmental importance. Representative marine As-containing compounds, of
which some are found in terrestrial systems, are shown in Table 1.1; their molecular
structures are shown Figure 1.1. Other inorganic As compounds of environmental
significance are listed in Table 1.2.
11
Table 1.1: Naturally occurring inorganic and organic arsenic species. (WHO, 2001)
(see Fig. 1.1 for structures 1–22)
Name
Structure
Arsenate
Arsenite
Methylarsonic acid, MMA
Dimethylarsinic acid, DMA
Trimethylarsine oxide
Tetramethylarsonium ion
Arsenobetaine, AB
Arsenocholine, AC
Dimethylarsinoylribosides
Trialkylarsonioribosides
Dimethylarsinoylribitol sulfate
1
2
3`
4
5
6
7
8
9 – 19
20 - 21
22
Arsenic (III) and (V) are the most often determined species in environmental
water, soil and sediment, while organic As species are common constituents of
biological tissue and fluids. Organic As, MMA and DMA can also be found in
dissolved forms in the water column. Under oxidizing and aerated conditions, the
predominant form of As in water and soil is As (V). Under reducing (acid and mildly
alkaline) and waterlogged conditions, As (III) can become the predominant As
compounds. The rate of conversion is dependent on the Eh and pH of the soil as well
as on other physical, chemical and biological factors. In brief, at moderate or high
Eh, As can be stabilized as a series of pentavalent (arsenate) oxyanions, H3AsO4,
H2AsO4–, HAsO42– and AsO43–. Figure1.2 shows the speciation of As under varying
Eh and pH.
12
Figure 1.1: Structures of naturally occurring inorganic and organic arsenic species.
(WHO, 2001)
13
Table 1.2: Inorganic arsenic species in the environment. (WHO, 2001)
Name
Synonyms
Inorganic As, trivalent
As(III) oxide
Formula
As trioxide, arsenous
oxide, white As
As2O3 (or As4O6)
arsenenous acid
arsenious acid
HAsO2
As(III) chloride
As trichloride, arsenous
trichloride
AsCl3
As(III) sulfide
As trisulfide orpiment,
auripigment
As2S3
As pentoxide
As2O5
arsenic acid
ortho-arsenic acid
H3AsO4
arsenenic acid
meta-arsenic acid
HAsO3
Inorganic As, pentavalent
As(V) oxide
arsenates,
salts of ortho-arsenic acid
H2AsO4–, HAsO42–,
AsO43–
Arsenic solubility is low under oxidizing conditions and the more typical
form of As is arsenate. At high pH or under reducing conditions, arsenate is reduced
to soluble arsenite and the amount of arsenite increases significantly under strong
reducing conditions. Under moderate reducing conditions, As solubility is controlled
by iron oxy-hydroxides or manganese oxides (Barrachina et al., 1999). With the
presence of sulfide and under reducing conditions, it can lead to the precipitation of
As2S3 in lake, river and marine sediments. The formation of sulfides in reducing
conditions occurs simultaneously with the reduction of arsenate to arsenite. Figure
1.3 shows the transformation pathway of inorganic As in the environment.
14
Figure 1.2: The Eh-pH diagram of arsenic in water at 25C and one
atmosphere (Kartinen and Martin, 1995 and WHO, 2001).
Arsenic is released into the atmosphere primarily as As2O3 and mainly
adsorbed by particulate matters. These particles are dispersed by the wind and are
returned to the earth by wet or dry deposition. Arsines released from microbial
sources in soils or sediments undergo oxidation in the air, reconverting the As to
non-volatile forms, which then settle back to the soil.
15
Arsenate
H3AsO4
reduction
Arsenite
H3AsO3
oxidation
+ S2sorption
sorption
AsS2-
+ Fe
Adsorption and
precipitation
precipitation
reduction
(also microbial
reduction)
As2S3
FeAsO4
Figure 1.3: Simplified transformation pathway of inorganic arsenic in the
environment (Prohaska and Stingeder, 2005).
1.5.2
The Toxicology of Arsenic
Arsenic is a common environmental agent whose toxic properties have been
known for centuries. Since ancient time, arsenicals have been used as agents of
suicide and murder. Arsenic as a toxic, poisonous and killing agent was closely
associated to the death of France’s famous ruler, Napolean Bonaparte.
Humans are exposed to many different forms of inorganic and organic As
species in food, water and other environmental media. Each As form has different
physicochemical properties and bioavailability. Zielhuis (1985) had classified at least
three groups of As-compounds: i) inorganic water soluble compounds; ii) inorganic
non- or low-solubility compounds and iii) organic As used to distinguish the
metabolic models and health risks of arsenic-compounds in order to establish the
quality standard or recommended limits of As.
16
The chemical forms and oxidation states of As are important with regards to
their toxicity which is directly related to their mobility in water and body fluids. The
toxicity of As compounds decreases in the following order; arsines > inorganic
arsenites (As (III)) > arsenoxides > inorganic arsenates (As (V)) > organic
pentavalent compounds > arsonium compounds > elemental As (Mandal and Susuki,
2002; Prohaska and Stingeder, 2005).
It appears that the stable, soluble inorganic arsenites and arsenates are readily
absorbed by digestion tract, abdominal cavity and muscle tissue. Excretion of
arsenate is faster than that for arsenite, mostly in urine (Förstner and Wittmann,
1983). Arsenate has a low order of toxicity than arsenite and does not inhibit any
enzyme system due to its lack of affinity to hydroxo and thiol groups, but adenosine
triphosphate (ATP) synthesis is inhabited by a AsO43- by uncoupling oxidative
phosphorylation and replacing the stable phosphoryl group. In contrast, arsenite
inhibits thiol-dependent enzymes, binds to tissue protein as keratin disulfides in
nails, hair and skin and retained in the body for a prolonged period.
Routes of As intake in vivo are considered respiratory for dust and fumes,
and oral for As in water, beverages, soil, and food. People from many countries all
over the world are suffering from the toxic effects of arsenicals as a result of natural
groundwater contamination caused by industrial effluent and drainage problems. A
number of As poisoning cases via contamination of groundwater in Argentina,
Bangladesh, Chile, India, Taiwan and United State have also been reported (Mandal
and Susuki, 2002). They also reviewed several As poisoning episodes from industrial
sources and contamination in food and beverage all over the world.
17
McArthur et al. (2004) had carried out an extensive study on natural organic
matter in sedimentary basin and its relation to As in anoxic groundwater. Water and
sediment samples were collected from several wells in southern West Bengal. This
investigation was aimed to explain the mechanism of As release to ground water by
reductive dissolution of FeOOH. Human excreta in latrines penetrates the upper
confining layer which has hydraulic continuity with the aquifer, may locally promote
additional reduction of FeOOH and add to the As problem. Generally, the complete
reduction of FeOOH contributes to high concentration of As (200-1180 g L-1).
Several epidemiological studies have shown that acute and chronic exposure
to As can cause a variety of adverse health effects to humans such as dermal
changes, respiratory, pulmonary, cardiovascular, gastrointestinal, hematological,
hepatic, renal, neurological, developmental, reproductive, immunologic, genotoxic,
mutagenetic, and carcinogenic effects (Brown and Ross, 2002; Buchet, 2005;
Leonard, 1985). Increased risks of lung and bladder cancer and arsenic-associated
skin lesions have been reported to be associated with ingestion of drinking water at
concentrations of As equal to and less than 50 µg L-1 (WHO, 2001).
1.6
Selenium
Selenium is classified as a metalloid that lies between nonmetallic sulphur
and metallic tellurium in Group 16 and between arsenic and bromine in Period IV of
the Periodic Table. It has an atomic number of 34 and an atomic mass of 78.96. In
physical state, Se occurs in grey metallic or red amorphous powder or vitreous form.
Selenium can exist in four valency states: –2, 0, +4 and +6.
18
Selenium is an essential trace element to life. However at very low
concentrations it can cause anomalies in organisms and at high concentrations it is
toxic (Haygarth, 1994; Merian, 1985). Selenium exists at low abundance in the
earth’s crust with concentration of 0.05 g g-1 (Haygarth, 1994). It is often associated
with sulfur-containing minerals and usually accompanies sulfur in volcanic effluents
which make the soils in the neighborhood of volcanoes tend to have enriched
amounts of Se (Malisa, 2001; WHO, 2003b).
Selenium has vast potential use in the industries. Selenium exhibits both
photovoltaic action, where light is converted directly into electricity, and
photoconductive action, where the electrical resistance decreases with increased
illumination. These properties make Se useful in the production of photocells and
exposure meters for photographic use, as well as solar cells. Selenium is also able to
convert alternating current electricity to direct current, and is extensively used in
rectifiers. Below its melting point, Se is a p-type semiconductor and is finding many
uses in electronic and solid-state applications such as in xerography for reproducing
and copying documents (Lide, 2007).
Selenium is widely used in glass and ceramic industry for decolorizing and
glazing. In heavy industry, it is used to improve the porosity of stainless steel casting
and to improve the machinability of copper and copper alloy (Green and Turley,
1961). Selenium is also used as pigments in plastic and paint due to its resistant to
heat, light and weathering. Selenium is an antioxidant, which makes it useful for
inclusion in inks, mineral and vegetables oil, and lubricants (Haygarth, 1994). Early
agricultural uses of Se compounds as pesticides were very limited and short-lived.
The recent use of Se compounds as feed additives for the prevention of Se deficiency
diseases in farm animals represents a source for environmental contamination
(WHO, 1987). Selenium sulfide is used in shampoos as an anti-dandruff agent.
Human activities, particularly mining, agricultural, petrochemical, and industrial
manufacturing operations may result in environment contamination with Se.
19
The concentration of Se in igneous rocks is relatively low, usually much
less than 1 µg g-1, and similar levels probably occur in metamorphic rocks.
Sedimentary rocks, such as sandstone, limestone, phosphorite, and shales may
contain from less than 1 and up to 100 µg g-1 of Se (WHO, 1987). The Se content in
a soil may indicate, to some extent, the parent material from which the soil has been
formed. Thus, in arid and semi-arid areas, soils with high Se content have been
derived from sedimentary rocks, usually shales and chalks.
The range of soil Se content is typically from 0.1 µg g-1 to 2 µg g-1. But at
seleniferous area, an average of Se concentration may be found to be between 45
µg g-1 and 80 µg g-1 (Quinn, 1985). In Great Lakes, USA, Se concentrations from
bottom sediments range from 0.35 µg g-1 to 0.75 µg g-1. While, oceanic study for
sediment samples reported that the Se concentrations range from 0.34 µg g-1 to 4.8
µg g-1 (Eisler, 2000). The concentrations of Se which are equal to or greater than 4.0
µg g-1 in sediments are a great environmental concern because of the potential for
bioaccumulation in fish and wildlife (Derveer and Canton, 1997). Under natural
conditions, the concentration of Se in water usually ranges from a few tenths to 2 or
3 µg L-1 (WHO, 1987). Surface waters seem much less likely to contain excessive
levels of Se than ground waters. Selenium concentrations with levels exceeding
50 µg L-1 have been documented in groundwater, especially in areas with
seleniferous soils, in sewage wastes, in irrigation drain water and in water of flyash
settling ponds (Eisler, 2000).
The 2004 WHO International Standards for Drinking Water proposed a
health-based guideline value of 0.01 mg L-1 for Se on the basis of human studies and
following the recognition that biota accumulated Se from water. In Malaysia, under
the Ministry of Health, the maximum permitted level of Se in drinking water is 0.01
mg L-1 (Food Act 1983 (Act 281) and Regulations 2, 2000).
20
1.6.1
Geochemistry of Selenium
The concentration of Se in soil depends on the parent material, topography,
climate, age of soil and man activities (Frankenberger and Karlson, 1994). Inorganic
Se species enter natural waters, groundwaters, soil and sediment from many sources.
The two most common sources of Se in the environment include the weathering of
rock and soils and organic compounds from decayed plant tissue and agricultural
products (Koll, 1993). Selenium also enters the geochemical cycle through human
activities which include agricultural drain water, sewage sludge, fly ash from coalfired power plants, oil refineries and mining (Hamilton, 2004).
The fate of Se in natural environments is affected by many physical, chemical
and biological factors, which are closely associated with changes in its oxidation
state. The concentration and speciation availability of Se are associated with the pH,
redox potential, solubility, complexing ability of soluble and solid ligands, and
microbial interaction (Belzile et al., 2000). Figure1.3 shows the availability of Se
species under varying Eh and pH. Changes in the valence state of Se from -2
(hydrogen selenide) through Se0 (elemental selenium), +4 (selenite) and +6
(selanate) are associated with its geological distribution, redistribution and use. Most
of the Se species found in soil and water are the inorganic selenite (SeO32-) and
selenate (SeO42-) forms. Soluble selenates which occur in alkaline soil, are slowly
reduced to selenites and are then readily taken up by plants and converted into
organoselenium compounds, including selenomethionine, selenocycsteine, dimethyl
selenide and dimethyl diselenide.
At equilibrium, the typical form of Se in soil is elemental selenium. Referring
to Figure 1.4 below, the biologically available Se is only present in relatively large
amount in acidic areas or neutral soils and declines as the soils become more
alkaline. The decline may be accelerated by active agricultural or industrial practices.
In dry areas with alkaline soils and oxidizing conditions, elemental selenium and
selenides in rocks and volcanic soils may oxidize sufficiently to maintain the
availability of biologically active Se.
21
Figure 1.4: The Eh-pH diagram of selenium in water at 25C and one atmosphere
(Séby et. al, 2001).
Selenite (Se(IV)) would form mineral salts which are generally less soluble
than selenate (Se (VI)) salts. Under acidic reducing conditions in soil, which may be
waterlogged and rich in organic matter, elemental selenium and selinides are the
dominant species. Elemental selenium, selinides and selenium sulfides are less
biologically available for uptake. At high redox potential and in well-oxygenated
alkaline soil, highly soluble selenate is the dominant species, and at neutral pH,
selenite occurs in approximately equal concentrations to selenate. Selenate is stable
in oxidized environments and is the form in which Se is most readily taken up by
plants, which can cause great environmental concern.
22
1.6.2 The Toxicology of Selenium
The toxicity of Se depends on the biologically active oxidized forms of
2-
SeO3 or SeO42- (Uden, 2005). In oxidizing conditions or alkaline soil, Se may be
sufficiently oxidized to maintain the availability of biological active forms that are
readily absorbed by plants. In acidic or neutral soil, it tends to remain relatively
insoluble and the amount of biologically active forms of Se available that can be
absorbed by plants constantly decreases.
Selenium dioxide is the primary problem involved with most industrial
exposure to the element as the oxide is easily formed when Se is heated. The dioxide
itself forms selenious acid when it mixes water or sweat and becomes an irritant.
Selenium compound released during fossil fuel combustion may pose an inhalation
hazard to people. Most probable forms of Se released during combustion are
selenious acid and elemental selenium. Acute poisoning through inhalation may
occur in industry which produces Se dust and fumes, selenium dioxide and hydrogen
selenide as the by products.
The considerable biological importance of Se was first recognized in the
1930s when it was discovered that certain well-defined and economically important
farm animal diseases were actually the result of chronic Se poisoning. These animal
diseases were restricted to agricultural areas in which large amounts of Se in the soil
were available for uptake by the plants, which were then consumed by the animals.
The farm animals showed severe signs of distress such as laboured breathing,
abnormal movement and posture, prostration, and diarrhea. Death often followed
within a few hours after the animals fell sick (WHO, 1987).
The capability of Se to accumulate in living tissue is a great concern as it can
cause adverse health effect. The Se capability to accumulate in living tissue is due to
its propensity to bioaccumulate within the base of food webs: from water and
sediment to aquatic plants and aquatic invertebrates (Hamilton, 2004). Tinggi (2003)
had summarized some effects of Se exposure to human. For an example, industrial
exposures in the manufacture of Se rectifiers have caused hypochromic anemia and
23
leucopenia, and damaged the nails of long-term workers employed in the industry.
There have been a number of reported cases of acute and subacute Se poisoning in
humans as a result of accidental ingestion of selenic acid and vitamin tablets that
contained high levels of Se. An ingestion of Se at high level is reported to cause
gastrointestinal disturbances (vomiting, diarrhea), hair and nail changes, and
neurologic manifestations. Examination of exposed individuals showed increased
levels of Se in the blood and urine (WHO, 1987).
1.7
Chromium
Chromium has been identified both as an essential element and as a chemical
carcinogen agent (Hoet, 2005). It is a transition element located in group 6 of the
periodic table. It has an atomic number of 24 and an atomic mass of 51.996.
Chromium demonstrates oxidation numbers of 2+, 3+, 4+, 5+, and 6+. Of these, the
compounds of the trivalent chromium, Cr (III) are the most stable, the most
abundant, less toxic and are mainly bound to organic matter in soil and aquatic
environment. In acid media, hexavalent chromium, Cr (VI) compounds are strong
oxidizing agent where Cr (VI) is readily reduced to Cr (III) at low pH.
Chromium and its compounds are widely used in the industrial,
manufacturing and commercial sectors (Katz and Salem, 1994). In metallurgical
industries, Cr is used as an alloying element that imparts the resistance to corrosion
property to stainless steels by the formation of a thin, transparent and protective film
of Cr2O3. The film stability can be improved by increasing the Cr contents of the
alloys and by the addition of nickel, molybdenum or other elements. Chromel is a
nickel-chromium alloy used in the manufacture of resistance wire for electrical
heaters and thermocouples.
24
Trivalent and hexavalent chromium compounds are widely used in
manufacturing and industrial due to its chemical and physical properties. The colours
of trivalent and hexavalent chromium compounds coupled with appropriate solubility
characteristics make them the preferred pigments and colourants in the manufacture
of paints, printing inks, floor coverings and vinyl sheeting. The inertness of the
trivalent oxide makes Cr compounds useful as corrosion inhibitors and as agents for
oxidizing and plating metals. The tendency of trivalent chromium to form complexes
with basic oxygen and/or nitrogen atoms in protein makes it possible for the tanning
of leathers to be completed in hours rather than in days. The leathers produced
become more resistant to wear and heat. The oxidizing properties of hexavalent
chromium compounds have found applications in the synthesis of organic dyestuffs.
Chromium and its compounds have become ubiquitous in modern society.
Chromium is found in all phases of environment, including air, water, rock
and soil. Almost all of the sources of Cr in the earth’s crust are in the trivalent state.
The concentration of Cr in rocks varies from an average of 5 µg g-1 in granitic rocks,
to an average of 1800 µg g-1 in ultrabasic and serpentine rocks (WHO, 1988).
Weathering of rocks produces Cr complexes that are almost exclusively in the
trivalent state. In most natural soils, Cr occurs in low concentrations of an average of
5 µg g-1. The highest concentrations of Cr which are at 125 g kg-1 are always found
in serpentine soils (Shanker et al., 2005). In freshwater, Cr concentrations generally
range from 0.1 to 117 g L-1 whereas the values for seawater range from 0.2 to 50 g
L-1 (Shanker et al., 2005). Chromium concentration varies widely in the atmosphere,
from background concentration of 5 to 7 pg m-3 in air samples from remote areas
such as Artic to at least 2 to 4 times higher concentration in urban areas than
background concentrations (WHO, 2003a).
25
As a guideline, the WHO (2004) recommended a maximum level of 50 g L-1
Cr in drinking water. In Malaysia, the quality criteria for drinking water is set under
the Food Act 1983 (Act 281) and Regulations 2 (2000) and the maximum permitted
value for total Cr is 50 g L-1. Due to the fact that the health effects are determined
largely by the oxidation state, WHO (2003a) proposed a different guideline values
for chromium (III) and chromium (VI). However, the available toxicological data
mainly in the study of carcinogenicity of Cr (VI) is yet not enough to support the
derivation of a new value.
1.7.1 Geochemistry of Chromium
Chromium compounds are highly varied and widely distributed in the
occupational, domestic and natural environments. Environmental Cr concentrations
reflect the element’s distribution in air, water, soil, plants and animals from both
anthropogenic and natural sources. Chromium compounds are released from
minerals containing Cr during the physical, chemical and biological weathering
processes by which rocks are abraded or dissolved. Once released, the Cr compounds
can be transported as wind or waterborne particulates. Volcanism is an alternative to
weathering for the release of Cr compounds.
The combustion of large quantities of coal and oil is also the major
anthropogenic source of environmental Cr. Emissions from Cr chemical
manufacturing facilities, from many cooling towers, and steel mills are other major
sources of airborne Cr. Industrial and domestic wastes are also dispatched to landfills
for disposal. Sewage sludge compost piles and steel mill slag heaps are additional
wastes to be considered as potential sources of Cr for the contamination of soil and
groundwater.
26
The distribution of compounds containing Cr (III) and Cr (VI) depends on the
redox potential, pH, the presence of oxidizing or reducing compounds, the kinetics of
the redox reactions and formation of Cr (III) complexes or insoluble Cr (III) salts
(WHO, 2003a). In soils, Cr (III) predominates. In the environment, Cr (VI) occurs
mostly as CrO42- or HCrO4- and Cr (III) as Cr(OH)2+. Figure 1.5 shows dissolved Cr
species under varying pH and Eh.
Figure 1.5: The Eh-pH diagram of chromium in water at 25C and one
atmosphere (Beverskog and Puigdomenech, 1997).
Most of the Cr in air will eventually settle and end up in waters or soils.
Chromium in soils strongly attaches to soil particles and as a result it will not
move towards groundwater. In water, Cr will be absorbed by sediments and become
immobilized. Only a small part of the Cr that ends up in water will eventually
dissolve.Chromium (VI) can easily be reduced to Cr (III) by organic matter. It is a
moderately strong oxidizing agent and will react with organic matter or other
reducing agents to form Cr (III). Therefore, in surface water rich in organic content,
Cr (VI) will exhibit a much shorter lifetime (EPA, 1998). In water, Cr (III) is a
27
positive ion that forms hydroxides and complexes and is adsorbed at relatively high
pH values. In surface waters, the ratio of Cr (III) to Cr (VI) varies widely, and
relatively high concentrations of the latter can be found locally. In general Cr (VI)
salts are more soluble than those of Cr (III), making Cr (VI) relatively mobile
(WHO, 2003a).
1.7.2 The Toxicology of Chromium
The importance of Cr is underscored by knowledge that it is an ubiquitous,
naturally occurring element usually found in rocks, minerals and geological
emissions. Chromium in excess amounts can be quite toxic, depending upon the
chemical species of Cr and the route of exposure (Crounse et al., 1983). Exposure to
Cr can occur from the large amounts of Cr released into the environment from the
industries, mining and processing of chromites ores. Moreover, Cr may make its way
into the human body from dietary intake and drinking water.
Chromium is not known to accumulate in the bodies of fish, but high
concentrations of Cr, due to the disposal of metal products in surface waters, can
damage the gills of fish that swim near the point of disposal. In animals, Cr can cause
respiratory problems, a lower ability to fight disease, birth defects, infertility and
tumor formation (WHO, 1988).
Chromium (III) is an essential nutrient for humans and Cr deficiency may
cause heart conditions, disruptions of metabolisms and diabetes. But the uptake of
too much of Cr (III) can cause adverse health effects as well, for instance skin rashes.
Chromium (VI) compounds are, in general, more toxic than Cr (III) compounds with
regards to acute and chronic oral toxicity, dermal irritancy and allergy, systemic
effects, cytotoxicity, genotoxicity and carcinogenicity (Katz and Salem, 1994).
Chromium (VI) is a danger to human health, mainly for people who work in the steel
and textile industry. Some epidemiological data suggest that an excess of lung cancer
has also occurred in the chromate-pigment industry (WHO, 1988). People who
28
smoke tobacco also have a higher chance of exposure to Cr. When present as a
compound in leather products, it can cause allergic reactions, such as skin rash.
Inhalation of Cr (VI) can cause nose irritations and nosebleeds.
CHAPTER 2
LITERATURE REVIEW
2.0
Sediment and Its Role in Freshwater Ecosystem
The particulate material that lie below the water in rivers, lakes, ponds,
streams and other aquatic systems are called sediments (MacDonald et al., 2003).
Sediments in aquatic system are primarily derived from rock weathering processes.
Transportation of the sediments particles from its pint of origin will sort them into
different size range and associated mineral fraction before they are deposited at the
bottom of water body. Re-suspensions and further transfers can occur to the
sediment before reaching at its ultimate resting point.
Sediments represent a complex and dynamic environment. Sediments also
represent essential elements of aquatic ecosystem because they support aquatic
organisms. Nutrients collect in the sediments, and many aquatic ecosystems depend
to a large extent on the cycling of nutrients back and forth between the sediment and
water. Sediment are also the rooting medium for aquatic plants and home for
invertebrates and benthic fish (Dixit and Witcomb, 1983).
30
Importantly, sediments cal also provide habitats for many wildlife species
during portions of their life cycle (MacDonald et al., 2003). For example, a variety
of fish species utilize sediments fro spawning and incubation of their eggs and
larvae. Many amphibian species burrow into the sediments in fall and remain there
throughout the winter period, such that sediment provides important overwintering
habitats. Therefore, sediments play a variety of essential roles in terms of
maintaining the structure and function of aquatic ecosystems.
2.0.1 Sediment Contamination
Some of the multiple sources that contribute to sediment contamination are
shown in Figure 2.1. Runoff and discharge from rivers, creeks, and drainage
channels produce some major “nonpoint” contaminant sources, as they carry storm
water and dry weather runoff from the upland watershed. Contaminants may also
come from point source discharges, such as accidental spills or regular municipal
wastewater and industrial discharges. Additional nonpoint contaminant sources
include atmospheric deposition and groundwater. Though a large portion of these
contaminants may be associated with suspended particles in the discharge or
receiving water body, each source influences water and sediment quality on different
spatial and temporal scales. This variety of sources, combined with various physical
mixing processes such as currents, water flow rate, sedimentation, tidal exchange,
and wave, can produce complex and widespread patterns of sediment contamination
(Battelle Memorial Institute, 2003).
Various contaminants from a variety of sources can be classified into several
groups. United State EPA through an overview report on sediment quality (Lyman et
al., 1987) had categorized five major types pf contaminants generally found in
sediments. The contaminants were defined as in Table 2.1.
31
Table 2.1: Major contaminants in sediments.
Contaminants Categories
Type of Contaminants
Nutrients
Phosphorous and nitrogen compounds such as
ammonia.
Bulk Organics
A class of hydrocarbons that includes oil and grease
A group of chemicals that are very resistant to decay
Halogenated Hydrocarbons
or Persistent Organics
like DDT and PCB
A group of organic chemicals that includes several
Polycyclic Aromatic
Hydrocarbons (PAHs)
petroleum products and by products
Iron, manganese, lead zinc and mercury;
Metals and Metalloids
Arsenic and selenium (metalloids)
Figure 2.1: Principal sources, fates and effect of sediment contamination in aquatic
ecosystem (Bridges et al., 2005).
32
The properties of sediments can influence the ultimate fate and effects of the
contaminants it contains. Sediment particles can vary from coarse sand with a
diameter of about 1 mm to fine silts and clays with diameters less than 0.01 mm.
Variations in the size and composition of these particles have an effect on the
binding of contaminants to them. Finer particles generally contain higher
contaminant concentrations due to a much greater surface area and greater number of
chemical sorption sites (Förstner, 2004).
Bottom sediments represent an important indicator of contamination because
they tend to accumulate contaminants in aquatic system. They therefore help identify
areas, which have become contaminated and reveal spread patterns from sources and
contaminant input history. They show much less temporal and spatial variation than
the water column data. Furthermore, metal levels in sediments are generally one or
two order magnitude higher than the amount of dissolved form in water (Beckett et
al., 1991).
2.0.2
Sediment Quality Issue and Assessment
Sediments are being used increasingly to assess human impact on the aquatic
environment. Sediments are frequently used to identify sources to contaminants,
determine dispersion pathway and locate contaminants sink in aquatic systems due to
their capability to transport and accumulate various contaminants (Simpson et al.,
2005). Sediments are also economically attractive to use as a monitoring tool and are
being increasingly employed in the early phase of environmental assessment of
aquatic system (Birch et al., 2001).
Contaminated sediments represent an important environmental concern for
several reasons. First, contaminated sediments have frequently been demonstrated to
be toxic to sediment-dwelling organism and fish. Exposure to contaminated
sediments can result in decreased survival, reduced growth or impaired reproduction
in aquatic organisms. Additionally, certain contaminants are taken up by benthic
33
organisms through a process called bioaccumulation. When large animals feed on
these contaminated prey species, the contaminants are taken into their bodies and are
passes along to other animals in the food chain in a process called biomagnifications.
As a result of the effects of toxic and bioaccumulative substance, aquatic organism,
birds and mammals can be adversely affected by contaminated sediments
(MacDonald et al. 2002).
Contaminated sediments can also adversely affect human health. Human
health can be potential affected due to direct exposure to contaminated sediments
during wading or swimming in affected water bodies. Consumption of contaminated
fish and shellfish also poses a risk to human health (MacDonald et al., 2003).
Sediment quality data are obtained using a variety of analytical technique
depending on the contaminants of interest. For example of metal or metalloids
contaminants, reliable and sensitive analytical methods have an important role in
determining and evaluating the environmental impact of the pollutions which also
cover other types of environmental samples including water, plants and animals
(Förstner and Wittmann, 1983). Some reliable techniques such as inductively
coupled plasma atomic emission spectrometry, inductively coupled plasma mass
spectrometry and neutron activation analysis have virtually ideal characteristics for
simultaneous multi-element determination.
Reliable analytical data of sediments can provide information on the
sediment quality conditions in order to evaluate the level of contamination and the
effect of contaminated sediment on aquatic organism, wildlife and human health.
According to MacDonald et al. (2003), assessing of sediment quality thorough
evaluating the contaminants data is conducted for several reasons as following:
-
To support broad assessment of environmental conditions.
-
To support the identification and assessment of sites with contaminated
sediments.
-
To evaluate the status and trends in environmental conditions.
-
To support ecological risk assessments.
34
-
To assess the efficacy of point or non-point source pollution control
efforts.
-
To assess the cumulative environmental effects of multiple facilities area.
-
To evaluate the feasibility of restoring aquatic habitats.
-
To assess the environmental impacts of various anthropogenic activities.
Countries like Canada and several states in America had established
guideline value for contaminants in the sediments. The guidelines documents are
usually known as Sediment Quality Guidelines (SQG). For example, Canada had
established Canadian Sediment Quality Guidelines for Protection of Aquatic Life
which covers freshwater and marine sediment quality (Canadian Council of
Ministers of Environment, 1999). SQG is one of usefully tool in assessing the
sediments quality conditions (Wisconsin Department of Natural Resources, 2003).
2.1
Analytical Technique for Elemental Analysis
Reliable and sensitive analytic methods have an important role in
determining and evaluating the environmental impact of elemental pollution. It is
realized that no single analytical technique can be used for all analysis. Several
requirements for an analytical method to be acceptable are (1) sensitivity, specificity
and accuracy; (2) rapidity and ease of operation; (3) the possibility of automation;
(4) low cost of the equipment and (5) reliability of result (Förstner and Wittman,
1983). Instrumentation of analytical technique can be divided into nuclear and nonnuclear techniques. Activation analysis and X-ray fluorescence spectrometry are
methods of analysis that are generally known for the nuclear analytical techniques.
The non-nuclear techniques can be found in most analytical laboratory such as
atomic absorption spectroscopy, inductively couple plasma mass spectrometry and
chromatography techniques.
35
2.1.1 Neutron Activation Analysis
Neutron activation analysis (NAA) is one of the popular methods in nuclear
analytical techniques. Historically, following the development of nuclear reactor in
the 1940s and sodium iodide scintillation detectors in the early 1950s, the
possibilities for applying NAA for trace element analysis of samples from many
disciplines have been recognized. Early development of NAA was taking place
rapidly. Then, the invention of high resolution solid-state Ge(Li) detectors in the
1960s and more recent advancements of computers and automation during 1970s and
1980s have made this technique applicable to several research studies such as
archeology, environmental science, forensics, geology, material science and life
science which particularly involve very large numbers of samples (IAEA, 1990).
2.1.2 Principles of Instrumental Neutron Activation Analysis
Neutron activation analysis has become the core tool for geochemical and life
science trace element research because the technique possesses several important
advantages. These include, substantial freedom from systematic errors, it is
complementary to other methods, freedom from analytical blank and other problems
related to dissolution, multi-element capability and sensitivity at sub-picogram
amounts. These characteristics of nuclear methods have been widely exploited,
particularly in research into trace element analytical methodology. NAA is being the
premier analytical technique in this study as it gives convenient on solid sample
preparation and analysis while providing high accuracy and sensitivity.
The physical phenomena upon which NAA are based are the properties of the
nucleus, radioactivity and the interaction of radiation matter. The NAA depends on
the irradiation of a stable nuclide AX with neutron using the AX(n, ) A+1X nuclear
reaction. The sequences of events during a typical (n, ) reaction are illustrated in
Figure 2.2. When a neutron interacts with a target nucleus by a non-elastic collision,
a compound nucleus is formed in a highly excited state. The high excitation energy
36
of the compound nucleus averages at 8 MeV due to the high binding energy of the
neutron with the nucleus. The lifetime of the compound nucleus is typically 10-16 to
10-14s. This is long enough that no traces remain to identify the particular process of
formation, but short enough that the nucleus can undergo a rapid de-excitation to a
more stable configuration, in a number of different ways that usually involve
emission of nucleus particles or prompt gamma rays. In most cases, the new nucleus
is radioactive and will further de-excite by emitting decay gamma rays. Once the
production A+1X is -ray emitter, a gamma-ray detection system can be employed to
measure both intensity and energy of the -ray used to indicate the target nuclide AX
and to determine the concentration of the element in the samples. About 70% of the
elements have nuclides possessing properties suitable for NAA (IAEA, 1990).
With the use of automated sample handling, gamma-ray spectrum
measurement with solid-state detector and computerized data processing it is often
possible to measure more than thirty elements without chemical separations. This
application of purely instrumental procedures for trace element analysis is frequently
called instrumental neutron activation analysis (INAA) (IAEA, 1990).
The most common approach to NAA is the “comparator” method, which is
commonly accepted as the most accurate way to quantify element concentrations.
According to this method, samples are irradiated simultaneously with standards
containing known amounts of the elements. After irradiation, both samples and
standards are measured under identical geometrical conditions with the same
detector. This procedure eliminates uncertainties in the nuclear parameters and
detector efficiencies.
37
p
PROMPT
GAMMA-RAY
TARGET
NUCLEUS
A
Z
A1
Z
X
RADIACTIVE
NUCLEUS
X
STABLE
NUCLEUS

A 1
Z 1
Y
INCIDENT
NEUTRON
COMPOUND
NUCLEUS
A1
Z
X
DECAY
GAMMA-RAY
d
Figure 2.2: Schematic diagram illustrating the sequence of events for a typical (n, )
reaction.
The measurement of induced radioactivity is being done by gamma-ray
spectrometry detector. The basic set-up of a gamma-ray spectrometer for use in
INAA is shown in Figure 2.3. It consists of a semiconductor detector with associated
preamplifier, a high-voltage (HV) power supply, a spectroscopy amplifier, an
analogue-to-digital converter (ADC), a multi-channel pulse height analyser (MCA)
and a computer- system with input/output facilities.
For application in INAA, only germanium detectors are of importance.
Germanium semiconductor detector exists in two versions, Lithium drifted
germanium detector or known as Ge(Li) detectors and Hyperpure (HP-Ge) or
intrinsic germanium detectors. The basic element of a semiconductor detector is a
single crystal of semiconductor material with P-I-N diode structure where N- and Prefers to the nature of the impurities in the crystal. N-impurities are pentavalent
atoms that act as a electron donor, P-impurities are trivalent atom, acting as electron
acceptor and I is the intrinsic layer.
38
For a Ge(Li) detector, lithium ions drifted into the crystal structure,
compensate for impurity centers and forming an active region. One of the advantages
of HP-Ge is that well-type detector can be more easily fabricated and repaired than
ever was attainable with Ge(Li) material, resulting also at more practical large willdiameters (up to 25 mm) and at highly competitive prices. Semiconductor detectors
are operated at liquid nitrogen (LN2) temperature (77K). The crystal is mounted in a
vacuum cryostat that is thermally connected to a copper rod, the ‘cold finger’which
transfers the dissipated heat from the crystal to the cooling medium. Ge(Li) detectors
always need to be stored at LN2-temperature; warming up of the detectors can lead to
almost irreparable damage. HP-Ge detectors can be stored at room temperature
without damaging the crystal as long as the HV bias is removed.
HIGH VOLTAGE
SUPPLY
PREAMPLIFIER
SPECTROSCOPY
AMPLIFIER
ANALOGUE TO
DIGITAL CONVERTER
GERMANIUM
DETECTOR
COMPUTER
MULTI CHANNEL
PULSE-HEIGHT
ANALYSER
Figure 2.3: Schematic set-up of gamma ray spectrometer for use in INAA.
One of the drawbacks of INAA, sometimes mentioned when considering its
use in a monitoring program, is its relatively long turn-around time, when compared
to other analytical techniques. Indeed, sometimes 3 or 4 weeks decay period is
required to obtained highest sensitivity. However, many elements can often be
determined with adequate sensitivity after shorter decay times. Moreover, INAA
with short-half life nuclides may also provide a very rapid measurement. In general,
INAA may be the first choice for materials research or study from the applied field
especially for samples with are difficult to be converted into solution form for
analysis, e.g., via AAS or ICPMS; and/or of which only milligram quantities are
available.
39
2.1.3 Nuclear Reactor
The research reactor is the most widely used source of neutrons for INAA,
particularly with respect to the number of samples processed and number of
elemental analysis performed. Five general types of research reactor are Slowpoke,
Argonaut, TRIGA, Pool and Heavy Water. The types of reactors are not mutually
exclusive and may overlap in some aspects, e.g., TRIGA reactors are the Pool type
(IAEA, 1990).
A research reactor is a major investment and it is also expensive to run. But,
normally the reactor would have been built for some other purposes, such as nuclear
research and training, material testing and isotope production. Besides that, neutron
activation analysis is a useful facility of reactor operation and therefore the cost of
irradiation can usually be kept to an affordable level.
The TRIGA reactor is one of the typical reactors used for neutron activation
analysis. It is designed as a general-purpose reactor and has incorporated in its
design the facility for flux equalization system, which makes it very suitable for
activation analysis. The TRIGA reactors range in power levels from 18 kW to 3 MW
with 250 kW and 1 MW being the most common operating levels. These reactors
operate with uranium-zirconium hydride homogenous solid fuel with an enrichment
of either 10% or 70%. The reactors are light water cooled, graphite reflected and of
the pool type. Most TRIGA reactors are capable of operating in the pulse mode and
most have a rotary specimen rack called Lazy Susan containing 40 irradiation
positions between the core and the reflector. The rotary specimen rack can be rotated
during the irradiation in order to get homogenous flux for all samples.
40
2.2
Elemental Speciation
Interest in chemical and elemental speciation procedures is expected to
rapidly expand as more of the scientific community recognizes that assessments of
environmental risk, toxicity, bioavailability, transport and metabolism must be done
on the specific chemical form or species, rather than on the total elemental
concentration. Speciation science strives to identify and characterize, as many as
possible, the element species in order to understand the environmental and biological
implications of individual element. It is a discipline which is a great relevance to
groups that include environmentalist, soil and sediment scientists, remediation
specialists, pharmaceutical scientists, and specialists in various fields of nutrition and
medicine. While there are several well-documented examples of varying degrees of
toxicity with regards to certain elements and tremendous advances in efforts to
understand the biological transport and metabolic mechanism of some elements,
there is still a vast wealth of knowledge yet to be gained in the area of elemental
speciation.
Determination of total metal concentration is not always the most suitable
measurement of real toxicity level due to existence of many difference species. It is
important to characterize and determine the forms of elements in a system since
different forms can have totally different properties. Some elements can be highly
toxic to various life forms while others are considered essential at a very small
amount or concentration, but become toxic at higher doses. For an example, Cr (III)
is an essential element while Cr (IV) is highly toxic (Kartz and Salem, 1994).
Inorganic arsenic in the form of As (III) is considered about 10 times more soluble
and mobile and also more toxic than As (V) (Herreweghe et al., 2003). On the other
hand, organic arsenic compounds; methylarsonate and dimenthylarsinate are much
less toxic than the inorganic arsenic compounds (Prohaska and Stingeder, 2005).
Therefore, considering the adverse environmental and human health impact, a study
of specific metal species with particular attention to the determination of the metals
origin and the understanding of their geochemical behavior – diagenesis, mobility,
transport and also biological availability has become increasingly important.
41
In nature, elemental species can be formed, transformed and transported
between environmental compartments through various ways involving chemical,
physical and biological processes. The elemental species in water, soil, sediment and
air have various pathways to enter plants, animals and also human beings which
often to be the last entity in the food chain. Exposure of toxic species to human
through foods and water consumption, inhalation, or through permeation of the skin
or mucous membranes has become great concern for toxicologists. The properties of
the elemental species such as the size, oxidation state and solubility can influence the
absorption of toxic species in human body. Further understanding of the route and
dose exposure, accumulation mechanism, metabolic reaction of the species will help
predict and model the fate, risk and effect towards human being.
Speciation study has shown an increasing interest in the analytical niche
during the last decade. It is well recognized that the total element concentration
determination does not provide adequate information to understand the effects
observed in the environment and in living systems. The International Union for Pure
and Applied Chemistry (IUPAC) (Templeton, 2000) has defined elemental
speciation in chemistry as follows:
i.
Speciation analysis. Analytical chemistry: analytical activities of
identifying and/or measuring the quantities of one or more individual
chemical species in a sample.
ii.
Chemical species. Chemical element: specific forms of an element
defined as to isotopic composition, electronic or oxidation state, and/or
complex or molecular structure.
iii.
Speciation of an element; speciation. Distribution of an element amongst
defined chemical species in a system.
The term speciation is widely used in dealing with numerous chemical forms.
Szpunar et al. (1996) described speciation analysis as the ability to define which
forms of a given element are present in a particular sample and at what levels
precisely these species occur. Marin et al. (1997) defined the term chemical
speciation as the identification and quantification of the different species, forms or
phases present in a sediment material, or the description of them. In terms of metal
42
speciation, Ge (2002) referred to it as the distribution of physico-chemical forms that
comprises the total concentration of a given metal in soil. In soil or sediment, metals
exist in several different forms and are associated with a range of components. It is
principally recognized that information about the physico-chemical forms of the
metals is required for understanding their environmental behaviour such as mobility,
pathways and bioavailability (Tack and Verloo, 1995).
2.3
Speciation Technique for Sediment Analysis
Element speciation analysis of sediment can provide insightful information
associated with risk assessment, fate, transport and chemical equilibria within the
substrate. Many studies on elemental speciation are conducted to determine their
inorganic or organic species. Speciation studies also cover other environmental
samples including water, soil, biological and air particulate.
The fundamental requirement in elemental speciation is the need to
quantitatively determine each of the forms of a given element independently and
without interference from the other forms. The study on metal speciation requires a
specific separation technique followed by sensitive method for determining the
inorganic compounds. The processes involved in speciation study are shown in
Figure 2.4. Further discussions will focus on techniques applied during the process to
determine inorganic species of arsenic and selenium in some solid samples. The brief
description of various speciation techniques applied is stipulated in Table 2.2.
43
SAMPLES
Gases
Solids
Liquids
Soils
Sediment
Air particulate
Tissue
Air
Waters
Biological fluids
TREATMENT
PRECONCENTRATION
-
acidic media
base hydrolysis
organic solvent
microwave radiation
-
solvent extraction
precipitation
coprecipitation
chromatographic separation
UV-vis
DETECTION
AAS
HG-FAAS
HG-GC-AAS
HPLC-HG-AAS
ETAAS
ICPMS
HPLC-ICPMS
HPLC-HG-ICPMS
ICP-AES
OTHERS
NAA
HPLC-AFS
CE
HG-ICP
HPLC-HG-ICP
Figure 2.4: Processes for speciation study in different samples (Burguera and
Burguera, 1997).
2.3.1 Extraction Technique
Extraction is an important stage in the determination of elemental species in
sediment. A challenge in speciation analysis is in establishing an appropriate
extraction method that will provide good recoveries while maintaining the species
integrity by avoiding transformations. Furthermore, at present, there are no soil or
sediment certified reference materials for arsenic and selenium species, which makes
any methodology development rather more challenging (Leermakers et al., 2006).
44
In metal speciation analysis, the extraction of inorganic and organic
compounds from the samples is an important step since not only high recovery is
required but the original chemical form of the compounds must also be preserved. So
far this procedure has not yet been fully established and there is no generally
acceptable method available that can be applied to determine various arsenic and
selenium species in the matrices of interest. However, several successful and
promising findings are available in the literatures (Gallardo et al., 2001; Hutton et
al., 2005; Ochsenkühn-Petropoulou et al., 2003; Peters et al., 1999; Sathrugnan and
Hirata, 2004; Thomas et al., 1997; Yusof et al., 1998).
To get data on the availability of metal species from solid samples,
dissolution or leaching in aqueous media is absolutely necessary. The concept of
elemental speciation by leaching is based on the thought that a particular reagent is
either specific to discrete phase or specific in its action (Hlavay et al., 2000). Various
reagents such as the purified water, solvents, acid extraction with diluted
hydrochloric and phosphoric acid have been proposed for the leaching of arsenic and
selenium from solid environmental samples particularly soils and sediments.
Extraction of arsenic and selenium inorganic species from solid samples in
water media had been carried out by Koll (1993), Pongratz (1998) and Sun et al.
(2004). Meanwhile, Cordos et al. (2006), Sathrugnan and Hirata (2004) and
Ochsenkühn-Petropoulou et al. (2003) had proven that water alone provided the
‘weakest attack’ on the sample to extract arsenic and selenium species. Solvents like
methanol and acetonitrile-water mix are usually employed for biological samples.
Tukai et al. (2002) had successfully extracted inorganic and organic arsenic in
marine macroalgae in methanol. Caruso et al. (2001) used an acetonitrile-water mix
to extract arsenic species in freeze-dried apple. Phosphate buffer was applied to
extract the mobilisable and bioavailable fraction of arsenic species from sediment
(Huerga et al., 2005 and Georgiadis et al., 2006). Extraction of inorganic selenium
species from sediments had been performed by using alkaline leaching (GómezAriza et al., 1998).
45
The use of diluted H3PO4 has been widely proposed to extract arsenic
species for various types of soil and sediment samples (Ellwood and Maher, 2003;
Gallardo et al., 2001; Hutton et al., 2005; Iserte et al., 2004; Ruiz-Chancho et al.,
2005; Ruiz-Chancho et al., 2007; Sathrugnan and Hirata, 2004; Thomas et al., 1997).
A range of 0.1 M to 2 M H3PO4 concentrations was studied that finally resulted in
satisfactory extraction efficiency. The diluted HCl of 0.5 M has been used to extract
selenium species in soil samples (Ochsenkühn-Petropoulou et al., 2003 and Bujdoš
et al., 2005). Ochsenkühn-Petropoulou et al. (2003) recommended that HCl
treatment should be the effective reagent for extracting selenium species in the soil
sample due to the high concentration recoveries. Meanwhile, Chappell et al. (1995)
extracted inorganic arsenic species from contaminated soil in 10 M HCl media and
yielded 97% of the total arsenic present. Cordos et al. (2006) had also employed 1
M and 10 M HCl in single extraction of inorganic arsenic species in soil samples.
The concentration of 1M obtained 39 - 80% while 10 M HCl produced better
extraction efficiency of 77 - 94%. The concentrated media of HNO3 had been
utilized for selenium species extraction in solid environmental samples (Moreno et
al., 2000; Savard et al., 2006; Saygi et al., 2007; Wang et al., 2001; Yusof et al.,
1997; Yusof et al., 1998, ). Approaches such as concentrated nitric acid or
perchloric acid extraction in conjunction with hydrofluoric acid are too aggressive
and lead to the destruction or alteration of studied species (Georgiadis et al., 2006;
Thomas et al., 1997,).
Mechanical devices have been applied in the extraction procedures as an aid
to enhance and optimize the extraction efficiency. The shaking technique had been
introduced using orbital or horizontal shaker at optimized extraction period (Bujdoš
et al., 2005; Cordos et al., 2006; Ellwood and Maher, 2003; Georgiadis et al., 2006;
Iserte et al., 2004; Pongratz, 1998; Sun et al., 2004). Caruso et al. (2001), GómezAriza et al. (1998), Huegra et al. (2005) and Moreno et al. (2000), had used
sonication technique in the extracting process.
46
Recently, microwave digester has also gained much attention in the
extracting process in the speciation study. Low power heating, suitable operating
time and appropriate extracting reagents have made microwave a reliable technique
for extraction of arsenic and selenium species from solid samples. Zanaton (1994),
Thomas et al. (1997), Tukai et al. (2002), Sathrugnan and Hirata (2004), RuizChancho et al. (2005) and Hutton et al. (2005) had used the microwave technique to
extract arsenic species while Yusof et al. (1997), Yusof et al. (1998), Peters et al.
(1999), Moreno et al. (2000), Wang et al. (2001) and Saygi et al. (2007) had applied
similar technique for extracting the selenium species in solid samples.
2.3.2 Usage of Microwave in Sample Digestion Prior to Extraction
Microwave technology is of considerable significance at home and in
analytical laboratories. Microwave-assisted methods have been widely used in
analytical chemistry and have attracted much attention in recent years. Luque-García
and Castro (2003) reviewed latest advances in the use of microwaves in various
analytical chemical fields including sample digestion for elemental analysis, solvent
extraction, sample drying, moisture measurement, analyte adsorption and desorption,
sample clean-up, chromagenic reactions, solid-phase retention, elution, distillation,
microwave plasma atomic spectrometry and synthetic reactions.
Apart from safety, the main advantage of using microwave is the ability to
control the microwave energy release to the sample and programmable addition of
solution (Nobrega et al., 2002). The merit of pressurized acid digestion in closed
vessels with microwave heating, particularly the increased speed and reduced losses
of volatile elements, are widely recognized (Yusof et al., 1994; Wen et al., 1997;
Wang et al., 2001). This feature is important when it comes to volatile element such
as arsenic and selenium. In the speciation analysis of solid samples, the time
necessary for the quantitative isolation of the species from the sample matrix can be
reduced from more than 24 hours to a few minutes by the application of microwave
technology. At the same time solvent consumption is reduced and the species
recoveries are improved (Szpunar et al., 1996).
47
Zanaton (1994) had obtained 99.3% recovery of inorganic arsenic species in
marine biological samples by performing suitable heating program in 7 minutes at
30% power in concentrated HNO3 using microwave digester model CEM MDS-81D.
The extraction of arsenic species in the marine macroalgae using microwave for 5
minutes at 60C had achieved efficiency greater than 88% with the appropriate
methanol/water mixture (Tukai et al., 2002). They also found that extraction
temperature and extraction time did not significantly influence the extraction of
arsenic in macroalgae.
Low power microwave extraction was successfully applied for arsenic
extraction from various sediment and soils samples. Thomas et al. (1997) had
extracted arsenic species using microwave in 2 M H3PO4 with 20% power for 20
minutes that obtained recoveries in sediment CRM 320 and IAEA Soil-7 of 82% and
87%, respectively. Sathrugnan and Hirata (2004) proposed low heating microwave
power of 50 W for 10 minutes to extract arsenic and selenium species in sediment
and coal fly ash. They obtained good extraction efficiency between 90 to 110% in
diluted 0.1 M H3PO4 media for arsenic and 60% for selenium species. Ruiz-Chancho
et al. (2005) and Ruiz-Chancho et al. (2007) established new approached of
microwave-assisted (60W power, 10 minutes) for extracting arsenic species from
soils by adding 0.5 M ascorbic acid together with 1M H3PO4 media and attained
relatively higher extraction efficiency and minimizing As (III) oxidation during the
extraction step. Hutton et al. (2005) extracted arsenic species using standard solution
in microwave-assisted extraction at 40% power in 0.3 M H3PO4 media, obtaining
recoveries between 90 to 110%. Gallardo et al. (2001) reported the total arsenic
extraction yield of 96% for sediment CRM 320 and 99% for sewage sludge CRM
007-040 after microwave digestion at 40 W power for 20 minutes in 1 M H3PO4 .
Inorganic selenium was extractable from the aquatic species using
microwave digestion at low power heating of 30% in concentrated HNO3 media
(Yusof et al. 1997). The similar approach was also used by Yusof et al. (1998) to
extract the Se (IV) from marine sediment in media mixture of HNO3 (70%), HClO4
(60%) and HF (48%). The presence of selenium species in muscles tissues was
48
determined by hydrolyzing them in 6 M HCl using microwave heating (100C, 414
kPa, 10 minutes) (Peters et al., 1999). Moreno et al. (2000) was able to extract
inorganic selenium species from sewage sludge after applying several steps of
microwave programs at power range of between 475 W and 570 W in concentrated
HNO3. Saygi et al. (2007) also applied several simultaneous heating programs with
power range of between 250 W and 550 W for 23 minutes in order to extract
inorganic selenium species from solid samples. Wang et al. (2001) studied the effect
of several extracting reagents such as HNO3, H2SO4/H2O2, H3PO4 and HNO3/HClO4
in environmental and natural waters on selenium speciation. The digestion reagents
such as HNO3 and H2SO4/H2O2, an appropriate selection of power program and a
suitable heating time would help to minimize the changes of element oxidation state
in digestion solutions.
2.3.3 Preconcentration and Separation Technique
The concentration levels for inorganic or organic element species in the
environmental samples are generally lower than detection limit of most detection
techniques. The influence of the matrix components of real samples presents
challenges in species determination. For many detection techniques, it is not possible
to determine different oxidation states of the element species. Therefore, the
separation and preconcentration techniques including solvent extraction,
coprecipitation, solid-phase extraction and chromatographic have been proposed in
order to address that problem.
A number of reagents have been used by many researchers as the means of
selectively removing the species from extracted samples of previous procedure and
also as the means of preconcentration prior to the quantification by ETAAS or NAA
methodology (Burguera and Burguera, 1997; Yusof et al., 1994). The
preconcentration techniques such as chelation, solvent extraction and coprecipitation
are frequently employed in conjunction with NAA technique (Alfassi and Wai,
1991). A selective extractions and preconcentration of inorganic arsenic species
49
using ammonium pyrrolidinedithiocarbamate (APDTC) into chloroform and APDTC
into methyl isobuthyl ketone (MIBK) has been reported (Mok et al., 1986; Mok and
Wai, 1988; Shi, 2000; Zanaton, 1994). Yusof et al. (1997) used a mixture of APDTC
and chloroform to preconcentrate the inorganic selenium species from aquatic
species. Chappell et al. (1995) extracted As (III) as arsenic trichloride into
chloroform from a solution with highly concentrated HCl followed by backextraction of the arsenic into water.
An extensive study for solvent stability has been evaluated on six types of
solvents, namely chloroform, cyclohexane, DIBK, MIBK, toluene and o-xylene for
extracting As (III), Sb (III) and Se (IV) using APDTC (Shi, 2000). MIBK is
considered to be the most effective solvent for the extraction purpose due to its
higher boiling point, lower solubility in water and acceptable density difference with
water. Apart from that, it does not have very strong odor and interfering elements in
it.
Abdullah et al. (1995) had successfully obtained concentrated Se (IV) from
seawater by extracting it in APDTC complex with chloroform and back-extracting
the fraction into nitric acid. Meanwhile, the total selenium had been extracted by coprecipitation with tellurium in an acidified sample. Simultaneous determination of
arsenic, selenium and antimony in natural water had been studied by Sun and Yang
(1999). Arsenic (III), selenium (IV) and antimony (III) can be simultaneously coprecipitated with Pb(PDC)2 (PDC=pyrrolidinedithiocarbamate) from pH 2 to 4,
while quantitative co-precipitated of the higher oxidation state forms can be
subsequently accomplished by reduction with titanium (III) chloride followed by
Pb(PDC)2 co-precipitation. They also found that pyrrolidinedithiocarbamate to be the
more suitable co-precipitant than oxine and thionalide for the studied species. The
co-precipitation technique for Se (IV) dibenzyldithiocarbamate complex with
phenolphthalein had been carried out by Saleh et al. (1990) and Yusof et al. (1998)
from water and marine sediment samples, respectively.
50
A selective complex formation of Se (IV) with Bismuthiol-II, which was
subsequently adsorbed on activated carbon had been successfully applied by Sakai et
al. (1994) to determine selenium species in natural water. Pyrzynska et al. (1998)
had proposed a speciation procedure for inorganic selenium in natural water samples
based on solid phase extraction on activated alumina and determined by graphite
furnace AAS. The application of solid phase extraction for inorganic selenium in
environmental samples was performed by Saygi et al. (2007). The selenium species
were determined by graphite furnace AAS after extraction on Diaion HP-2MG
adsorption resin.
The automated separation techniques such as hydride generation and
chromatographic column incorporated with detection system like AAS and ICPMS
have been employed in speciation study. Cordos et al. (2006) determined the content
and fraction of As (III), (V) and total arsenic leachable in water, 1M HCl and 10M
HCl in soil samples by hydride generation-quartz furnace atomic absorption
spectrometry. Ion chromatographic separation technique integrated with ICPMS
detection was successfully applied in speciation of the inorganic arsenic in drinking
water, soils and plants (Mattusch et al., 2000; Gallagher et al., 2001; Gault et al.,
2003). A liquid chromatographic separation of inorganic arsenic and selenium by
HPLC using mixed ion-pairing reagents followed by ICPMS had been performed by
Sathrugnan and Hirata (2004). The chromatographic separation allows direct
separation of metal ions using ion exchange columns or by adsorption (reversed- or
normal-phase) liquid chromatography if the metal species are complexed with
organic ligands.
51
2.3.4 Detection Technique
A number of detection techniques for speciation of arsenic and selenium
compounds are available. Spectrometric methods such as UV, visible, atomic
absorption, atomic emission, graphite furnace and inductively coupled plasma had
been employed for the determination of arsenic (Jain and Ali, 2000). Some other
reliable detection techniques including X-ray spectrometry, neutron activation
analysis (NAA), capillary electrophoresis, atomic fluorescence spectrometry and online combinations of some separation technique with the detection method or socalled hyphenated technique had also been applied for speciation study (Burguera
and Burguera, 1997).
Hyphenated techniques such as gas chromatography-mass spectrometry,
liquid chromatography or hydride generation integrated with detection system like
inductively coupled plasma mass spectrometry (ICPMS) and AFS for speciation
study has also been widely reported. A number of researchers had reported on the
use of liquid chromatography particularly HPLC integrated with ICPMS instrument
as the detection method (Caruso et al., 2001; Ellwood and Maher, 2003;
Ochsenkühn-Petropoulou et al., 2003; Rodas et al., 2005; Sathrugnan and Hirata,
2004). This method showed good accuracy, repeatability, robustness and high
selectivity. Recently, some studies on simultaneous determination of arsenic,
selenium and chormium species conducted using HLPC-ICPMS method achieved
good recovery and low detection limit (Martínez-Bravo, et al., 2001). The
combination of both liquid chromatographic and hydride generation separation
followed by AFS detection had been applied in the speciation of arsenic in soil and
sediment samples by Gallardo et al. (2001), Georgiadis et al. (2006), Huegra et al.
(2005), Hutton et al. (2005) and Thomas et al. (1997).
The main drawback of ICPMS instrumentation is that since arsenic has only
one isotope (m/z 75), the detection process can suffer interference from the ArCl
polyatomic ion produced during extraction of the plasma through the interface. For
the detection of selenium with ICPMS, the most abundant isotopes 80Se and 78Se are
not accessible for evaluation because of interference from polyatomic argon. The m/z
52
82 was not used because of the random presence of 82Kr as a contaminant in the Ar
cylinders. The other isotope 77Se can be subjected to interference from the formation
of the ArCl polyatomic species in chloride-rich samples (Bravo, et al., 2001).
Therefore much effort should be given to chromatographically separating the Clfrom arsenic and selenium species to eliminate the interference. Moreover, due to the
high cost of the combination techniques and of their maintenance, they are not
available in many laboratories (Burguera and Burguera, 1997).
Table 2.2: Summary of analytical arsenic and selenium speciation in environmental samples.
Analyte
Matrix
Extraction procedure
Separation procedures
Detection
Ref.
As
(inorganic)
Soil
Hydride generation (HG)
AAS
Chappell et al. (1995)
As
(inorganic
and organic)
As
(inorganic
and organic)
As
(inorganic
and organic)
As
(inorganic)
As
(inorganic)
As
(inorganic
and organic)
As
(inorganic)
Soil and sediment
Solvent Extraction
In
10M
HCl
followed
into
chloroform, back-extraction in water
Microwave
20% Power, 20 min
in 2M H3PO4
Shaking 2hrs in water
Chromatographic - HPLC
ICPMS
Thomas et al. (1997)
Chromatographic - HPLC
ICPMS
Pongratz (1998)
Microwave
40W, 20 min
in 1M H3PO4
Shaking 1hr in 0.5M H3PO4+ 0.1M
hydroxylamine hydroloride
Sequential extraction
Chromatographic - HPLC
HG-AFS
Gallardo et al. (2001)
Chromatographic - HPLC
ICPMS
Chromatographic - IC
ICPMS
Ellwood and Maher
(2003)
Gault et al. (2003)
Sediment
Sonication 2hrs
phosphate buffer
and
Chromatographic - HPLC
HG-AFS
Huerga et al. (2005)
Soil
Chromatographic - HPLC
HG-AFS
Hutton et al. (2005)
As
(inorganic
and organic)
As
(inorganic)
As
(inorganic)
As
(inorganic)
Soil
Microwave
40% Power, 25 min
in 0.3M H3PO4
Microwave
60W, 10 min
in 1M H3PO4+ 0.5M Ascorbic acid
Shaking at 20C in water, 1M HCl
and 10M HCl
Shaking at 300rpm in phosphate
buffer
Microwave
60W, 10min
in 1M H3PO4+ 0.5M Ascorbic acid
Chromatographic - LC
HG-AFS
Ruiz-Chancho et al.
(2005)
Hydride generation (HG)
QFAAS
Cordos et al. (2006)
Chromatographic - HPLC
HG-AFS
Georgiadis et al. (2006)
Chromatographic - LC
HG-AFS
Ruiz-Chancho et al.
(2007)
Soil
Sediment and
sewage sludge
Sediment
Sediment
Soil
Soil and sediment
Soil
in
water
53
Table 2.2: (continued)
Analyte
Matrix
Extraction procedure
Separation procedures
Detection
Ref.
As
(inorganic
and organic)
Se
(inorganic)
As and Se
(inorganic)
As and Se
(inorganic
and organic)
As
(organic)
As
(inorganic
and organic)
As
(inorganic
and organic)
As
(inorganic)
As
(inorganic
and organic)
As, Se, Cr
(inorganic)
Se
(inorganic
and organic)
Se
(inorganic
and organic)
Sediment
Shaking 1hr in 0.3 H3PO4
Chromatographic - HPLC
ICPMS
Iserte et al. (2004)
Sediment and coal
fly ash
Sediment
Microwave
50W, 10 min in 0.1M H3PO4
Shaking 2 hrs in water
Chromatographic - HPLC
ICPMS
Reverse electroosmotic flow
Capillary
electrophoresis
Sathrugnan and Hirata
(2004)
Sun et al. (2004)
Plant tissue
Shaking 2hrs in bidistilled water
Chromatographic - IC
ICPMS
Mattusch et al. (2000)
Apple
Sonication with acetonitrile –water
mix
Chromatographic - HPLC
ICPMS
Caruso et al. (2001)
Marine macroalgae
Microwave
At 60C, 5 min in methanol-water
mix
Chromatographic - HPLC
ICPMS
Tukai et al. (2002)
Water
Chromatographic - IC
ICPMS
Gallagher et al. (2001)
Water
Chromatographic - HPLC
ICPMS
Rodas et al. (2005)
Water
Chromatographic - HPLC
ICPMS
Anion-exchange resin and
derivatise using 4-chloro-ophenylenediamine
Chromatographic - LC
GCMS
Martínez-Bravo, et al.
(2001)
Gómez-Ariza et al. (1998)
Sediment
Sonication 2hrs
in alkaline solution 2M NaOH
Soil
Water 20C, 24hrs;
Hotwater 55C;
Methanol 20C, 24hrs and
0.5M HCl 4C
ICPMS
Ochsenkühn-Petropoulou
et al. (2003)
54
Table 2.2: (continued)
Analyte
Matrix
Extraction procedure
Separation procedures
Detection
Ref.
Se
(inorganic)
Se
(inorganic
and organic)
Se
(inorganic)
Soil
Shaking 1hr
in 0.5M HCl
Microwave
100C, 10min in 6M HCl
Hydride generation (HG)
QFAAS
Bujdoš et al. (2005)
Chromatographic - HPLC
ETAAS
Peters et al. (1999)
Waste water
Microwave
98C, 5min in 4M HCl
Reducing agent 12M HCl on heating
plate 98C, 55min
Hydride generation (HG)
AFS
Moreno et al. (2000)
Sewage sludge
i)
Environmental and
natural water
Microwave with 5 steps programme
between 10min to 15 min
in HNO3, H2SO4/H2O2, H3PO4
Microwave with 5 steps programme,
23min in concentrated mixture HNO3
+ H2O2
Reducing agent 4M HCl in
microwave for 13 min
Chromatographic - HPLC
Fluorimetric
detection
Wang et al. (2001)
Solid phase extraction on the
Diaion HP-2MG adsorption
resin
GFAAS
Saygi et al. (2007)
Se
(inorganic
and organic)
Se
(inorganic)
Muscle tissue
Water,
garlic,
onion, rice, wheat,
haxelnut
Microwave
with
2
steps
programme in HNO3 media
ii) Sonication 45 min in HNO3 media
55
56
2.4
NAA in Speciation Study
The nuclear analytical technique namely neutron activation analysis (NAA) is
well-known for its most reliable technique for trace-element determination in
environmental samples (Mok et al. 1986). In the decade of 1980s, some significant
studies on speciation of several elements were highlighted with particular interest in the
usage of the solvent extraction for the extraction and preconcentration steps followed by
neutron activation analysis (Paiva, 2004). The extraction and preconcentration steps are
complementary to NAA because direct irradiation of samples without separation will not
distinguish between the oxidation states of the various species involved. It was reported
that the use of large volumes of samples for irradiation without preconcentration was
unfeasible due to small concentration factor involved (Mok et al. 1986). Several
separation techniques such as solvent extraction, chelation and ion exchange and coprecipitation have been used in order to preconcentrate the relevant species prior to NAA
determination. Several speciation studies in conjunction with NAA determination are
showed in Table 2.3.
Solvent extraction or liquid-liquid extraction involves the partition of one or
more components between two liquids of limited miscibility that is caused by the
different solubilities of a given substance in the two phases. Solvent extraction was a
versatile, useful and popular separation technique because of its simplicity, speed and
applicability to both major and trace components (Holzbecher et al. 1976). If there are
constituents of the samples interfering with the analytical instrument, the analyte or,
alternatively the interfering species can be separated by solvent extraction. In addition,
large distribution ratios also allow for the determination of analytes below the detection
limit that increases the sensitivity of the analysis. If separation and preconcentration
were simultaneously required, solvent extraction could be offered as a potential tool
(Paiva, 2004).
57
One example of the solvent extraction application in speciation study is the work
that had been extensively carried out by Mok et al. (1986) to determine As (III) and As
(V) from natural waters. Quantitative extraction of the arsenic species was achieved by
extracting them in APDTC at pH 1-1.5 into chloroform followed by a nitric acid back
extraction and then subjected to NAA. The study showed that the advantage of using
dithiocarbamic acid derivatives for extraction was that the interfering matrix species
including the alkali metals, the alkaline-earth metals and the halogens t could be
effectively eliminated. High selectivity of solvent extraction can easily be obtained if
the conditions of the solutions are properly arranged. This can be done by adjusting the
pH of the solution where the extraction efficiencies of many metal-dithiocarbamate
complexes depend strongly on acidity. APDTC was much more stable in acidic solution
than Na- diethylthiocarbamate and therefore, it was recommended as a solvent extraction
reagent of many metal ions from acidic media (Cheng et al. 1982).
Co-precipitation has found applications mainly for the separation of minor
components or trace amounts of substances. The isolated precipitate was possible either
to determine the trace amount in the presence of the collector or to remove the collector
(Holzbecher et al. 1976). One of the important features of a co-precipitation method lied
in its potential for achieving extremely high concentration factors (103-104 fold)
(Mizuike, 1983; Sun and Yang, 1999). The co-precipitation process provides a solid
sample favorable for NAA. This procedure also eliminates most of the alkali metals,
alkaline earth metals and halogens. It indirectly decreased the background level of
irradiation and the radiation dose received by personnel (Sun and Yang, 1999). Some
metals like As, Bi, Sn, Sb and Te have the tendency to interfere with selenium signal
determined by hydride generation technique. However, the use of NAA would overcome
this problem due to the selective nature of the gamma-rays analysis (Yusof et al., 1998).
Saleh et al. (1990), Sun and Yang (1999) and Yusof et al. (1998) had applied
coprecipitation technique in the determination of inorganic selenium species prior to
analyse by NAA method.
58
Several solvent extraction and co-precipitation procedures apply additional agent
such as ethylenediaminetetraacetic acid (EDTA) as a masking agent for the extraction.
Mok et al. (1986) reported the use of EDTA as a masking agent that could reduce the
interferences caused by other metal ions present in complex natural water systems such
as seawater and acid mine waters. Zanaton (1994), Yusof et al. (1997) and Yusof et al.
(1998) applied EDTA as a masking agent in speciation study for marine biota, marine
sediment, seawater and other aquatic biota samples. EDTA had also been used in the
AAS for the purpose of masking and increasing sensitivity (Cheng et al. 1982).
The speciation study using NAA method usually allows for preconcentration and
separation of lower oxidation state species. The determination of higher oxidation state
species is accomplished with a previous reduction to lower oxidation state by a reducing
agent before the application of the extraction procedures. The reducing agents make it
possible to determine the total concentrations of the elements and the concentration of
the higher oxidation state species can be indirectly obtained by subtractions. Mok et al.
(1986), Zanaton (1994) and Yusof et al. (1997) used sodium thiosulfate as the reducing
agent for As (V) at low pH condition. Meanwhile, Sun and Yang (1999) applied titanium
(III) chloride to simultaneously reduce As (V), Sb (V) and Se (VI) in natural water
systems. Shi (2000) studied the ability of three different reducing agents, namely Lcysteine, potassium thiosulfate and potassium iodide to reduce As (V), Sb (V) and Se
(VI) to As (III), Sb (III) and Se (IV), respectively. L-cysteine and potassium thiosulfate
can quantitatively reduce As (V) and Sb (V) at pH 1. The reduction yield of Se (VI) to
Se (IV) by the proposed reducing agents was found to be very low. The concentrated
HCl ranges between 4 M to 12 M and followed by heating at boiling bath or hot plate to
temperature nearly of 100C was was found to be associated with reducing Se (VI) to Se
(IV) in several studies (Gómez-Ariza et al., 1998; Moreno et al., 2000; Sakai et al.,
1994; Savard, 2006).
59
The method for the determination of metal species particularly arsenic and
selenium which consists of selective separation and preconcentration followed by NAA
determination has been well established. NAA provided fairly low detection limits with
good accuracy and high sensitivity for small sample size of at least 100 mg (Saleh et al.,
1990; Yusof et al., 1997). NAA also offers some advantages over GFAAS and ICP-MS
such as eliminating the desorption step and recalibration. It was also non-destructive,
less time consuming than GFAAS and had no interference unlike ICP-MS (Savard,
2006).
NAA has been chosen as the primary method in speciation study due to the
availability and reliability of its technique. Contaminated sediments are usually associated
with high level concentration of several elements. In this case, NAA technique serves an
advantage as no dilution step is required to be carried out and it offers high specificity on
the interest element without any interference during analysis. However, the optimization
procedure for extraction and preconcentration steps must be conducted in order to obtain
the optimum condition and high recovery of particular species. The extraction and
preconcentration steps are also ideal to create an interference-free environment in the
matrix during the activation period.
Table 2.3: Summary of speciation study using NAA as a method of determination.
Analyte
Matrix
As (III) and As (V)
Extraction
Separation and preconcentration
Reducing agent
Ref.
Natural Water
Solvent extraction
APDTC in chloroform + EDTA at pH1 –
1.5, back extract with nitric acid
Sodium thiosulfate
Mok et al.
(1986)
Se (IV)
Water
Solvent extraction
Co-precipitation of metal
dibenzyldithiocarbamate with
phenolphthalein
Se (IV) and Se (VI)
Natural Water
Solvent and solid phase extraction
Se (IV)/ Bismuthiol-II complex and
adsorption on activated carbon
4M HCl +
NH2OH.HCL at
water bath 99C
Sakai et al.
(1994)
As (III) and As (V)
Marine biota
and seawater
Microwave with 2 steps programme,
7min, 30% power in concentrated
HNO3
Solvent extraction
APDTC in chloroform + EDTA at pH1 –
1.5, back extract with nitric acid
Sodium thiosulfate
Zanaton (1994)
As (III) and As (V)
Marine biota
and seawater
Microwave
5min, 48C, 30% power
in concentrated HNO3
Solvent extraction
APDTC in chloroform + EDTA at pH1 –
1.5, back extract with nitric acid
Sodium thiosulfate
Yusof et al.
(1994)
Se (IV) and Se (VI)
Aquatic biota
Microwave
7min, 48C, 30% power
in concentrated HNO3+H2O2
Solvent and solid phase extraction
APDTC in chloroform + EDTA
back extract with nitric acid
Sodium thiosulfate
Yusof et al.
(1997)
Se (IV)
Marine
sediment
Microwave
10min, 48C, 30% power
in concentrated HNO3+HClO4+HF
Solvent extraction
Co-precipitation of metal
dibenzyldithiocarbamate with
phenolphthalein
Saleh et al.
(1990)
Yusof et al.
(1998)
60
Table 2.3: continued
Analyte
Matrix
As (III,V),
Se (IV,VI) and
Sb (III,V)
Extraction
Separation and preconcentration
Reducing agent
Ref.
Natural Water
Solvent extraction
Co-precipitation of Pb-APDTC at pH 2-4
Titanium (III)
chloride
Sun and Yang
(1999)
As (III,V),
Se (IV,VI) and
Sb (III,V)
Natural Water
Solvent extraction
APDTC and back extract with nitric acid
L-cysteine and
potassium thiosulfate
Shi (2000)
Total Se
Geological
material
Preconcentration using thiolcotton fiber
6M HCl at boiling
bath 95-100C,
30min
Savard et al.
(2006)
Digestion block
in HNO3+H2O2+HF at 55-60C
61
CHAPTER 3
MATERIALS AND METHODOLOGY
3.0
Introduction
This chapter describes the materials and the methodologies used for the
determination of total arsenic, chromium, selenium and iron concentration and
species determination of arsenic and selenium in the contaminated freshwater
sediments. The study area of this project is also described. The rational for the
selection of sites sampling, parameters measured, sampling frequency, sampling
methodology, method of analysis and statistical analysis are also explained.
3.1
Study Area
This study was focused to two types of freshwater systems, river and lake
which are situated at the southern region of Peninsular Malaysia. The potential sites
for this study were surveyed prior to commencement of sampling. The information
such as industrial area, land use patterns and other human activities that could impact
the aquatic system at the proposed sampling sites are considered in the site selection
criteria. Briefly, the sampling sites were based on the following criteria:
1) Accessibility and ability to sample under all weather conditions;
2) Homogeneity of the sediment, and
3) Location of the industrial and settlement areas.
63
A total of 15 sediment sampling locations constituted of three major rivers in
Johor Bahru and three main lakes in the Universiti Teknologi Malaysia campus. The
sampling locations consist of eight and seven sites at the river and lake respectively.
The samplings were carried out for a total number of three series at both rivers and
lakes within a period of five months from August to December 2006 (Table 3.1).
Like other parts of Malaysia, the climate of the sampling areas is equatorial
monsoon where uniform and high temperatures are observed throughout the year.
The mean ambient temperature over a period of six months from July to December
2006 was about 26.7C based on the meteorological measurement recorded from the
nearest meteorological stations, Hospital Johor Bahru (01 ° 28 ' N, 103 ° 45 ' E) and
Senai Airport (01 ° 38 ' N, 103 ° 40 ' E). The total rainfall over the particular period
was averagely 1860 mm and the highest rainfall was observed during the month of
December. The relative humidity was averagely 82%. (Malaysian Meteorological
Services, 2006).
Table 3.1: Date of sampling carried out in the rivers and lakes.
Location
Frequency
Date
River
1
22nd August 2006
2
20th November 2006
3
14th December 2006
1
22nd August 2006
2
21st November 2006
3
13th December 2006
Lake
64
3.1.1 River
Three main rivers namely Sungai Skudai, Sungai Tebrau and Sungai Buluh
have their estuaries towards Johore Straits. The rivers were located in polluted and
slightly polluted river area which was categorized by the Department of
Environmental (2007) in Malaysian Environmental Quality Reports 2006. The
sediments were collected from three sampling points at Sungai Skudai and Sungai
Buluh respectively and two sampling points at Sungai Tebrau (Figure 3.1). The
sampling points at each river were situated approximately within 10 km to 20 km
along the respective river. The order of samplings was done starting from upstream
and moving towards downstream of the river. The coordinates and description of the
sampling sites were summarized in Table 3.2.
The first sampling point at Sungai Skudai was located at Kg. Jaya Sepakat
which was situated near the Singapore Public Utilities Board Complex (PUB) at
Skudai. This area is surrounded by oil palm plantation and squatter settlement and it
was formerly a water intake point by PUB. Industries almost do not exist in this area
of the river. The second sampling point was located at Kg. Laut beside a settlement
and shop houses where some lorry and car workshops were actively operating.
Additionally, the river was also polluted with domestic wastes from the presence of
squatter areas around the sampling point. The third sampling point was located at
Kg. Teluk Serdang, near the Taman Perling commercial area. A small Malay village
is located along the river. Fishing activities were also noticed in the area because the
location was close to the river mouth.
Similar to Sungai Skudai, the sampling points at Sungai Tebrau were close to
industries, palm oil plantation and housing estates. The first sampling point was
located near Ladang Tebrau where large scale land works at the palm oil plantation
area was being carried out during the sampling period. From the notice board erected
at the work area, it was believed that the land has been developed as a housing estate.
The second sampling point was located at Pandan, near a low cost housing estate. A
squatter area was also found along this location.
65
The third sampling area at Sungai Buluh was located at Pasir Gudang area.
Pasir Gudang is very well known as an industrial town where a lot of heavy
industries such as petrochemical, oleo chemical, biodiesel, machinery and chemical
were located. The first and second sampling points were located approximately 2 km
from each other and situated close to fat and oil factory and an oxidation pond. The
third sampling point was located under the highway bridge near Shell plant and
Feoso oil storage.
Figure 3.1: Sampling locations for river.
66
Table 3.2: The coordinates and description of the river sampling site
Name of
Sampling
location
point
Sungai Skudai
(SGS)
1
N 01 33’ 21.6”
E 103 39’ 36.3”
Kg. Jaya Sepakat, near PUB
Oil palm plantation and squatter
2
N 01 31’ 51.5”
E 103 40’ 14.6”
Kg. Laut
Settlement, shop houses and squatter
3
N 01 29’ 56.5”
E 103 41’ 00.4”
Kg. Teluk Serdang, near Taman
Perling
Village and fishing activities
1
N 01 32’ 53.4”
E 103 44’ 24.1”
Ladang Tebrau
Housing estate development, formerly
oil palm plantation
2
N 01 31’ 22.7”
E 103 46’ 05.5”
PandanHousing estate, squatter
1
N 01 26’ 39.8”
E 103 54’ 03.3”
2
N 01 27’ 01.2”
E 103 53’ 20.0”
3
N 01 27’ 23.2”
E 103 54’ 05.0”
Sungai Tebrau
(SGT)
Coordinates
Description of site
Near to fat and oil factory
Sungai Buluh
(SGSB)
Near to oxidation pond,
Near to highway bridge, Shell plant
and Feoso storage
3.1.2 Lake
Sediment samples were collected from several sampling points in each of 3
lakes located around Universiti Teknologi Malaysia campus (Figure 3.2). The lakes
had an average area of 0.5 km2 and its depth ranged from 0.5 m to 5 m. The first
lake sampled (known as TKR) was located behind a deer cage. This lake had a
fountain that provided continuous water aeration. The second lake sampled (known
as TUP) surrounded by student residencies whose rain drainage system ended into
the lake. Previously, small scale horticulture activity was conducted by students at
67
one side of the lake bank. The final lake sampled (known as TB) was used for water
recreation activities. It also acted as a water catchments pond as it was situated at the
low land of the hilly campus area. Table 3.3 shows the coordinates of sampling
points lakes.
Figure 3.2: Sampling locations for lake at Universiti Teknologi Malaysia.
Table 3.3: Sampling coordinates at the lakes
Location
Name of location
Coordinates
Lake
TKR
N 01 33’ 13.2”, E 103 38’ 09.1”
TUP
N01 33’ 39.7”, E 103 37’ 34.5”
TB
N 01 33’ 117.9”, E 103 38’ 16.2”
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3.2
Sediment Characteristic
The sediment collected from the rivers and lakes consist of fine- to mediumgrained size. It is generally accepted that fine-grained suspended and bottomsediment particles accumulate greater concentration of contaminants than coarse
particles. The fine-grain also supports a large part of the benthic community by
supplying the food in sediment organic matter associated with fine-grained particles
(Forstner, 2004).
Several samples collected from the lake were observed for living biota in the
sediment. Worms had been noticed in the sediment samples of lake TKR and TUP.
Similar biota was also sighted in the sediment collected from Sungai Buluh at
sampling point number two which was located near the oxidation ponds.
The flaky upper layer of the sediment approximately 0 to 3 cm depth usually
has lighter colour than the underneath layer. Most of the sediments had light brown
colour associated with high iron content. The sediment from Lake TUP had dark
brown colour and Sungai Buluh sediments were dark brown to black in colour. This
might be associated with organic matter input into the water body. This river
sediment also had a slightly odor that smell of H2S which signified the anoxic
condition in the sediment.
3.3
Sampling Methodology
The coordinates of sampling sites were obtained by using global positioning
remote sensing (GPRS) device. The quality of water bodies at the respective
sampling points was checked by measuring on-site physical parameters such as pH,
temperature and dissolved oxygen. Then, the sediment samples were collected at a
distance of about 1 m from the bank and at a depth of 0-15 cm using PVC corer
sampler of diameter 71 mm. The samples were scooped up with a polypropylene
spade into polyethylene bags. Air was purged out manually from the bags to
69
minimize air content and later kept airtight. The sample identification and date of
sampling were noted on the bag using marker pen. Next, the samples were
transported in ice loaded container to the laboratory on the same day and stored in
frozen state.
3.4
Chemicals and Reagents
Only acids of ultra high-purity grade were used during the course of this
study. The types of acids used were Concentrated HCl acid (Merck, Darmstadt,
Germany), H2SO4 acid (Merck, Darmstadt, Germany), H3PO4 (orthophosporic) acid
(Merck, Darmstadt, Germany) and HNO3 acid (Merck, Darmstadt, Germany).
All chemicals used were of analytical grade. The types of chemicals used are
Arsenic trioxide (As2O3) (BDH, Poole, England), sodium arsenate
(AsHNa2O4.7H2O) (Fluka, Steimheim, Switzerland), selenous acid (H2SeO3)
(Aldrich, Steinheim, Germany), sodium slenate (Na2O4Se) (Fluka, Steimheim,
Switzerland), ammonium pyrolidinedithiocarbamate (APDTC) (Fluka, Steimheim,
Switzerland), MIBK (Merck, Darmstadt, Germany), methanol (Merck, Darmstadt,
Germany), sodium dibenzyldithiocarbamate (Na-DBDTC) (Fluka, Steimheim,
Switzerland), phenolphthalein (Pp) (Riedel-de Haën, Germany),
ethylenediamminetetraacetic acid (EDTA) (Merck, Darmstadt, Germany) and
sodium thiosulfate (Na2S2O3. 5H2O) (GCE Lab. Chem.). Deionized distilled water
(DDW) with a quality of at least 18M resistivity was used for preparation of
solutions, dilution and for final rinsing of the acid cleaned labware. The water was
prepared using a Barnstead (USA) model Easypure RF –ultra pure water system by
passing distilled water through a mixed bed of anion and cation exchange resins.
70
3.5
Labware
For the determination of trace levels of elements, contamination and loss are
of prime consideration. The typical potential contamination sources include
improperly cleaned laboratory apparatus and general contamination within the
laboratory environment from dust. Sample containers can introduce positive and
negative errors in the determination of trace elements by contributing contaminations
through surface desorption processes. All reusable labware (glass, polyethylene,
Teflon, etc.) including the sample container were cleaned prior to use. Labware were
soaked for overnight and thoroughly washed with laboratory-grade detergent and
water, rinsed with water and additionally soaked for 24 hours in 10% dilute nitric
acid, followed by rinsing with DDW and oven drying.
3.6
Laboratory Apparatus
A number of 250 mL conical flasks, 50 mL conical flasks, 100 mL and
200mL beakers, measurement cylinders, 50 mL, 100 mL and 1000 mL volumetric
flasks, 200 mL separating funnels, filter funnels, assorted Gred A calibrated pipettes
and 50 mm watch glass were used in this experiment.
High quality plastic filter (Nalgene, USA) assembly with suction flask of
1000 mL capacity connected to a vacuum pump aspirator model A-3S (Eyela,
Japan), 0.45 m Whatman (cellulose nitrate) membrane filter disc, 150 mm
Whatman filter paper, 200 mL capacity of PTFE sample storage bottles (wide mouth
bottles) with polypropylene screw cap, 200 mL CEM Teflon PFA vessels and its
assemblies for microwave extraction and 3 mL polyethylene irradiation vials
(Kartell, Italy) were used. Apart from that, high quality disposable pipette tips and
Pasteur pipettes were used in order to prevent samples from being contaminated and
to increase precision.
71
3.7
Sample Processing Equipment
A number of laboratory equipments were used for various measurements of
related physical parameter analysis and sediment sample preparation prior to
analysis. A HORIBA Water Checker model U-10 (UK) was used to take in-situ
measurements of pH, temperature and DO of the bottom water body at each
sampling locations. The instrument was calibrated with buffer solution prior to use.
The coordinates of sampling sites were obtained through GPRS device, eTrex
Summit GPS (Garmin Ltd., USA). The frozen sediment samples were thawed in a
MBRAUN Unilab, (Germany) glove box and transferred to freeze-dryer container. A
freeze-dryer (ilShin Lab Co., Ltd, Seoul, Korea) was employed for drying of
sediments at approximately -40C before grinding it into powder with a planetary
ball mill grinder model Fritsch Pulverisette 5 (Laval Lab, Quebec, Canada). A
stainless steel siever tray was used to sieve the ground sediment samples and to
obtain particle size fractions of < 200 mesh ( 75 m). A laboratory analytical
balance, capable of weighing accurately up to 0.1 mg was used throughout the
experiment. The balance was calibrated daily with 200 mg standard weight (KERN
& Sohn GmbH, Germany) prior to use. A conventional microwave oven Panasonic
model NN-C20035 (Japan) which was operated at low power setting was used to
extract species of interest from sediment samples in diluted acid media. A HANNA
PH211 pH meter, capable of proper calibration and reading accuracy of  0.2
provided the pH measurement of the extracted samples before separation and
preconcentation procedure. The pH meter was also calibrated daily prior to use with
pH 7 and pH 4 buffer solutions (Hanna Instrument, Hungary). The solution of
extracted samples was stirred using a magnetic stirrer model CAT M6/1 with
maximum speed of 1400 rpm during the separation and preconcentration procedure.
72
3.8
Sample Preparation
The sediment samples used for analysis were prepared in dried form. Drying,
grinding and sieving processes were included in the handling operation of sample
drying. Frozen sediment samples were thawed and transferred into freeze-dryer
container where these procedures were conducted in a glove box unit. Then, the
samples were placed on the freeze-dryer chamber with drying settings at
approximately -40C and pressure of 10 mTorr for 48 to 72 hours. Next, the dried
sediments were ground with grinder mill for at least 15 minute in order to obtain
homogenous powdered form of approximately < 200 mesh ( 75 m). Sieving of
ground sediment to obtain particle size fractions of < 200 mesh was carried out and
the sediments were stored in polyethylene bottles in preparation for future analysis.
3.9
Standard Solutions
Standard solutions for the experiment consist of standard solutions for total
determination of arsenic, chromium, selenium and iron and stock solutions for
arsenic and selenium species analysis. All stock solutions were stored in Teflon
bottles and maintained at 4C. Appropriate dilutions of the stock solutions to the
require concentration were conducted daily.
3.9.1 Standard Solutions for As, Cr, Se and Fe
Single element stock solutions of As, Cr, Se and Fe were supplied by Merck
(Darmstadt, Germany) and used for standard chemical solutions for neutron
activation analysis method. The standard solutions provided by Merck were
treaceable mainly to NIST certified standard solution. The standards of As, Cr and
Se were prepared by pipetting aliquots of 10 or 100 g mL-1 of the standard solution
73
onto high quality Whatman filter paper which was cut in small round shape and
placed inside the polyethylene vials and heat sealed. The standard of Fe was
prepared by pipetting aliquots of 1000 g mL-1 and then followed by the same
procedure as for the standards of As, Cr and Se described previously. Table 3.4
shows the original concentration of the standard solutions used.
Table 3.4: Standard solutions of original concentration supplied by Merck.
Element
Concentration
Traceability
(mg L-1)
(Certificate no.)
As
1002  5
NIST SRM 3103a
Cr
1002  5
NIST SRM 3112a
Se
1002  5
NIST SRM 3149
Fe
10000  10
NIST SRM 3126a
3.9.2 Standard Solution for Arsenic (III) and Arsenic (V)
A standard solution of As(III) with concentration of 1000 mg L-1 was
prepared by dissolving 0.1321 g arsenic trioxide (As2O3) in 1 mL HCl in 100 mL
volumetric flask. Then, the DDW was added to the mark. A standard solution of As
(V) with the same concentration was prepared by dissolving 0.4164 g of sodium
arsenate (AsHNa2O4.7H2O) in concentrated H2SO4 and diluted with 100 mL of
DDW. All stock solutions were maintained at 4C. Appropriate dilutions of the stock
solutions to the required concentration were conducted daily.
74
3.9.3 Standard Solution for Selenium (IV) and Selenium (VI)
A standard solution of Se (IV) in concentration of 1000 mg L-1 was prepared
by dissolving 0.1632 g of selenous acid (H2SeO3) with 100 mL of DDW in
volumetric flask. Next, a standard solution of Se (VI) with the same concentration
was prepared by dissolving 0.2392 g of sodium slenate (Na2O4Se) with 100 mL of
DDW.
3.10
Certified Reference Material (CRM)
Certified reference materials (CRM) have a wide variety of uses in analytical
chemistry (Venelinov and Sahuquillo, 2006). The main role of RMs is to evaluate
the accuracy as well as the precision of measurements. They are treated in exactly
the same way as the test materials and can be used to characterize the performance of
the analytical system. Thus they are regarded as important tool in implementing
internal quality control in analytical laboratories. They can also be used for
methodology and instrumental calibration purposes. The CRM is employed in most
measurement system as they have already been technically certified with regards to
their property values as well as homogeneity and stability.
According to International Organization for Standardization (ISO), reference
materials is a substance for which one or more properties are established sufficiently
well for the purpose of calibrating a chemical instrument, validating a measurement
process or for assigning values to materials (Venelinov and Sahuquillo, 2006).
Taylor (1987) had defined 4 types of reference material. An internal reference
material is a material developed by a laboratory for its own internal use. An external
reference material is one provided by someone other than the end user. A CRM is a
reference material certified by an organization which establishes its traceability to an
75
accurate realisation of the unit in which the property values are expressed by and
uncertainty at a stated level of confidence. A standard reference material (SRM) is a
certified reference material issued by the National Institute of Standards and
Technology (NIST).
The most important criterion when choosing a CRM is that it should be a
reasonably close match to the samples to be analysed (IAEA, 1990). To provide
quality assurance controls, the reference materials having almost similar matrix were
used in the analysis. CRM of Marine Sediment Reference Material BCSS-1 and
Marine Sediment Reference Material PACS-2 provided by the National Research
Council of Canada (NRCC) and IAEA Soil-7 supplied by International Atomic
Energy Agency were applied throughout the analysis.
3.11
Preparation of Sediment Samples for Total As, Cr, Se and Fe
Powdered samples with weights between 0.1 g to 0.15 g were loaded into
polyethylene irradiation vials (1 cm inside diameter and 2 cm height) for the
determination of total concentration of As, Cr, Se and Fe. The samples were
prepared in triplicates and then heat-sealed. Two vials containing CRM with the
same matrix as the sediment samples were included in the batch. The CRM used
were Marine Sediment Reference Material BCSS-1 and IAEA Soil-7. Aliquots of the
appropriate single element standard solution were also irradiated along with the
samples. For blank correction, an empty vial and a vial pelletized with filter paper
were also irradiated.
76
3.12
Arsenic Species
Arsenic species from solid samples were determined by extracting the species
using microwave oven in a mild acid media. The preconcentration and separation
procedures were performed using APDTC into MIBK. The procedures applied in
this study followed that of Shi (2000).
3.12.1 Microwave Extraction
About 1.00 g of powdered sample was weighed in triplicate into Teflon
microwave digestion vessels. Then 15 mL H3PO4 were added. A total of 6 vessels
were placed on the turntable for simultaneous extraction under close system using a
conventional microwave oven which was operated at low power microwave setting.
The samples were allowed to cool to ambient temperature before being filtered with
a filter paper and finally made up to 100 mL with DDW for subsequent analysis.
These extracts were preserved by acidification to pH 2, refrigeration at 3-4C and
then preconcentration procedure was conducted within 24 h.
The optimization of microwave extraction process was carried out in order to
obtain the optimum condition for good recovery while maintaining As species
integrity. The effect of the microwave power, time and H3PO4 concentration on the
recovery was investigated by extracting the CRM of Marine Sediment Reference
Material BCSS-1 at different settings. Experiments on simulated extracts using
standard solution of 0.25 µg mL-1 were also carried out to study the stability of the
As species using the power, time and media concentration setting which obtained
high recovery from previous experiment.
77
3.12.2 Preconcentration and Separation
The arsenic species were determined by preconcentration and separation
procedures using APDTC into MIBK. The extraction solution was prepared by
dissolving 5 g of APDTC in 100 mL of DDW and was then filtered to remove the
insoluble materials. Next, MIBK was added into the solution to remove bromine and
other impurities. 12% (w/v) of EDTA solution was used as a masking agent. All
extraction solutions were prepared fresh daily.
Prior to the As (III) extraction, 100 mL of sample aliquot from microwave
extraction was adjusted to optimum pH value using concentration of 2 M HNO3.
Two mL of APDTC, 4 mL of EDTA solution and 10 mL of MIBK were added into
the sample aliquot. The samples were stirred vigorously using magnetic stirrer for
10 min and allowed to stand for 10 min for phase separation. The organic phase was
washed a few times with 5 mL DDW. Then 8 mL of organic phase was transferred to
a flask and 3 mL of 4 M HNO3 was added into organic phase to back extract arsenic.
The samples were stirred for 10 min and allowed to stand for 10 min for phase
separation. Finally after phase separation, 1 mL of the solution of HNO3 was
transferred into polyethylene vials which were heat-sealed and packed into larger
vials for neutron irradiation.
For the determination of As (V), a second aliquot of 100 mL sample was
adjusted to pH 1 with nitric acid. The reduction of As (V) to As (III) was achieved
using 1 mL of 25% sodium thiosulfate. The solution was shaken for 1 min and
allowed to stand for 5 min. Next, the same procedure for As (III) extraction process
was also carried out for As (V). This was followed by similar irradiation procedures
which included CRMs, standard solution and blank were applied for determination
of arsenic species. The difference of arsenic concentrations from the two sample
aliquots represents the total As (V) in the sample. The flow chart of the
preconcentration and separation of As (III) and As (V) can be viewed in Figure 3.3.
78
Sample aliquot 1, 100 mL
(As (III))
Sample aliquot 2, 100 mL
(As (V))
Adjust pH value
Adjust pH value
1 mL sodium thiosulfate (25%)
As (V)
As (III)
Stir, 1 min and stand, 5 min
2 mL APDTC (5%) + 4 mL EDTA (12%) + 10 mL MIBK
Stir, 10 min and stand, 10 min
Organic phase
As (III)
Wash a few times
with DDW
Aqueous phase
(remove)
8mL Organic phase +
3mL 4 M HNO3
Stir, 10 min and stand, 10 min
Aqueous phase
(back extract) of As (III)
Organic phase
(remove)
Pipette (~1.0 mL) and irradiate
Figure 3.3: Flow chart of the preconcentration and separation of As (III) and As (V)
in APDTC – MIBK system
79
3.12.2.1
Effect of pH
The extraction efficiency of As (III) and As (V) from APDTC-MIBK system
as a function of the pH was studied. 100 mL solution that contained 2 g mL-1 of As
species was adjusted to pH range of 1 to 10. Each pH solution was prepared in
duplicate. Similar procedure in extracting As (III) was applied throughout the
experiments.
3.12.2.2
Repeatability
Repeatability is important when assessing the performance of the extraction
procedure. Based on ISO definition, repeatability refers to the closeness of
agreement among a number of consecutive measurements made under the same
measurement procedure or operating conditions by the same operator (EURACHEM,
2002). Under the optimized preconcentration conditions, the repeatability of the
extraction by APDTC-MIBK was studied using a standard solution of As (III) and
As (V) at 2 µg mL-1. Data of seven extraction runs that were carried out on the same
day was collected. Low value of the relative standard deviations (RSD < 15%)
suggests that sufficient repeatability for As extraction has been achieved.
3.13
Selenium Species
Microwave extraction was applied to extract Se species from solid samples in
a mild acidic media. The preconcentration and separation of Se (IV) and Se (VI) by
co-precipitation technique were performed using Na-DBDTC with phenolphthalein.
Saleh et al. (1990), Yusof et al. (1998) had also suggested this particular procedure
for the extraction of Se species.
80
3.13.1 Microwave Extraction
About 1.00 g of powdered sample was weighed in triplicate into Teflon
microwave digestion vessels followed by the addition of 15 mL of HCl. Six vessels
were placed on the turntable for simultaneous extraction under a close system using
a conventional microwave oven which was operated at low power microwave
setting. The samples were allowed to cool to ambient temperature before being
filtered with a filter paper and finally made up to 100 mL with DDW for subsequent
analysis. These extracts were preserved by acidification to pH 2, refrigeration at 34C and the co-precipitation procedure was conducted within 24 hr.
Optimization of microwave extraction process was carried out in order to
obtain the optimum condition for good recovery while maintaining Se species
integrity. The effect on the recovery with regards to the microwave power, the period
of microwave usage and HCl concentration was investigated by extracting the CRM
of Marine Sediment Reference Material PACS-2 at different setting. Experiments on
simulated extracts using standard solution were carried out to study the stability of
the Se species using the power, time elapsed and media concentration settings which
obtained high recovery from previous experiment.
3.13.2 Preconcentration and Coprecipitation
Speciation of Se (IV) and Se (VI) were determined after co-precipitation with
sodium dibenzyldithiocarbamate (Na-DBDTC) and phenolphthalein (Pp). The
extraction solution was freshly prepared by dissolving 2 g of Na-DBDTC in 100 mL
methanol. The 5% Pp was prepared by dissolving 5 g of substance in methanol
followed by dilution to the 100 mL of DDW and 12% EDTA solution was prepared
by dissolving 12 g of the sodium form in 100 mL of DDW.
81
About 100 mL of sample aliquot from microwave extraction was first
adjusted to optimum pH value with 2M of HCl. Then, 2 mL of 2% DBDTC, 4 mL of
12% EDTA and 5 mL of 5% Pp were added to the sample aliquot. The sample was
stirred with a magnetic stirrer for 10 min and allowed to stand for 1 hr. The
precipitate formed was separated by filtration through a 0.45m membrane filter and
freeze-dried for 15 hr prior to irradiation. Approximately 0.15 g to 0.20 g of the
precipitate was transferred into polyethylene vials which were heat-sealed for
neutron irradiation.
Sodium thiosulfate of 25% acted as a reducing agent for Se (VI) into Se (IV)
and 1 mL was used into the second aliquot of 100 mL sample. Then, the same
procedures applied for Se (IV) extraction process was then also carried out for Se
(VI). Next, similar irradiation procedures which included CRMs, standard solution
and blank were applied for the determination of selenium species. The difference of
the two selenium concentrations represents the total Se (VI) in the sample. Figure 3.4
shows the flow chart for co-precipitation of Se (IV) and Se (VI).
3.13.2.1
Effect of pH
The extraction efficiency of Se (IV) and Se (VI) in the co-precipitation
procedure as a function of the pH was studied. About 100 mL solution containing 1
g mL-1 of Se species was adjusted to pH range of 1 to 10. Each pH solution was
prepared in duplicate. Similar procedure was used to extract Se (IV) throughout the
experiments.
82
3.13.2.2
Repeatability
Under the optimized co-precipitation conditions, the repeatability of the
extraction step by DBDTC-Pp was studied using standard solutions of Se (IV) and
Se (VI) at 1 µg mL-1. Data of seven extraction runs carried out on the same day was
collected. Low values of the relative standard deviations (RSD < 15%) suggests
sufficient repeatability for Se extraction.
Sample aliquot 1, 100 mL
(Se (IV))
Sample aliquot 2, 100 mL
(Se (VI))
Adjust pH value
1 mL sodium thiosulfate (25%)
Se (VI)
Se (IV)
Adjust pH value
Stir, 1 min and stand, 5 min
2 mL Na-DBDTC (5%) + 4 mL EDTA (12%) + 6 mL phenolphthalein (5%)
Stir for 10 min and
Stand for 1 hr
Filter by 0.45 m membrane
Freeze-dry for 15 hours
Weight (~0.15- 0.2 g) and irradiate
Figure 3.4: Flow chart separation-extraction procedure of Se (IV) and Se (IV) by
co-precipitation of Na-DBDTC with phenolphthalein.
83
3.14
Analysis Using Neutron Activation Analysis Technique
The NAA is based on gamma counting of the neutron activated elements in
the samples to be analysed. The irradiations were performed using a TRIGA Mark II
nuclear research reactor at Malaysian Nuclear Agency. The samples were irradiated
for 6 hours at 750kW power with a neutron flux of 2 x 1012 neutron cm-2 s1. The
standards, samples, CRM and blank were all irradiated together at the same time in
proper positioning in the nuclear reactor by the same irradiation interval. For arsenic,
the cooling period took at least 3 days while chromium, selenium and iron underwent
3 to 4 weeks of cooling before counting commenced. After proper decay time, the
batch of irradiation samples was counted in identical conditions by the same detector
and at the same geometry. A high resolution coaxial CANBERRA HP-Ge with a
resolution of 1.9 keV at 1332 keV gamma-rays line of Co-60 was used for counting
over a period of 3600s. The detailed specification of the gamma-detector is shown in
Table 3.5.
Each element of As, Cr, Se and Fe was observed for their specific gammarays energy. The signals from the 559.0 keV gamma-rays of 76As, 264.7 keV and
136.0 keV of 75Se were used to determine the elemental concentration in the
standards and samples. Chromium was analysed via the 320.1 keV of 51Cr, while,
iron was analysed through the 1099 keV and 1292 keV photopeak of 59Fe. The
applicability of the analytical technique for As, Cr, Se and Fe were evaluated by
analyzing the CRM.
The spectral data from the unknown standards, samples, and CRM were
processed using the spectrum analysis software for gamma peak search and peak
area analysis. This software allows the determination of the centroid channel
(energy), FWHM (full width-half max), net integrated peak area, and background.
84
Table 3.5: The specification of the CANBERRA HP-Ge detector.
Specifications
Geometry
: Closed end coaxial
Crystal Diameter
: 62.0 mm
Crystal Length
: 41.0 mm
Active Volume
: 123.8 cm3
Active Area
: 30.2 cm2
Operating Voltage
: 4000 V
Relative Efficiency
: 30%
Resolution:
Energy – 122 keV; FWHM – 0.70 keV
Energy – 1332 keV; FWHM – 1.9 keV
Peak to Compton Ratio – 58 : 1
The associated electronics with HPGe detector:
-
A pre-amplifier from CANBERRA built in with the detector.
-
An amplifier, to amplifying and shaping the signal.
-
A high voltage power supply to supply detector with the needed bias.
-
Minibin and power supply
-
Multi-channel analyzer card (MCA Card)
-
Personal computer with Genie 2000 Software for gamma analysis.
-
Printer.
85
The two peak areas of the two photo-peaks of interest for standard and sample
respectively are proportional to the activation rate and the amount of the element in the
standard and the sample after decay correction. The concentration of elements in the
samples was determined by performing calculation on equation 3-1 and 3-2 as listed
below:
Cs =
Where:
AS k S LC WC
*
*
*
* CC
AC k C LS WS
As
( 3-1)
= Corrected net count of selected peak for
interested element in sample
Ac
= Corrected net count of selected peak for
interested element in standard
ks
= Correction in counting due to dead time for
sample
kc
= Correction in counting due to dead time for
standard
Ls
= Counting live time for sample
Lc
= Counting live time for standard
Ws
= Weight of sample used
Wc
= Weight of standard used
Cc
= Concentration of interested element in
standard (e.g. ppm, ug g-1, mg kg-1)
Cs
= Concentration of interested element in
sample (e.g. ppm, ug g-1, mg kg-1)
Corrected net count A is calculated from the following equation:
A = Ao exp ( 0.693 * Dt / T1/2 )
Where:
Ao
( 3-2)
= net count of peak during counting
T1/2 = the half life of the radionuclide (in day or hour)
Dt
= the decay period (in day or hour)
86
3.14.1 Limit of Detection
The limit of detection is a measure of the lowest level at which a detector can
distinguish sample activity from background with no sample present. The lower
limit of detection is often calculated using Currie’s formula based on equation 3-3
(IAEA, 2001):
LOD = 2.71 + 4.65
Where:
B
(3-3)
LOD = limit of detection
B
= background under the gamma-ray peak
However, the limit of detection is depending on many parameters such as:

The amount of material to be irradiated and to be counted.

The neutron fluxes.

The duration of the irradiation time.

The total induced radioactivity that can be measured

The duration of counting time.

The detector size, counting geometry and background shielding.
CHAPTER 4
RESULTS AND DISCUSSION
4.0
Introduction
Sampling and analyses during the duration of the study proceeded
successfully and no major problems were encountered. This chapter explains and
discusses results of the experiments consisting of three sampling sessions that
spanned almost two years for the analysis of total As, Cr, Se and Fe, including the
analysis of inorganic As and Se species in two freshwater systems of the rivers and
lakes situated at the southern region of Peninsular Malaysia. The samples were
analyzed using NAA techniques conducted at the Malaysian Nuclear Agency, Bangi,
Selangor for elemental concentrations. The discussion includes an overview of the
river and lake water quality based on three parameters measured in-situ and the
determination of As, Cr and Se in both freshwater system and then they were applied
for the correlation study to the concentration of Fe present in the sediment. The total
concentrations of those elements were compared to several international guidelines
for freshwater sediments.
This chapter also includes the discussion on the preliminary study of As and
Se species in optimizing the extraction procedures for sediment samples. Besides
that, the availability of the species in both freshwater systems were determined and
discussed. The trends and patterns of the elements of interest and species in rivers
and lakes were made and compared using statistical analysis procedures.
88
4.1
Water Quality of The Water Bodies
The physico-chemical parameters of the water column such as pH,
temperature and DO are important because they have a significant effect on the
water quality. The three parameters are also the major factors influencing physiology
of water organisms and possibly contribute to metal forming in water (Forstner and
Wittmann, 1983). The measurements of those parameters were taken in-situ to gather
information on the current water quality and the environmental conditions of the
sampling locations. The results of the parameter measurements at the rivers and
lakes are presented in Appendix A. The overall average of the parameter values at
the six sampling locations are presented in Table 4.1.
pH plays a critical role in the chemistry of freshwater systems. A fall in pH
may allow the release of toxic metals that would otherwise be adsorbed to sediment
and essentially removed from the water system. A decrease in pH would increase
metal availability, lending itself to greater uptake by organisms and can cause
physiological damage to aquatic life (Connell and Miller, 1984). pH values of
surface waters usually range between 6.5 – 8.5, and only rarely are outside the range
of 4 – 9. Surface water has lower buffering capacity and consequently the pH of
surface water is more changeable. In water that is too acidic or too alkaline, there
could be very limited number of aquatic life. The acidification of surface water may
accelerate the leaching out of heavy metals and radionuclide from the bottom of the
sediments.
The pH levels recorded at the rivers ranged from 6.34 to 6.81. The average
level of pH measured from all the river sampling sites were within the National
Water Quality Standard for Malaysia (NWQS) threshold range for all classes (DOE,
2007; refer also Appendix B). In terms of pH level, the river system is still suitable
for the support of aquatic life. The high pH level at Sungai Buluh which is situated
at Pasir Gudang industrial area was a result of industrial discharge from several
chemical and oleo factory effluents nearby the sampling point. Previous study on
Sungai Skudai reported pH ranging from 5.26 to 7.15 and the mean pH value was
found to be 6.2. (Thanapalasingam, 2005). Elsewhere, pH values from continuous
89
water quality monitoring station managed by DOE, pH value of 6.3 was recorded at
Sungai Selangor, pH 6.4 at Sungai Terengganu and pH 6.6 at Sungai Melaka (DOE,
2007).
Table 4.1: Overall average of the water physico-chemical parameters in the rivers
and lakes
Water Parameters
Sites
pH
Temperature (C)
Dissolve Oxygen (mg L-1)
SGS
6.34  0.45
28.2  1.7
5.10  0.56
SGT
6.45  0.24
28.6  1.0
5.10  0.36
SGB
6.81  0.19
29.6  1.2
5.07  0.29
TKR
5.98  0.50
29.1  2.5
6.87  0.71
TUP
5.92  0.36
30.8  2.5
6.57  0.68
TB
6.76  0.54
30.3  1.3
6.64  0.42
Slightly lower pH level was observed from two sampling sites at the lake.
TKR and TUP show average pH value of 5.98 and 5.92, respectively compared to
TB site which showed an average value of 6.76. TKR site is located near a deer cage
where the low pH may result from the high organic contents coming from the
manure and food wastes entering the lake through surface run off. TUP site may also
exhibit similar factor where previously small scale horticulture activity was
conducted by students near the site. The surplus from the fertilizer used promotes
microbial activity in the lake. pH of the lake water generally affect by ground water
seepage, aquatic flora coverage and microbial activity (Kutty et al., 2005).
The temperature of water is one of the important characteristics that
determines, to a considerable extent, the trends and tendencies of changes in the river
water quality. Increased water temperature decreases the solubility of dissolved
oxygen and water temperatures above 27C are “unsuitable” for public use. At above
32C it would be considered “unfit” for public use (Chapman, 1992). Higher
90
temperature and combination of low DO levels may increase the toxicity of many
substances such as heavy metals, whilst the sensitivity of the organisms to toxic
substances also increases.
Generally, there was no significant difference in temperature measured at all
the rivers ranging from 28.2C to 29.6C. A slightly higher temperature of 29.6C
was observed at Sungai Buluh as a result of industrial wastes and effluents that enter
the river system. In a previous study of Sungai Skudai, the temperature that was
recorded ranged from 26.5C to 29.6C (Thanapalasingam, 2005). The lakes
temperature showed higher value than the temperature in rivers. This can be
explained where tree cover is less at the particular lakes which allow higher level of
incident sunlight and finally increase the water temperature. However, a fountain at
the lake TKR site gives a cooling effect and this helps to reduce the temperature in
the lake water. The temperature recorded at the lakes was found to be similar to other
study conducted at Tasik Chini, Pahang which ranging from 27.9C to 31.9C (Kutty
et al., 2005).
The oxygen content or DO is an important indicator of the pollution of a
water body. Oxygen is an absolute requirement for the metabolism of aerobic
organism and also influences inorganic chemical reaction. The amount of DO is
highly dependent on temperature. Apart from amount of degradable pollutants, the
amount of oxygen that can dissolve in pure water is inversely proportional to the
temperature of water. In a typical water system, the warmer the water, less DO can
be measured in it. However, DO also depend on several other factors such as the
amount of rainfall, saltiness of the water, the amount of decomposition in the water,
the amount of aquatic plant and presence of pollutants. The aquatic life would be put
under stress if the DO levels in the water drop below 5.0 mg L-1. Oxygen levels that
remain below 1 to 2 mg L-1 for a few hours can result in large fish kills. The NWQS
criteria for human consumption and aquatic life require that the DO ranging from 3
to 7 mg L-1 (DOE, 2007; refer also Appendix B).
91
The average levels of DO obtained from the rivers and lakes are within the
threshold values set by the NWQS. The DO levels at the rivers were relatively lower
than the lakes. The lowest DO was measured at Sungai Buluh. A low level of DO is
contributed from the discharge of organic matter and waste from the sewerage
plants, industries and agriculture activity into the water that can be observed along
the rivers. A previous study indicated that DO recorded from Sungai Skudai ranged
from 3.82 mg L-1 to 6.49 mg L-1 (Thanapalasingam, 2005). Elsewhere, pH recorded
from the downstream of Sungai Langat ranged from 3.02 mg L-1 to 3.89 mg L-1
where low DO concentrations had been related to sewage outfalls (Azrina et al.,
2006). On the contrary, the DO levels in the lakes showed higher DO level compared
to the DO levels from Tasik Chini obtained by Kutty et al. (2005) with an average
value of 3.76 mg L-1.
Previous studies conducted by DOE in 2006 showed that several rivers in
southern region of Peninsular Malaysia were categorized as heavily polluted river
(Figure 4.1). This includes Sungai Buluh which is located at Pasir Gudang area and
also Sungai Tebrau. Meanwhile, Sungai Skudai is categorized under slightly polluted
river. The Water Quality Index (WQI) is used to evaluate the status of the river water
quality consists of parameters such as DO, pH, BOD, COD, Ammoniacal Nitrogen
(AN) and Suspended Solid (SS). Sungai Buluh had indicated the lowest WQI value
of 32, lower than Sungai Tebrau (WQI 57) and Sungai Skudai (WQI 64). The water
of Sungai Buluh was classified as Class IV, while Sungai Tebrau and Sungai Skudai
were in Class III (Refer to Appendix B for water class definition). The state of health
in water system would be an indicator on the quality of the sediment in the water
bodies system.
92
Figure 4.1: Water Quality Status for River Basin of Peninsular Malaysia in 2006
with highlight of Sungai Skudai, Sungai Tebrau and Sungai Buluh (Kaw. Pasir
Gudang) (DOE, 2007)
93
4.2
Data Quality
The applicability of the analytical procedures for analysis of As, Cr, Se and
Fe was examined by analysing CRM. Certified reference material namely IAEA
Soil-7 supplied by International Atomic Energy Agency and Marine Sediment
Reference Material BCSS-1 and PACS-2 provided by the National Research Council
of Canada (NRCC) were applied as quality control material of each analytical
regiment implemented. Data of the certified values of these CRM are shown in
Appendix C.
The accuracy of the analytical result of the elements in the CRM was
evaluated using Z-score calculation (Crosby et al., 1995). The Z-score of an element
concentration is computed based on the following equation (4-1):
Z  score 
xc
u x2  u c2
(4.-1)
where x is the analytical result; c is the certified value, ux is the uncertainty of
analytical results, and uc is the uncertainty of certified value. The uncertainty of the
analytical results is based on counting statistics whilst the uncertainty of the certified
value is based on the certificate. For acceptance of results: -2 < z < 2 is anticipated.
However, if z < -3 or z > 3, it is considered that the result is “out-of-control” and
corrective action will be introduced.
The accuracy of the analytical results of the elements in the CRM was
evaluated using the Z-score calculation and showed As, Cr, Se and Fe are within the
acceptance criteria (Table 4.2). The results also show a fair level of consistency
between the certified and the measured value where the recovery ratios of As, Cr, Se
and Fe were 93 - 117%. Analytical results disclosed that the precision of the analysis
was satisfactory; generally better than 16.7% RSD. Limit of detection for elements
of interest is presented in Table 4.3.
Table 4.2: Analytical results for As, Cr, Se and Fe in CRMs.
Values are given in dry weight basis and correspond to the average and standard deviation.
IAEA Soil - 7
BCSS - 1
PACS - 2
As
Cr
Sea
As
Cr
Se
Fea
Se
(g g-1)
(g g-1)
(g g-1)
(g g-1)
(g g-1)
(g g-1)
(%)
(g g-1)
Certified value
13.4  0.4
60  7
0.40  0.10
11.1  0.7
123  7
0.43  0.06
3.80  0.10
0.92  0.22
Measured
value
13.7  0.5
70  4
0.37  0.03
11.5  0.8
126  7
0.48  0.08
3.78  0.11
0.98  0.10
(n = 20)
(n = 10)
(n = 10)
(n = 10)
(n = 10)
(n = 10)
(n = 10)
(n = 10)
Z-score
0.50
1.24
0.29
0.37
0.30
0.50
0.13
0.25
Recovery (%)
102
117
93
104
103
112
99
107
RSD (%)
3.3
5.7
8.4
7.1
5.6
16.7
3.0
10.2
a
x – Information value
Table 4.3: LOD for As, Cr, Se and Fe
Elements
LOD
As (g g-1)
Cr (g g-1)
Se (g g-1)
Fe (g g-1)
0.2
1
0.02
20
94
95
4.3
Total Concentration of Elements
Arsenic, chromium and selenium are among the elements widely studied in
environmental samples. The excessive presence of these elements is often associated
with anthropogenic activity and they are classified as toxic to human being if
exposure levels are sufficiently high. In the ionic form, As, Cr and Se are capable of
entering and adsorbing in life tissues including plants and animals. Aquatic sediment
can be the preeminent media for those elements to accumulate and finally enter the
food chain through benthic life which depend on the sediment as their habitats.
The concentrations of As, Cr, Se and Fe in sediment from 15 sampling points
from the rivers and lakes system were obtained. The results of As, Cr, Se and Fe
concentrations in rivers and lakes for each sampling site were presented in Appendix
D. A great deal of research has been directed towards the determination of toxic
elements in sediments so as to identify unusual occurrences of these elements within
the environment in association with urbanization and industrial development. Some
summaries of the main areas with which this study is associated were presented in
Table 4.5 and Table 4.7. The table should not be considered as exhaustive or
complete, it simply identifies those contamination sources and those toxic elements
for which extended occurrences has been studied. Results from previous findings
listed in the table were then used as a comparison in this study.
Iron was included in this study in order to relate any association of As, Cr
and Se in the presence of Fe and hence interpret natural or anthropogenic
contribution of these elements in river and lake system. The results of As, Cr and Se
were then compared with several sediment quality guidelines established
internationally. The contamination impact of the elements in sediments was
evaluated and estimated using enrichment factor (EF) and geoaccumulation index
(Igeo) tools. Genuinely, this study is hoped to generate the baseline data that can
either be future reference or as reference for authority to take necessary action for
preventing any anthropogenic input. The data may also useful for initiating a
guideline criterion for freshwater sediment quality.
96
4.4
Concentrations of Arsenic, Chromium and Selenium in Rivers
All the average concentrations of As, Cr and Se in surface river sediments are
presented in Table 4.4. Meanwhile, the graphical forms of the results are illustrated
in Figures 4.2 - 4.4 for the concentration of As, Cr and Se, respectively.
The concentrations of As in the sediment taken from all 8 sampling sites
from the rivers ranged from 10.17 g g-1 to 33.80 g g-1. The highest average
concentration was obtained from sampling site SGS3 (Sungai Skudai) and the lowest
concentration was obtained from sampling site SGB2 (Sungai Buluh). The sediment
of Sungai Skudai has the highest concentration of As followed by Sungai Buluh. The
As level showed an incremental trend towards the downstream in all rivers (Figure
4.2). The high As contents of the sediment can be attributed to the mobilization and
transportation process of As along the river depositing it near the river mouth.
Table 4.4: Results of average concentration of arsenic, chromium and selenium in
sediment of each sampling sites at river.
Element Concentration (g g-1)
Sites
As
Cr
Se
SGS1
19.40  0.80
122  14
1.31  0.14
SGS2
30.59  1.30
125  16
1.08  0.05
SGS3
33.80  1.25
103  9
0.88  0.02
Average
27.92  7.60
117  11
1.09  0.20
SGT1
12.26  0.63
50.36  5.50
1.72  0.19
SGT2
13.46  0.85
77.04  8.83
1.91  0.24
Average
12.86  1.00
63.90  19.00
1.82  0.10
SGB1
10.90  0.91
26.83  7.32
0.72  0.04
SGB2
10.17  0.75
50.82  7.81
0.93  0.12
SGB3
24.29  1.46
59.27  8.85
0.56  0.06
Average
15.12  7.00
46.04  15.00
0.74  0.20
97
Previous studies as presented in Table 4.5 indicated that As concentrations in
contaminated river sediments ranged from 1 g g-1 to 100 g g-1 (Barringer et al.,
2007; Doong et al., 2008; Karageorgis et al., 2003). Soil usually contains As
between 0.001 g g-1 and 0.04 g g-1 in the absence of industrial or agricultural
contamination (Reilly, 1991). This clearly shows that the As concentrations obtained
from the three river system is highly contaminated. The industrial effluents,
domestic waste inputs and agricultural activities along the river have led to high
enrichment of As in the river sediments.
Sediment samples taken from all the rivers in this study showed the
concentration of Cr of between 26.83 g g-1 at sampling site SGB1 (Sungai Buluh)
to 125 g g-1 at SGS2 (Sungai Skudai). The highest level of Cr was found in
sediment of Sungai Skudai of average 117 g g-1 followed by Sungai Tebrau and
Sungai Buluh with average value of 63.90 g g-1 and 46.04 g g-1, respectively
(Figure 4.3). Previous study by Thanapalasingam (2005) reported that average Cr
level in Sungai Skudai from 16 sampling points is 135.57 g g-1. This was explained
by high concentration of Cr in the effluent from the active zones along the Sungai
Skudai, especially electroplating and printing factories. It was reported elsewhere,
that the Cr concentrations in river sediments associated to some anthropogenic
activities ranged from 2 g g-1 to 2714 g g-1 as indicated in Table 4.4 (Boszke et
al., 2004; Doong et al., 2008; Karageorgis et al., 2003; Zhou et al., 2004).
Table 4.5 : Result of previous studies from several literatures for As and Cr in river sediment.
Location
As
Cr
General source of
contamination
Reference
Gao-ping River,
Taiwan
5.12 – 25.8 g g-1
35.7 – 2714 g g-1
Domestic and industrial
wastewater, flooding event
Doong et al., 2008
Wallkill River,
New Jersy
5.2 – 100 g g-1
Ex-mining site, agriculture,
municipal sewage plant
Barringer et al., 2007
Middle Odra River,
Poland
1.57 – 47.5 g g-1
Mining, heavy industry,
agriculture
Boszke et al., 2004
Pearl River
Estuary, China
58.1 – 117.8 g g-1
Industrial wasterwater,
domestic sewage, mining
Zhou et al., 2004
39 -180 g g-1
Tailings, industrial
effluents, agriculture
activity
Karageorgis et al., 2003
Axios River,
Greece
1 – 40 g g-1
98
99
The Se level at each sampling sites is indicates in Figure 4.4. The
concentration of Se in the river sediments were ranged from 0.56 g g-1 at SGB3
(Sungai Buluh) to 1.91 g g-1 SGT2 (Sungai Tebrau). The highest level of Se was
found in the sediment of Sungai Tebrau of average 1.82 g g-1. Meanwhile the
lowest Se in sediment was attained from Sungai Buluh of average 0.74 g g-1.
Sungai Skudai contained on the average 1.09 g g-1 of Se in the sediment and the
level decreased towards the downstream. Higher levels of Se in sediments of Sungai
Tebrau and Sungai Skudai as compared to Sungai Buluh could be due to sewerage
effluent from housing estates and squatter settlement sprawled along the rivers.
Effluents from industrial plants located along Sungai Buluh discharged into the
oxidation ponds which help improve on the effluent quality, thus reducing the
amount of Se later discharged into the river.
40.0
-1
As concentration (ug.g )
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
SGS1
SGS2
SGS3
SGT1
SGT2
SGB1
SGB2
SGB3
River
Figure 4.2: Average concentration of arsenic in sediment of river sampling sites.
100
150.0
-1
Cr concentration (ug.g )
125.0
100.0
75.0
50.0
25.0
0.0
SGS1
SGS2
SGS3
SGT1
SGT2
SGB1
SGB2
SGB3
River
Figure 4.3: Average concentration of chromium in sediment of river sampling sites.
2.00
-1
Se concentration (ug.g )
2.50
1.50
1.00
0.50
0.00
SGS1
SGS2
SGS3
SGT1
SGT2
SGB1
SGB2
SGB3
River
Figure 4.4: Average concentrations of selenium in sediment of river sampling sites.
101
4.5
Concentrations of Arsenic, Chromium and Selenium in Lakes
The average concentrations of As, Cr and Se in surface lake sediment at each
sampling sites is presented in Table 4.6. The graphical forms of the results are
illustrated in Figures 4.5 - 4.7 for the concentration of As, Cr and Se, respectively.
The concentrations of As in the lake sediment taken from the 7 sampling sites
ranged from 17.62 g g-1 to 61.60 g g-1. The highest average concentration was
obtained from sampling site TKRC and the lowest concentration was obtained from
sampling site TBB (Figure 4.5). The arsenic level at lake TKR showed the highest
average concentration of 56.81 g g-1 compared to the other two lakes.
Previous studies in several countries reported levels of As in lake sediment
ranging from 1 g g-1 to 201.5 g g-1 as presented in Table 4.7 (Linge and Oldham,
2002; Nikolaidis et al., 2004; Sompongchaiyakul and Sirinawin, 2006). This shows
that high levels of As contamination occurred in the lake sediment studied. It is
believed that usage of fertilizers, pesticide and herbicides for landscaping activities
around the campus are responsible for the general enrichment of As concentrations
in the lake sediment.
The sediment taken from the lake system contained Cr ranging from
173 g g-1 to 301 g g-1. The sampling site of TUPA contained highest average
concentration of As while the lowest concentration found to be at TKRA to be
(Figure 4.6). The lake TUP showed the highest Cr level in the sediment with average
value 273 g g-1 followed by lake TB and TKR. The Cr concentrations in
contaminated lake sediment ranged from 8 g g-1 to 130 g g-1 as reported by other
previous studies in Table 4.7 (Gatti et al., 1999; Loska and Wiechula, 2003;
Nikolaidis et al., 2004; Rosales–Hoz et al., 2000; Sompongchaiyakul and Sirinawin,
2006; Wang et al., 2003). This clearly indicates that the Cr concentrations obtained
from all the sediments of lake system is highly contaminated due to various sources
of human activities.
102
Table 4.6 : Results of average concentrations of arsenic, chromium and selenium in
sediment of each sampling sites at lake.
Element Concentration (g g-1)
Sites
As
Cr
Se
TKRA
48.49  3.60
173  19
0.55  0.11
TKRB
60.34  5.11
198  21
0.31  0.04
TKRC
61.60  8.43
195  23
0.42  0.07
Average
56.81  7.23
189  14
0.43  0.12
TUPA
38.86  2.67
301  22
0.87  0.10
TUPB
44.07  3.59
244  17
0.94  0.14
Average
41.46  3.70
273  40
0.91  0.05
TBA
45.68  2.51
242  15
0.35  0.07
TBB
17.62  1.60
188  17
1.08  0.10
Average
31.65  15.00
215  39
0.72  0.25
High amount of Cr in the sediment is always associated with industrial
pollution such as metallurgical, electroplating industry, dyeing or paint operations
(Kaushik et al., 2008; Kotaś and Stasicka, 2000). However, there was no industrial
activity existing near the lakes. According to Rosales-Hoz et al. (2000), Cr as well as
As contamination were closely associated with domestic wastewater effluents.
Therefore, high contamination of Cr may come from wastewater that flows from the
student residential drainage system or undetected leakage of underground sewage
system which enters the lake through water run off during the wet season.
103
80.0
-1
As concentration (ug.g )
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
TKRA
TKRB
TKRC
TUPA
TUPB
TBA
TBB
Lake
Figure 4.5: Average concentration of arsenic in sediment of lake sampling sites.
360
-1
Cr concentration (ug.g )
320
280
240
200
160
120
80
40
0
TKRA
TKRB
TKRC
TUPA
TUPB
TBA
TBB
Lake
Figure 4.6: Average concentration of chromium in sediment of lake sampling sites.
104
-1
Se concentration (ug.g )
1.50
1.20
0.90
0.60
0.30
0.00
TKRA
TKRB
TKRC
TUPA
TUPB
TBA
TBB
Lake
Figure 4.7: Average concentration of selenium in sediment of lake sampling sites.
The concentration of Se in the lake system ranged from 0.31 g g-1 to 1.08
g g-1. Sampling site TBB recorded the highest level of Se in sediment while
sampling site TKRB obtained the lowest concentration (Figure 4.7). The Se level at
lake TUP showed the highest average concentration of 0.91 g g-1. The high Se
content in the sediment of lake TUP was suspected originated from previous
horticulture activities especially on the usage of fertilizer and herbicide.
Several previous studies reported that Se concentrations in contaminated
sediment ranged from 0.48 g g-1 to 12 g g-1 as presented in Table 4.7 (Lemly,
1997; Peters et al., 1999; Wang et al., 2003; Zhang and Moore, 1997). This clearly
shows that the lake sediment from the sampling sites are considerably contaminated
with Se. Investigation carried out by Hillwalker et al. (2006) at two types freshwater
physical characteristic namely stagnant and flowing water, showed a significant
difference of Se distribution in the sediment. The sediment in the stagnant water such
as pond, lake and well has high potential to accumulate Se compared to the flowing
water such as rivers.
Table 4.7 : Result of previous studies from several literatures for As, Cr and Se in lake sediment.
Location
As
Cr
Songkhla Lake,
Thailand
4 – 26 g g-1
Maine Lake,
Greece
201.5 g g-1
Yangebup Lake,
Australia
General source of
contamination
Reference
8 -73 g g-1
Runoff water, wastewater
Sompongchaiyakul and
Sirinawin, 2006
51.33 g g-1
Landfill of municipal and
commercial waste
Nikolaidis et al., 2004
Village development,
townshop industry
Wang et al., 2003
Effluent from industry
Linge and Oldham, 2002
68.6 g g-1
Taihu Lake, China
Se
0.48 g g-1
21.8 g g-1
Chapala Lake,
Mexico
66.12 g g-1
Urbanization, agricultural,
industrial development
Rosales –Hoz et al., 2000
Infernao Lake,
Brazil
80.7 g g-1
Industrialization
Gatti et al., 1999
Peters et al., 1999
Macquarie Lake,
Australia
0.8 – 1.4 g g-1
Urban and industrial –
lead-zink smelter, fertilizer
plant
Belew Lake, North
Carolina
4 -12 g g-1
Wastewater from coal plant Lemly, 1997
105
Table 4.7 : Continued
Location
As
Cr
Benton Lake,
Montana
Rybnik Reservoir,
Poland
Oolitic Pond
(standing water)
Lee Creek
(flowing water)
Se
General source of
contamination
Reference
2.38 – 3.29 g g-1
Agricultural, seleniferous
lake basin
Zhang and Moore, 1997
Long-range transport,
atmospheric precipitation
Loska and Wiechula,
2003
129.8 g g-1
0.63 – 8.2 g g-1
Hillwalker et al., 2006
0.37 – 3.6 g g-1
106
107
4.6
Comparison in Elements Concentration to the Guideline
Recommendations for Freshwater Sediments
Several sediment quality guidelines were established to estimate the possible
toxicological significance of contaminants concentrations in the sediments. The
Canadian Council of Ministers of Environment (1999) had used the sediment quality
guidelines in ranking areas that warranted further detailed study of the actual
occurrence of adverse effects such as toxicity. They were also intended for use in
ranking chemicals that might be of potential concern. The Wisconsin Department of
Natural Resources (2003) had employed the sediment quality guidelines for the
following aspects:i.
To provide a reliable basis for assessing sediment quality conditions in
freshwater ecosystems.
ii.
To identify hot spots with respect to sediment contamination.
iii.
To determine the potential for and spatial extent of injury to sedimentdwelling organisms.
iv.
To evaluate the need for sediment remediation.
v.
To support the development of monitoring programs to further assess the
extent of contamination and the effects of contaminated sediment on
sediment-dwelling organisms.
Results of current study were made comparison to several guideline values
(Table 4.7 and Table 4.8). The background value for freshwater sediment is derived
from NOAA (Buchman, 1999; Appendix E). The probable effect level in freshwater
sediment is established under the Canadian Environmental Quality Guidelines
(Appendix E) and the severe effect level is derived from New York State
Department of Environmental Conservation (Appendix E). The probable effect level
represents the lower limit of the range of chemical concentrations that are usually or
always associated with adverse biological effects. Sediments with measured
chemical concentrations equal to or greater than the probable effect level are
considered to represent significant and immediate hazards to exposed organisms.
Biological assessment is recommended at these sites to determine the nature and
108
extent of effects that are being manifested as a result of the sediment associated
contaminants (Canadian Council of Ministers of Environment, 1999). The severe
effect level values is also known by the 50th percentiles or median which represents
the concentrations above which biological effects frequently occur and the analysed
sediments are considered to be severely impacted if exceeded the criterion value
(New York State Department of Environmental Conservation, 1999).
The range in concentration of As, Cr, and Se from both rivers and lakes
found to exceed the background values for freshwater sediment. Several sampling
sites at the river were below the probable effect level of 17 g g-1 for As and 90 g
g-1 in Cr concentrations. However, concentration of As and Cr reached 102% and
114% of the severe effect level, respectively, in very few samples.
Table 4.8 : Several guidelines value for arsenic, chromium and selenium
Arsenic (g g-1)
Chromium (g g-1)
Selenium (g g-1)
Observed ranged in
river system
10.17 – 33.80
26.83 - 125
0.56 – 1.91
Observed ranged in
lake system
17.62 - 61.60
173 – 301
0.31 – 1.08
1.10
7 - 13
0.29
Canadian probable
effect levels for
freshwater sediment b
17
90
na
Severe Effect Level c
33
110
na
Background a
na – not available
a - Buchman (1999)
b - Canadian Council of Ministers of Environment (1999)
c- New York State Department of Environmental Conservation (1999)
109
Arsenic concentrations in the range of 17.62 g g-1 to 61.60 g g-1 for most
lake sediments were substantially elevated over the probable and severe effect level
of 17 g g-1 and 33 g g-1, respectively. Similar indication was also observed for Cr
concentrations in lake sediment. The results indicated that the level of As and Cr
contamination in the lake sediment is potentially significant with regard to aquatic
life.
Table 4.9 : Selenium guideline values derived from the Guidelines for Interpretation
of the Biological Effects of Selected Constituents in Biota, Water and Sediment
Medium
No effect
Level of concern
Toxicity threshold
Sediment (g g-1)
<1
1–4
>4
Guidelines for Interpretation of the Biological Effects of Selected
Constituents in Biota, Water and Sediment was established by USDOI (1998) which
was based on three levels of selenium threshold; the no effect, the level of concern
and the toxicity threshold. The no effect level indicates that concentration less than
the given value do no produce discernible adverse effects on fish or wildlife and are
typical of the background concentrations in uncontaminated environment. The range
of elemental concentrations in the level of concern rarely produces discernible
adverse effects on some fish or wildlife species while any concentration values
greater than the toxicity threshold levels seem to produce adverse effects on
biological life.
The Se concentrations found showed low level of contamination in rivers and
lakes sediment by referring to the guidelines (Table 4.9). Only one sampling sites at
the lake, TBB exceeded the no effect level. Meanwhile, all the sampling sites of
Sungai Buluh exhibited Se concentrations below the no effect level. Se
concentrations in sediments at the other river and lake sampling sites lies between
levels of concern.
110
Generally, level of Se in the sediment was in the acceptable and tolerant
limits to aquatic organisms, while the sites where Se was observed to be at the level
of concern should have continuous assessment conducted as some aquatic organisms
may show adverse effects at this level. Toxic dietary exposure study showed that
thresholds for dietary toxicity in animal for Se level are generally reported as 2 to 5
g g-1 (USDOI, 1998). Continuous exposure to high Se content by the aquatic
organisms may also affect human dietary as Se has the characteristic of
bioaccumulating in the tissues of organisms.
4.7
Association of Arsenic, Chromium and Selenium to Iron Concentration
Particulate metals from natural and anthropogenic sources accumulate
together in sediment. In order to determine the level of metal pollution in a particular
area the two metal proportions need to be isolated and this can pose problems
because sedimentary metal loads can vary by several orders of magnitude, depending
on the mineralogy and grain size distribution. Usually, a normalization procedure is
suggested to overcome this problem (Cheevaporn and Diego-McGlone, 1997;
Whalley et al., 1999). With this procedure, the natural component of the total
concentration can be calculated by defining the ratio of natural concentrations to that
of some normalizing factor whose concentration is unaffected by human activities
which would then enable to detect and quantify any anthropogenic metal
contribution to the system.
Aluminum, iron, scandium, total organic carbon, and grain size can be used
in particular cases as geochemical normalisers (Breslin and Sanudo-Wilhelmy, 1999;
Cheevaporn and Diego-McGlone, 1997; Yusof and Wood, 1993). They will often
show strong relationships with site contaminants. Normalization based on Fe, Al or
Sc, as reference conservative elements having supposed natural distributions, is a
useful tool in estimating the anthropogenic over natural contribution in the chemical
content of soils and sediments. Presuming an existing linear dependence between the
111
conservative element and the heavy metal, it is possible with the use of simple linear
regression to define the heavy metal geochemical background and to isolate natural
and/or anthropogenic outliers.
Iron was chosen as an element of the normalization in this study because Fe
is abundant in crustal-derived sediments and has a reactive fraction associated with
particle surfaces similar to contaminant metals. Anthropogenic Fe is usually small
compared to the amount of Fe naturally present (Breslin and Sanudo-Wilhelmy,
1999). This is in agreement with the study conducted by Kaushik et al. (2008) whose
reported that the enrichment value of Fe in sediment of River Yamuna, India is less
than 1 indicating insignificant effect of anthropogenic flux of this element into
sediment even though Fe concentrations ranged from 4.15 g kg-1 16.2 g kg-1 was
found. Normalisation of the specific heavy metal concentrations in the bottom
sediments under aerobic conditions to Fe can also be used as a correction factor for
comparative assessment of sampling sites and river basin contamination by heavy
metals (Boszke et al., 2004).
The concentrations of As, Cr and Se in sediments are plotted against Fe
concentrations presented in Figure 4.8 and Figure 4.9 for river and lake, respectively.
The results of statistical evaluations were presented in Appendix F. Investigations
show that Fe has significant effects on the particular metals content in bottom
sediments of both the river and lake system. A study conducted by
Sompongchaiyakul and Sirinawin (2006) indicated that the major geochemical factor
that controls the dispersal and accumulation in the lake system is Fe in its oxides
form. Iron usually studied in the geochemistry of a aquatic sediment due to its high
adsorption capacities when compared to other oxides such as Al and Si oxides. Iron
highly affects trace metal cycling in lake sediment because they participate under
oxic conditions and dissolve under anoxic condition (El Bilali et al., 2002).
112
40
35
-1
Total As (ug g )
30
25
20
15
10
5
R² = 0.6721
0
10000
15000
20000
25000
30000
35000
40000
45000
-1
Total Fe (ug g )
160
140
-1
Total Cr (ug g )
120
100
80
60
40
R² = 0.8754
20
0
10000
15000
20000
25000
30000
35000
40000
45000
-1
Total Fe (ug g )
2.5
-1
Total Se (ug g )
2
1.5
1
0.5
R² = 0.0007
0
10000
15000
20000
25000
30000
35000
40000
45000
-1
Total Fe (ug g )
Figure 4.8: Concentrations of As, Cr and Se plotted against concentrations of Fe in
river sediments.
113
80
70
-1
Total As (ug g )
60
50
40
30
20
10
0
20000
R² = 0.6973
25000
30000
35000
40000
45000
50000
55000
-1
Total Fe (ug g )
320
300
260
-1
Total Cr (ug g )
280
240
220
200
180
160
R² = 0.1681
140
120
20000
25000
30000
35000
40000
45000
50000
55000
-1
Total Fe (ug g )
80
70
-1
Total As (ug g )
60
50
40
30
20
10
0
20000
R² = 0.6973
25000
30000
35000
40000
45000
50000
55000
-1
Total Fe (ug g )
Figure 4.9: Concentrations of As, Cr and Se plotted against concentrations of Fe in
lake sediments.
114
Positive correlation levels of Fe were significant with As and Cr in river
sediment for correlation coefficient value of 0.82 and 0.94, respectively. A study by
Whalley et al. (1999) at Humber Estuary, UK showed that As has statistically
significant relationship with Fe concentrations in the sediment (p < 0.001). Strong
correlation was found between Cr and Fe in river sediment. No statistically
correlation was observed between Se and Fe concentrations (p < 0.95). The result
indicates that Se concentrations in river sediment are not controlled by the amount of
Fe present.
Iron levels were found to be significantly correlated with As (r = 0.76, p<
0.02) in sediments of lake system. Nikolaidis et al. (2004) found that the correlation
between As and Fe in contaminated lake sediments was 0.92 and large fraction of As
was bound to Fe oxide. Therefore, strong correlation between As and Fe in both lake
and river sediment indicate that the sediment is a significant sink for As. Correlation
analysis shows significant relationship between Se and Fe concentrations (p< 0.005).
Se showed an inverse association to Fe concentrations in lake sediment with
correlation coefficient value of -0.81. However, there is no clear explanation to this
phenomenon. Even though Fe particularly in its oxyhydroxide form has strong
affinity for Se, but adsorption of Se to Fe is also controlled by other factors such as
pH, redox state and particle concentration (Balistrieri and Chao, 1990). Changes in
salinity and pH may also cause Se exchange to pore water and organisms may
accumulate Se at a greater rate that result in the reduction of Se concentrations in
sediment (Miao et al., 2006; Peters et al., 1999). Chromium was weakly correlated
and demonstrated an inverse association to Fe concentrations (r = -0.24, p< 0.36).
The result signifies that non-lithogenic factor like human activity may also influence
the amount of Cr in the lake sediment.
The distribution of element-to-Fe ratios in the sediment of river and lake
sampling sites is shown on Figure 4.10 and 4.11, respectively. In order to show
detail of the distribution ratios, the element-to-Fe ratios were then normalized with
specified factors (Miller and Mcpherson, 2001). Arsenic to Fe ratio is multiplied by
50 000, Cr and Se to Fe are multiplied by 10 000 and 1 000 000, respectively. The
highest ratio for Se was observed at Sungai Tebrau, possibly due to anthropogenic
115
input into the river system which may come from domestic and industrial activities
along the river. The ratio for Cr is relatively consistent at all sampling site which is
in agreement with its correlation to Fe that signifies natural background occurrence.
At several sites, As showed high ratio to Fe concentrations. This finding suggested
that As is prone to accumulate near the river mouth as a result of As transportation
from upstream and deposition at the river mouth.
Ratio of As, Cr and Se concentrations
to Fe concentration
100
As/Fe
90
Cr/Fe
80
Se/Fe
70
60
50
40
30
20
10
0
SGS1
SGS2
SGS3
SGT1
SGT2
SGB1
SGB2
SGB3
River
Figure 4.10: Ratios of concentration of As, Cr and Se to concentrations of Fe in
river sediments.
116
Arsenic, chromium and selenium ratio to Fe concentrations showed a
uniform level at lake TKR sampling sites. At sampling site TUPA, the three
elements were observed for the highest ratio compared to other sampling site.
Previously, the lake bank nearby the sampling site was used as a horticulture
learning center by the university. Usage from fertilizer and pesticide was suggested
to contribute to the higher levels of Cr, As and Se in the sediment at the respective
site.
Ratio of As, Cr and Se concentrations
to Fe concentration
140
(As/Fe)
120
(Cr/Fe)
(Se/Fe)
100
80
60
40
20
0
TKRA
TKRB
TKRC
TUPA
TUPB
TBA
TBB
Lake
Figure 4.11: Ratios of concentration of As, Cr and Se to concentrations of Fe in lake
sediments.
117
4.8
Evaluating Contaminant Impact
Several methods have been put forward to quantifying the degree of
contaminant enrichment in sediments (Battelle Memorial Institute, 2003; Abrahim
and Parker, 2008). Enrichment factor (EF) and geoaccumulation index (Igeo) are the
most convenient methods to evaluate and estimate the contamination impact in
sediments by giving a broad descriptive bands of contamination ranging from low to
high intensity. The value of EF and Igeo in the sediment analyzed from the river and
lake sampling sites is presented in Table 4.10.
Table 4.10: Enrichment factors (EF) and Index of Geoaccumulation (Igeo) in
sediment of rivers and lakes
Arsenic
Sites
Chromium
Selenium
EF
Igeo
EF
Igeo
EF
Igeo
SGS1
SGS2
SGS3
Average
12.3
21.2
20.7
18.1
2.5
2.9
3.0
2.8
1.0
1.2
0.9
1.0
1.8
1.9
1.7
1.8
11.8
10.6
7.7
10.0
1.1
0.9
0.7
0.9
SGT1
SGT2
Average
15.1
12.0
13.6
2.0
2.1
2.1
0.8
0.9
0.9
0.9
1.4
1.2
29.9
24.1
27.0
1.4
1.5
1.5
SGB1
SGB2
SGB3
Average
20.2
12.1
20.9
17.7
1.9
1.8
2.7
2.1
0.7
0.8
0.7
0.7
0.3
1.0
1.1
0.8
18.9
15.7
6.8
13.8
0.5
0.8
0.2
0.5
TKRA
TKRB
TKRC
Average
33.3
30.4
35.6
33.1
3.4
3.6
3.6
3.5
1.6
1.3
1.5
1.5
2.2
2.3
2.3
2.3
5.9
2.6
3.8
4.1
0.3
-0.2
0.1
0.1
TUPA
TUPB
Average
37.3
32.7
35.0
3.2
3.3
3.3
3.9
2.4
3.2
2.7
2.5
2.6
12.5
10.4
11.5
0.8
0.8
0.8
TBA
TBB
Average
27.5
16.2
21.9
3.3
2.4
2.9
2.0
2.3
2.2
2.5
2.3
2.4
3.5
14.7
10.9
-0.1
1.0
0.5
River
Lake
118
4.8.1
Enrichment Factor (EF)
Enrichment factor is defined by the ratio of chemical concentration of an
element in a weathered material to that in its fresh parent material. It corresponding
to each sediment sample as the ratio of the interest metal concentration in the sample
to the normalizing metal concentration in the sample, divided by the same ratio in
the parent rock (Battelle Memorial Institute, 2003). The enrichment factor is usually
applied in evaluating and estimating to which extend that sediment are impacted by
anthropogenic sources.
Metal ratios for the parent rock usually are determined by referring to
published metal concentration data. Wedepohl (1995) continental crust derived
values were applied in this study for calculating the ratio of crustal abundance
metals. Sediment metal enrichment factors have been previously calculated using
either Al (Pekey, 2006), Fe (Abrahim and Parker, 2008; Breslin and SanudoWilhelmy, 1999) or Sc (Yusof and Wood, 1993) as the normalizing element. In this
study, the enrichment factor is expressed as (4-1):
EF = (M / Fe) sediment / (M / Fe) crust
(4-1)
where: (M / Fe) sediment = the ratio of the metal concentration detected in a sample
to the Fe (normalizing metal) concentrations detected
in the same sample.
(M / Fe) crustal
= the ratio of the average metal concentration in the
crustal to the average Fe concentration in the crustal.
A value of EF ≤2 can be considered to be of lithogenic origin for a metal
whereas EF > 2 indicates the addition of an anthropogenic component and/or a
biogenical enrichment process (Grousset et al., 1995). Meanwhile, Pekey (2006)
divided the enrichment of element into three major groups with respect to their
corresponding median EF: elements without enrichment (EF < 10), elements with
119
medium-level enrichment (10 < EF < 100) and finally highly enrich elements (EF >
100). However, the evaluation of EF proposed by Grousset et al. (1995) was take
into consideration to be used in this study as the elements were analyzed based on
the average concentrations and not divided into their corresponding median EF
group.
The results in Table 4.10 show EF for As and Se at the rivers were elevated
more than the factor of 2. This indicates the anthropogenic inputs are present in the
study area. The effluent discharged from the industries and the used of agricultural
chemical containing arsenic in the palm oil estate near the rivers could contribute to
high enrichment of As and Se in the sediment (Thanapalasingam, 2005). Sungai
Skudai is highly enriched with As while Sungai Tebrau has the highest enrichment
of Se.
A study on the elemental EF in the sediment in the costal areas of South
Johore found that the maximum concentration of 41.4 g g-1 for As in the bay area
and reflected high EF value of between two to five magnitudes higher than that of
the reference sediment (Yusof and Wood, 1993). High enrichment of As in the
sediment of the bay area could be introduced from the effluents directly flow from in
land or transported by rivers that meet the near-coast marine system. The current
study on the three rivers meet the same costal area which studied by Yusof and
Wood (1993) were highly enriched with As contribute to high concentration of As in
the coastal sediment.
Chromium shows an EF less than 2 in all the rivers. The EF values suggest
that the high level of Cr concentrations in sediments could be originated from the
weathering of litogenous material of the river bed and along the river bank.
Therefore, anthropogenic inputs play insignificant factor in the present of Cr in river
sediment.
120
Similarly in the river, As and Se also show high EF values in the sediment of
the lakes. The EF value for As in the lake ranged from 21.9 to 35. The EF for Se in
the lake is found to range from 4.1 to 10.9. Lake TUP was observed to have a high
enrichment of As, Cr and Se. A high EF value has proven that the suggested reason
of high element-to-iron ratio at the site arose from previous the horticulture
activities. The As enrichment at lake TKR could be explained by an excessive input
of deer manure or their food waste through run-off process. Meanwhile, there is no
clear explanation on the As and Se enrichment at lake TB. However, the location of
the lake at the low land of the hilly area could promote the input of the elements
through the run-off process from the surrounding area through application of the
fertilizer and pesticide in conjunction with landscaping activities.
There may be also an additional source that accounts for the higher levels of
As in the lake sediments. According to Durant et al. (2004), it is possible that
vertical transport of sedimentary As from deeper sediment layers to surface layers
could be occurring by molecular diffusion or due to advection by groundwater
entering the lake.
4.8.2
Geoaccumulation Index (Igeo)
An approach of geoaccumulation index, Igeo was used to quantify the degree
of anthropogenic contamination and compare different metals that appear in different
ranges of concentration in contaminated sediments (Abrahim and Parker, 2008;
Lokeshwari and Chandrappa, 2006). This index is calculated as follows (4-2):
Igeo
where: Cm
= log2 Cm / 1.5 Bm
(4-2)
= measured concentration at sampling point;
Bm
= background concentration value for element;
1.5
= the background matrix correction factor due to lithogenic effects.
121
The geoaccumulation index scale consists of seven grades ranging from unpolluted
to very highly polluted. The description of seven Igeo scale is presented in Table 4.11.
In this study, the background value was taken from the value establish by NOAA as
presented in Table 4.8. (Buchman,1999).
Table 4.11: The Igeo scale
Igeo value
Igeo class
Designation of sediment quality
>5
6
Extremely contaminated
4–5
5
Strongly to extremely contaminated
3–4
4
Strongly contaminated
2-3
3
Moderately to strongly contaminated
1–2
2
Moderately contaminated
0–1
1
Uncontaminated to moderately contaminated
0
0
Uncontaminated
The pollution levels of As in the river system expressed in terms of the
geoaccumulation indices indicate that the river sediments is moderately to strongly
contaminated. Anthropogenic inputs from agricultural, industrial and urbanization
along the rivers contribute to excessive amount of As in sediments. The level of As
contamination in the river sediment is potentially significant with regard to the
health of the river ecosystem. Meanwhile, Cr and Se at most rivers were found to be
in Igeo Class 1 and 2, respectively with uncontaminated and moderate contaminated
indication. Present of Cr and Se in the river sediments may be attributable to
combination of natural and anthropogenic factors. Sediments from Sungai Skudai
recorded the highest contamination level of As and Cr.
122
The lakes sediment can be described as strongly contaminated with As based
on the high Igeo value. Arsenic contamination in the lake sediments was associated
with fertilizer and herbicide application for landscaping activity and domestic
wastewater discharge from student’s residential blocks into the drainage system.
Chromium was laid in Igeo Class 3 with moderate to strong contaminated indication.
Chromium contamination in the lake was likely caused by domestic wastewater or
from the weathering of litogenous material of the lake bed or around the bank
particularly at site TKR where the EF value showed less than the factor of 2
indicative of the enrichment originating from weathering of parent materials. Even
though the lake sediments showed an occurrence of Se enrichment, the negative Igeo
value found at a few sites are the result of relatively low levels of contamination
(Abrahim and Parker, 2008). The lake TUP shows the highest contamination level of
As, Cr and Se compared to the other two lakes.
Besides human factor, another possible source of As and Cr were due to the
vertical migration of the elemental species resulted from diagenetic process that
normally takes place in anoxic sedimentary conditions as notified from the
characteristic of the sediment for example the odor due to H2S and the greasy
appearance of the column of the sediment (Wood et al., 1997). Investigation
conducted by El Bilali et al. (2002) over 20 lakes in Ontario, Canada showed that the
trace elements enrichment in the surface sediment may not be solely attributed to
anthropogenic mobilization but also to the role played by Fe, and Mn oxides and
organic matter during burial and diagenesis process.
4.9
Speciation of Arsenic and Selenium in Sediments
Speciation of arsenic and selenium in environmental samples is gaining
increasing importance, as the toxic effect of the As and Se are related to its oxidation
state. Inorganic As and Se; As (III), As (V), Se (IV) and Se (VI) are the
predominantly species found in contaminated sediment or soil (Goh and Lim, 2004).
Inorganic species of As and Se from solid samples have been separated and
123
quantified using various methods as presented in Chapter 2 : Table 2.2. Even though
at present there are no CRM available specifically for As and Se species in sediment,
the determination of the species were made possible by validating the proposed
analytical method (Hutton et al., 2005; Leermakers et al., 2006; Ruiz-Chancho et al.,
2005). In this study, the CRM which certifies the total arsenic and selenium
concentration was applied to investigate on the recovery of the species during the
microwave extraction under the proposed range of media concentration, microwave
power and time of extraction. The results of total inorganic species found by
microwave extraction were compared with the certified values of the reference
material.
The standard species was spiked into the extraction media to trace on the
repeatability of the analysis and any loss or inter-conversion of the species. The
effect of pH on the extracted media was studied in order to assess the extraction
efficiency during the preconcentration step. The optimum conditions of the validated
studies were then applied for subsequent experiments of As and Se species in the
river and lake sediments.
4.9.1
Optimization of Arsenic Speciation Study
Several studies have shown that H3PO4 in the presence of low-power
microwave creates promising conditions for the extraction of As species in soil and
sediment. However, the extraction yields from several CRM of sediment varied
between 80 and 110% (Gallardo et al., 2001; Hutton et al., 2005; Sathrugnan and
Hirata, 2004; Thomas et al., 1997). Therefore, a microwave-assisted H3PO4
extraction was investigated, with microwave specific power, time and H3PO4
concentration in order to optimize an extraction procedure that extracts inorganic As
species from sediment samples. A sediment CRM BCSS-1 and spiked solution of the
As species of interest were studied to check for extraction efficiency and species
stability. The extraction efficiency of As (III) and As (V) for separation and
preconcentration procedure using APDTC-MIBK system was also investigated as a
function of the pH.
124
4.9.1.1 Microwave Extraction
In order to determine the optimum condition for sediment extraction using
microwave, the CRM BCSS-1 was treated using H3PO4 concentration of 0.25 M, 0.5
M and 1 M for 10 and 20 min at 20 and 25% microwave power. The certified value
for total As in BCSS-1 is 11.1 g g-1.
The mean values for As species extractable from various acid concentration
and microwave conditions was summarized in Table 4.12. These test revealed that
at low concentration of 0.25 M H3PO4 up to 43% of total As was extracted at all time
and microwave power applied. Good recovery of 92% for total As was achieved at
an operating time of 20 min treated at 25% power in 1 M H3PO4. The respective
microwave conditions and optimum acid media were employed for all subsequent
studies.
The stability study of As species was carried out at the optimum condition of
20 min at 25% power in 1M H3PO4 using standard solution of 0.25 µg mL-1 As (III)
and As (V). No significant loss or inter-conversion of As species was observed with
a high recovery percentage of 97 to 99% and RSD of 2.5 to 3.4% (Appendix G).
This test was carried out on six samples.
125
Table 4.12: Results of arsenic species under various microwave conditions and
H3PO4 concentration (expressed as µg g-1 dry mass).
H3PO4
(M)
0.25
0.5
1.0
As extracted
Power
(%)
Time
(min)
20
25
10
20
10
20
As (III)
As (V)
Total As
Recovery from
total (%)
0.240.01
3.330.13
3.57
0.300.01
3.140.20
3.44
0.430.01
3.960.20
4.39
0.700.06
4.100.21
4.8
32
31
40
43
As (III)
As (V)
Total As
Recovery from
total (%)
0.370.02
3.020.20
3.39
0.450.05
3.910.17
4.36
1.460.10
5.120.30
6.58
1.500.10
7.430.36
8.93
31
39
59
81
As (III)
As (V)
Total As
Recovery from
total (%)
0.610.06
3.600.30
4.21
1.120.10
4.250.21
5.37
1.740.14
5.780.31
7.52
2.220.17
7.980.42
10.2
38
48
68
92
n=3
4.9.1.2 Effect of pH and Repeatability
The investigation of extraction efficiency of As (III) and As (V) as a function
of pH showed that pH range affects the extraction efficiency. Results shown in
Figure 4.12 demonstrate that As (III) can be quantitatively extracted by APDTCMIBK in the pH range of 4 to 9 whereas As (V) is not extracted at all at pH 4 to 10.
As (V) can be extracted at pH 1 to 3 with a low efficiency of up to 10%. Therefore,
these two species can be separated from each other at pH 4 to 9 and pH 6 was
employed for all subsequent investigations. The detail results of extraction efficiency
of As (III) and As (V) are presented in Appendix G.
126
This study is consistent with those of Mok et al. (1986) and Shi (2000) who
reported that As (III) can be quantitatively extracted by APDTC-MIBK in the pH
range of 0.6 to 9. A small fraction between 2% to 6% of As (V) was found in the
extraction at pH  1 (Mok et al., 1986). However, Shi (2000) found that up to 25%
of As (V) was extracted at pH 2 - 5.
120
Recovery, %
100
80
60
40
As (III)
20
As(V)
0
1
2
3
4
5
6
7
8
9
10
pH
Figure 4.12: Extraction recovery of As (III, V) by APDTC-MIBK at different pH
Under the optimized preconcentration conditions, the repeatability of the
extraction by APDTC-MIBK had been studied using standard solution of As (III)
and As (V) at 2 µg mL-1. The standard deviations of extractable As concentration
were calculated from NAA data of seven extraction runs carried out on the same day.
The RSD of approximately 7% and 5% were obtained for As (III) and As (V),
respectively and low RSD values suggest that sufficient repeatability for As
extraction is achieved.
127
4.9.2
Optimization of Selenium Speciation Study
Similar procedures like As speciation study were applied in validating the
extraction method for Se species in sediment. A sediment CRM oPACS - 2 and
spiked solution of the Se species of interest were investigated to check for extraction
efficiency and species stability in low concentration of HCl media. The extraction
efficiency of Se (IV) and Se (VI) for separation and co-precipitation procedure was
also studied as a function of pH.
Several studies have shown that mild HCl extracts significant amount of Se
species in solid environmental samples such as soil and muscles tissue using
different mechanism of extraction (Bujdoš et al., 2005; Ochsenkühn-Petropoulou et
al., 2003; Peters et al., 1999). About 94 % extraction efficiency was achieved by
Ochsenkühn -Petropoulou et al. (2003) using 0.5 M HCl in temperature of 4C
where the results also indicate the combination of other organic Se species.such as
selenourea, selenoethionine and selenomethionine. Sathrugnan and Hirata (2004)
obtained about 60% of extraction efficiency for inorganic Se in coal fly ash but no
quantitative amount of Se species was extract from sediment using microwave
extraction in 0.1 M H3PO4. Meanwhile, some other studies applied microwave
extraction method for inorganic Se determination in a mixture of concentrated acid
but no further information on the extraction efficiency was available (Yusof et al.,
1997; Yusof et al., 1998).
4.9.2.1 Microwave Extraction
The optimum condition for sediment extraction using microwave was studied
using the CRM PACS-2 in HCl concentration of 0.1 M, 0.25 M, 0.5 M and 1 M for
10 and 20 min at 20 and 25% microwave power. The certified value for total Se in
CRM PACS-2 is 0.92 g g-1.
128
The mean value for Se species extractable from various acid concentration
and microwave conditions was presented in Table 4.13. The study shows that at low
concentration of 0.1 M HCl the total Se species extracted ranged from 32% to 36%
at all operating times and microwave power applied. High recovery of 86% for total
Se species was achieved at an operating time of 20 min treated at 25% power in 1 M
HCl. The respective microwave conditions and optimum acid media were employed
for all subsequent studies.
Table 4.13: Results of selenium species under various microwave condition and HCl
concentration (expressed as µg g-1 dry mass).
HCl
(M)
0.1
Se extracted
Se (IV)
Se (VI)
Total Se
Recovery
from total
(%)
Power
20
(%)
Time
10
20
(min)
0.0730.006 0.0990.004
0.2280.020 0.2220.010
0.301
0.321
33
35
25
10
20
0.1010.010
0.1930.020
0.294
32
0.1210.010
0.2110.010
0.333
36
0.25 Se (IV)
0.1070.002
0.1240.005
0.1290.005
0.1430.010
Se (VI)
0.2580.020
0.2780.003
0.2480.030
0.3750.020
Total Se
0.365
0.402
0.377
0.518
Recovery
from total
(%)
40
44
41
56
Se (IV)
0.1380.002
0.1420.030
0.1520.010
0.1700.003
Se (VI)
0.3000.010
0.3300.004
0.3740.020
0.4770.040
Total Se
0.438
0.472
0.526
0.647
Recovery
from total
(%)
48
51
57
70
Se (IV)
0.1520.009
0.1570.010
0.1660.002
0.1810.010
Se (VI)
0.3360.010
0.3760.020
0.4710.020
0.6080.030
Total Se
0.488
0.533
0.637
0.789
Recovery
from total
(%)
53
58
69
86
0.5
1.0
n=3
129
This study achieved better extraction efficiency as compare to Ochsenkühn Petropoulou et al. (2003) who obtained 43% for total Se (IV) and Se (VI) extract in
soil sample from 0.5 M HCl media. In mine tailing sample, Bujdoš et al. (2005)
managed to extract 5.8% to 23.5% of Se mobile fraction using 0.5 M HCl.
Meanwhile, Sathrugnan and Hirata (2004) and Iserte et al. (2004) were unable to
extract quantitative amount of inorganic Se from sediment sample using mild H3PO4
media.
The stability study of Se species using a 0.25 µg mL-1 standard solution of Se
(IV) and Se (VI) was carried out at the optimum condition of 20 min at 25% power
in 1M HCl. No significant loss or inter-conversion of Se species was observed with
a satisfactory Se (IV) recovery percentage of 97% and RSD of 10% while Se (IV)
achieved a high recovery of 99%. (Appendix H). This test was carried out on six
samples.
4.9.2.2 Effect of pH and Repeatability
The investigation of extraction efficiency of Se (IV) and Se (VI) by coprecipitation technique as a function of the pH showed that the pH range affects the
extraction efficiency. The effects of pH on the extraction of Se (IV) and Se (VI) after
co-precipitation of Na-DBDTC with phenolphthalein are shown in Figure 4.13.
Good quantitative extraction of Se (IV) was observed at pH 2 and 3 with recovery of
101% and 91%, respectively. Above pH 3, the efficiency of extraction of Se (IV)
begins to decrease at consistent level. Saleh et al. (1990) also observed similar
pattern of extraction efficiency of Se (IV) in the same co-precipitation system where
high recovery was obtained at pH 2 - 3 and it decreased rapidly after pH 4.
According to literature study, Se (VI) cannot be co- precipitated by NaDBDTC even at low pH (Cheng et al., 1982). No significant amount of Se (VI) was
found in the standard at all pH range. Therefore, these two species can be easily
separated from each other and a pH value of 2 was employed for all subsequent
studies. The detail results of extraction efficiency of Se (IV) and Se (VI) are shown
in Appendix H.
130
120
Revovery, %
100
80
60
Se (IV)
40
Se (VI)
20
0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
pH
Figure 4.13: Extraction recovery of Se (IV, VI) by co-precipitation technique at
different pH.
The repeatability of the co-precipitation technique using Na-DBDTC with
phenolphthalein had been studied using standard solutions of 1 µg.mL-1 Se (IV) and
Se (VI) under the optimum conditions for co- precipitation. The standard deviations
of extractable Se concentrations were calculated from NAA data of five extraction
runs carried out on the same day. The RSD of approximately 4% and 3% were
obtained for Se (IV) and Se (VI), respectively and low RSD values suggest that
sufficient repeatability for Se extraction is achieved.
4.10
Concentration of Arsenic and Selenium Species in River and Lake
The results obtained for As species in river and lake sediments are shown in
Table 4.14. The results of each sampling session are presented in Appendix I. These
results clearly indicated that the majority of As was present as As (V), with As (III)
accounting for < 18% of the total As. The extraction efficiency, relative to the total
As concentrations, varied from 68 to 99%. Some of the values were lower than the
131
values obtained during the optimization of the extraction, suggesting that the
sediment contained a slightly different matrix than those used for optimization.
However, extraction efficiencies were still at least as good as those described in
studies carried out by Gallardo et al. (2001), Hutton et al. (2005), Thomas et al.
(1997).
Hutton et al. (2005) also discovered that low recoveries of the As species in
the sediment samples were not due to interferences from that matrix or during the
analysis stage. But, it was more likely that some of the As is strongly bound or
complexed. According to Ellwood and Maher (2003), the presence of humic material
and mineral As like arsenopyrite have little effect on As extraction efficiency. A
longer extraction process would possibly yield better recoveries, but this could lead
to inter-conversions or loss of the species.
The majority of As extracted was As (V) which shows the predominance of
oxidized As phases at the sampling sites. Low ratios of As (III) to As (V) had been
observed at all sampling sites ranging from 0.03 to 0.24. By using ANOVA
(Appendix I), the difference in the ratio of As (III) to As (V) in lake and river
sediment were found to be statistically insignificant at  = 0.05 (P =0.3).
This study is consistent with those of Pettine et al. (1992) and Abdul-Moati
(1990) who found that arsenate was the predominant arsenic species in the river and
lake respectively. Pettine et al. (1992) reported that the ratio between oxidized and
reduced species appears to be significantly influenced by the presence of iron and
manganese oxides. As (V) are the more stable species and can be strongly adsorbed
onto clay, iron and manganese oxides (Mandal and Suzuki, 2002). Abdel-Moati
(1990) monitored arsenic in the Nile delta lakes and found As (V) to be the dominant
arsenic species (85–95%). Increased As (III) (14–33%) was found near local sewage
discharge points.
132
Table 4.14: Arsenic speciation analysis in river and lake sediment
As (III)
g g-1
As (V)
g g-1
Recovery
from totals
(%)
Ratio
As (III)/ As (V)
SGS1
SGS2
SGS3
Average
1.10  0.31
0.73  0.26
1.79  0.47
1.21  0.54
13.3  1.3
27.0  3.4
30.1  5.0
23.5  4.0
74.1
90.6
94.3
86.3
0.08
0.03
0.06
0.06
SGT1
SGT2
Average
0.88  0.33
1.99  0.58
1.44  0.48
11.0  3.0
11.4  1.0
11.2  0.3
96.8
99.6
98.2
0.08
0.17
0.13
SGB1
SGB2
SGB3
Average
0.69  0.23
0.55  0.17
1.07  0.27
0.77  0.19
7.4  0.9
7.2  1.1
19.6  1.1
11.4  2.2
74.3
76.4
85.2
78.6
0.09
0.08
0.05
0.07
TKRA
TKRB
TKRC
Average
2.45  0.11
3.54  0.64
2.23  0.20
2.74  0.70
40.1  1.2
45.3  2.4
40.6  4.3
42.0  2.9
87.7
81.0
69.6
79.4
0.06
0.08
0.06
0.06
TUPA
TUPB
Average
6.68  0.44
3.04  0.32
4.86  0.60
27.6  1.7
35.7  0.7
35.7  2.5
88.2
87.9
88.0
0.24
0.09
0.16
TBA
TBB
Average
2.83  0.39
0.94  0.15
1.89  0.50
28.2  1.9
11.1  0.9
19.7  1.7
68.0
68.3
68.2
0.10
0.08
0.09
River
Lake
Sampling locations like SGT2 and TUPA had shown slightly higher
percentage of 15% and 18% As (III), respectively while other locations constituted <
7% As (III) of the total As. Sediments at both sites may suggest undergoing an early
sign of anaerobic condition. Sewage discharge from housing estate and drinking
water factory in the vicinity of SGT2 site could contribute to the biological activity
in the sediment and create anoxic environment which most likely encourage the
reduction process of As (V) to As (III). The site at TUPA, however was formerly
used for horticulture activities where an excessive application of pesticide and
fertilizer may suggest for the presence of higher levels of As (III) in the sediment.
133
The environmental conditions of the sediment have a greater influence on As
speciation and distribution than does the total concentration of arsenic in the
sediment. Arsenic from-enriched sediments can be released to water column under
anaerobic conditions making the existing conditions conducive to the reduction of
As (V) to As (III) (Bhumbla and Keefer, 1994). The presence of sulfides and the
hydrous oxides of iron and manganese act as important sinks through adsorption
process and modes of transport for arsenic that is directly controlling the
mobilization of arsenic in an aquatic environment (Mok and Wai, 1994).
Selenium species concentrations in river and lake sediments are shown in
Table 4.15 and the results of each sampling session are presented in Appendix I. The
dominant species of Se was present as Se (VI) which was found to be about 61% to
86% of the total Se. Meanwhile, Se (IV) accounts for < 24% of the total Se
concentrations. The extraction efficiency, relative to the total Se concentrations,
varied from 71% to 94%. Some of the values were lower than the values obtained
during the optimization of the extraction procedure, suggesting that the sediment
contained a slightly different matrix than those used for the optimization step.
Low recoveries of inorganic Se in the samples may be contributed from the
presence of other Se species like organic Se compound that can also be found in the
sediment. Gomez-Ariza et al. (1998) obtained significant amount of organic Se
compounds such as dimethylselenide, dimethyldiselenide, dietyselenide and
diethyldiselenide in sediments collected from areas in the Southwest of Spain.
Selenium species of selenourea and selenoethionine was also extractable in 0.5 M
HCl media from sediment at warm springs area of Thermopyles, Freece
(Ochsenkühn -Petropoulou et al., 2003). Since the sediment obtained varies in
nature, from high in organic matters to mostly clay, it was anticipated that the
determination of Se (IV) and Se (VI) was likely suppressed by the interference of
dissolved organic carbon as reported by Workman and Soltanpour (1980) when they
found out that recoveries of inorganic Se in some extracts were poor.
134
Table 4.15: Selenium speciation analysis in river and lake sediment
Se (IV)
g g-1
Se (VI)
g g-1
Recovery
from totals
(%)
Ratio
Se (IV)/ Se (VI)
SGS1
SGS2
SGS3
Average
0.17  0.02
0.15  0.04
0.14  0.02
0.15  0.02
1.11  0.09
0.80  0.10
0.61  0.18
0.84  0.26
93.8
84.3
80.4
86.1
0.16
0.18
0.23
0.19
SGT1
SGT2
Average
0.22  0.05
0.16  0.01
0.19  0.05
1.33  0.20
1.54  0.13
1.43  0.15
86.9
86.2
86.5
0.18
0.11
0.15
SGB1
SGB2
SGB3
Average
0.17  0.06
0.13  0.02
0.13  0.08
0.14  0.02
0.60  0.10
0.72  0.10
0.43  0.04
0.58 0.15
91.4
86.2
89.3
89.0
0.27
0.20
0.31
0.26
TKRA
TKRB
TKRC
Average
0.04  0.01
0.07  0.01
0.10  0.02
0.07  0.01
0.40  0.01
0.25  0.02
0.29  0.02
0.31  0.05
70.9
87.9
83.3
80.7
0.09
0.29
0.36
0.25
TUPA
TUPB
Average
0.15  0.01
0.12  0.03
0.13  0.02
0.66  0.03
0.81  0.02
0.7  0.10
87.7
94.0
90.9
0.23
0.15
0.19
TBA
TBB
Average
0.05  0.03
0.14  0.02
0.10  0.01
0.21  0.03
0.80  0.04
0.51  0.05
77.1
83.0
80.1
0.27
0.18
0.22
River
Lake
Low ratios of Se (IV) to Se (VI) had been observed at all sampling sites with
values ranging from 0.09 to 0.36. The low Se (IV) to Se (VI) ratios suggest that
oxidizing environment prevails in both freshwater body systems thus promoting the
formation of the Se (VI) than the Se (IV) species. By using ANOVA (Appendix I),
the difference in the ratio of Se (IV) to Se (VI) in river and lake sediment were found
to be statistically insignificant at  = 0.05 (P =0.7). The ratio of both Se species was
fairly uniform in the river and lake sediment samples.
135
The distribution of Se in contaminated aquatic sediment is very much
influenced by its chemical form and speciation. According to Goh and Lim (2004),
Se (IV) is strongly adsorbed by soil or sediment while Se (VI) in only weakly sorbed
and leaches easily. Selenite is present in mildly oxidizing and neutral pH
environments while Se (VI) is predominant in oxidized and under ordinary alkaline
conditions.
CHAPTER 5
CONCLUSIONS AND SUGGESTIONS
5.0
Conclusions
Since sediments are the ultimate repository of most of the contaminants that
enter freshwater, it is appropriate that regulatory attention addresses the ecological
risks that these sediment contaminants might pose. There is an increasing public
awareness and concern for the health of our waterways and ecosystem, and an
expectation that water quality will be improved, but any improvement in water
quality must address sediments as an important component of aquatic ecosystem and
a source of contaminants to the benthic food chain.
Freshwater resources such as rivers, lakes and groundwater are the vital
elements in human lives. Sediments act as a useful component in monitoring and
assessing any physical and chemical changes which are related to contamination in
the aquatic environment. Assessment and management of sediment quality
conditions contributes to preserving and preparing future remediation plan for
freshwater resources. Data on the respective study can serve as a baseline for long
term studies in predicting the trends of water and sediment quality in water
resources. It can also provide a better understanding of the behavior of the sediment
quality and the important factors influencing them.
The study of three water parameters; pH, temperature and DO at rivers and
lakes demonstrated that human activities slightly affected the quality of the water
bodies at several sampling locations. Sungai Skudai, Sungai Tebrau, lake sampling
137
sites of TKR and TUP showed an average pH parameter which was lower than the
NWQS optimal Class I value of 6.5 to 8.5 except for Sungai Buluh and lake TB
which were within the threshold value. Sungai Skudai and Sungai Tebrau met the
threshold level for Class IIB while lake TKR and TUP were in Class III. Meanwhile,
DO levels did not comply with the NWQS threshold level for Class 1 at all sampling
sites but met the threshold value for Class IIA and IIB. However, the temperature of
the water bodies at all sampling locations showed insignificant variation towards
local studies conducted previously.
The applicability of the analytical procedures using NAA technique for
analysis of As, Cr, Se, Fe and species of As and Se has been successfully examined
by analyzing CRM. The analytical results achieved recovery above 93% and with
precision of generally better than 16.7% RSD. All results of elements studied were
within the Z-score accepted criteria.
Arsenic, chromium and selenium were present in the sediment of all
sampling locations and the concentrations exceeded the background values for
freshwater sediment criteria established by NOAA. The results obtained showed that
the range of concentrations of As in the rivers and lakes were 10 - 34 g g-1 and 18 62 g g-1, respectively. The concentrations of Cr in the rivers ranged between 27
g g-1 to 125 g g-1, while in the lake sediments the concentrations ranged between
173 g g-1 to 301 g g-1. The Se concentrations of the river sediment and lake
sediment ranged between 0.56 g g-1 to 1.91 g g-1 and 0.31 g g-1 to 1.08 g g-1
respectively. Human related activities such as agricultural, industrial, urbanization,
landscaping may have been contributed significant amount of As, Cr and Se into the
freshwater sediments.
Arsenic was found to be significantly correlated with Fe in sediments of river
and lake system (r = 0.82 and r = 0.76; respectively). Strong correlation between Cr
and Fe (r = 0.94) suggested that Fe fractions played an important role in the sorption
of Cr in river sediments. This indicated that the sediment was a substantial sink for
As and Cr.
138
Enrichment factor (EF) and geoacculumation index (Igeo) were employed for
quantifying the degree of As, Cr and Se enrichment in the sediments. Arsenic and
selenium showed values of EF > 2 in river and lake sediment which indicates an
excessive anthropogenic input entering the aquatic system. A value of EF≤ 2 for Cr
in river sediment could be signified by lithogenous material input originated from
natural weathering processes and sedimentation. The contamination levels of As in
the river system expressed in terms of Igeo indicated that the river sediments were
moderately to strongly contaminated and are categorized in Igeo Class 3. Chromium
and selenium in rivers were categorized in Igeo Class 1 and 2 indicating
uncontaminated and moderate contamination levels. The sediments of Sungai Skudai
showed the highest contamination levels of As and Cr. The Igeo value of Class 4
indicated that the lakes sediment was strongly contaminated with As. Chromium
and selenium in lakes were found to be in in Igeo Class 1 and 3, respectively. The
sediments of lake TUP showed high values of Igeo for As, Cr and Se.
Arsenic and selenium were determined for their inorganic species in both
river and lake sediments. Significant amounts of the inorganic species of As (III), As
(V), Se (IV) and Se (VI) in the sediments were extracted using the microwave
digestion at the optimized time and power setting in mild concentration acid media.
Combination of organic separation and NAA technique have been applied to
determine the As and Se species of interest.
A satisfactory recovery of extractable inorganic As species was achieved
using microwave digestion at an operating time of 20 min and 25% power treated in
1 M H3PO4. The As (III) and As (V) were successfully separated by APDTC into
MIBK media with high extraction efficiency achieved at pH 6. Meanwhile, a
sufficient amount of extractable Se species was also obtained under microwave
digestion procedure in 1 M HCl media at an operating time of 20 min and 25%
power. Both inorganic Se species, the Se (IV) and Se (VI) were separated after
coprecipitation of Na-DBDTC with phenolphthalein at an optimum media condition
of pH 2.
139
Investigation of the As and Se inorganic species in river and lake sediments
showed that As (V) and Se (VI) were the dominant species. There was statistically
insignificant difference in the ratio of As (III) to As (V) and Se (IV) to Se (VI)
between lake and river sediments. Low ratios of As and Se species in surface
sediments suggested that oxidizing environment prevailed in both freshwater body
systems thus promoting the formation of the oxidized species.
5.1
Suggestions
An excessive amount of As, Cr and Se found in freshwater sediments in the
populated areas should be made a strong factor for the recommendation of the
development of a suitable mechanism to monitor, evaluate and manage any
contaminants input into the aquatic ecosystem. An identification of geological
background, point and non-point sources of contamination, and assessment of the
physical as well as chemical interactions of contaminants in sediment body provide a
better understanding of distribution, mobilization, transportation and bio-availability
of the contaminants particularly in aquatic environment. These can be conducted in
future research work.
Currently there is no sediment quality guideline established locally. An
establishment of a national sediment quality guidelines would be useful in gaining
better estimation of contaminants impact and assessment in the level of pollution by
taking into consideration factors such as local climate, geological and environmental
conditions. The formulation of an integrated framework for planning, designing,
implementing and interpreting the results of sediment quality investigations should
be governed by several bodies such as DOE, water management districts,
universities, and county governments through cooperative instigation.
140
Speciation studies have become an important tool in characterizing and
determining the forms of elements in a sediment system. Speciation analysis requires
suitable reference materials particularly for sediment samples to be available to
verify accuracy and to meet quality assurance needs. There is a clear need to produce
sediment CRMs by local or international body for elemental species to validate
methods in general and to evaluate their accuracy, in particular. Various approaches
can be developed for speciation studies and to intensify future research work in the
related field.
141
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157
APPENDIX A
The range of the water physico-chemical parameters.
RIVERS
Water Parameters
Sites
pH
Temperature (C)
Dissolve Oxygen (mg L-1)
22nd
Aug.
20th
Nov.
14th
Dec.
22nd
Aug.
20th
Nov.
14th
Dec.
22nd
Aug.
20th
Nov.
14th
Dec.
SGS
6.59 7.00
6.12 6.60
5.785.97
28.830.6
29.429.9
26.428.1
4.775.33
4.254.64
5.465.77
SGT
6.626.74
6.326.59
6.176.23
28.429.6
27.828.9
26.928.7
4.885.27
4.754.98
4.905.83
SGB
6.626.82
6.776.92
6.817.14
28.229.5
29.430.8
28.431.4
4.985.39
4.775.25
4.625.18
LAKES
Water Parameters
Sites
pH
Temperature (C)
Dissolve Oxygen (mg L-1)
22nd
Aug.
21st
Nov.
13th
Dec.
22nd
Aug.
21st
Nov.
13th
Dec.
22nd
Aug.
21st
Nov.
13th
Dec.
TKR
6.53 6.71
5.86 6.14
5.435.74
31.532.0
29.229.6
26.026.2
6.296.31
6.496.85
7.467.81
TUP
5.596.28
6.016.34
5.605.74
32.032.1
31.933.4
28.128.3
6.306.36
5.715.96
7.027.47
TB
6.997.54
6.446.69
6.076.28
30.431.2
31.131.5
28.428.7
6.526.74
6.176.19
6.957.34
158
APPENDIX B
NATIONAL WATER QUALITY STANDARDS FOR MALAYSIA (NWQS)
Parameters
(Units)
Classes
l
llA
llB
lll
lV
V
Ammonical Nitrogen
mg/l
0.1
0.3
0.3
0.9
2.7
>2
BOD
mg/l
1
3
3
6
12
> 12
COD
mg/l
10
25
25
50
100
> 100
DO
mg/l
7
5-7
5-7
3-5
<3
<1
pH
-
6.5-8.5
6.5 - 9.5
6-9
5-9
5-9
TCU
15
150
150
mmhos/cm
1000
1000
-
6000
-
Floatables
-
N
N
N
-
-
-
Odour
-
N
N
N
-
-
-
/oo
0.5
1
-
-
-
-
-
N
N
N
-
-
-
Total Dissolved Solids
mg/l
500
1000
-
-
-
-
Total Suspended Solids
mg/l
25
50
50
150
300
> 300
C
-
Normal
+2
-
Normal
+2
-
-
NTU
5
50
50
-
-
-
Faecal Caliform*
counts/100ml
10
100
400
Total Coliform
counts/100ml
100
5000
50000
Colour
Electrical Conductivity
o
Salinity
Taste
o
Temperature
Turbidity
Note:- N No visible floatable materials/debris
or No objectionable odour
or No objectionable taste
* Geometric Mean
@ Maximum not to be exceeded
5000
5000
(2000)@ (2000)
50000
50000
>50000
159
Class
l
Uses
Conservation of natural environment Water supply l practically no treatment necessary (except by disinfection of
boiling only)
Fishery l - very sensitive aquatic species
llA
Water supply ll - conventional treatment required
Fishery ll sensitive aquatic species
llB
Recreational use with body contact
lll
Water supply lll - extensive treatment required Fishery lll common, of economic value and tolerant species
lV
Irrigation
V
None of the above
160
APPENDIX C
Certified Reference Material
161
162
163
164
165
166
167
APPENDIX D
Results of As, Cr, Se and Fe concentration in river and lake sediments.
RIVERS
Sites
SGS1
SGS2
SGS3
SGT1
SGT2
SGB1
SGB2
SGB3
Sampling
session
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
NA – Not Available
Elements Concentration
As (g g-1)
Cr (g g-1)
Se (g g-1)
Fe (%)
19.9  0.7
15.1  0.9
23.0  2.8
35.4  0.3
30.1  1.0
24.2  0.6
35.2  1.0
29.2  0.5
36.4  0.8
10.8  0.1
17.4  0.7
8.6  0.2
13.4  1.5
12.0  0.8
15.8  2.9
8.8  0.6
NA
13.0  0.6
8.6  0.4
9.5  0.2
12.5  1.4
29.6  0.8
26.8  2.9
16.5  0.8
140  6
117  4
110  6
130  8
79  4
166  2
111  4
93  4
107  4
27  1
31  3
19  1
71  10
59  5
102  5
28  1
NA
27  2
93  6
32  2
28  2
71  5
56  2
52  2
1.20  0.05
1.47  0.15
1.40  0.05
0.90  0.03
1.15  0.04
1.35  0.08
1.10  0.14
0.71  0.03
1.00  0.09
1.70  0.14
2.46  0.24
1.20  0.05
1.30  0.05
2.37  0.20
2.23  0.07
0.80  0.12
NA
0.70  0.04
1.40  0.04
0.94  0.08
0.60  0.11
0.80  0.07
0.37  0.04
0.70  0.04
4.31  0.20
3.73  0.19
3.98  0.12
3.39  0.19
3.00  0.10
4.63  0.15
4.08  0.20
3.68  0.20
4.67  0.21
2.20  0.08
2.31  0.17
1.99  0.05
2.76  0.39
2.60  0.05
3.21  0.18
1.18  0.06
NA
1.56  0.06
3.15  0.16
1.78  0.82
1.48  0.08
2.90  0.41
3.14  0.18
2.82  0.06
168
LAKES
Sites
TKRA
TKRB
TKRC
TUPA
TUPB
TBA
TBB
Sampling
session
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Elements Concentration
As (g g-1)
Cr (g g-1)
Se (g g-1)
Fe (%)
29.2  1.3
83.5  1.3
45.6  2.1
67.0  6.4
61.2  4.3
56.1  0.5
69.2  5.5
58.0  1.0
52.5  2.2
16.2  1.1
14.6  0.2
85.8  3.7
31.8  1.2
43.4  6.1
57.0  0.8
46.4  2.3
47.2  1.4
43.4  2.5
18.6  0.3
22.3  1.5
12.0  0.8
124  7
211  5
183  9
173  9
206  9
215  10
162  5
245  7
177  16
338  5
315  12
249  24
284  14
134  6
314  9
233  9
255  9
239  5
147  2
254  17
162  7
0.79  0.01
0.37  0.05
0.67  0.06
0.41  0.06
0.35  0.03
0.34  0.02
0.47  0.07
0.42  0.03
0.51  0.08
1.02  0.05
0.85  0.07
0.90  0.09
1.01  0.05
1.08  0.08
0.88  0.19
0.21  0.02
0.39  0.06
0.45  0.05
1.06  0.04
1.09  0.09
1.24  0.02
3.15  0.11
4.20  0.18
3.77  0.18
4.57  0.20
5.17  0.18
5.39  0.23
3.98  0.10
4.83  0.17
4.37  0.22
1.89  0.09
1.74  0.09
3.74  0.17
2.66  0.15
3.54  0.13
4.34  0.20
4.08  0.20
4.48  0.18
4.36  0.16
3.03  0.17
2.35  0.15
2.41  0.11
169
APPENDIX E
Details on the international guideline for freshwater sediment.
170
171
172
173
Buchman, M. F., 1999. NOAA Screening Quick Reference Table, NOAA HAZMAT Report 99-1, Seattle WA,
Coastal Protection and Restoration Division, National Oceanic and Atmospheric Administration, 12 pages.
174
APPENDIX F
Statistical evaluation of As, Cr and Se correlation to Fe in sediments.
RIVERS
Correlation and Regression Analysis
As
Cr
Se
r
0.8198
0.9354
0.0258
R2
0.6721
0.8750
0.0007
Adjusted R2
0.6175
0.8541
-0.1659
Standard Error
5.7271
13.8407
0.5152
P-value
0.0127
0.0006
0.9517
8
8
8
Observations
LAKES
Correlation and Regression Analysis
As
Cr
Se
r
0.7537
- 0.2408
-0.8049
R2
0.6973
0.1681
0.8216
Adjusted R2
0.6368
0.0017
0.7859
5280.5590
44.6910
0.1438
0.0194
0.3610
0.0049
7
7
7
Standard Error
P-value
Observations
175
APPENDIX G
a) The stability study of As species
Test sample
As (III)
(g g-1)
As (V)
(g g-1)
1
0.247
0.251
2
0.255
0.239
3
0.235
0.242
4
0.246
0.253
5
0.234
0.254
6
Average
Recovery (%)
RSD (%)
0.237
0.243  0.010
97 %
3.4 %
0.245
0.247  0.010
99 %
2.5 %
b) The extraction efficiency of As (III) and As (V) to pH function
As species
pH
Amount found
(g g-1)
Recovery (%)
As (III)
1
1.65  0.1
83
2
1.68  0.08
84
3
1.75  0.06
88
4
1.85  0.01
93
5
1.97  0.02
99
6
2.00  0.02
100
7
2.00  0.20
100
8
9
1.97  0.05
1.83  0.09
99
92
10
1.40  0.30
70
176
As species
pH
Amount found
(g g-1)
Recovery (%)
As (V)
1
0.083  0.003
4.13
2
0.084  0.010
4.18
3
0.011  0.010
0.56
4
0.006  0.030
0.28
5
< 0.005
0
6
< 0.005
0
7
< 0.005
0
8
9
< 0.005
< 0.005
0
0
10
< 0.005
0
c) The repeatability of the extraction by APDTC-MIBK
Test sample
As (III)
(g g-1)
As (V)
(g g-1)
1
1.77
1.88
2
1.87
1.96
3
1.88
2.12
4
1.85
1.92
5
1.95
2.08
6
2.13
1.89
7
Average
Recovery (%)
RSD (%)
2.05
1.93  0.12
97
7
2.03
1.98  0.1
99
5
177
APPENDIX H
a) The stability study of Se species
Test sample
Se (IV)
(g g-1)
Se (VI)
(g g-1)
1
0.275
0.240
2
0.245
0.261
3
0.221
0.255
4
0.214
0.252
5
0.266
0.241
6
Average
Recovery (%)
RSD (%)
0.233
0.243  0.03
97 %
10 %
0.236
0.248  0.01
99 %
4%
b) The extraction efficiency of 1 g mL-1 Se (IV) and Se (VI) to pH function
Se species
pH
Amount found
(g g-1)
Recovery (%)
Se (IV)
1
0.430  0.003
43
1.5
0.620  0.010
62
2
1.01  0.01
101
2.5
0.98  0.03
98
3
0.91  0.02
91
3.5
0.89  0.01
89
4
0.88  0.02
88
5
6
0.88  0.03
0.88  0.03
88
88
< 0.0002
0
Se (VI)
1-6
178
c) The repeatability of the co-precipitation technique by DBDTC-Pp
Test sample
Se (IV)
(g g-1)
Se (IV)
(g g-1)
1
0.89
0.93
2
0.90
0.92
3
0.96
0.96
4
0.97
0.98
5
Average
Recovery (%)
RSD (%)
0.92
0.93  0.04
93
4
0.95
0.95  0.02
95
3
179
APPENDIX I
a) Results of As and Se inorganic species in river and lake sediments.
RIVER
Elements Concentration
Sites
Sampling
session
As (III)
-1
SGS1
SGS2
SGS3
SGT1
SGT2
SGB1
SGB2
SGB3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
As (V)
-1
Se (IV)
-1
Se (VI)
(g g )
(g g )
(g g )
(g g-1)
1.220.24
0.750.15
1.330.11
0.600.05
1.080.26
0.580.06
2.110.57
1.450.43
1.820.19
0.670.05
1.280.28
0.700.03
1.460.02
2.250.73
2.380.37
0.670.04
NA
1.000.13
0.490.05
0.540.07
0.590.04
1.190.15
0.690.13
1.20.2
13.30.8
11.60.3
14.40.3
29.52.0
27.80.6
22.42.7
33.61.2
24.41.7
33.42.0
7.490.97
13.43.3
9.370.35
12.11.2
11.00.6
11.51.1
6.620.76
NA
8.130.83
6.990.65
6.240.26
8.440.74
20.90.4
26.02.0
14.10.8
0.190.10
0.140.02
0.170.01
0.110.04
0.180.02
0.160.03
0.190.01
0.090.02
0.150.01
0.200.06
0.250.01
0.210.02
0.150.01
0.150.01
0.180.05
0.130.01
NA
0.100.01
0.140.02
0.120.01
0.120.02
0.130.02
0.080.03
0.170.09
0.880.10
1.240.13
1.200.11
0.700.08
0.810.10
0.890.04
0.690.19
0.540.06
0.590.06
1.130.19
1.950.37
0.900.13
0.970.06
1.810.01
1.820.18
0.580.01
NA
0.560.01
1.090.11
0.690.09
0.390.09
0.560.01
0.250.03
0.460.01
180
LAKE
Elements Concentration
Sites
TKRA
TKRB
TKRC
TUPA
TUPB
TBA
TBB
Sampling
session
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
As (III)
As (V)
Se (IV)
Se (VI)
(g g-1)
(g g-1)
(g g-1)
(g g-1)
1.540.12
3.260.10
2.550.10
2.960.73
4.840.90
2.830.30
1.430.15
2.590.10
2.680.34
2.530.18
2.340.15
15.171.00
1.820.27
3.650.57
3.660.12
3.520.78
2.520.29
2.460.10
0.850.19
1.850.25
0.120.02
25.21.0
56.31.4
38.61.2
50.02.1
52.72.6
33.32.5
46.55.6
42.23.6
33.13.7
11.71.1
9.980.51
61.13.5
12.70.7
11.50.8
16.90.7
23.11.6
26.51.4
35.12.5
12.10.9
12.71.1
8.520.70
0.036 0.006
0.0120.001
0.0680.002
0.0730.003
0.0620.014
0.0890.012
0.100.02
0.110.01
0.100.01
0.170.01
0.160.02
0.120.01
0.140.04
0.130.01
0.100.01
0.0450.002
0.0610.034
0.0540.007
0.130.01
0.120.02
0.180.02
0.510.01
0.230.01
0.450.01
0.310.02
0.210.03
0.240.02
0.250.01
0.310.01
0.300.02
0.640.01
0.610.03
0.730.02
0.850.02
0.860.01
0.730.20
0.120.01
0.260.01
0.260.03
0.660.26
0.810.07
0.940.03
181
b) ANOVA : Analysis of arsenic species in river and lake
SUMMARY
Groups
River
Lake
Count
8
7
ANOVA
Source of Variation
Between Groups
Within Groups
SS
0.868738
8.913634
Total
9.782372
Sum
Average
Variance
0.647635
0.080954 0.001849
3.943392
0.563342 1.483448
df
1
13
MS
0.868738
0.685664
F
P-value
F crit
1.267002 0.280682 4.667193
14
c) ANOVA : Analysis of selenium species in river and lake
SUMMARY
Groups
River
Lake
Count
8
7
ANOVA
Source of Variation
SS
Between Groups
0.001099
Within Groups
0.078722
Total
0.079821
Sum
1.639476
1.554642
df
1
13
14
Average
Variance
0.204935 0.004071
0.222092 0.008371
MS
0.001099
0.006056
F
P-value
F crit
0.181485 0.677069 4.667193