LEVELS OF CADMIUM, CHROMIUM AND LEAD IN Clarias
gariepinus (CAT FISH) INHABITING SOME STREAMS OF
BLANTYRE CITY- MALAWI
Dixon Gift Mlelemba, Chemistry Dpt, Chancellor College, P.O. Box 280, Zomba, Malawi
Email: dix.el@hotmail.com
ABSTRACT
Cadmium, Chromium and lead levels in Clarias gariepinus, sediment and pore-water from
Nasolo, Naperi Limbe and Mudi streams were determined. Samples were digested in nitric acid
and absorbance read using atomic absorption spectroscopy. Cadmium concentrations ranged
from below detection limit to 0.061 mg l-1 in pore-water, from 0.102 to 0.945 mg kg-1 in Clarias
gariepinus and from below detection limit to 0.2977 mg kg-1 in sediment. Chromium levels
ranged from below detection limit to 0.258 mg l-1 in pore water, 0.017 to 7.576 mg kg-1 in
sediment and from below detection limit to 0.021 mg kg-1 in Clarias gariepinus. Lead values
ranged from no detection to 0.116 mg l-1 in pore water, 0.089 to 2.580 mg kg-1 in sediment and
from 0.096 to 0.377mg kg-1 in Clarias gariepinus. Based on Pearson’s correlation, pH of pore
water was strongly and negatively correlated to cadmium (-0.848; p = 0.007) and chromium
concentration (-0.971;
p = 0.029) in Clarias gariepinus indicating increased metal
bioavailability at low pH. There was also relatively higher levels of cadmium in Clarias
gariepinus compared to pore water with p<0.05. pH values for sediment were lower than pH
values of pore water in all streams under study. There was a wider range of bioconcentration
factor (BCF) and biota to sediment accumulation factor (BSAF) in the streams studied. BCF for
cadmium was found to be up to 16.67 in Nasolo stream while BSAF was up to 34.33 in Naperi
stream. BCF for chromium of up to 0.021 in Mudi stream and BSAF of up to 0.038 in Naperi
i
stream have been found. BCF and BSAF values indicate high levels of cadmium and low levels
of chromium in Clarias gariepinus. The research has revealed that levels of heavy metals in
Clarias gariepinus are lower than maximum limit levels of World Health organization. In
addition, consumption of Clarias gariepinus (catfish) does not pose health hazard with regard
studied heavy metal contamination.
ii
TABLE OF CONTENTS
ABSTRACT ......................................................................................................................................... i
TABLE OF CONTENTS.......................................................................................................................iii
TOPIC 1 ........................................................................................................................................ 1
INTRODUCTION, LITERATURE REVIEW AND OBJECTIVES ............................................................... 1
1.2 Introduction and literature review ............................................................................... 1
1.2 Objectives ..................................................................................................................... 3
1.2.1 General objective .................................................................................................. 3
1.2.2 Specific objectives ................................................................................................. 3
TIPIC 2 ......................................................................................................................................... 4
METHODS AND MATERIALS ............................................................................................................ 4
2.1 Overview .......................................................................................................................... 4
2.2 Sampling and sample preparation ................................................................................... 4
2.2.1 Determination of heavy metals in Clarias gariepinus ........................................... 4
2.2.2 Determination of heavy metals in pore-water samples ....................................... 5
2.2.3 Determination of heavy metals in sediment ........................................................ 5
2.2.4 Determination of pH in pore-water ...................................................................... 5
2.2.5 Determination of pH in sediment ......................................................................... 6
2.2 Preparation of standard and working solutions .............................................................. 6
2.3.1 Cadmium ............................................................................................................... 6
2.3.2 Chromium .............................................................................................................. 6
2.3.3 Lead ....................................................................................................................... 6
2.4 Data analysis..................................................................................................................... 7
TOPIC 3 ........................................................................................................................................ 8
RESULTS AND DISCUSSION ............................................................................................................. 8
3.1 Cadmium....................................................................................................................... 8
3.2 Chromium ..................................................................................................................... 9
3.3 Lead............................................................................................................................. 10
TOPIC 4 ...................................................................................................................................... 11
CONCLUSION AND WAYFORWARD............................................................................................... 11
REFERENCE ................................................................................................................................ 12
Appendices................................................................................................................................ 15
iii
iv
TOPIC 1
INTRODUCTION, LITERATURE REVIEW AND OBJECTIVES
1.2 Introduction and literature review
Heavy metal is a general term applied to a metal or metalloid, which has atomic density
greater than 4g/cm3 (at least 5 times or more than water). Toxic heavy metals are
persistent environmental contaminants because they can not be degraded or destroyed. To
a small extent, they enter the body system through food, air and water. They bioaccumulate over a period of time because they cannot be metabolized (Lenntech, 2004).
Heavy metal toxicity can lead to damaged or reduced mental and central nervous
functioning, damage of vital internal organs and lowering of energy levels in the body.
There are more than 20 heavy metals but this research looked at cadmium, lead and
chromium. These metals are highly toxic such that they can cause damaging effects even
at low concentrations (Tuberose, 2007). There is great concern of trace metals in foods,
which has prompted several bodies such as World Health Organization [WHO] to
establish maximum allowable concentrations of these metals in food (WHO, 1984).
Problems of heavy metal contamination especially mercury toxicity from fish
consumption has been reported in other parts of the world (Edorh, 2007; Rose et al, 1999;
Piotrowski and Inkship, 1981). Trace metal studies in Nigerian urban fish indicated high
levels of lead and cadmium due to accumulation of these metals from contaminated food
and polluted environment, which poses great health hazard to consumers (Abulude et al,
2007). Other studies investigated bioavailability of heavy metals in tuna fish from the
Red Sea and Persian Gulf. The results from these studies were compared with
international literature values (Waqar, 2001)
Despite comparatively low industrial activities in Blantyre city, the streams are becoming
exposed to unwanted ecological effects of heavy metals due to uncontrolled disposal or
poor management of industrial effluent. Other sources of water pollution are surface
runoffs from domestic and agricultural activities coupled with vehicular emissions into
1
drainage systems. These drainage systems are connected to the city’s streams without
being subjected to pretreatment. Studies have shown that some streams in Blantyre city
are polluted with metal pollutants such as lead, chromium, cadmium and nickel. These
studies revealed further that waste water treatment plants in the city do not significantly
reduce heavy metals in waste water (Sajidu et al, 2007). Water from these treatment
plants is channeled to various streams in the city. Studies on soil samples near major
roads in Blantyre city have shown relatively high concentrations of heavy metals
(Masamba and Chimbalanga, 2001; Lakudzala et al, 1999; Kadewa et al, 2001).
Consequently, these metals are washed into city streams, which lead to more pollution.
Studies from the same area have shown that earthworms can accumulate heavy metals in
their body tissues (Kaonga, 2007).
Heavy metal pollution is a reality in Africa but many nations have not yet conducted
systematic studies to estimate the impact of the phenomenon; detailed surveys on
accumulation of these pollutants in aquatic ecosystems and evaluations of the impact of
heavy metals on the environment and public health is also lacking (Edorh, 2007). A lot of
data about heavy metal pollution has been accumulated on soil and water. Therefore this
research was carried out in view of scarcity of information on bioavailability of heavy
metals in Clarias gariepinus, commonly known as catfish and to find out the effect of
heavy metal pollution on Clarias gariepinus. Marine organisms such as fish accumulate
contaminants from aquatic environment and therefore fish have been used extensively in
monitoring pollution of aquatic environment (Henry et al, 2004).
Levels of cadmium, chromium and lead were determined in sediment and pore-water in
relation to levels of these heavy metals in Clarias gariepinus (cat fish) because Clarias
gariepinus spends most of its time in sediment and pore-water. pH levels were also
determined because metal ions have different solubility at different pH levels and this
affect concentrations of heavy metals. Biomagnification effects such as bioconcentration
factor (BCF) and biota to sediment accumulation factor (BSAF) have been used to relate
pollutant residues in Clarias gariepinus to the pollutant concentration in pore-water. BCF
is the ratio of chemical concentration in an organism to that in surrounding water.
2
Bioconcentration occurs through uptake and retention of a substance from water only,
through gill membranes or other external body surfaces while BSAF occurs through
sediment-mediated exposures and is calculated by concentrations of chemicals in an
organism divided by the concentrations of the same chemicals in sediment.
1.2 Objectives
1.2.1 General objective
The research determined levels of cadmium, chromium and lead in Clarias gariepinus in
relation to levels in sediment and pore-water
1.2.2 Specific objectives
This research was designed to:
(i) Find levels of cadmium, lead and chromium in pore-water, sediment and Clarias
gariepinus.
(ii) Compare concentrations of lead, cadmium and chromium of pore-water to that of
sediment and Clarias gariepinus.
(iii) Compare pH values of pore-water and sediments and find their relationship to
heavy metal concentrations in Clarias gariepinus, pore-water and sediments.
3
TOPIC 2
METHODS AND MATERIALS
2.1
Overview
Samples were collected from Mudi, Nasolo, Naperi and Limbe streams in triplicates.
Two sampling points were identified for each stream to represent upper and down stream.
Fish, water and sediment samples were digested in nitric acid and concentration of heavy
metals was determined using atomic absorption spectrophotometer method (AOAC, 1990
and APHA, 1985). All chemicals and reagents used in this procedure were of analytical
grade (AR). Buck Scientific Atomic Absorption Spectrophotometer Model 200A was
used in this research. Detection limits for each metal on the instrument are: cadmium:
0.005 mg.L-1, chromium: 0.005 mg.L-1 and lead: 0.1000mg.L-1.
2.2
Sampling and sample preparation
2.2.1
Determination of heavy metals in Clarias gariepinus
Clarias gariepinus samples were collected and packed in plastic bags, which were kept in
cooler box. Samples were kept frozen pending analysis. Samples were dried at 105 oC
and blended. 0.5g of the sample was ashed at 550 oC overnight in a muffle furnace.
Ashed samples were then transferred quantitatively to 100ml glass (Pyrex) beaker.
Crucibles used for ashing were washed with 25ml of 20% nitric acid (HNO3) solution as
part of qualitative transferring. The washouts were added to the ashed samples in a
beaker and then warmed in fume hood just up to boiling. The solution was left to cool
and then filtered using gravity into a 50ml volumetric flask and made to the mark with
distilled
water
(AOAC,
1990).
Samples
Spectrophotometer.
4
were
run
on
Atomic
Absorption
Figure1: Sample collecting at Mudi stream (MDI)
2.2.2
Determination of heavy metals in pore-water samples
Pore-water samples were collected in 1-litre plastic bottles. Pore-water was collected
from the points where fish was found. 1ml concentrated nitric acid was added to each
sample. Samples were digested in nitric acid and filtered. The filtrate was diluted to the
mark in 100ml volumetric flask with distilled water (APHA, 1985). Heavy metal
concentrations were determined using Buck Scientific AAS.
2.2.3
Determination of heavy metals in sediment
Sediment samples were collected in plastic bags. Sediment samples were collected from
points where fish was found. Sediment samples were air dried and ground using Ritsch
electric grinder (model: RM 100). Samples were then sieved in 2mm sieve. 10ml of
concentrated nitric acid was added to 2g of the sample and refluxed in a 100ml beaker for
45 minutes, and then evaporated to dryness. 5ml of 3:1 HCl and HNO3 (aqua regia) was
added to dried sample and then filtered (Bamgbose, 2000 cited in Kaonga, 2007). Buck
Scientific AAS was used to determine concentrations of heavy metals.
2.2.4
Determination of pH in pore-water
pH of water samples was measured on the same day of sampling using Metrohm pH
meter model 827, which was calibrated using buffers of pH4 and 7.
5
2.2.5
Determination of pH in sediment
40g of ground and sieved sample was stirred for 30 seconds in every 3 minutes for time
lapse of 15 minutes in 40ml of distilled water to get suspension of sediment in water. The
mixture was allowed to settle for 5 minutes. Then the pH of the supernatant was
measured after calibrating the pH meter using buffers of pH 4 and 7.
2.2 Preparation of standard and working solutions
2.3.1 Cadmium
1.000 g of cadmium metal was dissolved in 20 ml of 1+1 HCl and then diluted to 1000
ml to make 1000 mg l-1 Cd stock solution. An intermediate stock solution of 100 mg. L-1
Cd was made from the stock solution and a series of working standards of the following
concentrations were prepared: 0.0, 0.5, 1.0, 2.0, 3.0, 5.0, 7.0 and 10.0 mg l-1 Cd. The
absorbance was determined on AAS and wavelength set at 228.9 nm.
2.3.2 Chromium
2.828 g of anhydrous potassium dichromate (K2Cr2O7) was dissolved in 200 ml distilled
water and 1.5 ml concentrated HNO3 was added and then diluted to 1000 ml with
distilled water to make 1000 mg l-1 Cr. An intermediate tock solution of 100 mg l-1 Cr
was made from the stock solution and a series of working standards of the following
concentrations were prepared: 0.0, 0.5, 1.0, 2.0, 3.0, 5.0, 7.0 and 10.0 mg l-1 Cr. The
absorbance was determined on AAS and wavelength set at 357.9 nm.
2.3.3 Lead
1.598 g of lead nitrate (Pb(NO3)2) was dissolved in 200 ml distilled water and 1.5 ml
concentrated HNO3 was added and then diluted to
1000 ml to make 1 000 mg l-1 Pb. An
intermediate stock solution of 100 mg l-1 Cr was made from the stock solution and a
series of working standards of the following concentrations were prepared: 0.0, 0.5, 1.0,
6
2.0, 3.0, 5.0, 7.0 and 10.0 mg l-1 Cr. The absorbance was determined on AAS and
wavelength set at 283.7 nm (APHA, 1985).
2.4
Data analysis
The Statistical Package for Social Scientists (SPSS) version 11.0 was used for
correlations. Pearson correlations were used because levels of heavy metals in sediments
and pore-water were assumed to be linearly related to the levels in Clarias gariepinus.
Microsoft excel was used for standard deviation of the mean, t-test, biota to sediment
accumulation factor (BSAF) and Bio-accumulation factor (BCF). Graphs were plotted
using Microsoft Excel. Independent sample t-test was used because of an assumption that
sampling points are independent of each other.
7
TOPIC 3
RESULTS AND DISCUSSION
3.1
Cadmium
The range of cadmium concentration in pore-water ranged from no detection to 0.061 mg
l-1 and from 0.102 mg kg-1 to 0.945 mg kg-1 in Clarias gariepinus. Maximum allowable
concentration of lead in fish is 0.0002 mg kg-1 (USEPA, 1987) and the results indicate
exceeding levels. Based on Pearson’s correlation, there was significant negative
correlation between the pH of pore-water and cadmium concentration in biota (-0.848; p
= 0.007). The results indicate increased metal bioavailability in Clarias gariepinus at low
pH. This means that more of the metal will be in solution form at low pH resulting in
increased metal uptake by Clarias gariepinus. Clarias gariepinus indicated significantly
higher levels of cadmium than pore-water (p<0.05). This explains bioaccumulation of
cadmium in Clarias gariepinus over a long period as shown by high ratios of BCF and
BSAF. BCF for cadmium was found to be up to 16.67 in Nasolo stream while BSAF was
up to 34.33 in Naperi stream.
Cadmium levels
1
0.9
0.8
Concentration (mg/L or mg/Kg)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Nasolo (BNC)
Nasolo (SRN)
Naperi
(Rainbow )
Naperi (Moi
Rd)
Limbe
(Mpingw e)
Sampling point
Figure 2
8
Limbe (High
Way)
Mudi (MDI)
Mudi (SRN)
Pore-water
Sediment
Clarias gariepinus
3.2
Chromium
Concentration of chromium in pore-water ranged from no detection to 0.258 mg l-1,
0.0167 mg kg-1 to 7.6367 mg l-1 in sediment and no detection to 0.021 mg k-1 in Clarias
gariepinus. Levels of chromium in Clarias gariepinus were far below maximum
allowable limit of 0.008 mg kg-1 (USEPA, 1987). There was significant negative
correlation between amount of chromium in pore-water and pH of pore-water (-0.971; p
= 0.029). Low pH of pore water result in increased amount of the metal in pore water.
This phenomenon explains why there was significant correlation between the level of
chromium in Clarias gariepinus and pH of pore water (-0.935; p = 0.020). At low pH,
more of the metal will be in solution form resulting in increased metal bioavailability in
Clarias gariepinus at low pH. Level of chromium in sediment was significantly higher
than the level in pore-water because p<0.05. Levels of chromium were high in sediments
and little traces in Clarias gariepinus. This could suggest that more of chromium was in
precipitated and settled in sediments.
Chromium levels
8
7.5
7
Conentration (mg/L or mg/Kg)
6.5
6
5.5
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Nasolo
(BNC)
Nasolo
(SRN)
Naperi
(Rainbow)
Naperi (Moi
Rd)
Limbe
(Mpingwe)
Stream
Figure 3
9
Limbe (High
Way)
Mudi (MDI)
Mudi (SRN)
Pore-water
Sediment
Clarias gariepinus
3.3
Lead
Lead concentrations ranged from below detection limit to 0.1157 mg l-1 in pore-water,
0.089 mg l-1
to 2.580 mg kg-1 in sediment and 0.096 mg kg-1 to 0.3767 mg kg-1 in
Clarias gariepinus. Lead concentration in Clarias gariepinus was less than WHO limit of
0.004 mg kg-1 (USEPA, 1987). The results showed that sediment concentration was
significantly higher than pore-water concentration (p<0.05). There was a significant
correlation between levels of lead in sediment and pH of sediment (-0.856, p = 0.007).
This means that lead precipitated more at low pH and become part of solid in the
sediment. This agrees with what other studies have found that reduced sorption efficiency
of lead ion removal with a decrease in pH could be attributed to the presence of H+ ions
in the mixture, which compete with lead ions for the binding sites (Mataka et al, 2007).
Lead levels
3
Concentration (mg/L or Mg/Kg)
2.5
2
1.5
1
0.5
0
Nasolo (BNC)
Nasolo (SRN)
Naperi
(Rainbow)
Naperi (Moi Rd)
Limbe
(Mpingwe)
Limbe (High
Way)
Mudi (MDI)
Mudi (SRN)
Stream
Pore-water
Sediment
Clarias gariepinus
Figure 4
10
TOPIC 4
CONCLUSION AND WAYFORWARD
The research generally found out that concentrations of heavy metals in Clarias
gariepinus are above allowable limits set by United State Environmental Protection
Agency (USEPA) and have been adopted by many countries. Generally, cadmium
showed the following trend in concentrations: Clarias gariepinus >sediment>pore-water,
while chromium showed a different trend: sediment>pore-water> Clarias gariepinus and
for lead: sediment> Clarias gariepinus >pore-water. There is no clear pattern of heavy
metal accumulation in parameters studied. pH levels of pore-water were found to be
higher than pH levels of sediments in all streams under study. The research therefore has
generated data that can be used for assessment of effects of heavy metal pollution on
Clarias gariepinus.
However, this study did not look into contribution of organic matter and wet season
samples. Only three toxic metals were studied and there is a gap that should be filled in
by future researchers. Frakas argued that levels of heavy metals in water bodies and fish
are a result of uptake and release processes with characteristic kinetics for elements in
their biological half life time, which are also influenced by the age of fish, feeding habits
and by season (Frakas et al, 2000). It is therefore important to look at other types of fish
and different age groups or other living organisms which have not yet been studied and
compare the findings with data that is already available. There is also need to carry out
further studies at microscopic level to determine variations in heavy metal accumulation
and distribution in different organs of Clarias gariepinus.
11
REFERENCE
Abulude, F. O., Obidiran, G. O., Elemide, O. A., and Abidakun, B., (2007). “Trace
metals distribution in Nigerian urban fishes”. Electronic Journal of Environment,
Agriculture and Food Chemistry, Vol. 6, (11), December Issue: 2512-2516. Available
online at <http://www.ejeafche.uvigo.com>
American Public Health Association, American Water Works Association and Water
pollution Control Federation, 1985. Standard Methods of examination of
Water/wastewater, 16th ed., APHA, AWWA and WPCF, New York: 150-152.
Association of Official Analytical Chemists, AOAC, (1990). Official methods of
analysis, 15th Ed. Washington DC.
Becker, E. W., (1983). Handbook of microalgal Mass Culture.
Edorh, P., (2007). “Heavy metal action”. TWAS newsletter, volume 19: 2. Available
online at <http://www.ictp.trieste.it/~twas/pdf
Farkas, A., Salanki, J and Varanka, I., (2000). “Heavy metal concentrations in fish of lake
Balaton”. Lakes and Reservoirs: Research and Management 2000: 271 – 279.
Förstner, U. and Prosi, (1979). Heavy metal pollution in freshwater ecosystems.
Biological Aspects of Freshwater Pollution (De. O. Ravera). Pergamon Press, New
York: 129-161.
Holum, J. R., (1983). Elements of general and biological chemistry, 6th Ed., John Wiley
and sons, New York: 324-326.
Kaonga,C.C, (2007). Levels of selected heavy metals and related physoco-chemical
parameters of algae, earthworms, soil and water in Blantyre city, Malawi: 42-57.
12
Khrishnakumar, P. K., (1994). “Effects of environmental contaminants on the health of
mytilus edulus”. Marine ecology series, number 106: 249-261.
Lenntech Water Treatment and Air Purification, (2004). “water treatment”. Lenntech,
Rotterdamseweg, Netherlands.
Masamba, W. R. L., Chimbalanga, R.M., (2001). “Heavy metal pollution in the city of
Blantyre, Malawi: lead, zinc and cadmium”. Proceedings of the first Chancellor
College Research Dissemination Conference. University of Malawi, Chancellor
College, Zomba: 315-332.
Mataka L.M., Masamba W.R.L., Henry E.M.T, and Sajidu S.M.I., (2007). Cadmium
removal from aqueous solutions using Moringa stenopetala and Moringa oleifera seed
powders:11
Ogwuegbu, M. O. and Ijioma, M. A., (2003). “Effects of certain heavy metals on the
population due to mineral exploitation”. Proceedings of International Conference on
Scientific and Environmental Issues In the Population, Environment and Sustainable
Development in Nigeria, University of Ado, Ekiti State, Nigeria: 8-10.
Piotrowski, J. K., and Inkship, M. J., (1985). “Review of Health Effects of
Methylmercury”. Journal of Applied Toxicology, Volume 5: 113-133.
Rose, J., Hutcheson, M. S., West, C. R., and Pancorbo, O., (1999). “Fish Mercury
Distribution in Massachusetts, USA Lakes”. Environmental Toxicology and
Chemistry, Vol. 18 (7): 1370-1379.
Sajidu, S.M.I., Masamba, W. R. L., Henry, E. M. T., Kuyeli, S. M., (2007). “Water
quality assessment in streams and waste water treatment plants of Blantyre, Malawi”.
13
Journal of Physics and Chemistry of the Earth, 07: 045. Available online at
<http://www.sciencedirect.com>
Tuberose,
(2007).
“Information
for
transformation”
Available
online
<http://www.tuberose.com/Heavy_Metal_Toxicity.html>
World Health Organization (W.H.O.), (1984). “Guide lines for drinking water quality.”
Health criteria and other supporting information, General. Vol.
14
at
Appendices
Appendix 1: Correlation Table
pH
pore-water
pH
pore-water
P Corr
Signf
n
pH
sediment
P Corr
Signf
n
Cadmium
sediment
Lead
Clarias
gariepinus(fish)
Chromium
sediment
Chromium
Clarias
gariepinus(fish)
Chromium
Pore-water
-0.84819
-0.02608
0.035834
0.072296
-0.32777
-0.93477
-0.97051
0.490372
0.50947
0.303829
0.007781
0.951129
0.946272
0.864917
0.428024
0.019802
0.02949
8
8
6
7
8
8
6
8
8
5
4
-0.2872
1
-0.54939
0.716816
0.076133
-0.85538
0.486315
-0.18314
-0.40601
-0.21539
0.015536
0.258825
0.069879
0.8578
0.006765
0.328035
0.664222
0.318259
0.72789
0.984464
6
7
8
8
6
8
8
5
4
0.490372
8
,
8
-0.54939
0.258825
-0.5737
0.465272
0.614895
0.619209
0.179443
0.938908
0.633387
0.438555
0.311865
0.352452
0.193903
0.380791
0.733725
0.005484
0.563329
0.710981
6
6
6
5
6
6
4
6
6
3
3
P Corr
-0.45596
0.716816
-0.5737
1
0.044218
-0.48858
-0.01586
-0.03016
-0.33586
0.305405
0.678704
Signf
0.303829
0.069879
0.311865
0.925006
0.265909
0.979812
0.948814
0.461438
0.617279
0.525084
7
7
5
7
7
7
5
7
7
5
3
P Corr
-0.84819
0.076133
0.465272
0.044218
1
0.070267
0.052046
0.035697
0.484524
0.904301
0.575223
Signf
0.007781
0.8578
0.352452
0.925006
0.868682
0.922002
0.933125
0.223689
0.035024
0.424777
1
,
,
,
8
8
6
7
8
8
6
8
8
5
4
P Corr
-0.02608
-0.85538
0.614895
-0.48858
0.070267
1
-0.86681
0.227013
0.389365
0.555042
0.61008
Signf
0.951129
0.006765
0.193903
0.265909
0.868682
0.025427
0.588749
0.340371
0.33148
0.38992
8
8
6
7
8
6
8
8
5
4
P Corr
0.035834
0.486315
0.619209
-0.01586
0.052046
-0.86681
Signf
0.946272
0.328035
0.380791
0.979812
0.922002
0.025427
6
6
4
5
6
6
P Corr
0.072296
-0.18314
0.179443
-0.03016
0.035697
Signf
0.864917
0.664222
0.733725
0.948814
8
8
6
7
n
Lead fish
Lead
Pore-water
-0.45596
0.50947
n
Lead
Pore-water
Lead
sediment
-0.34014
-0.34014
n
Lead
sediment
,
Cadmium
Clarias
gariepinus(fish)
Cadmium
Pore-water
-0.2872
Signf
n
Cadmium fish
1
Cadmium
sediment
P Corr
n
Cadmium
Pore-water
pH
sediment
n
,
8
-0.33141
0.475576
-0.32349
-0.70492
0.521081
0.340417
0.676512
0.501964
6
6
6
4
3
0.227013
-0.33141
1
0.520802
-0.0912
0.723638
0.933125
0.588749
0.521081
0.185703
0.884045
0.276362
8
8
6
8
5
4
15
1
,
,
8
Appendix 1: (continued)
Correlation Table
pH
pore-water
Chromium
sediment
P Corr
Cadmium
Clarias
gariepinus
Cadmium
Pore-water
Lead
sediment
Lead
Clarias
gariepinus
Lead
Pore-water
Chromium
sediment
Chromium
Clarias
gariepinus
Chromium
Pore-water
-0.40601
0.938908
-0.33586
0.484524
0.389365
0.475576
0.520802
1
0.578646
0.474685
8
8
6
7
8
8
6
8
8
5
4
P Corr
-0.93477
-0.21539
0.633387
0.305405
0.904301
0.555042
-0.32349
-0.0912
0.578646
1
1
Signf
0.019802
0.72789
0.563329
0.617279
0.035024
0.33148
0.676512
0.884045
0.306722
n
Chromium
fish
Cadmium
sediment
-0.32777
n
Chromium
Pore-water
pH
sediment
,
,
5
5
3
5
5
5
4
5
5
5
2
P Corr
-0.97051
0.015536
0.438555
0.678704
0.575223
0.61008
-0.70492
0.723638
0.474685
1
1
Signf
0.02949
0.984464
0.710981
0.525084
0.424777
0.38992
0.501964
0.276362
0.525315
4
4
3
3
4
4
3
4
4
n
16
,
,
2
4
Appendix 2: Cadmium levels
Pore-water
Sediment
Fish
*BCF
**BSAF
Sampling point
(mg l-1)
pH
(mg kg-1)
pH
(mg kg-1)
Nasolo (BNC)
0.039 ±0.0032
7.610 ±0.095
ND
6.643 ±0.006
0.327 ±0.231
8.44
-
Nasolo (SRN)
0.057 ±0.001
6.457 ±0.006
0.103 ±0.005
6.977 ±0.006
0.945 ±0.006
16.67
9.17
Naperi (Rainbow)
0.061 ±0.001
7.333 ±0.005
0.012 ±0.000
6.780 ±0.053
0.102 ±0.001
1.67
8.53
Naperi (Moi Rd)
ND
7.350 ±0.000
0.009 ±0.001
6.597 ±0.015
0.319±0.001
-
34.33
Limbe (Mpingwe)
0.043 ±0.001
7.607 ±0.012
ND
6.887 ±0.023
0.264 ±0.000
6.18
-
Limbe (High Way)
0.054 ±0.004
7.577 ±0.006
0.016 ±0.001
6.730 ±0.027
0.298 ±0.003
5.48
18.96
Mudi (MDI)
0.033 ±0.002
7.637 ±0.006
0.092 ±0.001
6.040 ±0.017
0.377 ±0.031
11.42
4.11
Mudi (SRN)
0.040 ±0.002
7.093 ±0.006
0.298 ±0.001
6.153 ±0.055
0.544 ±0.061
13.70
1.83
* BCF = Bioconcentration factor
**BSAF = Biota to sediment accumulation factor
17
Appendix3: Lead levels
Pore-water
Sediment
Fish
BCF
BSAF
Sampling point
(mg l-1)
pH
(mg kg-1)
pH
(mg kg-1)
Nasolo (BNC)
0.039 ±0.003
7.610 ±0.095
ND
6.643 ±0.006
0.327 ±0.231
8.44
-
Nasolo (SRN)
0.057 ±0.001
6.457 ±0.006
0.103 ±0.005
6.977 ±0.006
0.945 ±0.006
16.67
9.17
Naperi (Rainbow)
0.061 ±0.001
7.333 ±0.006
0.012 ±0.000
6.780 ±0.053
0.102 ±0.001
1.67
8.53
Naperi (Moi Rd)
ND
7.350 ±0.000
0.009 ±0.001
6.597 ±0.015
0.319 ±0.001
-
34.33
Limbe (Mpingwe)
0.043 ±0.001
7.607 ±0.012
ND
6.887 ±0.023
0.264 ±0.000
6.18
-
Limbe (High Way)
0.054 ±0.004
7.577 ±0.006
0.016 ±0.001
6.730 ±0.021
0.298 ±0.003
5.48
18.96
Mudi (MDI)
0.033 ±0.002
7.637 ±0.006
0.092 ±0.001
6.040 ±0.017
0.377 ±0.031
11.42
4.11
Mudi (SRN)
0.040 ±0.002
7.093 ±0.006
0.298 ±0.001
6.153 ±0.055
0.544 ±0.061
13.70
1.83
18
Appendix 4: Chromium levels
Pore-water
Sediment
Fish
BCF
BSAF
Sampling point
(mg l-1)
pH
(mg kg-1)
pH
(mg kg-1)
Nasolo (BNC)
0.039 ±0.003
7.610 ±0.095
ND
6.643 ±0.006
0.3267 ±0.231
8.44
-
Nasolo (SRN)
0.057 ±0.001
6.457 ±0.006
0.103 ±0.005
6.977 ±0.006
0.945 ±0.006
16.67
9.17
Naperi (Rainbow)
0.061 ±0.001
7.333 ±0.006
0.012 ±0.000
6.780 ±0.051
0.102 ±0.001
1.67
8.53
Naperi (Moi Rd)
ND
7.350 ±0.000
0.009 ±0.001
6.597 ±0.015
0.319 ±0.001
-
34.33
Limbe (Mpingwe)
0.042 ±0.001
7.607 ±0.012
ND
6.887 ±0.023
0.264 ±0.000
6.18
-
Limbe (High Way)
0.054 ±0.004
7.577 ±0.006
0.016 ±0.001
6.730 ±0.027
0.298 ±0.003
5.48
18.96
Mudi (MDI)
0.033 ±0.002
7.637 ±0.006
0.092 ±0.001
6.040 ±0.0173
0.377 ±0.031
11.42
4.11
Mudi (SRN)
0.040 ±0.002
7.093 ±0.006
0.298 ±0.001
6.153 ±0.0551
0.544 ±0.061
13.70
1.83
19
18