Research Journal of Environmental and Earth Sciences 4(11): 939-944, 2012
ISSN: 2041-0492
© Maxwell Scientific Organization, 2012
Submitted: June 15, 2012
Accepted: July 28, 2012
Published: November 20, 2012
Examination of Some Pesticide Residues in Surface Water, Sediment and Fish Tissue of
Elechi Creek, Niger Delta, Nigeria
1
F. Upadhi and 1O.A.F. Wokoma
1
Department of Biology, Faculty of Natural and Applied Science, Rivers State University of Education,
Rumuolumini, P.M.B. 5047, Port Harcourt, Rivers State, Nigeria
Abstract: An investigation into the levels of selected pesticides in surface waters, sediment and fish (Mudskipper)
in the Elechi creek was carried out in two seasons and at three pre-determined sites. A higher concentration of 2, 4diamine was observed in all stations and matrixes, while propoxur was least observed. Pesticide concentration in
sediment is significantly different from that of water and fish tissue, which had the highest residual concentration.
Concentration of pesticides ranged from 0.01 to 0.04 µg/L in water, 0.01 to 0.06 µg/gdw in sediment and 0.01 to
0.07 µg/gdw in fish, respectively. There was bioaccumulation of pesticides in fish samples. Observed residues are
generally higher than stipulated limit of 0.01 µg/L by USEPA for pesticides of aquatic life, therefore, possess an
ecological risk to the ecosystem and consequently human health.
Keywords: 2, 4-diamine, bioaccumulation, endosulfan, lindane, pesticides, propuxor
Pesticides use has increased worldwide,
particularly in its use to salvage the food supply to the
ever increasing global population. Although it is
undisputed that pesticides are essential in modern
agriculture. There is growing concern about possible
environmental contamination from agrochemicals,
industries and household and rain water runoff from
agricultural systems, disposal of outdated stocks,
containers and packets and discharge of waste from
industries (Domagalski and Kuivila, 1993; Thurman
et al., 2000; Satya et al., 1995). These compounds when
discharged into aquatic system play an important role in
contaminating such systems. Atmospheric transport
also represents an important source of pesticides
residue accumulation in water bodies (Schmiit and
Linder, 1990). It has been recognized that the persistent
and bioaccumulation tendency of these substances, their
metabolites and residues in the environment make them
not only remain where they are applied but instead
partition
between
the
major
environmental
compartments in accordance with their physic-chemical
properties and may thereby become transported several
kilometers from the point of their original release
(Agarwal, 2009). Such environmental distribution may
lead to exposure of living organisms including man that
are far removed from intended targets. Researchers
have detected pesticides residues in heptachlor,
endosulfane, Aldine, DDT and PCBs. Many of these
pesticides have also been detected in sediment, aquatic
plants and fish (Osibanjo et al., 1994).
INTRODUCTION
Rapid population growth coupled with Urban and
coastal developments in many parts of the world have
generated global concern. There is the fear that
anthropological population would reduce biodiversity
and productivity of marine food resources. Studies have
shown that human populations that consume large
amount of marine food have higher levels of Persistent
Organic Pollutants (POPs) such as Polychlorinated
Biphenyls (PCBs) and some heavy metals.
There has been a focus on the effect of people who
consume large amount of marine food, including
products of marine fish (Bjorn, 2003). In addition,
natural environment are important for recreation and
tourism, human and socio-economic interest. There is
also increased awareness that nature has its own
intrinsic value of the same marine and estuarine
environments, whether the pollution is visual (such as
oil pollution and plastic) or invisible (as in the case of
chemical) (Bjorn, 2003). Another main reason for
concern about pollution in the marine environments
(organisms) is that human beings are directly or
indirectly exposed to these pollutants, when they
consume food from polluted areas.
The toxicity of pesticides to target and non-target
organisms generally depends on the amount present in
the environment, the proportion available to the biota
and ultimately in the amount actually encountered and
absorbed by the organism (Mark et al., 1996).
Corresponding Author: O.A.F. Wokoma, Department of Biology, Faculty of Natural and Applied Science, Rivers State
University of Education, Rumuolumini, P.M.B. 5047, Port Harcourt, Rivers State, Nigeria
939
Res. J. Environ. Earth Sci., 4(11): 939-944, 2012
Osibanjo and Jensen (1980) have estimated the
contamination of certain pesticides residues in some
fish specimen brought from road side market in Nigeria
as well as those caught from an uncontaminated pond at
the International Institute of Tropical Agriculture
(IITA) Ibadan, Heterobanchus sp. and Clarias sp., were
shown to contain lindane residues 35.2 and 12.7 µg/g
fat weight which were above World Health
Organization (WHO) acceptable daily intake. There is
evidence of bioaccumulation of pesticides in higher
tropic levels with possible deleterious effects, but also
an indication that human beings are at risk with these
pesticides through fish consumption (Giddings et al.,
2000).
Muskipper (Periophtalmus) contains a great
number of species, they are distributed in all tropical
sea coasts and one species (P. papilio) are well
distributed in West Africa. Arm -like elongated pectoral
fins with which they move along a dry surface
distinguishes them from other fish species (Nilkolsky,
1963). Mudskipper inhabits the intertidal zone of the
marine/ mangrove ecosystem district which is subject to
the influence of the sea and tides as well as in flowing
fresh water. They are commonly found in the coastlines
of the Niger Delta (including the Elechi creek) where
they are a highly sought after fish protein. This
underscores the need to ascertain their pesticide loading
so as to safeguard human life.
Three sampling stations were established along the
creek, at the Timber Market, Kidney Island and Custom
Security post (near Nigerian Port Authority-NPA).
These sampling stations were chosen based on
ecological settings and human activities in the area.
Sampling was done in both dry (February-March) and
wet (May-June) seasons in 2009. A total of 36 samples
were collected and four parameters were analyzed in
water, sediment and fish tissue.
Sediment samples were taken with a van veen
sampler. Composite samples were pooled from five sub
samples (0-10 cm), of a 10-m2 area, homogenized and
wrapped in aluminum foil. Samples were immediately
stored in ice (<6 h) after collection and stored at -20ºC
in the laboratory until solid phase extraction (Thomas,
2007).
Fish samples, Mudskipper (Periophtalmussp) were
caught by using fishing gears that are used by
fishermen in the area (cast nets, gill net). The cast net
were constructed traditionally by the local fishermen
with 25×25 mm pieces of lead (approximately 25 g)
attached at less than 1m intervals round the three ends
(circumference of the net). Fish caught from each
sampling stations were kept together in labeled plastic
bags and transferred to the laboratory. In the laboratory,
samples were dried in the oven for <3 days at
temperature of about 100ºC, homogenized and wrapped
in dried labeled plastic bags and kept in the refrigerator
prior to analysis (APHA, 1989).
Water samples were taken from 0.3 m below the
surface with a pre-cleaned glass bottle using hydro bins
sampler. For sampling, turbulent midstream positions of
water bodies were chosen to approximate mean
concentration of river water. All foreign bodies were
removed and the samples thoroughly homogenized.
After collection, water samples were stored in ice
during transport (<6 h) and were kept at 4ºC in the
laboratory until solid phase extraction.
MATERIALS AND METHODS
The study area Elechi creek (in Port Harcourt,
Rivers State Nigeria) is a mangrove intertidal wetland
within the upper reaches of the Bonny river system,
adjoining a populated municipal environment. The
creek is characterized by high sea flow and low fresh
water input from adjoining swamp forest and municipal
sewers within Diobu area of Port Harcourt (Davies
et al., 2006). The creek is located between latitude 4º
151 to 4º 501 N and 6º 501 E. The vegetation of the area
is predominantly mangrove and fresh water swamps
with sparse occurrence of Nypa palm and other coastal
vegetation. The tidal amplitude is between 1.5 to 2 m in
normal tide and water level increases and decreases
depending on the lunar cycle (Ogamba, 2003).
The bulk of the intertidal area is predominantly
mangrove vegetation namely:
•
•
•
•
Sample extraction: The procedure applied for the
extraction of pesticides was similar to those reported by
Laabs et al. (1999) and Steinwandter (1990).
Water samples were extracted using ultrasonic
extraction. Sox let extraction was done with 20 mL of
hexane: dichloromethane (3:1) for 30 min. The extract
was concentrated with the aid of rotator evaporator.
Pre-elution was carried out with the HPLC methanol.
The concentration solvent extract was then analyzed for
pesticides.
Sediment samples were homogenized and dried
with anhydrous sodium sulphates. A sub- sample of the
sediment (10-20 g) was weighed into a clean extraction
bottle. Pesticides were extracted by ultrasonic
extraction using a mixture of dichloromethane and nhexane in a ratio 2:3, having been subjected to a
vigorous shaking in a sonication bath for 5 h. The
Avicennia africana
Rhizophoraracemosa
R. mangle
Nypafruticans
The area receives municipal effluents (>1,500
metric ton/day), solid waste (3,500 kg/day), oily waste
from average (150 L/day) in addition to other
discharges from sawmills and abattoir (Ogamba, 1998).
940
Res. J. Environ. Earth Sci., 4(11): 939-944, 2012
solvent was separated and concentrated with a rotator
evaporator. Pre-elution was carried out with HPLC
methanol. The concentration extract was then analyzed
for pesticides.
One gram of dried tissue was weighted into a clean
extraction bottle. Pesticides were extracted using
acetone, water and dichloromethane, having been
subjected to vigorous shaking in a silication bath for
5 h. The solvent was separated and concentrated in
rotator evaporator and eluted using HPLC methanol and
analyzed
using
high
performance
liquid
chromatography.
The solvent of the mobile phase of the HPLC is
methanol and water (1:1). This was prepared by
measuring 250 mL of HPLC grade methanol into a 500
mL flask and made up with 250 mL of distilled water.
The HPLC model CECIL 1010 was switched on. The
wavelength of the system was determined by using UV
visible equipment. Little quantity of the stock solution
was diluted with methanol and its wavelength
determined by scanning. A peak of 202 nm was
reached. The system wavelength was then set at 202 nm
and the sensitivity of the 0.05 nm of the UV detector
component set. The flow rate was set at 1 mL/min,
afterwards, the purging of the system commenced by
allowing the system to run for some time. The purging
was carried out through a washing solution of 30%
methanol, 70% water. Bubbling helium gas into the
solution carried out degassing of the mobile phase was
then set up and connected with HPLC system and
allowed to run through the system of 20 min.
Each sample residues was dissolved in 1 mL
methanol. The extracted residues was then loaded and
injected into the valve of the chromatography system.
The resulting chromatograph for each sample was
printed out. The various retentions time noted,
concentration determined and recorded.
RESULTS
Data analysis: The data were analyzed separately for
each station using descriptive analysis (mean, range).
The Duncan’s Multiple Ranges (DMR), F-test was used
to test for the level of significance at 0.05 level of
probability for the stations and season.
Water sample: Twelve water samples were collected
and analyzed, the result indicated that there was lower
concentrations of pesticides residues in water samples
(Table 1) than in sediment and fish samples. Higher
concentrations of pesticides were recorded in the wet
season than in dry season for water samples. No
diamine residue was recorded in water samples,
propoxur concentrations was highest in water samples
than in sediment and fish samples. Station 2 had the
highest concentration of pesticides residues for water
samples. The order of pesticides concentration in water
samples is 2, 4-diamine>paraquat>propoxur>lindane.
Sediment sample: Twelve sediment samples were
equally collected and analyzed for various pesticides
residues examined in this study, the result observed that
higher pesticides residues were found in sediment
samples than in water samples with 2, 4-diamine having
higher concentration, whilst lindane has the least
residue concentration (Table 2). Higher pesticides
residue concentrations were recorded in the wet
Table 1: Seasonal (mean) concentration of pesticides in surface waters (µg/L) in elechi creek
2, 4-diamine
Diazinun
Paraquat
Endosulfan
Pesticides
----------------------------------------------------------------------------------------------------stations
1
2
3
1
2
3
1
2
3
1
2
3
Wet season
0.03
0.05
0.04
ND
ND
ND
0.01
ND
ND
0.01
ND
ND
mean
Dry season
0.02
0.02
0.03
ND
ND
ND
ND
0.01
ND
ND
ND
ND
mean
Average
0.02
0.04
0.04
ND
ND
ND
0.01
0.01
ND
0.01
ND
ND
mean
Standard
0.01
0.01
0.00
deviation
Range
0.01
0.01
0.03
0.05
Table 2: Seasonal (Mean) concentration of pesticides residues in elechi creek sediment (µg/gdw)
2, 4-diamine
Diazinun
Paraquat
Endosulfan
Pesticides
-----------------------------------------------------------------------------------------------------Stations
1
2
3
1
2
3
1
2
3
1
2
3
Dry season ND
0.01
0.01
ND
ND
0.02
ND
ND
ND
0.01
ND
ND
mean
Wet season ND
0.03
0.02
ND
0.03
ND
ND
ND
0.01
ND
0.01
ND
mean
Average
ND
0.02
0.02
ND
0.03
0.02
ND
ND
0.01
ND
0.01
ND
mean
Standard
0.01
0.01
deviation
Range
0.01
0.01
0.03
0.02
941
Lindane
-------------------------1
2
3
ND
ND
ND
Propoxur
-----------------------1
2
3
ND
ND ND
ND
0.01
ND
0.01
0.01
ND
ND
0.01
ND
0.01
0.01
ND
Lindane
-------------------------1
2
3
ND
ND
ND
Propoxur
-----------------------1
2
3
ND
ND ND
0.03
ND
ND
0.06
ND
ND
0.03
ND
ND
0.06
ND
ND
Res. J. Environ. Earth Sci., 4(11): 939-944, 2012
Table 3: Seasonal (Mean) concentration of pesticides residues in elechi creek fish tissue (µg/gdw)
2, 4-diamine
Diazinun
Paraquat
Endosulfan
Pesticides
------------------------ ----------------------- ---------------------- -------------------Stations
1
2
3
1
2
3
1
2
3
1
2
3
Dry season
ND
0.05 ND 0.05 ND 0.04 ND ND
ND
ND ND ND
mean
Wet season
0.07 0.03 ND 0.02 ND ND ND ND
0.03 0.03 ND ND
mean
Average mean
0.07 0.04 ND 0.03 ND 0.04 ND ND
0.03 0.03 ND ND
Standard
0.01
0.01
deviation
Table 4: Bioaccumulation of pesticide in fish tissue across sampling stations in elechi creek
Station 1
Station 2
------------------------------------------------------------------------------------------Sediment
Fish
BAF in
Sediment
Fish
BAF in
Pesiticides
µg/gdw
µg/gdw
fish
µg/gdw
µg/gdw
fish
2, 4-diamine
ND
0.07
0.02
0.04
0.02
Diazinon
ND
0.03
0.03
ND
Paraquat
ND
ND
ND
ND
Endosulfan
ND
0.03
0.01
ND
Lindane
0.03
0.03
1.00
ND
0.02
Propoxur
0.06
0.01
0.16
ND
0.03
season than in the dry season for sediment samples. The
order of pesticides concentration in sediment is 2, 4diamine>paraquat>endosulfan>lindane> propoxur.
Twelve fish samples were collected and analyzed,
the result showed high concentration of pesticides in
fish samples than in water samples with 2, 4-diamine
having the highest concentration whilst paraquat and
endosulfan had the least residue concentrations
(Table 3). Pesticides mean concentration in fish
samples was highest during wet season than dry season.
2, 4-diamine, diazinon, paraquat, endosulfan, lindane
and propoxur bio accumulated in fish samples.
Bioaccumulations of pesticides in fish from
designated stations of Elechi Creek are shown in
Table 4. Bio Accumulation Factor (BAF) is expressed
as the ratio of the contaminant in an organism to the
concentration in the ambient environment at a steady
state, where the organism can take in the contaminant
through ingestion with its food as well as through
content (USEPA, 2010b). The pesticides (2, 4-diamine,
diazinon, paraquat, endosulfan, lindane and propoxur)
bio accumulated in mudskipper and the levels of
bioaccumulations of residual concentration was in the
following
order;
paraquat>endosulfan>2,
4diamine>diazinon>propoxur>lindane.
Lindane
------------------------1
2
3
0.03
0.02 ND
Propoxur
--------------------1
2
3
ND 0.03 ND
ND
ND
0.01 0.01
ND
ND
0.03
0.02
0.01 0.01
0.03
ND
Station 3
-----------------------------------------------Sediment
Fish
BAF in
µg/gdw
µg/gdw
fish
0.02
ND
0.02
0.04
2.00
0.01
0.03
ND
ND
ND
0.01
µg/gdw for stations 3 at F = 0, paraquat mean
concentration was 0.01 µg/gdw for station 3 at F = 0,
endosulfan mean concentrations was 0.01 µg/gdw for
station 2 at F = 0, lindane mean concentration was 0.03
µg/gdw for station 3 at F = 0, while propuxur mean
concentration was 0.06 µg/gdw for station 1 at F = 0.
High concentrations of pesticides residues in this study
conform with the findings of Ezemonye (2005) who
said that sediment are known to act as a sink for
pollutants and therefore have the tendency of
accumulating pesticides.
The mean concentrations of pesticides in fish
samples were 0.07 and 0.04 µg/gdw for 2, 4-diamine in
stations 1 and 2 at F = 0.27, diazinon mean
concentration was 0.03 µg/gdw for station 1 at F = 8.33,
paraquat mean concentration was 0.03 µg/gdw for
station 3 at F = 0, endosulfan mean concentration was
0.03 for station 3 at F = 0, lindane concentrations were
0.03, 0.02 and 0.01 µg/gdw for stations 1, 2 and 3 at
F = 3.00, while propoxur mean concentrations were
0.01 and 0.03 µg/gdw for stations 1 and 2 at F = 0.
High concentration of pesticides in fish samples agree
with Charles et al. (2000) discovery that fish are mobile
so may have been exposed to compounds in other parts
of the hydrologic system, secondly, rate of residue
accumulation and bioaccumulation in fish increases
with temperature, Kidwell et al. (1990) equally added
that accumulation in fish was due to lipid content.
Mean concentrations of pesticides residues in water
samples were; 0.02, 0.04 and 0.04 µg/L for 2, 4diamine in stations 1, 2 and 3 at F = 10.81, paraquat
mean concentrations were 0.01 and 0.01 µg/L for
stations 1 and 2 at F = 0, endosulfan mean
concentration was 0.01 µg/L for station 1 at F = 0,
lindane mean concentration was 0.01 µg/L for station 1
DISCUSSION
The study recorded highest concentrations of
pesticides residues in sediment and fish samples than in
water sample at p>0.05.The mean concentration of
pesticide residues for sediment samples were 0.02 and
0.03 µg/gdw for of 2, 4-diamine in stations 2 and 3, at
F = 17.14, diazinon mean concentration was of 0.03
942
Res. J. Environ. Earth Sci., 4(11): 939-944, 2012
at F = 0, while propoxur mean concentration were 0.01
and 0.01 µg/L for stations 1 and 2, respectively. Lower
concentration of pesticides in water recorded in this
study according to Osibanjo et al. (1994) was due to the
hydrophobic nature of pesticides that make their
presence in water to be at ultra-trace level and their
accurate determination difficult, the adsorption of these
compound to particulate matter and sediment is an
important mechanism for their removal from the water
column, consequently the sediment component of
aquatic ecosystems can be the ultimate sink of these
pesticides.
Higher concentration of pesticides were recorded
in the wet season than in the dry season, this
corroborated the conclusion of Ezemonye (2004) that
pesticides up to 60 times entered the river during wet
season than in the dry season. This observation suggests
that rainfall significantly increases pesticide mass
loading to the aquatic environment. A comparison with
the data of pesticides in surface water, sediment and
fish samples from other studies, shows that the
concentration of pesticides in surface water, sediment
and fish in this study were lower (Wilfred and Duseln,
1995). The concentration observed in this study were
lower than pesticides concentrations reported in Warri
Rivers in Delta State Nigeria (Thomas, 2007) and this
may be attributed to lack of detailed studies on
environmental contaminations by pesticides and
minimal usage of this pesticides in the Niger Delta
Region. The two principal mechanisms of pesticides
uptake within the ecosystem are through bioconcentration and bio-magnifications (Thompson et al.,
1997). In spite of the seemingly lower residues of these
pesticides the observed residues were higher than the
Environmental Protection Agency (EPA) standard of
0.01 Ng/L for protection of aquatic life and human
beings.
tolerable limits adopted by (EPA) for survival of
aquatic organisms clearly indicates the ecological risk
associated with the exposure of those species and the
likelihood of their being transferred along the food
chain and the danger their continued increase usage
portends to human health.
Measures to reduce the use of pesticides along the
continuum from post application control, integrated
control and bio-intensive system to organic farming
should therefore be encouraged. The central objective
of this is to reduce pesticides emission to the
environment and to reduce the volume of active
ingredient used. There is also need to undertake such
research that will give early warning signal on the lethal
limits of pesticides in Nigeria fish species. It is
therefore imperative that safe limits/standard for fish
and other aquatic fauna in the Nigerian waters should
be developed using data obtained from pesticides
ecotoxicological studies.
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CONCLUSION
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