HEAVY METAL CONCENTRATIONS IN SURFACE WATER AND BIOACCUMULATION IN FISH (CLARIAS GARIEPINUS) OF...

European International Journal of Science and Technology Vol. 2 No. 7 September 2013

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HEAVY METAL CONCENTRATIONS IN SURFACE WATER AND

BIOACCUMULATION IN FISH (CLARIAS GARIEPINUS) OF RIVER

OWAN, EDO STATE, NIGERIA.

Enuneku, Alex1*

, Ezemonye, Lawrence.I.2, Adibeli, Frances

3.

1,3 Department of Animal and Environmental Biology,

Faculty of Life Sciences,

University of Benin, Nigeria.

2Ecotoxicology and Environmental Forensic Unit,

National Centre for Energy and Environment,

Energy Commission of Nigeria,

University of Benin, Nigeria;

Corresponding Author*

E-mail: [email protected]

Phone: +2348030773314

ABSTRACT

Heavy metals (Iron, Zinc, Nickel and Manganese) concentrations were determined in surface water and

tissues of fish (Clariasgariepinus) from River Owan. Water and fish samples were collected from three

stations (Upstream, Midstream and Downstream). The physiochemical parameters were analysed using

APHA standards. Heavy metal concentrations in water and fish were analysed using an atomic absorption

spectrophotometer. Heavy metal concentration in surface water and fish were in the order: Fe>Ni>Mn>Zn

and Fe>Zn>Mn>Ni.In fish,Fe recorded the highest level of bioaccumulation (58.96mg/kg) and Nickel (Ni)

had the least bioaccumulation (2.38mg/kg). Fe and Ni had higher concentrations in surface water than

recommended benchmarks of WHO and FEPA, an indication of risk to human health. Fe and Znhad higher

concentrations in fish than WHO and FEPA guidelines for fish consumption. There is need for a constant

monitoring of the heavy metals concentrations in the surface water and fish in Nigerian waters.

1.0 INTRODUCTION

The escalating environmental contamination of the environment by toxic substances is of growing

concern in Nigeria and Worldwide (Ezemonye and Enuneku 2005).A wide range of contaminants are

continuously introduced into the aquatic environment mainly due to increased industrialization,

technological development, growing human population, oil exploration and exploitation, agricultural and

domestic wastes run-off (Lima et al., 2008). Among these contaminants, heavy metals constitute one of the

most dangerous groups because of their persistent nature, toxicity, tendency to accumulate in organisms and

undergo food chain amplification and more still, they are non-degradable (Fufeyin and Egborge, 1998).

European International Journal of Science and Technology ISSN: 2304-9693 www.eijst.org.uk

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When released into the environment, heavy metals find their way into the aquatic systems and

deposited in aquatic organisms like fishes through the effects of bioconcentration, bioaccumulation and the

food chain process and eventually threaten the health of humans that consume them.

Heavy metals concentrations in aquatic ecosystems are usually monitored by measuring their

concentrations in water, sediments and biota (Oguzie, 2003).

Bioaccumulation is the building up of a chemical to a toxic level in an organism’s body (Ezemoye

and Enuneku, 2012).Fishes are notorious for their ability to concentrate heavy metals in their muscles and

since they play important role in human nutrition, they need to be carefully screened to ensure that

unnecessarily high level of some toxic trace metals are not being transferred to man through fish

consumption (Adeniyiet al., 2008).Several studies have indicated enhanced level of both essential and non-

essential heavy metal load in muscle and liver tissues of fishes (Obasohan, 2007; Adeniyiet al., 2008). It is

important to always determine the bioaccumulation capacity of heavy metals in organisms especially the

edible ones in order to assess potential risk to human health (Otitoloju, 2002). Assessment of toxic heavy

metals in fishes can serve as a bio-indicator of their impacts on these organisms as well as give an insight to

the degree of pollution of the water body in particular (Farkaset al., 2000).

The aim of this study is to determine the concentration of heavy metals (Iron, Zinc, Manganese and

Nickel) in surface water and bioaccumulation of these metals in fish of River Owan.

2.0 MATERIALS AND METHODS

2.1 Study area

River Owan lies within latitudes and longitude (5º 30' N, 6º 30' N and 7º 30' E, 7º 30' E) respectively,

andone of the major rivers in Edo state, Nigeria. This area is located within the equatorial region where

rainfall is bimodal in pattern, peaking usually in July and in September, with a brief drop in August and

minimal in February and March. The climate in this area is tropical with two main seasons; the wet (April –

October) and dry (November – March) seasons.

The river is used by the villagers for various activities such as fishing, washing, transportation,

cooking, bathing, swimmingand drinking. It also serves as a dumping ground for various domestic wastes.

The river receives copious amounts of wastes from residence, abattoirs sited along its course and also from

sawmills around. Industrial effluents as well as domestic sewage/wastes are deposited in the river either with

partial or no pre-treatment and hence, increasing concentration of different kinds of pollutants especially

heavy metals.

European International Journal of Scien

Plate 1: Map showing samplin

2.1.1 Sample stations

Station 1was located upstream o

serves as a major dumping site for refu

2was located at the midstream of the

swimming were more intensive at this p

the downstream of the river. Few huma

which occur along the bank and also fish

2.2 Sample collection

Surface water samples were co

downstream). They were taken to the la

dissolved oxygen and major ions whic

oxygen (DO) and biochemical oxygen

ence and Technology Vol. 2 No. 7

ling site.

of the river. The water at this point is relatively

fuse and it is a point of discharge of saw dust fr

the river. Various human activities such as w

s point and the water is relatively polluted. This s

man activities were operated here except for som

ishing. The water here is also relatively polluted.

collected from three stations of the river (upstre

laboratory for the determination of pH, electrica

ich include Cl-, SO4

2-, PO4

3- and NO3

-.Water sa

demand (BOD) determination were collected

September 2013

ely polluted because it

t from sawmill.Station

washing, bathing and

s stationwas located at

ome farming activities

tream, midstream and

ical conductivity, total

samples for dissolved

d using 250ml reagent


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bottles with glass stoppers. For dissolved oxygen (DO), the oxygen content of the water was immediately

fixed by adding 1ml each of Winkler’s solutions A (Manganoussulphate) and B (Potassium hydroxide in

Potassium iodide). The water samples for BOD were immediately wrapped in black polythylene bags and

transported to the laboratory.Water samples for heavy metal were collected in acid washed polyethylene

bottles. The bottles were rinsed thoroughly with deionised water after being washed in dilute nitric acid

(HNO3). In the field the bottles were rinsed several times with the river water and 1 litre sample was then

collected at about 50cm below the water surface. The water samples were acidified with concentrated nitric

acid for preservation. The acid pretreatment ensured that heavy metals did not get absorbed to the surface of

the container during transportation and storage.

Fish samples were also collected and sampled. Fish were caught with gill nets, hooks and lines and

local traps. The gill nets were set between 4.00pm and 6.00pm and inspected the following mourning

between 7.00am and 9.00am. The fish samples were preserved in ice and taken to the laboratory. They were

kept frozen in the refrigerator pending heavy metals analysis in the laboratory.

2.3 Sample preparation/chemical analysis for fish samples

The fish samples were dried at 105oC. Then 0.5g of the dried samples was weighed into conical

flask.9ml of HCl3 and 3ml HNO3 was added. The mixture was heated to obtain clear solution and made up

to 100ml mark in a standard flask with distillated water.

2.4 Determination of physicochemical parameters and heavy metals in water and fish.

The physiochemical parameters were determined according to APHA, 1992.Heavy or trace metals

were determined after digestion of the solution of the samples. Water samples digestion was carried out by

taking 10ml of the sample and adding 4ml Perchloric acid, 20ml concentrated nitric acid and 2ml

concentrated tetraoxosulphate VI acid. This was digested using aluminum block digester 110. The mixture

was heated until white fumes evolved and clear solution obtained.

After digestion, the samples for were allowed to cool and then transferred to 100ml volumetric flask.

This was made up to mark with distilled water and thoroughly mixed. The sample was allowed to stand

overnight (in place of centrifuge) to separate insoluble materials. It was then filtered through 0.45Millipore

type filter. Iron (Fe), copper (Cu), lead (Pb), manganese (Mn), Nickel (Ni) and chromium (Cr) were

determined (Atomic Absorption Spectrometry).

2.5 STATISTICAL ANALYSIS

Basic statistical measurement of central tendency and dispersion to characterize stations in terms of

physiochemical conditions and inter station comparisons were carried out to test for significant differences

in the heavy metals concentration using parametric analysis of variance (ANOVA). If significant value

(P<0.05) were obtained, Duncan multiple range (DMR) test where performed to determine the location of

significant differences using the computer SPSS 16.0 windows application.

Correlation analysis was used to determine the relationship between the water physicochemical

parameters, heavy metals concentration in the water and fish. Non–Parametric Spearman correlation was

used.

Bioaccumulation factor (BAF) was determined according to Deminaet al. (2009)

BAF = �� (��/��)

�� (��

��)


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3.0 RESULTS

3.1 Physical and chemical characteristics of the water

The results of the physical and chemical characteristics including heavy metal concentrations of

water from Owan River at the different sampling stations are summarized in Table 1. These show the mean,

standard deviation, minimum and maximum monthly values for each parameter analyzed for the different

stations.


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Table 1: Summary of Physical and Chemical Characteristics including Heavy metal Concentrations of Water from Owan River

n=4 STATION 1 STATION 2 STATION 3 FEPA

STANDARD

PARAMETERS ×�± SD MIN- MAX ×�± SD MIN- MAX ×�± SD MIN- MAX P-VALUE

pH 5.35±0.19C 5.11-5.57 5.81±0.03

B 5.77-5.82 6.05±0.08

A 5.94-6.11 P<0.01 6.5-8.5

EC (uS/cm) 43.00±2.16A 41.00-46.00 37.75±2.50

B 35.00-41.00 43.00±1.41

A 42.00-45.00 P<0.01

TDS (mg/l) 20.88±1.44A 19.00-22.50 18.67±1.40

B 17.70-20.70 21.25±0.96

A 20.00-22.00 P<0.05 500

DO(mg/l) 5.31±0.73 4.27-5.87 4.81±0.66 3.86-5.31 5.41±0.74 4.35-5.98 P>0.05 7.5

BOD (mg/l) 2.97±0.19 2.70-3.15 2.81±0.18 2.56-2.98 3.13±0.20 2.86-3.33 P>0.05

Chloride(mg/l) 13.68±0.76A 12.86-14.67 11.67±0.59

B 10.84-12.23 13.56±0.79

A 12.94-14.70 P<0.01 200

SO42-

(mg/l) 0.88±0.01 A

0.87-0.88 0.74±0.04 B

0.69-0.78 0.88±0.02 A

0.86-0.89 P<0.01 500

PO43-

(mg/l) 0.47±0.03 0.45-0.52 0.42±0.04 0.40-0.48 0.46±0.04 0.43-0.52 P>0.05 <5

NO3- (mg/l) 0.54±0.01

B 0.53-0.55 0.47±0.01

C 0.46-0.48 0.55±0.00

A 0.55-0.56 P<0.01 10

Ni (mg/l) 0.45±0.08 A

0.37-0.56 0.36±0.07 A

0.29-0.45 0.22±0.04 B

0.18-0.28 P<0.01 0.05

Mn (mg/l) 0.19±0.11 0.03-0.30 0.20±0.12 0.03-0.32 0.10±0.06 0.02-0.15 P>0.05 0.05

Fe (mg/l) 1.12±0.64 0.16-1.49 0.78±0.45 0.11-1.04 0.59±0.34 0.09-0.78 P>0.05 1.0

Zn (mg/l) 0.11±0.02 A

0.10-0.13 0.12±0.02 A

0.10-0.14 0.09±0.01 B

0.07-0.10 P<0.05 1.0

P<0.05 – Significantly different

P<0.01 – Highly significantly different

P>0.05 – No significant difference

Similar superscript – No significant different


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From the correlation matrix positive correlation was observed between Electrical conductivity and (Total

dissolved solid, Chloride, Sulphate and Nitrate); Total dissolved solid and (Chloride, Sulphate andNitrate);

Dissolved oxygen and Iron; Chloride and (Sulphate and Iron); Sulphate and Nitrate; Nickel and Zinc; and

Manganese and Iron.

Negative correlation was observed between pH and (Nickel and Iron), and Zinc, and (Biochemical

oxygen demand and Dissolved oxygen).

3.2 Heavy metals concentrations in water, Bioaccumulation infish and Bioaccumulation Factor.

The various heavymetals concentrations in surface water,bioaccumulation in fish

(Clariasgariepinus)and bioaccumulation factor in the sampledriver are shown in figures 1.

Figure 1: Graph showing heavy metal concentrations in water, bioaccumulation in fish and

bioaccumulation factors.

FromTable 3 above, the bioaccumulation of heavy metals in fish is highest for iron (58.96) and least

for nickel (2.38). The concentration of heavy metals in water is highest for iron (0.38) and least for zinc

(0.11).

The Bioaccumulation factors (BAFs) for the different heavy metals were6.93 for nickel,28.12 for

manganese, 70.91for nickel and 261.87 for zinc. This follows the order: Zinc > Iron > Manganese > Nickel.

4.0 DISCUSSION

Heavy metals have been used as indices of pollution because of the high toxicity to human and

aquatic life (Omogberale and Ogbeibu, 2005). Ezemonye (1992), Egborge (1991) and Edema (1993) have

linked the concentration of heavy metals in the aquatic ecosystems with effluents from industries, refuse and

sewage. In the study, the four heavy metals (Fe, Ni, Mn and Zn) concentrations in surface water of River

Owan decreased in the sequence: Ni >Mn> Fe >Zn at Station 1 and Fe > Ni >Mn> Zn at Stations 2 and 3.

The result obtained in this study showed that Ni and Mn had high values in all three stations which were

greater than the recommended benchmarks by WHO (WHO, 2003). The concentration levels of these metals

would impair the portability of the water.

0

50

100

150

200

250

300

Ni Mn Fe Zn

BIOACCUMULATION IN FISH mg/kg) CONCENTRATION IN WATER (mg/kg)

BIOACCUMULATION FACTORS


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Heavy metals have been used as indicator of pollution because of their high toxicity to human and

aquatic life (Ezemonye and Kadiri, 1998). Heavy metals are very toxic because, as ions or in compound

forms, they are soluble in water and may be readily absorbed into aquatic organisms. Fish accumulate heavy

metals directly because of the intimate contact they have with the aquatic medium and also because they

have to extract oxygen from the medium by passing enormous volumes of water over their gills. Fish have

been considered good indicators for heavy metal contamination in aquatic system because they are easy to

obtain in large quantities as well as they occupy high trophic level in the aquatic food chain (Buikenaet al.,

1982).

From the heavy metals (Nickel, Manganese, Iron and Zinc) studied, the bioaccumulation of Fe

(58.96mg/kg) was highest, followed by Zn (28.50mg/kg), then Mn (4.62mg/kg). Ni (2.38mg/kg) showed the

lowest accumulation in fish tissues. The high values of Fe and Zn recorded might be due to the disposal of

industrial and domestic wastes from residential areas which may contain higher levels these metals. The

concentration of the heavy metals in the fish (Clariasgariepinus) under study was observed to be higher than

that recorded in the water. Fish has been reported to accumulate metals from water by diffusion via skin and

gills as well as oral consumption/ drinking of water (Nusseyet al., 2000; Oguzie,

2003).Clariasgariepinusaccumulated metals (Fe, Zn, Mn and Ni) in levels which exceed Federal Ministry of

Environment permissible limits and World Health Organization recommended benchmarks. Based on these

standards, the fish is not fit for consumption.

5.0 CONCLUSION

The study showed that River Owan is relatively polluted as compared with the ecological benchmarks

recommended by World Health Organization; and consumption of the water and fish from the river could

affect the health of humans. In view of the importance of fish to diet of man, it is necessary that biological

monitoring of the water and fish meant for consumption should be done regularly to ensure continuous

safety of the aquatic food. Safe disposal of domestic sewage, agricultural and industrial effluents should be

practiced and where possible, recycled to reduce the concentrations of these metals in the aquatic

environment.

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