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International Journal of Research in Pure and Applied Chemistry 2013; 2(1): 5-9ISSN 2277–3843
Original Article
DETERMINATION OF HEAVY METALS IN SOIL, WATER, SEDIMENT,
FISH AND CRAY FISH OF JABI LAKE IN THE FEDERAL CAPITAL
TERRITORY, FCT, ABUJA - NIGERIA
*UMAR, M. A. and EBONG, M. C.DEPARTMENT OF CHEMISTRY, UNIVERSITY OF ABUJA, ABUJA, FCT, NIGERIA
*For correspondence, contact Umar, M. A. on +2348065512367 or e-mail: mfonmfon4ever@yahoo.com
Received 01 May 2013; accepted 29 May 2013 Abstract
Water, Sediment, Soil, Crayfish and Fish from the Jabi Lake were analysed for copper (Cu), zinc (Zn), cadmium (Cd), nickel (Ni) and lead (Pb). Crayfish and Fish samples were bought from the Fishermen while still alive. Water samples were collected from different points in the lake while sediment was collected at the point of municipal runoff entry. Soil (control) sample was collected at a point 15m from the lake at a depth of 5m. Standard procedures were employed in sample preparation and the heavy metals concentrations were determined using flame atomic absorption spectrophotometry (AAS). The result showed that the pollution of sediment in Jabi lake is related to the pollution in water because they follow the same pattern of decreasing concentrations of heavy metals: Zn > Cu > Cd > Ni > Pb. The pattern of decreasing concentrations for Fish and Crayfish were Cu > Zn > Cd > Ni > Pb. Average concentrations of Zn in water (4.72 ±0.63) and Cd (0.28 ±0.32) were found to be higher than International permitted range, while others (Cu, Ni and Pb) were within the range. Cu, which showed bioaccumulation in Fish and Crayfish samples to the magnitude of 357.90 and 138.70 with concentrations of 107.37 ±0.94 and 41.61 ±1.38 respectively, was higher than International accepted range. Concentrations of other metals (Zn, Ni, Cd and Pb) however fell within accepted range. Concentration values for soil(control) for all metals under study fell within accepted range, thus exonerating the surrounding soils of Jabi Lake as being the possible source of heavy metal contamination in the lake. The study showed that the most important source of heavy metals pollution in the lake was the sewage disposal point and erosional runoffs from the flower farms. Jabi Lake was polluted with Zn and Cd. Crayfish and Fish samples were polluted with Cu. However, the lake is not heavily burdened with Ni and Pb, but they should be controlled to avoid excessive concentrations.
© 2013 Universal Research Publications. All rights reserved
Key Words: Heavy Metals, Jabi Lake, Water, Cray Fish, Fish, Sediment, Soil, Bioaccumulation
INTRODUCTION
The fate of heavy metals introduced by human activities, chemical and geochemical processes into the aquatic ecosystem have recently become the subject of widespread concern; since beyond the tolerable limits they become toxic (Gbaruko and Friday, 2007; WHO, 1971; Koller, et al., 2004; Umar, et al., 2010). Pollution of water bodies could occur due to run-offs flowing through agricultural areas where fertilizers and pesticides may have been applied and catchment settlements where there may have been indiscriminate waste disposals (Suhendan et al., 2010). Water, sediments and the biota are generally metal reservoirs in aquatic environment and may assume several orders of magnitude greater than the amount found in water (Smical, 2008).
It is known that heavy metals are the most important form of pollution and they may accumulate in the tissues of Cray fish and Fish which are often at the top of aquatic food
chain. Sediments may concentrate large amounts of metals from water, making Crayfish and Fish which are bottom dwelling to pick up these metals from the sediment which might be toxic for human consumption (Papagiannis et al., 2004). The effects of heavy metals on the health of Abuja residents are of great interest today, especially for the realities of their dependence on aquatic food products from Jabi Lake in Abuja Municipal.
There are a few studies about heavy metals in Jabi Lake (Umar and Abdullahi, 2010). In fact, data on heavy metals in the samples undertaken in this research from Jabi Lake became very important due to the research findings of Speciation of Heavy Metals in Jabi Dam sediments by Umar and Abdullahi (2010) that “a significant percentage of the total metal was associated with the non-residual fractions, indicating that they could be potentially bio-available”. It was therefore thought necessary to investigate the concentrations of Cu, Zn, Cd, Ni, and Pb in soil, Available online at http://www.urpjournals.com
International Journal of Research in Pure and Applied Chemistry
Universal Research Publications. All rights reserved6
International Journal of Research in Pure and Applied Chemistry 2013; 2(1): 5-9 Sediment, Fish and Cray fish found in Jabi Lake, sincedetermination of harmful and toxic substances including heavy metals in water, sediment and biota, gives direct information on the significance of pollution in the aquatic environment. The aim of this study was to estimate the extent of pollution of Jabi Lake and the potential risk to the residents.
JABI LAKE
Jabi Lake, which is a man-made reservoir of water from the foot of Katampe rocks, is located within Kado and Jabi districts of the Federal capital Territory (FCT). Due to increases in urbanization around the lake area, the initial intention of meeting the water need of FCT residence for which the lake was created was dropped as the lower Usman Dam was constructed in Bwari for the purpose of
servicing the water needs of the Federal Capital Territory (FCT Water Board, 2005).
Increases in urbanization and socio-economic activities within and around Jabi Lake poses threat to its pollution with heavy metals. The Lake may have experienced several episodes of heavy metal pollution emanating from flower farming and block molding industries around the lake as well as discharge of erosion run offs into the lake which may undoubtedly carry municipal wastes. The presence of heavy metals in the water and sediments would lead to bioaccumulation in the aquatic life. These bioaccumulations may have a profound effect on the citizenry which depend on these aquatic lives such as fishes and Cray fish as the main source of food. Consequently, the potential long term impact on public health and ecosystem
cannot be ignored.
SAMPLING AND SAMPLE SITES
Water samples were collected in triplicate from five (5) different points in the lake. Point one (1) was the discharge
point of municipal runoff (SDP); point two (2) was middle of the lake (ML); point three (3) was Under the Jabi Bridge(UB); point four (4) was River Entry Point (EX) and point Five (5) was the location Near Water Board (NWB).
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International Journal of Research in Pure and Applied Chemistry 2013; 2(1): 5-9 Sediment sample was collected in triplicate from thedischarge point of municipal runoff only as there was difficulty of taking samples at other locations for which water was sampled due to depth. Fish and Cray fish samples were bought fresh from the local fishermen operating in the Jabi Lake and apportioned randomly in triplicate. Soil sample was collected in triplicate from a location 15m from the edge of the lake at a depth of 5m and stored in well-labeled metal free polythene bags ready for treatment and analysis.
SAMPLE PREPARATION
Fish, Crayfish, sediment and soil samples were spread on cardboard papers and dried under the sun for two days after manual removal of debris. They were later dried in oven at a temperature of 60oC. The dried samples were entirely
transferred to new well labeled polythene bags.Each of the three replicate of fish, Crayfish, sediment and soil samples were ground to get a good representative and homogeneous mixture. The samples were respectively poured into a mortar and ground with a pestle, one after the other, into fine powder. The mortar was washed and dried after each sample pounding to avoid contamination. The ground samples were sieved using 2mm screen and quickly transferred into sample bottles ready for digestion.
Water samples from the 5 different locations were collected as grab samples into pre-cleaned plastic bottles in triplicate form and treated with trioxonitrate (v) acid (HNO3). They
were stored in a cool box and transported to the laboratory. For digestion of the respective samples, 1g each of the three replicate of the sieved soil and sediment samples were
weighed into 100ml beaker. 10ml concentrated HNO3 and
5ml of concentrated HClO4 were added in the ratio of 2:1
respectively. These were covered with a watch glass. The mixtures were placed on a hot plate under fume cupboard and heated to dryness with colour changing to white and allowed to cool before leaching. The residue was then dissolved in 5ml of 20% HNO3. The dissolved mixture was
made up to a volume of 20cm3 with distilled water. Finally,
the filtrates were collected in a small rubber container in preparation for the determination of the concentration of the heavy metals under study (Pb, Cd, Ni, Zn and Cu). Two grams (2g) weight of each portions of Cray fish and Fish samples were taken in triplicates for each sample and acid digested using a mixture of nitric acid and perchloric acid (1:3). These were wet oxidized as described above. Water samples were thoroughly mixed and aliquots of 50ml taken in triplicates. These were digested with a mixture of nitric acid and perchloric acid (1:3) until clear solutions were obtained. Digests were filtered and stored in plastic bottles.
AAS ANALYSIS
Flame atomic absorption spectrometer (AAS-buck scientific VGP 210 model) was used in the analysis. The concentrations of the metals were determined in triplicates. The accuracy and precision of the analytical procedure were determined. A series of standards were prepared for instrumental calibration by serial dilution of working solutions (100ppm) prepared from analytical grade stock solutions (1000ppm) from BDH poole, USA. A standard and blank sample was run after every seven samples to check for instrumental drift.
RESULTS AND DISCUSSIONS
HEAVY METAL CONTENTS IN WATER
The heavy metal content in waters of Jabi Lake is presented in Table 1 and Figure 1. The results indicate that the average concentrations of heavy metals in water in decreasing order at the different sampling points is Zn ˃ Cu
˃ Cd ˃Ni ˃ Pb, with the corresponding values (mg/l) of 4.7 ± 0.63, 0.30 ± 0.24, 0.28 ± 0.32, 0.08 ± 0.01 and 0.05 ± 0.01 respectively. However, water samples at river entry point (Ex) for Cu; under bridge (UB) for Cu, Zn, Cd and Ni; mid lake (ML) for Cd and Pb; Near Water Board (NWB) for Cu Zn; and Sewage Disposal Point (SDP) for Cd, were not detected. This does not entirely mean that the metals concern are not present, but may be below the detection limit of the instrument being used.
TABLE 1: Concentration of Heavy Metals in Water Samples at the Different Sampling Points in Jabi Lake
Samples Cu (mg/L) Zn (mg/L) Cd (mg/L) Ni (mg/L) Pb (mg/L)
River Entry Point (Ex) ND 5.00 ± 0.75 0.37 ± 0.63 0.25 ± 0.02 0.01 ± 0.01
Under Bridge (UB) ND ND ND ND O.17 ± 0.01
Mid Lake (ML) 0.23 ± 0.40 3.64 ± 1.05 ND 0.01 ± 0.00 ND Near Water Board (NWD) ND ND 0.20± 0.06 0.01 ± 0.00 0.01 ± 0.01 SEWAGE Disposal point (SDP) 0.37 ± 0.26 5.51 ± 1.40 ND 0.04 ± 0.01 0.017 ± 0.01
AVERAGE 0.30 ± 0.24 4.72 ± 0.63 0.28 ± 0.32 0.08 ± 0.01 0.05 ± 0.01
ND –Not Detected.
Zn (4.7 ± 0.63)mg/l and Cd (0.28 ± 0.32) exceeds the International acceptable range of 0.03 - 0.2mg/l and 0.05 – 0.1mg/l respectively; thus giving a convincing indication that the water of Jabi Lake is contaminated with Zinc and Cadmium.
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International Journal of Research in Pure and Applied Chemistry 2013; 2(1): 5-9Figure 1: spatial Distribution of Heavy Metals in Water Samples
However, the concentrations of other metals (Ni, Cu and Pb) under study are within the International permitted range in the respective water samples, with Pb having the overall lowest concentrations. The pollution of the Lake by Zinc may be attributed to pollutant residual of the boating activities within the lake. The concentration of all these metals (Cu, Cd, Ni and Pb) in the water is almost similar throughout the Lake (at all the sampling points). This may indicate that they are within background concentration level in the water of the lake.
HEAVY METAL CONTENTS IN SOIL, SEDIMENT, CRAYFISH AND FISH
The heavy metal contents in soil, sediment, Crayfish and Fish are presented in Table 2 and Figure 2, indicating wide variations of heavy metal concentrations among the respective samples.
TABLE 2: Concentration of Heavy Metals in Soil, Sediment, Crayfish and Fish Samples
Samples Cu (mg/kg) Zn (mg/kg) Cd (mg/kg) Ni (mg/kg) Pb (mg/kg)
Soil (control) 3.96 ± 0.71 7.82 ± 0.89 1.08 ± 0.44 0.41 ± 0.02 0.25 ± 0.13 Crayfish 107.37 ± 0.94 14.22 ± 2.9 1.06 ± 0.58 0.53 ± 0.05 0.21 ± 0.03 Fish 41.61 ± 1.38 1.87 ± 1.76 1.13 ± 0.63 0.45 ± 0.04 0.22 ± 0.22 Sediment 4.10 ± 1.04 5.01 ± 1.05 1.36 ± 0.41 0.17 ± 0.02 0.15 ± 0.03 The result shows that the pattern of decreasing
concentrations of heavy metals in soil (control) and sediment are: Zn > Cu > Cd >Ni > Pb. However, the pattern of decreasing concentrations in Crayfish and Fish samples is Cu > Zn > Cd >Ni > Pb. The concentrations of all the metals for the respective samples under study were within the International permitted range (Balfour et al, 2012), except the concentrations of Cu for Crayfish (107 ± 0.94)mg/kg and Fish (41.61 ± 1.38)mg/kg, which were higher than the International permitted range of 2.0 – 20mg/kg. This gives a convincing indication that Crayfish and Fish of Jabi lake is polluted with Cu.
Figure 2: Distribution of Heavy Metals in the different samples in Jabi Lake
Figure 2 shows that Pb recorded the lowest concentrations across all the samples under investigation, which could possibly be due to the embargo placed on mechanic workshops around the lake. The concentrations of Cu in Crayfish and Fish which were above the threshold alert could be a direct consequence of inflows from the flower farms (Njogu et al, 2011).
Pearson correlation analysis (p <0.05) reveals that concentrations for water samples at different sampling points were correlated for all metals under study except lead between entry point and under bridge. The correlation analysis between water and sediment gave a positive correlation for cadmium (r=0.94). Other metals under study were inversely correlated between water samples and sediment (Cu: r = -1.00; Zn: r= -1.00; Ni: r= - 1.0; and Pb: r = - 0.24), which means that the concentration of heavy metals in Sediment were higher than that in water, possibly due to adsorption on particulate matter and dissolved carbon.Concentrations of Cu in fish and crayfish samples gave inversely correlation (r = -0.44 and r = -0.91) to sediment, indicating a bioaccumulation of copper in the biota. Only crayfish sample gave an inverse correlation (r = -0.40) for Zn with sediment.
Inter-metallic relationships for water samples reveal positive correlation and significant regression relation among the metals. The positive correlation coefficients with p < 0.05 were: Cd - Zn (r = 0.2), Ni – Cu (r = 0.4), Ni – Zn (r = 0.5), Pb – Cu (r = 0.8), Pb – Zn (r = 0.4) and Pb – Ni (r = 0.9). There was however inverse relationships between Zn – Cu (r = -0.2), Cd – Cu (r = -0.9), Ni – Cd (r = -0.5) and Pb – Cd (r = -0.8). Sediment samples gave positive correlations between Ni – Zn (r = 0.1), Ni – Cd (r = 0.9) and Pb – Cu (r = 0.8) whereas the inverse relationships were between Zn – Cu (r = -0.7), Cd – Cu (r = 0.6), Ni – Cu (r = 0.7), Pb – Zn (r = 0.9), Pb – Cd (r = -0.03) and Pb – Ni (r = -0.1). It was a complete inverse relationship in Fish samples between Cu – Zn (r = -0.1), Cu – Cd (r = -0.9), Cu – Ni (r = -0.8) and Cu – Pb (r = -0.9); others were positive relationships between Cd – Zn (r = 0.3), Ni – Cd (r = 0.7), Pb – Zn (r = 0.5), Pb – Cd (r = 0.9) and Pb – Ni (r = 0.5) with Ni – Zn giving an inverse relation (r = -0.5). Crayfish samples gave the most significant inter-metallic correlation between Zn – Cu (r = 0.8), Cd – Cu (r = 0.7), Cd – Zn (r = 0.9), Ni – Zn (r = 0.3),
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International Journal of Research in Pure and Applied Chemistry 2013; 2(1): 5-9 Ni – Cd (r = 0.4), Pb – Cu (r = 0.9), Pb – Zn (r = 0.6) andPb – Cd (r = 0.4); inverse relationships however were between Ni – Cu (r = -0.3) and Pb – Ni (r = -0.6). The positive correlations between heavy metal concentrations suggested either a common or a similar geochemical behavior origin. The inverse correlations and low positive correlations (r = 1) could mean that the contaminations are coming from different sources or have different chemical behavior in the lake bed.
BIOACCUMULATION STUDIES
Bioaccumulation of metals in fish and crayfish were quantified by a bioaccumulation factor (BAF), which is the ratio of particular metal concentration in the specimen to the concentration of that metal in the water column. The values of bioaccumulation factors were calculated using the following equation:
BAF = Concentration (mg/kg tissue) / concentration (mg/l water)
Table 3: Bioaccumulation Factor for Fish and Crayfish in relation to Water
Heavy Metals Water (mg/L) Crayfish (mg/kg) Fish (mg/kg)
BAF= Conc. (mg/kg tissue) Conc. (mg/L Water) Crayfish Fish Cu 0.30 ± 0.24 107.37 ± 0.94 41.61 ± 1.38 357.90 138.70 Zn 4.72 ± 0.63 14.22 ± 2.90 1.87 ± 1.76 3.01 0.40 Cd 0.28 ± 0.32 1.06 ± 0.58 1.13 ± 0.63 3.79 4.04 Ni 0.08 ± 0.01 0.53 ± 0.05 0.45 ± 0.04 6.63 5.63 Pb 0.05 ± 0.01 0.21 ± 0.03 0.22 ± 0.02 4.20 4.40 ppm = mg/kg = mg/L = µL/L = µg/g = µg/mL
Table 3 shows that the BAF values for Crayfish is 358(Cu), 3(Zn), 4(Cd), 7(Ni) and 4(Pb); that of Fish is 139(Cu), 4(Cd), 6(Ni) and 4(Pb) with Zn showing no bioaccumulation for Fish. The bioaccumulation as witnessed in the above results may be due to the fact that heavy metals dissolves more in lipids than water, that is why the Fish and crayfish samples are able to have concentrations of the metals in a higher proportion than that found in water. Bioaccumulation, especially Copper, in Fish and Crayfish samples is consistent with the findings on Jabi Dam by Umar and Abdullahi (2010), that “a significant percentage of the total metal was associated with the non-residual fractions, indicating that they could be potentially bioavailable”, with the bioaccumulation pattern for both Fish and Crayfish in decreasing order being Cu > Ni > Pb > Cd > Zn. These BAF values are low compared to BAF values reported in other studies (Njogu et al., 2011).
In conclusion, results of this study agree with the report of Umar and Abdullahi (2010) that Jabi Lake is contaminated with Zn. The study however reveals an increase in Cd contamination in the lake waters. Crayfish and Fish samples recorded contamination with Cu as witnessed in the bioaccumulation studies. Jabi Lake is not heavily burdened with Ni and Pb, but they should be controlled to avoid excessive concentrations.
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