Variability in Levels of Heavy Metals in Water and Fish

Overview

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Key numbers

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• et al. (2008), among notable and highly demanded fish species in the creek included Cat fish
• season average iron value of 2.10 ±1.35mg/l was higher than 1.62 ± 0.44 mg/l for dry season
• (Table 3). Results of ANOVA analysis showed significant differences in Fe values between
• seasons (p < 0.05). Copper ranged between below the detection limit (BDL) and 0.83mg/l,
• among zones, and was least (0.21 ± 0.18mg/l) at the lower zone and highest (0.25 ±
• 0.19mgL-1) at the middle zone (Table 1). Seasonal trend (Table 3) revealed dry season had
• higher copper mean (0.28 ± 0.25mg/l) than wet season (0.18 ± 0.12mg/l). Statistical analysis
• 3.03mgL-1) and lowest (2.58 ± 2.63mgL-1) mean Pb content was recorded at middle zone and
• lower zone respectively (Table 1). Seasonally (Table 3), Pb value was higher (3.89 ± 3.73
• mg/l) in the dry season than in wet season (2.89 ± 1.58mg/l). However, ANOVA on the
• 0.38mg/l (Table 2). Zn mean, (Table 1) increased slightly from the lower zone (0.18 ±
• 0.05mg/l) to the upper zone (1.29 ± 1.33mg/l). However, wet season (Table 3) mean Zn
• concentration (0.84 ± 0.83mg/l) was higher than the dry season of 0.52 ± 0.57mg/l. Zn mean
• Chromium varied from 0.89mg/l to 35.47mg/l throughout the study. Mean Cr content (Table
• 8.07mgL-1), with a grand average value of 9.82 ± 2.60mgL-1 (Table 2). Season-wise (Table 3),
• the dry season Cr mean value (10.70 ± 7.27mg/l) was higher than the wet season value of
• 8.94 ± 4.93mg/l. However, ANOVA showed there were no significant difference in Cr mean
• 0.48 mg/l. Mean Cd varies slightly among zones, with the lowest (0.12 ± 0.11mg/l) at upper
• zone and highest (0.14 ±0.09mg/l) at middle zone (Table 1). Cd grand mean in this study was
• 0.15 ± 0.05mg/l (Table 2). Seasonally (Table 3), Cd mean value in dry season (0.16 ±
• Table 1. Spatial (Zone) variation (Means ± standard deviation) of Metals in Badagry Creek
• Pb (mg/l) 3.18 ±3.13a 4.40 ±3.03a 2.58 ±2.63a > 0.05
• Cr (mg/l) 8.28 ±4.35a 10.41 ±6.11a 10.78 ±8.07a > 0.05
• Cd (mg/l) 0.12 ±0.11a 0.14 ±0.09a 0.13 ±0.11a > 0.05
• Table 2. Grand mean ± standard deviation of Metals in Badagry Creek water (November,
• Pb (mg/l) 3.39 ±1.35 <1
• Cr (mg/l) 9.82 ±2.60 10
• Cd (mg/l) 0.15 ±0.05 <1
• Table 3. Seasonal Variation (Mean ± Standard Deviation) of Metals in Badagry Creek water
• Pb (mg/l) 3.89 ±3.73 2.89 ±1.58 > 0.05
• Cr (mg/l) 10.71 ±7.27 8.94 ±4.93 > 0.05
• Cd (mg/l) 0.16 ±0.12 0.11 ±0.06 > 0.05
• (Chrysichthys nigrodigitatus) from the three zones of Badagry creek are shown in Tables 4 -
• The values vary at different zones of the creek. Fe in the finfish muscles ranged from 15.14 to
• 187.32mg/kg. The lower zone had the highest mean Iron value (73.74 ± 56.77mg/kg) while
• 25.76mg/kg. Lower zone with the highest Lead mean value (18.38 ± 5.21mg/kg) while the
• least mean content (10.21 ± 1.80mg/kg) was obtained at the upper zone. Zn levels varied
• and lower zones respectively. Cr content varied from 18.64mg/kg to 229.34mg/kg, with
• In the liver of Chrysichthys nigrodigitatus, Fe concentration ranged from 19.45 to
• 564.92mg/kg with a grand mean of 174.51 ± 56.58mg/kg. Fe mean content was highest at the
• 1.91mg/kg) was recorded at the middle zone. Pb content in the fish liver was from 7.34 to
• 27.27mg/kg, with a grand Pb mean of 15.10 ± 2.64mg/kg. Pb mean content was least at the

Methods (brief)

• chromium (Cr) in water and fish ( Chrysichthys nigrodigitatus) samples collected bi-monthly
• investigated using atomic absorption spectrophotometer (AAS) method. With an exception of
• cadmium, metals concentration was lower in the water samples and higher in the fish tissues,
• Keywords: Chrysichthys nigrodigitatus, Heavy metals, Bioaccumulation, Atomic absorption
• this paper, the levels of Pb, Cd, Cu, Fe, Zn and Cr in water samples and in tissues of Cat fish
• Water samples were taken bi-monthly throughout this period at the designated stations for
• Water samples were collected just below the water surface at each station in acid-washed and
• set of sample, and samples were transported to the Nigerian Institute for Oceanography and
• sample collection, preservation and analysis was a week for each set of samples.
• The fish species (Chrysichthys nigrodigitatus) were collected from the landings from
• 2.3.1 Preparation and Digestion of Water Samples
• 25ml of preserved water samples were measured into a conical flask, 10ml of aqua regia
• in fume cupboard at 120⁰C. The digested sample in the conical flask was allowed to cool and
• aspirated for metal analysis in an AAS and quantified against known standards (APHA,
• 2.3.2 Preparation and Digestion of Fish Samples
• sample preparation. Fish were dissected with a dissecting set between the pectoral fin and
• constant weight. Thereafter, 2g of separated organs were placed into digestion flasks and
• ultrapure Conc. HNO3 and H2O2 (2:1 v/v) was added. The samples were left overnight at

Implications

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Wiki pages this source may touch

• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Cadmium
• Lead
• Arsenic
• Chromium

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