Heavy Metals Concentration in Prawn (Macrobrachium Sp) Harvested from Oron River, in Akwa Ibom State, Nigeria
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Abstract
The concentrations of Mercury, Cadmium, Arsenic and Lead in prawns (Macrobrachium sp) harvested from Oron river in Akwa Ibom State, Nigeria were studied. It was an analytical study. The heavy metal analysis was done according to the standard methods for heavy metal determination using the FS 240 Varian Atomic absorption spectrophotometer. Each of the specimens were weighed and individually pulverised to a uniform particle size, ten(10) grams of each pulverised sample was taken and subsequently put in a 200ml digestion conical flask. 30ml of aqua regia which constitutes hydrochloric acid, nitric acid and hydroflouric acid in the ratio 1:3:1 was added and placed uprightly for 10-15 minutes. The mixture was heated in a water bath at approximately 120oC until the whole sample dissolves and a yellow tint of the solution appeared. The solution was filtered using a filter paper into centrifuge tubes and made up to 50ml mark with deionized water. It was transferred into sample vials for analysis
The analysis of the samples indicated presence of heavy metals but values obtained for arsenium and cadmium were below permitted limits set by FAO/WHO. Lead had the highest concentration in sample C, with 49.93ppm. Also, the analysis recorded highest value of Lead and lowest value of Arsenic with values of49.78±0.11and0.17±0.09 respectively. For Mercury, the highest concentration occurred in sample A and lowest in samples C and D, with concentration of 5.9ppm and 2.2ppm respectively. Arsenic recorded its highest concentration in sample C and lowest in sample B with concentration values of 2.0ppm and 0.3ppm respectively whereas Cadmium's concentration was highest in sample D and lowest in sample A with concentration values of 0.27ppm and 0.08ppm, respectively. The statistical analysis shows a significant difference at α0.05 in the mean concentrations of heavy metals recorded in the prawn samples from Oron river, Akwa Ibom State