Poisonous Metal Levels in Sediment and Selected Biota in Coastal Waters of Nigeria

Abstract

Sediment and biota samples were collected biannually from the Bonny/New Calabar River Estuary in Niger Delta, Nigeria and analysed for poisonous metals of interest to the International Atomic Energy Agency (Pb, Cd, and Hg) using atomic absorption spectrophotometer A-500 and Direct Mercury analyser (DMA-80). Results for biota showed that Cd ranged from 0.003 to 0.558 ± 0.01mg/kg, Hg ranged from 0.014 ± 0.004 to 0.021± 0.010 mg/kg, Sediment: Cd ranged from 0.022 ± 0.001 – 0.82 ± 0.0002 mg/kg; Hg 0.010 ± 0.005 to 0.027 ± 0.009 mg/kg. Lead was below the detection limit of the instrument   both in biota and sediment. The concentrations of the respective poisonous metals were within the permissible limit of the World health organization. The study showed high concentration of Cd in Crayfish compared to other seafood.  The bioaccumulation factor showed higher level of Hg compared Cd while the Analysis of variance for the three stations did not show any significant variation among the three stations. Regular monitoring and comparison of level of contamination with regulatory bodies are advocated to prevent the concentration of the metal contaminants from getting to an alarming level.