HEAVY METALS AND HYDROCARBONS IN SEDIMENT AND CRAB (CARDISOMA ARMATUM) AND ECOLOGICAL RISK ASSESSMENT OF AMADI CREEK, PORT HARCOURT

Abstract

Food security is hinged on quality and integrity of the surrounding environment. Food quality and security of coastline communities are tied to the constituents of benthic organisms in the area. This study assessed the heavy metals and hydrocarbons status of sediment and crab (Cardisoma armatum) in Amadi Creek in Port Harcourt. Sediment and crab samples were collected from five stations along a 10 km transect for four months. The heavy metals results for sediment showed the following: Zn (18.624 ± 1.254), Pb (0.791 ± 0.072), Cd (0.031 ± 0.012), Cr (3.323 ± 1.079), Ni (1.848 ± 1.329) and V (0.067 ± 0.102 mg/Kg). The heavy metals ranges in the crab were Zn (20.838 ± 7.803), Pb (0.000 ± 0.000) Cd (0.004 ± 0.014), Cr (0.500 ± 0.239), Ni (1.181 ± 0.562) and V (0.055 ± 0.112 mg/Kg). Hydrocarbon results for sediment were TPH (10.020 ± 11.255), PAH (1.377 ± 1.587 mg/Kg), while the crab had ranges of TPH (1.732 ± 2.235) and PAH (0.003 ± 0.007 mg/Kg). The results were within regulatory permissible limits of EGASPIN and WHO. ANOVA at p>0.05 indicated no significant spatial difference between the heavy metals and hydrocarbon concentrations in the sediments and crab at the various stations along the transect. Sediment heavy metal Ecological Risk Assessment revealed that contamination degree and pollution load index were < 1 (indicating no pollution); geo-accumulation index was grade 0 (unpolluted), individual potential risks and potential ecological risk index were < 40 and < 150 respectively (indicating low ecological risk). Sediment to biota transfer factor indicated that Zn was the only heavy metal biomagnified in the crab. Human health risk assessment of the heavy metals in the crab was less than 1 indicating no obvious health risk for cancer over a lifetime of exposure.