Accumulation of PAHs,Me-PAHs, PCBs and total Mercury in sediments and Marine Species in Coastal Areas of Dakar, Senegal: Contamination level and impact

Abstract

Persistent Organic Pollutants (POPs) have widely aroused public concern due to their ubiquity, environmental persistence, long-range transportability, bioaccumulation capacities and potentially adverse effects on living organisms. Dakar is located in the industrial zone of Senegal (80% of industrial activities) and inhabits 25% of Senegalese population leading to an ideal sink of these persistent organic pollutants. In the present paper, Polychlorinated Biphenyls (PCBs) and polycyclicAromatic Hydrocarbons (PAHs) were analyzed in sediments and marine organisms. The contamination level of PAHs,Me-PAHs and PCBs in surface sediment and aquatic organisms (one macroalgae, two invertebrate species, four fish species and macroalgae) were determined. The concentration levels in the sediment were detected from 2 to 636 μg/kg dw for Σ16PAHs, from 3 to 31 μg/kgdw for Σ18Me-PAHs and from 4 to 333 μg/kg dw for Σ28PCBs for the selected stations in Dakar costal area. PAHs concentrationsdetermined in edible tissues were lower than sediment samples. Tilapia species present the highest mean levels of PAHs and Me-PAHs at 92 ± 54 and 183 ± 39 μg/kg dw respectively. For PCBs, the highest level was determined in Perna perna species (up to 1228 μg/kg dw) and the lowest level was found in Penaeus kerathurus species. At the base of the food chain, Ulvalactula species displayed low PCB concentrations detected at 7 ± 6 μg/kg dw. The totalmercury concentration was also reported in this paper in order to complete the background of pollution degree and to study the potential processes of biomagnification and/or bioaccumulation of contaminants in marine food chain. Mercury concentration were detected in the sediment ranging from 5 to 95 μg/kg dw. For marine species, considering all organisms, the mean concentration of mercury varies between 5 and 442 μg/kg dw. Pyrogenic process was the predominant source of PAHs contamination in our sampling sites. Based on Sediments Quality Guidelines (ERM–ERL/TEL–PEL approaches) rare biological adverse effects of total mercury, PCBs and PAHs on aquatic ecosystems were expected in Dakar coastal area. Finally, in the context of human health, the edible marine species qualities obtained from three stations of Dakar coastal areas have been also evaluated. Based on the European Union legislation, the selected species present good quality for human consumption based on PCBs, PAHs and mercury