ASSESSMENT OF METAL CONTAMINATION IN COASTAL SEDIMENTS OF THE LEVRIER BAY AREA, ATLANTIC OCEAN, MAURITANIA

This work presents an assessment of marine pollution due to heavy metals accumulated in surface sediments collected from the Levrier bay coastline in NW Atlantic, Mauritania. The samples were subjected to HCl and HNO3 digestion, and an atomic absorption spectrophotometer was used to determine the concentrations of all metals (Cd, Pb, Cu and Zn) with the exception of Hg that was analysed by DMA-80 Direct Mercury Analyzer. The ranking of the metals at all studied sites was Al>Zn > Cu >Pb> Cd>Hg, and all the sediments samples displayed lower concentrations than the calculated worldwide mean of unpolluted sediments. The data were classified according to seasons. . Eight common pollution indices (i.e. EF, Igeo, QoC(%), CF, SPI, PLI, C-d and PERD)were applied to ascertain the sediment quality. The enrichment (EF) factor resulting from Pb, Cu and Zn were <1 in surface sediments at all sampling sites and for Cd at Cap Blanc, indicating no enrichement . EF values in COMECA and Baie de l'Etoile for Cd were 1 < EF < 3, indicating a low enrichment. EF values for Cd at IMROP were 3 < EF < 5 indicated a moderate enrichment. The value of the geoaccumulation (Igeo) factor from all metals analysed was less than 0 in all sampling sites, which classified the sediments as uncontaminated The value of contamination (CF) factor for all elements analyzed was lower than 1 across all sampling sites, implying a low contamination.The values of Sediment Pollution (SPI) Index were 0<SPI<2, indicating a natural status of sediments in COMECA, Baie de l'Etoile and Cap Blanc. The SPI values at IMROP were 2<SPI<5, which showed a low pollution of sediments on this site. The value of the pollution load (PLI) index was <1, which indicated that no metal pollution existed in sediments in all studied sites. The values of the contamination degree (Ca) were <6 in all sampling sites, indicating a low degree of contamination. The values of the Potential Ecological Risk (PERI) index were 21.5<PERI <28.4 in all sampling sites, indicating a low ecologic risk.These results provide an important reference for future comparisons in the West African sub-region on the state of contamination of marine and coastal areas.