Distribution And Source Oftrace Metals In Coastal Water Of the Bay Of Tangier (north West Morocco)

摘要

In this paper, the assessment of pollution originated by effluents of industries and urban sewage from Tangier (Morocco) is presented. Sediment and pore water samples from Mghogha River were collected at forty stations, characterized and several metals were analysed (Fe, Mn, Cu, Cd, Zn, Pb, Cr and Hg). The metallic concentrations in labile sediment fractions were determined in order to asses their bioavailability, using ammonia acetate as leaching extractant. Elevated concentrations of lixiviable Hg, Cu and Cd were found and their contents in pore water were detected, exceeding sometimes the recommended quality criteria. As consequence of the obtained results, water samples of eight stations were collected along the bay of Tangier in order to evaluate the influence of the discharges in the coast. Higher dissolved metal concentrations were found in river samples than in seawater, although below EPA criteria. They produced a metal plume flowing into coastal water, principally for Zn, Cu and Fe. Outstanding particulate Pb, Zn and Cu concentrations were found in seawater sites, where high salinities favoured the association of trace metals to particles. In addition, high organic pollution of river owing to urban and industrial sewages was detected even for coastal seawater samples. The principal component analysis (PCA) method was employed for searching the pollution sources. Therefore, the influence of pollution from Mghogha River over the beach of Tangier Bay has been shown in this paper.