Sedimentary records of anthropogenic contribution to heavy metal content in Oum Er Bia estuary (Morocco)

Levels of heavy metals (Cd, Hg, Cr, Cu, Fe, Mn, Ni, Pb and Zn), organic carbon content and textural characteristics in the superficial and cored sediments of Oum Er Bia estuary have been studied. The anthropogenic fluxes of heavy metals were determined in two sediment cores collected in the estuary, facing urban sewages. A dated estuarine core from the inter-tidal area was assessed using ²¹⁰Pb and ¹³⁷Cs data. These data indicate that the mean sedimentation rates are 0.38–68 cm year^?1. The analytical results and the radio-dating of sediment cores show extremely high concentrations of Zn, Pb and Cu in the sediments that can be ascribed mostly to the discharge of the liquid effluent from the sewage since the late 1960s, decreasing towards the present day. The pollution intensity of the estuary is determined by the enrichment factors, which show that the Oum Er Bia estuary is moderately polluted to polluted.     

Evaluation of the anthropogenic influx of metal and metalloid contaminants into the Moulay Bousselham lagoon, Morocco, using chemometric methods coupled to geographical information systems

Superficial and cored sediment samples from the Moulay Bousselham lagoon and sub-watershed were analyzed for Al, Fe, Cu, Zn, Pb, Mn, Ni, Cr, As, Hg, and Cd. The temporal and spatial distributions of the main contamination sources of heavy metals were identified and described using chemometric and geographic information system (GIS) methods. Sediments from coastal lagoons near urban and agricultural areas are commonly contaminated with heavy metals, and the concentrations found in surface sediments are significantly higher than those from 50–100 years ago. The concentrations of these elements decrease sharply with depth in the sediment column, and the elements are preferentially enriched in the <2-μm-sized fraction of the sediment. The zones of enhanced risk of heavy metals were detected by means of GIS-based geostatistical modeling. According to sediment pollution indices and statistical analysis, heavy metals (Pb, Cu, Ni, Zn, Cr, and Hg) that pose a risk have become largely enriched in the lagoon sediments during the recent period of agricultural intensification.