SEASONAL DYNAMICS OF TRACE METALS IN THE WATERS FROM THE LAGOON AREA II OF ÉBRIÉ SYSTEM (CÔTE D'IVOIRE)

This study was carried out over the period from June 2019 to May 2020. Its main objective was to monitor the seasonal dynamics of As, Cd, Cr, Cu, Fe, Mn, Hg, Pb, Ni and Zn in the waters of the lagoon area II of Ébrié system. To this end, the study of the seasonal dynamics of the temperature, pH, salinity, conductivity, transparency, dissolved oxygen content and TOC content of these waters, as well as the mean depth of this ecosystem, was also studied with the aim of approaching their implication in this process. With the exception of the TOC content determined according to NF EN 1484 standard and the trace metals contents obtained according to MA 203-Met ICP-MSMS standard in the lab, the other physical and chemical parameters were determined in situ in the water samples collected. The trace metals contents of these waters decrease from its dry season to its flood season. The marine water inputs would favour a relatively high presence of these trace metals in them in their dry and rainy seasons, due to their basic character and their relatively high transparency and salinity in these seasons. The waters of Comoé river would partially disadvantage this process in its flood season, due to the slightly acidic character and low transparency and salinity of these waters in this season. Over all the study period, the relatively high temperature, conductivity, and oxygen content of these waters would have been conducive to the presence of these trace metals in dissolved form in them through the decomposition of organic matter. The relatively important organic matter content of these waters and the relatively shallow depth of this ecosystem would have disadvantaged this process over all the study period.