Evaluation de la Pollution MÃ©tallique des SÃ©diments Superficiels de la Lagune Potou en PÃ©riode dâ€™Ã©tiage (Littoral de la CÃ´te dâ€™Ivoire)
Authors: Diangone Eric , Nâ€™guessan Yao Alexis , Toalo Lou Kala Marie-Claude , Sylvain Monde , Aoua Coulibaly 
Published: December 2020

La prÃ©sente Ã©tude vise Ã  Ã©valuer la pollution mÃ©tallique des sÃ©diments superficiels de la lagune Potou (littoral de la CÃ´te dâ€™Ivoire en pÃ©riode dâ€™Ã©tiage). La mÃ©thode utilisÃ©e Ã  cet effet repose en premier sur lâ€™Ã©chantillonnage des sÃ©diments et sur la dÃ©termination de leurs concentrations en ETM (Ã‰lÃ©ment Trace MÃ©tallique) Ã  lâ€™aide de la technique spectromÃ©trique. Ensuite, lâ€™estimation du niveau de la pollution mÃ©tallique des sÃ©diments, a Ã©tÃ© faite en comparant les concentrations des mÃ©taux obtenues Ã  celles de la croÃ»te continentale de Wedepohl (1995) et Ã  celles des sÃ©diments non polluÃ©s de Calamari et Naeve (1994) et Kikouama et al. (2009). De mÃªme, lâ€™estimation du niveau de la pollution mÃ©tallique des sÃ©diments a Ã©tÃ© rÃ©alisÃ©e par le calcul de plusieurs indices de pollution dont le facteur dâ€™enrichissement et lâ€™index de gÃ©o-accumulation. Lâ€™approche mÃ©thodologique sâ€™est enfin achevÃ©e par lâ€™Ã©valuation des risques des sÃ©diments en place Ã  partir des valeurs guides TEC (Threshold Effects Concentrations) et PEC (Probable Effect Concentration) et par lâ€™Ã©tude de la distribution spatiale des diffÃ©rents contaminants au sein de la zone Ã©tudiÃ©e. Au total, 15 ETM ont Ã©tÃ© identifiÃ©s dans les sÃ©diments du milieu, Ã  savoir lâ€™aluminium (Al), lâ€™arsenic (As), le calcium (Ca), le cadmium (Cd), le chrome (Cr), le cuivre (Cu), le fer (Fe), le potassium (K), le magnÃ©sium (Mg), le manganÃ¨se (Mn), le sodium (Na), le nickel (Ni), le plomb (Pb), lâ€™antimoine (Sb), et le zinc (Zn). Ces ETM ont des teneurs variables Ã©voluant en moyenne entre 0,81 et 46693,33mg/Kg. Cette importante variabilitÃ© est aussi constatÃ©e au niveau des valeurs dâ€™enrichissement en ETM. Celles-ci sont comprises en moyenne entre 0,03 et 4,15mg/Kg. Concernant lâ€™index de gÃ©o-accumulation, les valeurs trouvÃ©es sont en majoritÃ© nÃ©gatives sauf chez le zinc (0,77mg/Kg) et lâ€™antimoine (1,4 mg/Kg). Lâ€™ensemble de ces rÃ©sultats a montrÃ© que les sÃ©diments de la lagune Potou sont de mauvaise qualitÃ© car polluÃ©s par le cuivre, le fer, le zinc et lâ€™antimoine. Ces mÃ©taux, en particulier le zinc et lâ€™antimoine, peuvent exercer un effet nÃ©faste sur les organismes aquatiques du milieu lagunaire ainsi que sur lâ€™Homme.
This paper focuses on evaluating the metallic pollution of the superficial sediments of the Potou lagoon (Coast of CÃ´te d'Ivoire) during the low water period. The method used for this study is based, first of all, on the sampling of the sediments and on the determination of their respective concentrations in MTE (Metal Trace Element) using the spectrometric technique. The estimation of the level of metallic pollution of the sediments was made by comparing the concentrations of the metals obtained with those of the continental Wedepohl crust (1995) and those of the unpolluted sediments of Calamari and Naeve (1994) and Kikouama et al. (2009). It was also achieved by calculating several pollution indices including the enrichment factor and the geo-accumulation index. The methodological approach was finally completed by assessing the risks of sediments in place from the TEC (Threshold Effects Concentrations) and PEC (Probable Effect Concentration) guide values and by studying the spatial distribution of the various contaminants at the site within the study area. A total of 15 MTE were identified in the sediments of the medium, namely: aluminium (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), antimony (Sb), and zinc (Zn). These MTE have variable contents ranging on average between 0.81 and 46693.33 mg / kg. This important variability is also found in the MTE enrichment values. These are on average between 0.03 and 4.15. Regarding the geo-accumulation index, the values found are mostly negative except for zinc (0.77) and antimony (1.4). All of these results showed that the sediments of the Potou lagoon are of poor quality because they are polluted by copper, iron, zinc, and antimony. These metals, in particular zinc and antimony, can have a detrimental effect on the aquatic organisms that inhabit the environment as well as humans.