Metal Pollution and Ecological Risk Assessment in Sediment of Artificial Estuary: Case of Vridi Channel, Côte d’Ivoire

Abstract

This study focused on a yearly monitoring of sediment pollution in Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb, Zn and the ecological incurred risks in Vridi channel. The results, expressed per dry weight, showed that the annual mean were 0.96 (± 0.16) mg/Kg for Cd, 22.36 (± 2.41) mg/kg for Co, 33.98 (± 4.61) for Cu, 31760.5 (± 5652.7) mg/kg for Fe, 981.2 ± (377.5) mg/kg for Mg, 302.9 (± 415.4) mg/kg for Mn, 42.53 (± 9.79) mg/kg for Ni, 83.37 (± 6.66) mg/kg for Pb and 27.11 (± 11.72) mg/kg for Zn. The measured oligo-elements (Fe, Mn, Mg, Zn) originated from naturals sources and were away from accumulation, except from Fe which moderately accumulated. That hence the low sediment contamination by these metals. As for toxic trace metal (not essential) to living organisms (Co, Cu, Pb, Cd, Ni), they resulted from anthropogenic origin. These sediments were moderately contaminated in Co, Cu and Ni, significantly in Pb and strongly in Cd. All the studied trace metals were mainly from continental origin, except Cd which showed a marine origin. This estuary displayed a steady state of progressive deterioration and presented a very high ecological risk. © JASEM https://dx.doi.org/10.4314/jasem.v21i4.20

Fractionation distribution and ecological risk assessment of some trace metals in artificial estuary: Vridi channel (Côte d'Ivoire)

“…These results obtained confirm those obtained by Yao et al [13]in these sediments. This state of Vridi channel is essentially due to high anthropogenic pressures doing on this estuary.…”

“…An increase in the concentration of major cations (Na + , K + , Ca 2+ , Mg 2+ ), due to an increase of the salinity, would for the formation of this fraction by competing on various adsorption sites [17,41]. The reducing character of sediments of this estuary [13] and microbial activities would contribute to it too, by reduction of their Fe-Mn oxihydroxides and sulphides compounds [14,44]. These phenomena have a particular importance for Cd with regard to Co and Cu.…”

“…All the reducible fraction of trace metals studies, superior to 50 %, illustrates that they in their majority outcomes of the rejections of anthropogenic activities, particularly those of autonomous harbor of Abidjan and its industrial zone, well as those of industrial zone of Yopougon [13]and those transported by the Comoé river [25]. The strong positive correlation between Co, Cu and Zn (Tableau 3) shows that these trace metals are the same origin.…”

“…Therefore, the ecological risk assessment dues to trace metals in sediments are so important. Although, the total concentration of trace metals in sediments gives valuable information on overall pollution level [12][13], they don't provide enough information to understand their various forms, mobility, bioavailability or potential risk to environment [14][15]. In opposite, a fractionation distribution (metal speciation analysis) can give more information about it and be a good indicator of the aquatic ecosystem quality for the metallic pollution.…”

“…So, its biodiversity and sustainable development are seriously threatened. For illustration, Yao et al [13] have shown the progressive degradation of this estuary with its high ecological risk, due to the metallic pollution. For this reason, it is important to purchase this kind of study in this bay for more information.…”