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

Abstract

BACKGROUND: The modified of Community Bureau of Reference (modified BCR) sequential extraction procedure has been one of common methods used for the trace metals speciation in sediments and allowed to the assessment of the ecological risk state of aquatic ecosystem based on ecological risk indexes. OBJECTIVE: The modified BCR sequential extraction procedure was used to the fractionation distribution of Cd, Co, Cu, Ni, Pb and Zn in sediment samples of Vridi channel, and three ecological indexes based on this method were used to assessment contamination and ecological risk state of these sediments. RESULTS: show that Cd, Co and Cu are mostly under their exchangeable form and bound to carbonates (92.07%, 31.20% and 32.02% respectively for Cd, Co and Cu), Pb mostly bond to Fe-Mn oxihydroxides (32.52%) and to organic matters and sulphides (32.21%), Zn mostly under its residual fraction (18.33%) and bond to Fe-Mn oxihydroxides (20.41%) and Ni mostly under its residual fraction (42.06%). These sediments present high contamination and ecological risk states of mainly in Cd, particularly its exchangeable form and that bound to carbonates. CONCLUSION: This present state of Vridi channel is essentially due to the strong anthropogenic pressures doing on this ecosystem. This study deserves to be widened in other hazardous pollutants to establish unequivocal the sanitary state of this estuary.

Simultaneous Effects of the Climate Change and the Recent Hydromorphological Modification of Vridi Channel (Côte d'Ivoire) on Some Its Hydrochemical Characteristics

“…Given its position, the water seasons of this estuary result from those of Atlantic Ocean in front of Abidjan district defined by Durand and Skibich [13] and those of Ébrié system defined by Durand and Guiral [14]. Yao and Trokourey [10,15] and Yao et al [16] define them as follow:…”

“…This fact is the consequence of the dysfunction and obsolescence of the sanitation system in Abidjan district [19]. Also, this estuary is also the transit point for many pollutants carried by continental waters in Atlantic Ocean in general, and in particular those by the coastal rivers Agnéby and Mé, and from the Comoé river [16,10,15]. This is due to the development and intensification of agriculture with intensive use of phytosanitary products in their watersheds.…”

“…For illustration, Pottier et al [20] mentioned that the Comoé River is responsible for two thirds of the metal pollution of Ebrié system. All these pressures ended up degrading this marine estuary and seriously threatening its biodiversity [16,10,15].…”

“…The monitoring of the variation of these parameters in aquatic ecosystems makes it possible to identify origins of their pollution and/or of their water exchange. Sediments are commonly used for characterizing anthropogenic impacts and/or climate change on aquatic ecosystems, because they are considered as a memory indicator of these ecosystems [9,10].…”

Impact of the Climate Change and the Recent Development of an Artificial Tropical Estuary on the Mobility and Distribution of Phosphorus: Case of Vridi Channel (Côte d'Ivoire)

“…This biodiversity is highly threatened by strong anthropogenic pressures. For illustration, the studies carried out by Yao et al [30] and Yao et Trokourey [31,32] in its former hydromorphology showed a relatively high pollution of its surperfcial sediments by trace metals. This is also the case with those of Konan et al [33] who highlighted a relatively high pollution of these substrates by polycyclic aromatic hydrocarbons.…”