Evaluation de la contamination des éléments traces métalliques dans les sédiments de la rivière N’zi, Côte d’Ivoire

Abstract

Les éléments traces métalliques s’accumulent dans les systèmes aquatiques et peuvent dégrader la qualité des eaux et présenter une menace pour la santé humaine et la faune. Cependant peu d’étude existe sur la concentration totale des métaux dans les cours d’eau ivoiriens impactées par les activités agricoles. Pour contribuer à la mise en place d’une base de données, nous avons étudié la distribution et le niveau de contamination du Cu, Hg, Pb, Ni et Zn dans les eaux et les sédiments de la rivière N’zi. La concentration des éléments traces métalliques (Cu, Hg, Pb, Ni et Zn) ont été mesurées dans les sédiments de la rivière N’zi pour évaluer le niveau de pollution. Le degré et les sources de contamination ont été déterminés par le calcul des indices de pollution métallique : facteur de contamination (FC), indice de géoaccumulation (Igeo), facteur d’enrichissement (FE) indice global de pollution (PLI). Les valeurs de Igeo pour le Cd et le Cu ont été supérieures à 0 et les valeurs de FC pour le Cd, Cu et le Hg ont été supérieures à 1 dans la station de Moofoué, ce qui suggère que les sédiments de Moofoué sont modérément contaminés par ces éléments. Les valeurs de PLI ont montré que tous les sédiments sont non pollués. Les valeurs de FE pour le cuivre ont excédé 1,5 ce qui dénote une origine anthropique pour le Cd et le Cu.
 Traces metal elements accumulate in aquatic systems and can degrade water quality and pose a threat to human health and wildlife. However, few studies exist on the total concentration of metals in ivorian rivers impacted by agricultural activities. To help set up a database, we studied the distribution and level of contamination of Cu, Hg, Pb, Ni and Zn in the waters and sediments of the N’zi River. The concentrations of the trace metals (Cu, Hg, Ni, Pb and Zn) were measured for the surface sediments of the N’zi River, Côte d’Ivoire, to evaluate the level of contamination. Sediment pollution assessment was carried out using contamination factor (CF), pollution load index (PLI), geoaccumulation index (Igeo) and enrichment factor (EF). The Igeo value for Cd and Cu were > 0 and the CF values for Cd, Cu and Hg were > 1 in sediments of the Moofoué station, which denotes a moderate contamination in these metals. The PLI indicated that all stations were no polluted. The EF value for Cd and Cu were >1.5 in the sediments, suggesting anthropogenic impact on the metal levels in the river. The concentrations of Cd and Cu are likely to result in harmful effects on sediment-dwelling organisms which are expected to occur frequently based on the comparison with sediment quality guidelines.

Contamination and Potential Risks of Heavy Metals in the Sediments of the Chari and Logon Rivers in N’Djamena, Chad

“…The results obtained by Muhammad in the sediments of Weihe River (China) show contamination [36]. The results obtained in this study are clearly weaker than those obtained by Ouattara in the N'zi River in Côte d'Ivoire [36].…”

“…Similarly, the results obtained by Banu et al, (2013) [35] are much higher than our results (28.30 -36.4 mg/kg) and also those recorded by Rabee et al, (2011) (8 -59 µg/g) [27]. The values obtained by Muhammad et al, (2020) [36] in Weihe River in China are much higher. For Cr VI, the concentrations vary from 0.02 mg/kg to 0.04 mg/kg in S1 (low water in June) for a mean of 0.031 ± 0.009 µg/kg.…”

“…The same is true for the results of Leila in the sediments of the Boumerzouk Basin in Algeria showing heavy metal contamination [23]. The results obtained by Muhammad in the sediments of Weihe River (China) show contamination [36]. The results obtained in this study are clearly weaker than those obtained by Ouattara in the N'zi River in Côte d'Ivoire [36].…”

Evaluation of Agricultural Contamination Level by Heavy Metals and Pesticides in Sediments of Rivers and Water Bodies for Shrimp Fishing in the Lower Ouémé: Case of the Aguigadji, Ahlan and Sele Stations in Benin

“…In the country and in the sub-region, authors have also identified heavy metals in sediments. These include scientific works [23] [31] [32] [33], which found a range of heavy metals in sediments from the Gogounou, Kandi and Banikoara cotton belts in Benin, the Weija water reserve in Ghana, the lake at the Nangbéto hydroelectric dam in Togo and sediments from the N'zi river in Côte d'Ivoire. Lead concentrations were highest at all the stations, with the highest concentration of 265.96 ± 21.02 mg/Kg recorded at the Aguigadji station during the rainy season.…”

Fractionation, Mobility and Environmental Risk of Trace Metals in the Sediments from N’zi River, Côte d’Ivoire

“…In rural areas, agricultural activities, through the massive use of fertilizers and pesticides, represent the main sources of contamination of trace metal elements in aquatic environments [6][7][8].…”