Ecological risk assessment of potentially toxic elements (Heavy Metals) in water and Sediments of the Congo River: Seasonal variations and cadmium dominance
DOI:
https://doi.org/10.59228/rcst.026.v5.i2.289Keywords:
Cadmium, Heavy metals, Sediment contamination, Ecological risk assessment, Seasonal variabilityAbstract
Rivers act as major pathways for the transport and accumulation of contaminants in aquatic ecosystems, particularly in rapidly urbanizing tropical regions. This study assessed the seasonal variability of heavy metal contamination in sediments from the Maluku–Kinshasa section of the Congo River (Democratic Republic of Congo). Sediment samples were collected during the dry and rainy seasons and analyzed for Cd, Co, Cr, Cu, Pb, and Zn concentrations. Multiple geochemical indices including contamination factor (CF), geo-accumulation index (Igeo), enrichment factor (EF), pollution load index (PLI), Nemerow pollution index, and potential ecological risk index (PERI) were used to evaluate sediment quality and ecological risk. Results revealed clear seasonal variability, with significantly higher contamination levels during the rainy season. Among the analyzed metals, cadmium (Cd) showed the highest contamination factors and contributed most to the ecological risk index. Global indices (PLI and Nemerow) indicated moderate to high pollution during the rainy season, while dry season conditions reflected relatively low contamination levels. Multivariate statistical analysis highlighted strong seasonal clustering of samples, indicating hydrological control over metal transport and deposition. The findings suggest that rainfall-driven runoff plays a key role in mobilizing metal-contaminated particles into the river system. Cadmium was identified as the dominant ecological risk driver in the studied section. These results emphasize the importance of seasonal monitoring and targeted management strategies to mitigate metal inputs in tropical urban river systems.
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