TITLE:
Assessment of the Ecological Risk Associated with Seasonal Variability in Water and Sediment Contamination by Heavy Metals along the Coast of Senegal
AUTHORS:
Jessica Carmelia Mbemba Peleka, Robert Faomowe Foko, Mathilda Osiris Mahouekpo, Mouhamadou Lamine Daffe, Awa Ndong, Fatoumata Bah, Aminata Touré, Mathilde Cabral, Mamadou Fall, Cheikh Diop
KEYWORDS:
Heavy Metals, Potential Ecological Risk, Seasonal Variation, Coastline, Senegal
JOURNAL NAME:
Open Journal of Marine Science,
Vol.15 No.4,
October
29,
2025
ABSTRACT: Pollution of water and sediment by heavy metals (HMs) poses a significant threat to aquatic ecosystems due to their toxicity and persistence. This study aimed to evaluate the ecological risk associated with the seasonal and spatial variation in heavy metals concentrations in the water column and sediments across five sites along the Senegalese coastline. Water and sediment samples were collected using standardized methods and analyzed for HMs by flame atomic absorption spectrophotometry (AAS) after acid digestion. The highest mean concentrations of HMs in water were as follows: Pb (0.96 mg/L) > Fe (0.76 mg/L) > Cr (0.47 mg/L) > Cd (0.20 mg/L) > Cu (0.08 mg/L) > Mn (0.06 mg/L) and in sediments: Fe (442.38 mg/kg) > Pb (44.51 mg/kg) > Mn (27.65 mg/kg) > Cr (16.55 mg/kg) > Cu (16.31 mg/kg) > Cd (3.75 mg/kg). In water, the concentrations of Pb, Cd, and Cr exceeded the 2012 USEPA threshold values across all sites and seasons. In contrast, in sediments, most HMs were below the reference values in the sediment quality guidelines, except of the Soumbédioune site during the dry season where Cd exceeded the probable effect limit (PEL). Assessment using the enrichment factor (EF), geo-accumulation index (Igeo) and contamination factor (CF) indicated moderate to high levels of pollution that Pb, Cd and Cr had, while Mn, Cu and Fe showed low pollution levels. The ecological risk index also showed that, regardless of the season, only the Rufisque and Soumbédioune sites presented a moderate risk; the other sites are classified as low risk. Principal component analysis (PCA) reveals that during the dry season, in water and sediments, the Soumbédioune site is more impacted by Cd, while Rufisque has higher Pb levels. This study could serve as a reference for monitoring water and sediment quality along the Senegalese coast in view of the urbanization and industrialization of Senegal’s coastal cities.