Potentially toxic elements accumulation in the surface sediment of the Bouregreg estuary, Morocco: Implications for environmental changes and human activities over the last decades

This study investigates the sources, spatiotemporal distribution, contamination levels, and ecological risks of six potentially toxic elements (PTEs) in surface sediments of the Bouregreg Estuary, Morocco, an ecologically significant estuarine system undergoing urbanization and management improvements. The mean PTEs concentrations (mg/kg) were Zn (47.32) > V (30.72) > Pb (17.41) > Cr (14.31) > Cu (9.92) > Cd (1.17). Cd emerged as the most concerning pollutant (up to 2.12 mg/kg), exceeding the background value, showing moderate to strong pollution (Igeo), moderate to very high contamination (CF), and moderate to high ecological risk (ERI). Followed by Pb which showed low to moderate contamination (up to 23.21 mg/kg) according to the CF, correlating with fine, organic-rich sediments near urban areas. Significant seasonal and spatial variations, influenced by anthropogenic pressures and sediment characteristics, were confirmed through principal component analysis and correlation analysis. Historical comparisons indicate an overall improvement in the estuary's ecological health. However, persistent Cd and Pb hotspots emphasize the need for targeted management strategies to safeguard the estuary's ecological integrity and community health.