Potentially toxic elements contamination and ecological risk assessment in surface sediments of Moulouya Estuary (Northeastern, Morocco)

Abstract

Potentially toxic elements (PTEs) in aquatic ecosystems are a major environmental concern posing serious risks to aquatic life and human health. Understanding their distribution, sources, and effects is crucial for effective environmental management and the protection of biodiversity and natural resources. This study assessed the variability, bioavailability, contamination degree, and ecological risks of PTEs in surface sediments of the Moulouya Estuary. The levels of PTEs were determined using an inductively coupled plasma-optical emission spectrometry (ICP-OES). The mean concentrations of PTEs can be classified in the following order: Zn > Cr > As > Pb >Cu > Cd. The highest values were found in sites (S2, S4, and S5) that receive metals from anthropogenic activities. The mineralogical study showed that the sediment studied is dominated by Ca, which influences the PTEs mobility and makes them bioavailable in the aquatic environment, which means aquatic organisms can easily assimilate them. The PTEs contamination degree was determined by several pollution indices (CF, CD, PLI, EF, Igeo), which indicate that surface sediment shows low to moderate contamination levels. However, the Potential Ecological Risk indicates a moderate to considerable risk in the study area. The multivariate analysis indicates that As, Zn, Cr, Pb, and Cu are derived from anthropogenic activities (urban wastewater, fertilizers, and fishing boats), while Cd could have mixed sources. The results highlight suggest that human activities pose an ecotoxicological risk in the Moulouya Estuary. To minimize these risks and protect the aquatic ecosystem and human health, periodic monitoring and management strategies should be continued. These measures will enable early detection of changes in PTE levels and the implementation of the necessary interventions to reduce their harmful effects.