Spatiotemporal patterns, source apportionment, and ecological risk of major and trace elements in sediment cores from Anzali International Wetland

Wetlands, critical yet vulnerable ecosystems worldwide, are increasingly threatened by contamination from anthropogenic activities. This study investigates the spatial and vertical distribution of 17 major and trace elements in sediment cores from the Anzali International Wetland, a Ramsar site in Iran under pressure from urbanization, agriculture, and industry. Cores were sliced at 2-cm intervals and analyzed via ICP-MS to reconstruct historical trends and evaluate spatiotemporal distributions, sources, and ecological risks using geoaccumulation index (I_geo), enrichment factor (EF), and pollution load index (PLI). Multivariate analyses (PCA, HCA) identified lithogenic (Al, Fe), carbonate-associated (Ca, Sr), and anthropogenic (Cd, Pb, Zn) elemental groupings. Severe Cd contamination (I_geo > 5; EF > 40) was found at site 1, linked to industrial/agricultural discharges, while sites 2 and 3 showed moderate heavy metal enrichment. Cd, Cr, and Ni exceeded sediment quality guidelines, indicating significant ecological risk. Vertical profiles revealed contamination peaks at 24-26 cm (Site 1) and 50-62 cm (Site 2), correlating with historical pollutant influx. Sediment texture and organic matter influenced metal binding. PLI confirmed significant pollution (PLI > 3) across all sites, with Cd posing the highest risk. This study underscores the critical role of integrated sediment core analysis in reconstructing pollution history and informing targeted management strategies to protect and restore vulnerable aquatic ecosystems globally.