Multimedia ecological risk deciphering and sediment source apportionment of potentially toxic elements in a typical coastal bay: A combined PMF-SOM-GIS approach.

As transitional zones of landsea interactions, bays are facing increasingly severe anthropogenic pollution pressures. To systematically assess these impacts, in this study, a comprehensive multimedia assessment framework encompassing seawater, surface sediments, and typical marine organisms was constructed to investigate the ecological risks, and anthropogenic driving mechanisms of potentially toxic elements (PTEs) in Sanmen Bay. The results indicate significant spatial heterogeneity of PTEs, with elevated clusters concentrated primarily in the northwestern nearshore and inner bay areas. The enrichment of Cd and Hg in sediments is severe, with mean contamination factors (CFs) reaching 3.44 and 3.02, respectively. Their individual potential ecological risk indices (Eri) peaked at 103.23 and 120.72, constituting the core ecological stress to the regional benthic environment. By applying a PMF-SOM-GIS multi-model strategy to the surface sediments, this study corroborates that the regional sedimentary enrichment is driven by both natural backgrounds and intensive anthropogenic activities. Four dominant sources were quantitatively apportioned: a natural geological background slightly disturbed by agricultural nonpoint sources (33.3%), a mixed nonpoint source of fertilizer application and mariculture (15.8%), a point source of port-industrial wastewater discharge (28.7%), and a mixed source of coal combustion and shipping (22.2%). Ultimately, this study elucidated the biogeochemical cycling of PTEs in Sanmen Bay, providing a practical, data-driven analytical strategy for pollutant source apportionment in similar coastal ecosystems.