[Characterization and Risk Assessment of Heavy Metal Pollution in Amphibian Habitats in the Yellow River Basin]

Heavy metal pollution risk assessment in aquatic habitats at the basin scale is a crucial approach for maintaining biodiversity and ecological security. Taking amphibian habitats in the Yellow River Basin as the study object， we established 52 sampling sites across the basin during the dry seasons of March-April 2023 and June 2024. Surface sediments from these habitats were collected and analyzed for the concentrations of six heavy metals： Cd， Zn， Cr， Cu， Ni， and Pb. Spatial distribution characteristics of these metals were assessed using spatial interpolation methods. Pollution levels and potential ecological risks were evaluated using the geo-accumulation index （I_geo） and the potential ecological risk index （RI）， while principal component analysis was employed to identify potential pollution sources. The results showed that， spatially， heavy metal concentrations in the middle and upper reaches were generally higher than those in the source and lower reaches. Cr， Cu， and Zn in the upper reaches exhibited the highest concentrations， followed by the middle reaches. The mean I_geo values of the six metals followed the order： Cd>Zn>Cr>Cu>Ni>Pb， indicating moderate to severe pollution levels for Cd. Due to the elevated Cd concentrations， the overall ecological risk of heavy metals in the study area was at a relatively high level， with higher risks in the middle and lower reaches and the lowest in the source region. Source analysis revealed that Cu， Zn， Cd， and Pb mainly originated from industrial mining， metal smelting， and transportation activities， while Ni and Cr were primarily derived from agricultural activities and the weathering of parent materials. To mitigate the ecological hazards posed by heavy metal contamination in the Yellow River Basin and improve habitat quality， it is essential to strengthen the regulation of Cd and enhance environmental management in industrial pollution hotspots across the basin.