Century-long metal(loid) sources dynamics and potential ecological risk revealed by lake sediments in a Yangtze floodplain lake.

Metal(loid) contamination is an important environmental concern in lakes of the middle-lower Yangtze River Basin, yet long-term changes in contaminant sources and ecological risk remain poorly resolved. We used a 210Pb-dated sediment core from Wushan Lake to reconstruct century-scale contamination dynamics by integrating enrichment factor (EF), geoaccumulation index (Igeo), potential ecological risk index (RI), positive matrix factorization (PMF), and time-series analyses. Sediments deposited before the mid-1980s showed generally limited anthropogenic enrichment, followed by increased accumulation of Cd, As, Mn, and Cu. RI increased toward recent sediments and was dominated by Cd, but is interpreted as a screening-level indicator rather than evidence of realized ecological effects. PMF supported a predominantly lithogenic component and two anthropogenic-related mixed components. Under the primary model, agriculture-related influence was greater during the late 20th century, whereas industrial-urban-related influence became more prominent after the early 2000s; this temporal succession is treated as model-supported rather than uniquely resolved. Cr and Ni were mainly associated with the lithogenic component, highlighting the importance of site-specific geochemical baselines. After accounting for temporal trends and autocorrelation, most socioeconomic associations weakened, with only As remaining significantly related to the dominant socioeconomic gradient. Recent declines in Cu, Mn, and Pb accumulation coincided with strengthened pollution control but cannot be uniquely attributed to management interventions. Overall, integrating dated sediment archives, local baselines, receptor modeling, and time-series analysis provides a useful framework for reconstructing long-term contamination dynamics while accounting for uncertainty in source attribution and management-related interpretation.