Spatiotemporal controls of soil Pb distribution and ecological risk in the Qorveh mining region, Western Iran.

To investigate the spatiotemporal variability of lead (Pb) in mining environments, 100 topsoil samples were collected from different locations across a semi-arid mining district in western Iran over a 4-month monitoring period, with sampling conducted at different sites in each month. Key explanatory variables, namely, pH, electrical conductivity (EC), soil organic carbon (SOC), zirconium (Zr), and elevation and slope as topographic attributes alongside normalized difference vegetation index (NDVI), were integrated into the Geographic and Temporal Weighted Regression (GTWR) framework. Pb was selected because of its strong association with mining activities, high environmental persistence, and ecological significance. The effectiveness of the GTWR model was evaluated and compared with Ordinary Least Squares (OLS), Geographically Weighted Regression (GWR) and Temporally Weighted Regression (TWR) using multiple statistical evaluation metrics and model-fitting criteria. In addition, the ecological implications of Pb contamination were assessed using the risk quotient (RQ) index. The evaluation metrics demonstrated the superiority of GTWR (R2 = 0.79) over the other models. The results indicate that Pb distribution was influenced by geological, geochemical, and biological factors, with Zr showing a predominantly spatially positive association, EC exhibiting spatially variable effects, and NDVI and pH showing relatively stable temporal associations with Pb. Furthermore, RQ values exceeded the ecological threshold throughout the study area, indicating widespread potential ecological risk. Integrating GTWR with ecological risk assessment provides a useful framework for characterizing heterogeneous Pb patterns and supporting the identification of priority areas for environmental monitoring and risk management in mining-affected landscapes.