[Solid-solution Partitioning Coefficients and Environmental Risk of Cd and Pb in Soil in Chang-Zhu-Tan Area]

The leaching risk of heavy metals in soil has a large spatial variability on a regional scale. Taking the Chang-Zhu-Tan area as the research object, this work studied the distribution and influencing factors of available contents and solid-solution partition coefficient (K_d) of Cd and Pb in soil with land uses and clarified the environmental risk of heavy metals in soil based on K_d values measured by CaCl₂ (soil-to-water ratio, 1:0.5). The results showed that the contents of available Cd and Pb in soil followed the order of forest land>suburban farmland>urban green space>industrial green space. The average K_d of Cd in soil was 449.79 L·kg^-1, and that of Pb was 27604.07 L·kg^-1, indicating that the mobility of Cd in the soil was significantly higher than that of Pb. The K_d values of forest soil were significantly lower than that in the other land uses. The K_d values were mainly affected by soil pH and the total content of heavy metals in soil. Adopting the available content of heavy metals measured by CaCl₂ (soil-to-water ratio, 1:10) as a dependent variable, the multiple regressions effectively predicted the K_d values of Cd and Pb in soil, with R² values of 84.2% and 67.6%, respectively. The environmental risk assessment indicated that the leaching risk in 93.8%-96.1% of the sampling sites could be ignored, whereas a few sampling sites near factories with low pH may pose a risk to the groundwater environment. The mobility of heavy metals in soil and the distribution of pollution sources determined the leaching risk of heavy metals. The results provide a method and theoretical support for preventing the environmental risk of heavy metals in soil on a regional scale.