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 (Kd) of Cd and Pb in soil with land uses and clarified the environmental risk of heavy metals in soil based on Kd 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 Kd 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 Kd values of forest soil were significantly lower than that in the other land uses. The Kd 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 Kd 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.
Keywords: available contents; heavy metals; leaching risk; regression prediction; urbanized area.