Leaching characteristics and potential risk assessment of heavy metals Pb-Cd from mining soils in an acid rain environment

To investigate the pollution characteristics of Pb and Cd in mining soil, dynamic leaching tests was conducted to explore the leaching characteristics. Pollution was evaluated using the Risk Index (RI) and Assessment Code (RAC). The results showed that under simulated acid rain, the soil had a certain buffer capacity, the pH value of leaching solution varied between 5.0 and 8.5. Heavy metals release also varied, with the highest amount of Pb dissolved being 2.27 mgꞏL-1, while that of Cd was relatively low, the highest is 0.93 mgꞏL−1. Moreover, heavy metals with larger particle sizes showed a greater propensity for dissolution when subjected to acid rain. BCR extraction revealed that the initial heavy metal status was mostly residual. After leaching, heavy metal morphology changed drastically, with the residual state of reducing significantly. RAC and RI indicated a moderate risk of Pb and Cd pollution under different treatment conditions