RESUMO
There has been a growing interest in soil replacement and in-situ stabilization techniques in recent years. Many techniques in the remediation of contaminated soils have been proven to be effective methods. In this study, lime and calcium phosphate were added to immobilize the heavy metals in contaminated soils. The long-term application potential of these techniques were evaluated by taking the demonstration project of the soil remediation in Tongguan of Shaanxi as the case study.The status of heavy metal contamination in the study area resulted from artisanal gold mining was discussed. The strategies of remediation and the evaluation of the remediation results including the safety of agricultural practices were also studied. The results showed that soil was seriously contaminated in the study area with Cd, Pb, and Hg, and the residue mining waste was the main source. The potential ecological risk index ranged from 668 to 10969, suggesting that all the samples posed a very strong ecological hazard. Based on the pollution status, the soil replacement method and stabilization method were applied. Acceptable remediation results were obtained with lower total metal content (except Cd) and decreased heavy metal availability. However, the metal content of agricultural products was higher than the permissible value according to GB 2762-2012, which means that agricultural practices pose risks on remediated soils. Soil replacement and stabilization would be practical techniques for heavy metal polluted soil remediation. However, a consecutive investigation should be conducted for the assurance of food safety.