In situ passivation effect of fertilizer passivation solutions with various pH on Pb-F contaminated soil

Abstract The Maoniuping rare earth mine in Mianning, Liangshan Prefecture, is the largest rare earth deposit in China and the second largest rare earth deposit in the world. During the mining of rare earths, F and Pb, both types of heavy metal waste can directly or indirectly enter the soil, causing local soil contamination, which in turn poses a threat to the health of local residents. In this study, soil samples were incubated with fertilizer passivation solutions with pH values of 4, 5, 6, 7, 8, and 9, with the soil water content adjusted to 50% of the maximum water holding capacity in the field. The Pb-F contamination of the soil samples was analyzed to determine the existing states of the soil F and Pb and to study the remediation effect of fertilizer passivation solutions on the Pb-F contaminated soil. The results showed that under different passivation conditions, the pH, Pb, and F of the soil substantially changed and the passivation effect was enhanced over time. The pH of the soil significantly increased. The analysis of the effects of F and Pb treatment revealed that when the passivation fertilizer solution of pH 5 was used, the available Pb and F in the soil decreased the most, and the residual state of Pb and F increased to 77.86% and 57.24%, respectively.