Distribution Patterns of Pb in Pb-Contaminated Soil with Composts and Apatite

Abstract

In the present investigation, hydroxyapatite powder and organic compost in various mix ratios were incorporated into two types of high-concentration synthesized Pb-contaminated soils, which were then processed with sequential extraction schemes after distinct incubation periods to investigate the distribution of Pb forms in them. The use of compost can provide soil microbial populations with energy needed for their growth, while facilitating the activity of soil microbial populations and maintaining a balanced ecosystem.  The results showed that the alkaline Tk series soil was less prone to Pb contamination after stabilization for a month when no hydroxyapatite and compost were applied, making it more difficult for Pb in the soil to interact with cations and start exchange processes. The two soils tested next had greater PbR contents following the addition of hydroxyapatite. According to this finding, hydroxyapatite served to stabilize the Pb in the soil samples and stopped it from precipitating, maintaining the Pb content at a specific level to prevent contamination. We discovered that the PbE concentration of the Tk series soil decreased as the concentration of compost increased when hydroxyapatite and compost were applied to the two types of Pb-contaminated soils in different mix ratios. This finding suggests that boosting the compost concentration increased the soil's pH value and improved its fertility. On the other hand, the Lp series soil's PbE concentration rose as the compost concentration did, suggesting that a rise in compost concentration prevented plants from absorbing soluble nutrients from the soil, making it simpler for Pb to precipitate via cation exchange and leading to Pb contamination.  We hope that the research findings can be widely applied to contaminated soil treatment, serving as a reference especially for soil remediation and rehabilitation at soil treatment sites.