Effect of Weathered Coal on the Leaching Behavior of Lead-Contaminated Soil with Simulated Acid Rain

Abstract

Lead (Pb) has progressively become a widespread contaminant in the environment because of its intensive use and inherent stability. The contamination of Pb in agricultural soils is a major environmental problem. This paper considers the use of weathered coal humic acids for in situ remediation of Pb-contaminated soils. The effectiveness of acid rain on leaching in soil column was investigated. To determine the mobility and availability of Pb, we also investigated the soil pH and available soil Pb content from different depths in addition to the leachate pH and Pb concentrations at different times. Weathered coal has the potential to adjust the soil pH and leachate pH through metal-bridging mechanisms and deprotonation processes. We found that weathered coal humic acid and simulated acid rain significantly decreased the available surface soil Pb concentrations. The decrease in the available Pb concentrations in the surface layers of the soil was related to a significant increase in the available Pb concentrations in the middle layers of the soil. The application of weathered coal humic acid could reduce the Pb concentration of soil leachates. The removal of Pb was efficient, particularly at the 1000-mg-kg−1 Pb pollution level, with a maximum decrease of 85.8 %.