Remediation Potential Biochar Application for Pb Contaminated Soil.

In recent years, soil contamination by harmful substances such as heavy metals has become a worldwide problem. The ways to remediate soil contamination with low environmental impacts such as bioremediation and phytoremediation are much needed to be promoted. Biochars have been used as a soil improving material. However, further researches are required for the remediation potential and heavy metal dynamics when biochars are applied to soils.

  In this study, a Japanese Andisol applied with PbCl₂ was used to investigate Pb dynamics by creating Pb adsorption isotherms when biochars derived from poultry manure (BPM) and wood chips (BWC) were applied to the soil. The isotherm for the soil showed that the soil had the maximum adsorption capacity of about 27,000 mg Pb kg^-1 soil. The BPM and BWC had the maximum adsorption capacities of over 200,000 mg Pb kg^-1 biochar, respectively. In addition, an effect of phosphate (PO₄) contained in particularly BPM to immobilize Pb as Pb₃(PO₄)₂ complexes was evaluated by XRD.

  Furthermore, a pot experiment using a Pb-resistant plant such as buckwheat planted in the Pb-contaminated soil mixed with the biochars was conducted. The soil in pot received 0, 600, or 3000 mg Pb kg^-1 soil, 1% (w/w) of each BPM or BWC, and the presence or absence of buckwheat plant. After the cultivation, pH and Pb concentration of the soil, Pb in leachate, and Pb in the plant were analyzed from each pot. In this experiment, a potential of the biochar application to promote phytoremediation from the Pb-contaminated soil with varying Pb concentrations was evaluated.