Chapter 13 - Functionalized biochars for the (im) mobilization of potentially toxic elements in paddy soils under dynamic redox conditions: a case study

Abstract

Contamination of paddy fields with potentially toxic elements (PTEs) has become a global environmental problem. Biochar has been widely used as an amendment for the stabilization of PTEs in soils. However, in many cases, the pristine biochar has limited effectiveness in remediating soils contaminated with multi-PTEs. Recently, functionalized biochar has gained intensive attention as an amendment for alleviation of PTE contamination in paddy soils. In this chapter, we report results from a case study focusing on the impact of functionalized biochars, for example, a naturally P-containing pig carcass–derived (P-rich) biochar and a Fe-modified green waste–derived (Fe-rich) biochar on the immobilization of PTEs (e.g., As, Cd, and Pb) under redox conditions in a paddy soil. The results demonstrate that the P-rich pig carcass–derived biochar could be applied as an amendment for mitigating the mobilization and toxicity of Pb in paddy soils. The raw and Fe-rich green waste–derived biochars are effective in immobilizing Cd in paddy soils under both reducing and oxidizing conditions. Moreover, modification of the raw biochar with Fe materials may improve its ability in As immobilization, especially under reducing conditions. Hence, functionalized biochars could be used as soil amendments for remediation of paddy soils contaminated with PTEs. The efficacy of these biochars on immobilizing different PTEs varies with biochar types, soil redox conditions, and elemental types.