Biochar enhances the simultaneous stabilization of chromium and lead in contaminated soil by Penicillium oxalicum SL2

Abstract

Traditional microbial remediation techniques face challenges in simultaneously addressing soil contamination by both chromium (Cr) and lead (Pb). This study introduces a novel composite system comprising biochar and the phosphate-solubilizing microorganism P. oxalicum SL2—for the simultaneous stabilization of Cr and Pb in contaminated soil. In this study, we found that the functional strain P. oxalicum SL2 was able to reduce Cr(VI), which is more toxic and migratory in soil, to Cr(III) with the assistance of biochar, and synchronously enhanced the stability of Cr and Pb in the soil, which transformed them toward a more stable endowment form. The efficiency of Cr(VI) reduction stabilization in soil was 77.6% within 30 d. Meanwhile, the effective concentrations of Pb in the soil decreased by about 27.3%. Furthermore, the biochar-P. oxalicum SL2 system significantly increased the activities of urease and acid phosphatase and promoted nutrient cycling. The principal environmental factors, such as Cr(VI), CaCl₂-Pb, HNO₃-Pb, Eh, S-UE, and S-ACP, were recognized as significant determinants influencing the structure and composition of fungal and bacterial communities in soil. Notably, the growth of Lysinibacillus, Brevundimonas, and Paenibacillus collectively reduced the bioavailability of Cr and Pb in the soil. This research presents an innovative strategy for the remediation of soils contaminated with heavy metals, utilizing a combination of biochar and phosphate-solubilizing microorganisms.