Using biochar to immobilize the heavy metal Cd mobilized by covered soil‐cultivated edible fungi <i>Dectyophora rubrovolvata</i>

Abstract Because of the worsening soil Cd pollution, the safe production of covered soil‐cultivated edible fungi Dectyophora rubrovolvata is facing serious threats. However, the use of biochar for heavy metal immobilization differs from conventional soil remediation processes as a result of rhizospheric soil acidification and the presence of dissolved organic matter. Therefore, this study investigated changes in soils Cd availability and speciation, and soil dissolved organic matter components after D. rubrovolvata cultivation and biochar addition. The results showed that mycelium inoculation increased soil HAc‐Cd, CaCl 2 ‐Cd and DTPA‐Cd concentrations by 4.7%, 131.7% and 11.4%, respectively. Treatment with three types of biochar reduced soil HAc‐Cd, CaCl 2 ‐Cd and DTPA‐Cd concentrations by 8.7%–25.2%, 16.4%–24.5% and 10.7%–15.8%, respectively, and significantly decreased mycelium Cd absorption. The dissolved organic matter secreted by mycelium and soil acidification led to the transformation of residual Cd in soil to exchangeable Cd. Biochar mitigated the migration of Cd activated by mycelium by neutralizing soil acidification, adsorbing dissolved organic matter, and specifically adsorbing Cd elements. In conclusion, biochar demonstrates effective immobilization of heavy metals in soil used for D. rubrovolvata cultivation and reduces mycelium Cd absorption.