Chemical stabilization of Cd-contaminated soil using fresh and aged wheat straw biochar

Metal mining and smelting activities can introduce a substantial amount of potentially toxic elements (PTE) into the environment that can persist for an extended period. That can limit the productivity of the land and creates dangerous effects on ecosystem services. The effectiveness of wheat straw biochar to immobilize Cd in contaminated soil due to metal smelting activities was investigated in this study. The biochar carbon stability and long-term provisioning of services depend on the biochar production conditions, nature of the feedstock, and the biotic and abiotic environmental conditions in which the biochar is being used. Within this context, three types of wheat straw biochar were produced using a screw reactor at 400 degrees C, 500 degrees C, and 600 degrees C and tested in a laboratory incubation study. Soil was amended with 2 wt% of biochar. Both fresh and aged forms of biochar were used. Biochars produced at lower temperatures were characterized by lower pH, a lower amount of stable C, and higher amounts of acidic surface functional groups than the freshly produced biochars at higher production temperatures. At the end of the 6 months of incubation time, compared to the soil only treatment, fresh and aged forms of wheat straw biochar produced at 600 degrees C reduced the Cd concentration in soil pore water by 22% and 15%, respectively. Our results showed that the aged forms of biochar produced at higher production temperatures (500 degrees C and 600 degrees C) immobilized Cd more efficiently than the aged forms of lower temperature biochar (400 degrees C). The findings of this study provide insights to choose the production parameters in wheat straw biochar production while considering their aging effect to achieve successful stabilization of Cd in contaminated soils.

Automated summary

This study investigated the immobilization of Cd in contaminated soil due to metal smelting activities using wheat straw biochar. Results demonstrated that biochars produced at higher temperatures were more efficient in immobilizing Cd, providing important insights for reducing heavy metal pollution in agricultural production.