Study on the Remediation Effect of Modified Biochar-attapulgite Composite on Cadmium-contaminated Soil

This study investigated the effects of Fe-modified and Mg-modified biochar/attapulgite composite materials on soil pH, organic matter content, and available Cd through field experiments. It also analyzed the transformation of Cd chemical forms in the soil and the accumulation of Cd in different parts of rice at various growth stages to clarify the remediation effects and mechanisms of the modified composites on soil Cd pollution. The results indicate that Mg-modified biochar/attapulgite composites (Mg-modified materials) effectively increased soil organic matter and pH, thereby improving basic soil properties. At a dosage of 7 500 kg·hm^-2, Mg-modified materials reduced acid-soluble Cd proportion in the soil to 22.15% and increased residual Cd proportion to 37.16%, lowering the content of available Cd and decreasing Cd accumulation in various rice tissues. The Cd content in different rice tissues followed the order: root > stem > leaf > husk > grain. At the 7 500 kg·hm^-2 application rate, both Fe- and Mg-modified materials effectively inhibited Cd accumulation in all rice tissues with the Cd content in mature rice grains was 0.85 and 0.80 mg·kg^-1, respectively representing reductions of 44.81% and 48.05% compared with the control, and 27.97% and 32.20% compared with the unmodified composite material, respectively. This study provides theoretical and data support for the promotion and application of modified biochar/attapulgite composites in agricultural fields.