Enhanced arsenic immobilization from contaminated soil to crops, carbon sequestration, and soil fertility using laterite Biochar composites

Arsenic's water solubility facilitates its entry into the food chain, threatening health, food security, and the economy. Restricting arsenic within the crop root zone is crucial, as contaminated topsoil of agricultural fields can't be removed. This study evaluates the arsenic immobilization capacity of the Laterite Biochar Composite (LBC) in the soil through batch, column, and pot studies. The batch experiments assess the adsorption, thermodynamic, and kinetics behavior of LBC. At the same time, a column study examines the arsenic restriction capacity within a 25 cm soil depth, representing the root growth region of the paddy. The pot experiment demonstrates that progressively increasing LBC dose reduces arsenic uptake from roots to grains in rice plants grown in arsenic-contaminated soil (106 mg arsenic/kg soil). The research's novelty lies in the innovative synthesis of LBC and experiment design, revealing insight into a dual arsenic immobilization mechanism in the soil through the formation of iron plaque over the root as a mass transfer barrier between the soil interface and the root surface. LBC decreases arsenic levels in rice seeds by 99.5%, 76%, and 63.5% at 2%, 1%, and 0.5% wt% LBC in the soil during pot experiments, respectively, while enhancing soil health by increasing soil microbial activity, mineral content, and organic carbon.