Arsenic contamination in groundwater is a global concern and poses significant threats to human health, food security, and agricultural economies because arsenic’s water solubility allows it to easily enter the food chain, especially through irrigated crops like rice and wheat. Since removing contaminated topsoil from agricultural fields is impractical, restricting arsenic within the crop root zone is crucial. A recent study published in Scientific Reports by Prashant Singh, Anuj Saraswat, and Abhijit Maiti investigates the effectiveness of a novel Laterite BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More Composite (LBC) in immobilizing arsenic in contaminated soil, reducing its uptake by rice plants, and improving soil fertility.

LBC is a unique organic-inorganic material specifically designed to restrict arsenic mobility from contaminated soil to crops. While laterite is known for its arsenic adsorption capacity in water, its large-scale use in soil is limited due to potential negative impacts on fertility. Biochar, on the other hand, is a proven soil conditioner that improves soil fertility but has lower arsenic restriction ability. The innovative synthesis of LBC combines laterite with biochar, enhancing arsenic adsorption efficiency while simultaneously improving soil quality. This study evaluated LBC’s performance through batch, column, and pot experiments, using soil with a high arsenic concentration of 106 mg arsenic/kg soil.

The research unveiled a dual mechanism for arsenic immobilization. Firstly, LBC promotes the formation of iron plaque on the outer surface of rice roots. This iron plaque, composed of iron, aluminum, and manganese minerals, acts as a protective layer, significantly limiting the movement of arsenic into the rice plant. XPS analysis confirmed the presence of various iron oxidation states, predominantly Fe(III), and indicated that arsenic is adsorbed by the iron plaque mainly as As(V). The study found a 365.6% increase in iron plaque formation with a 2% LBC treatment compared to the control, demonstrating its effectiveness as a mass transfer barrier. Secondly, LBC forms organometallic complexes within the soil. XRD analysis of LBC incubated in soil (LIS) showed the formation of hydrated iron oxide, arsenic-adsorbed iron, and aluminum minerals, indicating successful arsenic adsorption and complexation between LBC and soil particles. FTIR and XPS analyses of LIS confirmed changes in the chemical environment, with the appearance of new peaks and shifts in binding energies, suggesting the formation of metal-organic carbon bonds and oxygen-containing functional groups. These organometallic complexes contribute to the long-term stability of LBC in the soil and its arsenic immobilization capacity.

The pot experiments demonstrated a remarkable reduction in arsenic uptake by rice plants. LBC decreased arsenic levels in rice seeds by 99.5% at a 2% LBC concentration, 76% at 1%, and 63.5% at 0.5% weight percentage in the soil. This reduction brought the grain arsenic concentration below the World Health Organisation’s recommended safe limit of 0.1 mg/kg with a 2% LBC amendment. Furthermore, LBC significantly improved rice plant growth and yield. Plant height increased by 78.1% with 2% LBC treatment at 105 days after transplanting, which is crucial as a longer transportation path also helps restrict arsenic mobility from root to seeds. Total dry matter increased from 10.0 g/pot in the control to 99 g/pot with 2% LBC, and grain yield saw an impressive 801% increase with 2% LBC (18.3 g/pot compared to 2.03 g/pot in control). LBC also mitigated arsenic-induced rice plant mortality.

Beyond arsenic immobilization and yield enhancement, LBC significantly improved soil health. It increased total carbon content by 110% with 2% LBC, soil organic carbon (SOC) by 34.5%, and soil microbial activity, as indicated by a 28.8% increase in dehydrogenase enzyme (DHA) activity. This enhanced microbial activity contributes to improved soil properties, carbon sequestration, and nutrient cycling. The study concludes that LBC offers a sustainable solution for safe food production, promoting fertility and mitigating climate change.

Source: Singh, P., Saraswat, A., & Maiti, A. (2025). Enhanced arsenic immobilization from contaminated soil to crops, carbon sequestration, and soil fertility using laterite Biochar composites. Scientific Reports, 15(1), 17933.