Effects of Biochar on Arsenic-Contaminated Soil: Chemical Fractionation, Vegetation Growth, and Oral Bioaccessibility.

Contamination by arsenic (As) is a pressing environmental and public health issue requiring urgent remediation strategies. One cost-effective and eco-friendly method involves adding stabilizing agents to soils to reduce As mobility. However, remediation projects must also address potential ecotoxicological effects. These effects may include harmful impacts on both aquatic and terrestrial organisms, including plants, disruption of ecosystem balance, and the potential bioaccumulation of toxic substances in the food chain. Biochar from organic fraction of municipal solid waste (OFMSW) shows promise for As-contaminated soil remediation. Pot experiments were conducted with soil contaminated with As (100 mg kg^-1) and amended with biochar produced at three different temperatures (300, 500, and 700 °C) and addition rates (1 and 5%, w/w). Chemical fractionation showed higher As concentration in a less accessible fraction (F4). Biochar amendments did not significantly differ from the control in As immobilization, but enhanced maize (Zea mays) growth and reduced As uptake, with the most promising results seen with 1% of biochar produced at 700 °C. The bioaccumulation factor (BCF) and translocation factor (TF) were both lower than 1, indicating a low absorption of As and minimal translocation from the root to the shoot. The bioaccessible percentage was higher in the samples treated with biochar compared to the control. According to the results, biochar showed no satisfactory potential for As immobilization and its approach of pretreatment/modification should be tested regarding possible improvements in the immobilization performance of As. Since most contaminations involve multiple contaminants simultaneously, it is essential to test the interactions between arsenic and other pollutants to understand the effects of biochar in such complex scenarios, which will be explored in future studies. Graphical abstract.