Mitigation of arsenite toxicity in barley using iron-biochar nanocomposites and Bacillus sp.: impacts on soil immobilization, plant stress, and health risk

Abstract Gradual rise in arsenic (As) pollution due to reuse of unprocessed industrial wastewater for cultivation of crops is causing lethal effects on human health. Moreover, consumption of As-contaminated grains as a food is a global concern. Hence, effective alternatives to manage this problem are urgently needed. This research studied the combined role of iron-biochar nanocomposites ( Fe-BCNC) and plant growth promoting (PGPR) Bacillus sp. in arsenite [As (III)] detoxification in soil. The investigation focused on the growth of barley, Hordeum vulgare (H. vulgare), in an As (III)-contaminated soil and assesses As-associated health risks. Specifically, the study highlighted the impact of various treatment combinations of Fe-BCNC and PGPR with respect to As fractions in soil, As translocation, bioaccumulation, grain quality attributes, stress markers (like antioxidant enzymes) and health risks associated with As (III)-contaminated food intake. The Fe-BCNC was added into the soil at the rate of 80 g kg−1 of soil before sowing. The results revealed that As applied at 25 and 50 mg kg−1 enhanced phytotoxicity, causing reduced growth, and worsening physiological and biochemical attributes of H. vulgare. Fe-BCNC and PGPR promoted reductions in As toxicity in both soils (25 and 50 mg kg−1 As) by improving plant height (26, 52%), grain weight (75, 76%), physiological such as electrolyte leakage (37, 46%) and grain quality attributes such as crude protein (49, 59%) further regulated by antioxidant enzymes (CAT 31, 26; SOD 31, 25%; POD 48, 30%) under stress conditions. The combined treatment of Fe-BCNC with PGPR enhanced As immobilization in soil (40, 47%), respectively, with the highest proportion of iron, aluminum and manganese associated to As. Moreover, the same combination resulted in reduced As accumulation and translocation, lowering health risk (92, 94%) and cancer index (2 × 10–4, 2 × 10–3) in both soils, respectively. Formulations of Fe-BCNC and PGPR and their combination as biodynamic amendment could be crucial to alleviate As-related issues and prevent health risks in end consumers. This research helps achieving Sustainable Development Goals 2 (zero hunger) and 15 (life on land) by ameliorating food production, remediating tinted soil, and reconstituting the environment.