Microbe-Assisted Remediation Potential in Arsenic-Impacted Agricultural Soils of Laksar, Uttarakhand

Arsenic contamination in agricultural soils poses a major threat to environmental safety, food security, and sustainable farming systems across South Asia. This study investigates the extent of arsenic accumulation in agricultural soils of Haridwar district, Uttarakhand, and evaluates microbe-assisted remediation as a potential strategy to mitigate arsenic toxicity. Ten soil samples from arsenic-affected sites were analyzed for physicochemical, elemental, and microbial characteristics. The soils were predominantly sandy loam and exhibited moderate ionic strength (EC 316 µS/cm), neutral pH (7.2), reducing redox potential, and low moisture content. CHNS profiles (C/N = 8.83) and (C/H ratios =2.40) indicated nutrient-limited conditions that constrain microbial redox processes. Arsenic concentrations reached 11.4 ppm along with elevated levels of Cu, Zn, Fe, Mn, and Se. Strong positive correlations of As with pH (R² = 0.904), iron (R² = 0.808), and manganese (R² = 0.797) suggested alkaline conditions and Fe–Mn redox cycling are key drivers of arsenic mobilization. High phosphate, calcium, and magnesium further contributed to competitive desorption and enhanced arsenic solubility. Microbial functional assessments using CLPP and enzyme assays revealed suppressed metabolic activity and reduced carbon utilization under metal stress, reflecting ecosystem perturbation. Overall, the findings demonstrate that the interplay of soil geochemistry and microbial activity drives arsenic behavior in agricultural systems. Microbe-assisted approaches focused on modulating redox conditions, stabilizing Fe–Mn phases, and improving nutrient balance offer a promising pathway for reducing arsenic bioavailability and restoring soil health in contaminated agricultural landscapes.

Keywords: Arsenic contamination, Agricultural soils, Soil geochemistry, Microbe-assisted remediation