Efficacy of Cotton Stalk Biochar on Sorption Behavior and Leaching Potential of Imidacloprid in Agricultural Soils: A Comprehensive Study

This study investigates the sorption behavior and leaching potential of imidacloprid in agricultural soils to address concerns about groundwater contamination. Specifically, the study examines the effect of amending soils with 0.5% and 1% cotton stalk biochar (CBC), synthesized at 700°C, on the sorption kinetics and behavior of imidacloprid. Employing batch equilibrium techniques and high-performance liquid chromatography, imidacloprid sorption in soils is systematically analyzed. Results reveal a two-stage sorption process, consistent across soils with and without biochar, characterized by rapid initial uptake followed by slower adsorption. The pseudo-second-order kinetic model and the Freundlich isotherm effectively characterize imidacloprid’s sorption behavior, indicating nonlinear sorption phenomena. However, the results of the degradation kinetics indicate minimal effect of biochar on imidacloprid degradation. Additionally, the groundwater ubiquity score (GUS) assessment indicates a high leaching potential of imidacloprid in unamended soils, with a maximum value of 3.72. Biochar amendment significantly reduced GUS values by 76%–89% across soils, bringing them below 1.8 and reclassifying the pesticide as a nonleacher. Application of 0.5% CBC reduced the GUS values to 0.87–1.48, whereas amendment with 1% CBC resulted in a further decline to 0.39–0.60. This underscores CBC’s efficacy in enhancing soil sorption capacity, mitigating imidacloprid’s mobility, and minimizing environmental risks associated with groundwater contamination. These findings align with the United Nations Sustainable Development Goals (SDGs), especially SDG 6 (Clean Water and Sanitation) by reducing pesticide leaching into groundwater and SDG 15 (Life on Land) through promoting sustainable soil management techniques. Utilization of agricultural waste-derived biochar also aligns with SDG 12 (Responsible Consumption and Production) by valorizing biomass and promoting circular economy principles in agriculture. Practically, the results highlight cotton stalk biochar as a cost-effective and sustainable soil amendment that can be applied in agricultural fields to reduce pesticide leaching, safeguard groundwater resources, and support environmentally friendly farming practices.