Enhancing chlorpyrifos sorption potential of agricultural soil by biochar and compost addition

Chlorpyrifos (CP) is a toxic and broad-spectrum pesticide. Owing to the extensive soil and crop application of CP to control insects/pests, its significant concentrations have been reported in different crop plants, fruits, vegetables and other food items locally and internationally. The strategies to immobilize pesticide residues in the soil are of great concern to restrict their offsite transport. A batch study was conducted to evaluate the potential of biochar and compost in enhancing CP sorption. Soil samples were supplemented with biochar and compost at two levels, i.e. 0.25% and 0.50% w/w basis. The sorption of CP was assessed at five applied concentrations viz. 5, 10, 50, 100 and 200 mg L^-1. CP sorption exhibited linear trend and increased with increasing concentration upto 50 mg L^-1 after that it decreased with its increasing levels. Freundlich model well fitted and explained the sorption behavior of CP in un-amended as well as amended soil as indicated by the correlation coefficient (R²) values (˃ 0.90). Both biochar and compost addition significantly increased the sorption potential of the soil. With both amendments sorption capacity increased with increasing level. However, biochar-amended soil showed significantly higher sorption capacities (K_f, 28.68 and 218.83 mg kg^-1) for CP compared to compost-amended soils (15.95 and 111.85 mg kg^-1) at 0.25 and 0.50%, respectively. Conclusively, above organic amendments have potential to effectively sorb CP and could be used to remediate CP polluted areas by immobilizing CP and ultimately decreasing its bioavailability.