Monitoring of Neonicotinoid Pesticides in Water-Soil Systems Along the Agro-Landscapes of the Cauvery Delta Region, South India.

The prophylactic use of neonicotinoids in paddy fields has raised concern due to its toxicity to ecological systems and human health. The present study evaluated the concentrations of neonicotinoids such as clothianidin, imidacloprid, thiamethoxam, acetamiprid, and thiacloprid in the water-soil systems of the paddy fields, and their potential discharge into the groundwater along the Cauvery delta region, South India. Though neonicotinoids are extensively sprayed in the paddy fields, the concentration of residues analyzed by QuEChERS, combined with LC-MS/MS found no detectable residues at concentrations above LOD. The LOD and the LOQ values for water and soil were 0.001 ppm and 0.0025 ppm and 0.025 ppm and 0.05 ppm respectively. The results of the study found that neonicotinoids are less persistent in the water-soil systems of the delta region as they are readily exposed to photolysis and undergo rapid microbial degradation. Further, the hydropedological characteristics of the highly saturated delta soil facilitate ready leaching followed by vertical migration and infiltration into the soil aquifers.