Compound-Specific Isotope Analysis Provides Direct Evidence for Identifying the Source of Residual Pesticides...

Compound-specific isotope analysis stands as a promising tool for unveiling the behavior of pesticides in agricultural environments. Using the commercial formulations of persistent fungicide procymidone (PRO) and less persistent insecticide diazinon (DIA), respectively, we analyzed the concentration and carbon isotope composition (δ¹³C) of the residual pesticides through soil incubation experiments in a greenhouse (for 150 days) and lab conditions (for 50-70 days). Our results showed that the magnitude of δ¹³C variation depends on pesticide specificity, in which PRO in the soil exhibited little variation in δ¹³C values over the entire incubation times, while DIA demonstrated an increased δ¹³C value, with the extent of δ¹³C variability affected by different spiking concentrations, plant presence, and light conditions. Moreover, the pesticides extracted from soils were isotopically overlapped with those from crop lettuce. Ultimately, the isotope composition of pesticides could infer the degradation and translocation processes and might contribute to identifying the source(s) of pesticide formulation in agricultural fields.