From degradation to detection: Assessing enantioselective behavior of chiral triazole fungicides in horticultural stream waters

Abstract

Chiral pesticides constitute nearly 40 % of active ingredients used in agriculture, yet their enantioselective environmental behavior is often overlooked in risk assessments. This study examined the enantioselective degradation of three widely used triazole fungicides—cyproconazole, epoxiconazole, and tebuconazole—in surface water from horticultural streams, and assessed their enantiomeric distribution in environmental samples. Laboratory degradation experiments were conducted under light and dark conditions using racemic standards. Enantiomers were separated and quantified via LC-MS/MS using a Lux Cellulose-2 chiral column. Under light conditions, degradation followed simple first-order (SFO) kinetics, showing faster dissipation of the (+)-enantiomers compared to the ( )-enantiomers. For cyproconazole, DT 50 values ranged from 2.64 to 2.74 days for (+)-enantiomers and 2.78–2.90 days for ( )-enantiomers; epoxiconazole and tebuconazole followed the same trend. The enantiomeric fraction (EF) increased over time in degradation assays, reaching values of up to 0.62 for cyproconazole and 0.73 for tebuconazole, confirming progressive enrichment of the ( )-enantiomers. In real surface water samples, EF values were >0.5 in 86 % (EF A ) and 90 % (EF B ) of detections for cyproconazole, 100 % for epoxiconazole, and 98 % for tebuconazole. These results represent the first EF data reported for cyproconazole in environmental waters and confirm the occurrence of enantioselective pollution. The consistent enrichment observed in both experimental and field data highlights the role of stereoselective degradation processes in shaping environmental profiles. Given the differential toxicity and persistence of individualenantiomers, these findings support the need for enantiomer-specific monitoring and risk assessment of chiral pesticides.