Chiral pesticides stereoselectively accelerate N₂O emission through aerobic denitrification

As farmland represents the largest nitrous oxide (N₂O) emitter, widely used chiral pesticides frequently coexist with N₂O. To explore the underlying molecular mechanisms of chiral pesticides regulating N₂O emissions, this study experimented with Paracoccus denitrificans PD1222 on anaerobic/aerobic denitrification under cis-epoxiconazole (EPO) stress. The (+)-EPO increased 13.51-fold N₂O emissions under anaerobic denitrification by inhibiting the denitrification genes, while (-)-EPO merely enhanced 4.22-fold N₂O emissions through improving electron transfer and nitrous oxide reductase assembly. Anaerobic conditions suppressed glucose metabolism and NADH production, disrupting the energy supply for denitrification under EPO stress. Aerobic conditions hindered electron transfer and intracellular iron transport, reducing denitrifying enzyme activity and causing a further 1.29-10.47-fold increase in N₂O emissions and extra nitrite accumulation. These findings revealed that oxygen intensified the ecological risk of cis-epoxiconazole monomers stimulating N₂O emissions and underscore the potential risks of agrochemical applications to climate change and ecosystem stability.