Quinone outside inhibitors (QoIs) are a class of fungicides that prevent fungus growth through the inhibition of mitochondrial respiration by blocking the electron transport chain. With widespread agricultural use of these highly effective fungicides and multiple applications throughout the growing season, occurrence in surface waters raises concerns of the chronic exposure of non-target organisms to both trace amounts of the parent fungicide in addition to the unknown effects of photoproducts generated when QoIs are exposed to sunlight. This study examined the role sunlight photolysis may play in environmental transformation of QoIs. Four fungicides (dimoxystrobin, fluoxastrobin, fenamidone, and kresoxim-methyl) were photolyzed using a solar simulator in aqueous solutions as well as on quartz and kaolinite surfaces to simulate soils. The rate of degradation as well as the production of significant photoproducts was measured. A potential indirect photolysis component was also explored by the addition of nitrate and nitrite. Direct photolysis was observed for all compounds; photolysis rates were enhanced in the presence of nitrate and nitrite and were also enhanced when compounds were bound to a surface.

Aqueous and surface-bound photolysis of quinone outside inhibitor fungicides

ACS Spring 2022

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