In the summer of 2015, ~10,000 fish died in the Whitewater River in Minnesota. The cause of this large kill event was never determined. Strobins, a class of fungicides were detected in the river. Strobins, sometimes called strobilurins, are known to be toxic to non-target organisms, and may lead to autism in humans. They are used extensively in agriculture across both the US and Europe, and have been detected in both Minnesota and other waters. They have also been detected in multiple vegetables and fruits sold in stores. Little is known about strobins’ fate once applied. The purpose of this study is to determine the photolysis rate of five common strobin fungicides, both in the dissolved state and once sorbed to solid particles. The half-life of the strobins azoxystrobin, fluoxastrobin, and picoxystrobin range from 5.1-6.2 hours under simulated sunlight at 765 W/m2, and pyraclostrobin has a much smaller half-life at 0.1 hours (7 minutes). The quantum yield of azoxystrobin, fluoxastrobin, and picoxystrobin range from 0.077 to 0.28, with pyraclostrobin having a much greater QY of 0.44. Indirect photolysis may also play a role in the degradation of strobins with lower direct photolysis quantum yields. Comparisons between photolyses conducted in ultrapure water and natural waters reveal the relative importance of direct and indirect photolysis for these compounds. Three strobins, azoxystrobin, fluoxastrobin and picoxystrobin produce a major photo-product during direct photolysis. These products appear to photo-degrade at a much slower rate than the parent compound. Pyraclostrobin produced multiple photo-products which appear to be photo-stable.

Degradation of strobin fungicides in aquatic and soil environments

2019 Spring National Meeting

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