Isoproturon (IPU) works as a photosynthesis inhibitor to treat broad-leaf weeds. Once leaching into sunlit surface waters, IPU mainly undergoes photosensitized degradation promoted by excited triplet states of dissolved organic matter. In the absence of light, however, IPU is regenerated from a more hydrophilic intermediate (IPU*) through first-order kinetics. We propose that IPU* is an endoperoxide formed from the photo-oxidation of IPU, and this intermediate is prone to regenerate the parent compound at a significantly slower rate than its photo-formation. Water constituents such as pH, salts and oxygen levels all impact the kinetics of this reversion. Carbonate buffer and low oxygen levels were observed to accelerate the rebound effect, while acidic solutions readily degraded IPU* to products other than IPU. The dark product-to-parent reversion of IPU suggests the possible accumulation of IPU in the aphotic zones beneath sunlit surface waters, and alters our understanding of its environmental fate.

Dark formation of isoproturon from its semi-persistent photodegradation product

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.