Isoproturon (IPU) is a phenylurea herbicide used to control broad-leaf weeds. Recent studies have indicated that triplet-induced photo-oxidation may be the main degradation pathway for IPU in sunlit surface water.  We, however, observed a significant rebound of IPU in the dark resulting from an unidentified semi-stable intermediate. This study investigated transformation rate constants of IPU intermediates formed from photo-generated triplet state aromatic ketones.  We also examined the role of dissolved organic matter using Suwannee River (SR) and Pony Lake (PL) fulvic acids as photosensitizers, respectively. The half-life for the back reaction of the main IPU intermediate to reform IPU was 32 �2 hours. Interestingly, the rate of IPU rebound was inhibited 3-fold more in the presence of PL fulvic acid than SR fulvic acid. Thus, the dark reformation of IPU from this semi-stable byproduct in natural waters may influence the overall photofate of this herbicide.

Diurnal kinetics of triplet-induced transformation of isoproturon in the presence of aromatic ketones and fulvic acids

246th National Meeting (2013)

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