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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Chemistry Research » Research » Publications at this Location » Publication #336821

Research Project: Insect, Nematode, and Plant Semiochemical Communication Systems

Location: Chemistry Research

Title: Comparison of direct and indirect photolysis in imazosulfuron photodegradation

item Rering, Caitlin
item WILLIAMS, KATRYN - University Of California
item HENGEL, MATT - University Of California
item TJEERDEMA, RONALD - University Of California

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2017
Publication Date: 4/3/2017
Citation: Rering, C.C., Williams, K.L., Hengel, M.J., Tjeerdema, R.S. 2017. Comparison of direct and indirect photolysis in imazosulfuron photodegradation. Journal of Agricultural and Food Chemistry. 15:3103–3108.

Interpretive Summary: Imazosulfuron, an herbicide used in rice and sod production in the US, degrades into relatively harmless products when exposed to sunlight. The particular mechanism for this degradation in water was studied by selectively promoting certain decay pathways and observing shifts in degradation rates. These preliminary results suggest that the herbicide will decay fastest in water that contains very little organic matter and low dissolved oxygen. Because these conditions are routinely observed in rice fields, dissipation of the chemical is predicted to be rapid.

Technical Abstract: Imazosulfuron (IMZ), a sulfonylurea herbicide used in rice cultivation, has been shown to undergo photodegradation in water, but neither the photophysical mechanism nor the role of indirect photolysis is known. The purpose of this study was to investigate the underlying processes that operate on IMZ during aqueous photodegradation. Our data indicate that in the presence of oxygen, most photochemical degradation proceeds through a direct single-excited state pathway, whereas triplet-excited state IMZ enhanced decay rates under low dissolved oxygen conditions. Oxidation by hydroxyl radical and singlet oxygen were not significant. At dissolved organic matter (DOM) concentrations representative of rice field conditions, fulvic acid solutions exhibited faster degradation than rice field water containing both humic and fulvic acid fractions. Both enhancement, via reaction with triplet-state DOM, and inhibition, via competition for photons, of rates was observed in DOM solutions.