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PubMed | Unit of Plant Protection Products and Autonomous University of Madrid
Type: | Journal: Chemosphere | Year: 2016

Photolysis is an important route for the abiotic degradation of many pesticides. However, the knowledge of the photolytic behaviour of these compounds and their commercial formulations under environmentally-relevant conditions are limited. The present study investigated the importance of photochemical processes on the persistence and fate of the herbicide sethoxydim and its commercial formulation Poast

Sevilla-Moran B.,Unit of Plant Protection Products | Mateo-Miranda M.M.,Unit of Plant Protection Products | Alonso-Prados J.L.,Unit of Plant Protection Products | Garcia-Baudin J.M.,Unit of Plant Protection Products | Sandin-Espana P.,Unit of Plant Protection Products
International Journal of Environmental Analytical Chemistry | Year: 2010

Photochemical behaviour of sethoxydim-lithium, a cyclohexanedione oxime herbicide, has been investigated in ultrapure and natural waters (mineral, well and river water). Photodegradation experiments were carried out under laboratory conditions using a solar silulator (Suntest equipment) and under natural solar irradiation in order to evaluate reaction kinetics of the active ingredient. Besides, the effect of humic acids (HA) on the degradation rate under simulated solar radiation was also studied. The photodegradation rates of sethoxydim-lithium in all the different waters and light sources studied followed first-order kinetics. Results showed that dark reactions were negligible. Experimental data showed that half-lives of the herbicide under simulated irradiation were higher in natural waters than in ultrapure, showing the lowest degradation rate in river water (t1/2=135.5 ± 0.3 min). Under natural sunlight, sethoxydim-lithium photodegradation followed the same behaviour, with half-lives that range from 82 to 437 min for ultrapure and river water respectively, showing a strong dependence on the composition of water. However, rates of degradation of sethoxydimlithium were faster under simulated radiation compared to natural sunlight (e.g. t1/2 (ultrapure water) 59.8 ± 0.2 min vs. 82.1 ± 0.7 min). The presence of different concentrations of HA (1-20 mgL-1) retarded the photolytic degradation relative to ultrapure water with half-lives from 92 to 196 min. © 2010 Taylor & Francis.

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