Hydrolysis and Photolysis of Herbicide Clomazone in Aqueous Solutions and Natural Water Under Abiotic Conditions

• Published in: Journal of Integrative Agriculture Vol. 12; no. 11; pp. 2074 - 2082
• Main Authors: CAO, Jia, DIAO, Xiao-ping, HU, Ji-ye
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2013; Science Press; School of Agriculture, Hainan University, Haikou 570228, P.R.China%School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R.China; Elsevier
• Subjects: abiotic; clomazone; clomazone hydrolysis photolysis photoproducts abiotic; HPLC-MS; hydrolysis; photolysis; photoproducts; 光解动力学; 天然水; 异恶草酮; 水溶液; 水解; 除草剂; 非生物; photoproducts; abiotic; photolysis; hydrolysis; clomazone
• ISSN: 2095-3119; 2352-3425
• DOI: 10.1016/S2095-3119(13)60506-7

The hydrolysis and photolysis of clomazone in aqueous solutions and natural water were assessed under natural and controlled conditions. Kinetics of hydrolysis and photolysis of clomazone were determined by HPLC-DAD. Photoproducts were identiifed by HPLC-MS. No noticeable hydrolysis occurred in aqueous buffer solutions （（25±2）°C, pH （4.5±0.1）, pH （7.4±0.1）, pH （9.0±0.1）;（50±2）°C, pH （4.5±0.1）, pH （7.4±0.1）） or in natural water up to 90 d. At pH （9.0±0.1） and （50±2）°C the half-life of clomazone was 50.2 d. Clomazone photodecomposition rate in aqueous solutions under UV radiation and natural sunlight followed ifrst-order kinetics. Degradation rates were faster under UV light （half-life of 51-59 min） compared to sunlight （half-life of 87-136 d）. Under UV light, four major photoproducts were detected and tentatively identiifed according to HPLC-MS spectral information such as 2-chlorobenzamide, N-hydroxy-（2-benzyl）-2-methylpropan-amide, 2-[2-phenol]-4,4-dimethyl-3-isoxazolidinone and 2-[（4,6-dihydroxyl-2-chlorine phenol）]-4,4-dimethyl-3-isoxazolidinone. These results suggested that clomazone photodegradation proceeds via several reaction pathways：1） dehalogenation;2） substitution of chlorine group by hydroxyl;3） cleavage of the side chain. Photosensitizers, such as H2O2 and ribolfavin, could enhance photolysis of clomazone in natural sunlight. In summary, we found that photoreaction is an important dissipation pathway of clomazone in natural water systems.