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Type: Journal article
Title: Abiotic degradation (photodegradation and hydrolysis) of imidazolinone herbicides
Author: Ramezani, M.
Oliver, D.
Kookana, R.
Gill, G.
Preston, C.
Citation: Journal of Environmental Science and Health Part B-pesticides Food Contaminants and Agricultural Wastes, 2008; 43(2):105-112
Publisher: Marcel Dekker Inc
Issue Date: 2008
ISSN: 0360-1234
Statement of
Mohammadkazem Ramezani, Danielle P. Oliver, Rai S. Kookana, Gurjeet Gill, Christopher Preston
Abstract: The abiotic degradation of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was investigated under controlled conditions. Hydrolysis, where it occurred, and photodegradation both followed first-order kinetics for all herbicides. There was no hydrolysis of any of the herbicides in buffer solutions at pH 3 or pH 7; however, slow hydrolysis occurred at pH 9. Estimated half-lives for the three herbicides in solution in the dark were 6.5, 9.2 and 9.6 months for imazaquin, imazethapyr and imazapyr, respectively. Degradation of the herbicides in the light was considerably more rapid than in the dark with half lives for the three herbicides of 1.8, 9.8 and 9.1 days for imazaquin, imazethapyr and imazapyr, respectively. The presence of humic acids in the solution reduced the rate of photodegradation for all three herbicides, with higher concentrations of humic acids generally having greater effect. Photodegradation of imazethapyr was the least sensitive to humic acids. The enantioselectivity of photodegradation was investigated using imazaquin, with photodegradation occurring at the same rate for both enantiomers. Abiotic degradation of imidazolinone herbicides on the soil surface only occurred in the presence of light. The rate of degradation for all herbicides was slower than in solution, with half-lives of 15.3, 24.6 and 30.9 days for imazaquin, imazethapyr and imazapyr, respectively. Abiotic degradation of these herbicides is likely to be slow in the environment and is only likely to occur in clear water or on the soil surface.
Keywords: Humic Substances; Nicotinic Acids; Niacin; Imidazoles; Quinolines; Herbicides; Soil Pollutants; Chromatography, High Pressure Liquid; Environmental Pollution; Hydrolysis; Dose-Response Relationship, Drug; Kinetics; Adsorption; Hydrogen-Ion Concentration; Photochemistry; Half-Life
RMID: 0020080168
DOI: 10.1080/03601230701794968
Appears in Collections:Agriculture, Food and Wine publications

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