Abiotic Degradation of Imidazolinone Herbicides in the Presence of Humic Acid and Soil surface
Abiotic (photolysis and hydrolysis) degradation of imazapyr, imazethapyr and imazaquin, was investigated at constant temperatures of 25℃ and 30℃, respectively. Photodegradation was determined in aqueous solutions of humic acid (1:1, 1:2, and 1:3) and deionised purified water (Milli-Q ) as well as on the soil surface, while the hydrolysis rate was studied in buffer solutions of different pH values (3, 7 and 9). The photodegradation of the imazaquin enantiomers was also determined in an aqueous solution and was analysed with a chiral column (Chiralcel OJ(R)). The photodegradation rates of all three herbicides in various media followed first-order kinetics. The half-life (T1/2) of imazapyr and imazethapyr was estimated to be approximately 9 days in water and 24.6 to 30.9 days, respectively, on the soil surface. Imazaquin was much more susceptible to photolysis with half-lives of 1.8, 2.8 and 15 days in Milli-Q water, humic acid (1:3) and soil, respectively. The presence of humic acid in solution decreased photodegradation rates of the three herbicides compared with the degradation rates in Milli-Q water. This effect could have been due to the competitive absorption of photons by humic acids and/or screening effect of humic acid on herbicide molecules. Irrespective of the buffer solution pH (3, 7 or 9), there was no hydrolysis observed for any of the three herbicides investigated. Photodegradation of the imazaquin enantiomers was nonselective and the enantiomer fraction (EF- the area of the first eluting peak/sum of areas of both peaks) showed no change during the experiment.
imazapyr imazethapyr imazaquin photodegradation abiotic enantiomer soil HPLC
Mohammadkazem RAMEZANI Danielle P OLIVER Rai S KOOKANA Gurjeet GILL Chris PRESTON
School of Agriculture, Food and Wine, University of Adelaide, PMB 1, Glen Osmond, SA 5064, Australia CSIRO Land and Water, PMB 2, Glen Osmond, SA 5064 Australia
国际会议
2007环境科学与技术国际会议(The 2007 International Symposium on Environmental Science and Technology)
北京
英文
2007-11-13（万方平台首次上网日期，不代表论文的发表时间）