Department of Chemistry, University of Alaska, Anchorage, AK 99508, USA.
Pest Manag Sci. 2012 Aug;68(8):1141-7. doi: 10.1002/ps.3275. Epub 2012 Mar 28.
Clomazone is a popular herbicide used on California rice fields and exhibits rapid anaerobic microbial degradation (t(1/2) = 7.9 days). To test the potential of direct and indirect photolytic degradation as a cofactor in the overall degradation rate, sacrificial time-series microcosms were amended with water, non-sterilized soil + water and sterilized soil + water. Clomazone was added to each microcosm, which was then exposed to natural and artificial sunlight over 35 days. Water and acetonitrile extracts were analyzed for clomazone and metabolites via LC/MS/MS.
The calculated pseudo-first-order degradation rate constants (k) were k(water) = 0-0.005 ± 0.003 day(-1) , k(sterile) = 0-0.005 ± 0.003 day(-1) and k(non-sterile) = 0.010 ± 0.002-0.044 ± 0.007 day(-1) , depending on light type. The formation of ring-open clomazone, a microbial metabolite, correlated with clomazone degradation. Trace amounts of 5-hydroxyclomazone (m/z = 256 → 125), aromatic hydroxyclomazone (m/z = 256 → 141) and an unknown product (m/z = 268 → 125) were observed.
The photolytic degradation rate depends on both light type and the quality of the chromophores that induce indirect photolysis. Microbial degradation was found to be sensitive to temperature fluctuations. Overall, microbes are shown to be more detrimental to the environmental fate of clomazone than photolysis.
氯甲唑是加利福尼亚稻田中常用的除草剂，具有快速的厌氧微生物降解特性（t(1/2)=7.9 天）。为了测试直接和间接光解降解作为整体降解速率的辅助因子的潜力，牺牲时间序列微宇宙中加入了水、未灭菌土壤+水和灭菌土壤+水。向每个微宇宙中添加氯甲唑，然后在 35 天内暴露于自然光和人工阳光下。通过 LC/MS/MS 对水和乙腈提取物中的氯甲唑和代谢物进行分析。
计算得到的拟一级降解速率常数（k）分别为 k（水）=0-0.005±0.003 天（-1）、k（无菌）=0-0.005±0.003 天（-1）和 k（非无菌）=0.010±0.002-0.044±0.007 天（-1），这取决于光照类型。开环氯甲唑的形成与氯甲唑的降解有关，氯甲唑是微生物的代谢产物。检测到痕量的 5-羟基氯甲唑（m/z=256→125）、芳香族羟基氯甲唑（m/z=256→141）和一种未知产物（m/z=268→125）。
光解降解速率取决于光照类型和诱导间接光解的发色团的质量。微生物降解对温度波动很敏感。总的来说，微生物对氯甲唑的环境归宿的危害大于光解。
