Enantioselective Degradation of Rac-Metolachlor and S-Metolachlor in Soil

Separation of chiral enantiomers and the dissipation of rac-metolachlor and S-metolachlor in soil were evaluated using achiral high-performance liquid chromatography (HPLC) and chiral gas chromatography (GC) methods. Under the experimental conditions the possible metabolite was considered to be N-(2-ethyl-6-methyl-phenyl)-2-hydroxy-acetamide. Because of the presence of two chiral elements (asymmetrically substituted carbon and chiral axis), the baseline separation of metolachlor enantiomers was not achieved. S-metolachlor degraded faster in soil than rac-metolachlor. After a 42-day incubation, 73.4% of rac-metolachlor and 90.0% of S-metolachlor were degraded. However, due to the absence of biological processes the degradation process in sterilized soil showed no enantioselectivity. The results indicated that enantioselective degradations could greatly affect the environmental fate of metolachlor and should be considered when the environmental behavior of these compounds was assessed.

Rac-异丙甲草胺及S-异丙甲草胺与镉复合污染对土壤酶活性的影响

在实验室控制条件下,研究了Rac-异丙甲草胺及S-异丙甲草胺与Cd处理下对土壤过氧化氢酶和脱氢酶活性的影响。结果表明,各处理对过氧化氢酶活性表现为先激活后抑制,对脱氢酶活性表现为激活-抑制-激活;异丙甲草胺与Cd复合污染对土壤过氧化氢酶和脱氢酶活性的影响表现出一定的交互效应;Rac-和S-异丙甲草胺对过氧化氢酶活性表现出一定的手性差异,对脱氢酶活性无显著手性差异。