中文摘要：

应用急性毒性试验方法,在对映体水平上研究了除草剂Rac-及S-异丙甲草胺对斜生栅藻（Scenedesmus obliquus）和普通核小球藻（Chlorella vulgaris）的急性毒性特征及腐殖酸对除草剂毒性的影响.结果表明,Rac-及S-异丙甲草胺的急性毒性与浓度及暴露时间呈正相关,Rac-及S-异丙甲草胺对微藻细胞的急性毒性存在立体选择性差异.Rac-异丙甲草胺对普通核小球藻和斜生栅藻的EC50,96 h分别是S-异丙甲草胺的2.25和1.81倍,S-异丙甲草胺对微藻细胞的生态毒性较大,而斜生栅藻对Rac-及S-异丙甲草胺的敏感性更强,且Rac-及S-异丙甲草胺对斜生栅藻和普通核小球藻的急性毒性存在一定的线性相关性.腐殖酸的加入能够改变Rac-及S-异丙甲草胺对微藻细胞生态毒性,对S-异丙甲草胺的生态毒性的影响更为明显（P〈0.05）.

英文摘要：

The enantioselective toxicity of the chiral herbicides Rac-and S-metolachlor to Scenedesmus obliquus and Chlorella vulgaris was determined,and the effect of humic acid was studied by using acute toxicity testing method.The results indicated that the toxicity of Rac-and S-metolachlor increased with increasing concentration and exposure time.The EC50,96 h ratio of Rac-metolachlor to S-metolachlor was 2.25 for C.vulgaris and 1.81 for S.obliquus,indicating that S-metolachlor had higher effect on two algaes,and S.obliquus was more sensitive to Rac-and S-metolachlor.Linear correlation between toxicity on S.obliquus and C.vulgaris was observed.The toxicity of Rac-and S-metolachlor changed with humic acid,with more significant change was observed in S-metolachlor（P0.05）.