中文摘要：

以除草剂阿特拉津和丁草胺为供试毒物，研究了它们对麦穗鱼的单一及联合毒性。结果表明，阿特拉津与丁草胺对麦穗鱼的96h半致死浓度（LC50）分别为41．64、0．33mg／L，安全浓度（SC）分别为4．164、0．033mg／L。因此，阿特拉津对鱼类是一种低毒除草剂，丁草胺则对鱼类具有较高的毒性。在阿特拉津与丁草胺的联合毒性试验中，24、48、96h的相加指数分别为0．056、0．053、0．084，表明阿特拉津与丁草胺对麦穗鱼的联合毒性存在协同效应。

英文摘要：

Single and joint toxicities of herbicides atrazine and butachlor to topmouth gudgeon （Pseudorasbora parva） were investigated at 20 ℃. The 96 h-LC50 of atrazine and butachlor to topmouth gudgeon （size = （4. 95±0.25） cm and weight = （1.52±0.23） g） were 41.64 mg/L and 0.33 mg/L, respectively, and the corresponding safe concentrations were 4. 164 mg/L and 0. 033 mg/L. Such results showed that butachlor was highly toxic to the fish and that atrazine was non toxic （its water solubility = 30 mg/L）. The 24,48 and 96 h additive indexes estimated from the joint toxicity test data were 0. 056,0. 053 and 0. 084, respectively, indicating the joint presence of atrazine and butachlor was more toxic than that predicted from their single toxicity data.