有机磷农药的构效关系及其对浮游生物的毒性效应

以定量构效关系理论和实验室内急性毒性试验相结合研究了六种有机磷农药对四尾栅藻（S.quadricanda）和多刺裸腹溞（Moina macrocopa）的生态毒性。有机磷农药的毒性取决于磷原子的电正性,各取代基种类和构象对电荷分布作用显著。根据构效关系原理,磷氧双键（P=O）被磷硫双键（P=S）取代后毒性降低;羟基（-OH）被甲、乙、丙氧基（-CH3O、-CH3CH2O、-CH3CH2CH2O）取代后有机磷农药毒性依次增强;磷氧单键（P-O）毒性高于磷碳单键（P-C）。该实验中毒死蜱、辛硫磷（-CH3CH2O）毒性高于其它四种（-CH3O）,敌敌畏和敌百虫（P=O）毒性高于乐果（P=S）,敌敌畏（P-O）又高于敌百虫（P-C）,甘氨酸异丙胺盐取代羟基（-OH）的草甘膦毒性最低。毒性试验结果表明,毒死蜱、辛硫磷、敌百虫、敌敌畏、乐果、草甘膦异丙胺盐对四尾栅藻的96 h EC50分别为6.34、6.62、59.53、82.12、141.37和7.25 mg.L-1。它们对多刺裸腹溞的48 h LC50分别为0.20、0.12、0.28、0.17、1.12和5.03 mg.L-1。六种有机磷农药对多刺裸腹溞的毒性强度结果与QSAR分析具有较高的一致性,即表征有机磷农药毒性特征的取代基团作用的毒性强弱顺序为：-OH〉=O〉-O;对四尾栅藻毒性试验结果中,由于草甘膦异丙胺盐作用于植物类靶位点的特殊性,导致其对四尾栅藻毒性显著增强。综合以上研究,以构效关系理论和浮游生物毒性试验相结合进行有机磷农药的生态风险评价将更加便捷和准确。

Analysis of structure -activity relationship and toxicity of organophosphorus pesticide to plankton

The toxicity of six organophosphorus pesticides to Scenedesmus quadricanda and Moina macrocopa were studied using quantitative structure-activity relationship theory （QSAR） and acute toxicity tests. According to QSAR theory, the toxicity of organophosphorus pesticides was determined mainly by the electropositivity of center phosphorus atom, which was influenced by the type. More specifically, toxicity was reduced as P=O bonds were replaced by P=-S bonds. Replacement of hydroxy（-OH） by methoxy（-CH30）, ethoxy（-CH3CH20） and propoxy（-CH3CH2CH20）, however, successively increased. Toxicity of organophosphorus pesticides was also reduced as P-O bond were replaced by P-C bond. Specifically, the toxicity of chlorpyrifos and phoxim was higher than four other organophosphorus pesticides as -CH3CH20 replaced -CH30, dichlorovos and trichlorphon were more toxic than glyphosate compared, while dichlorovos was more toxic than trichlorphon. Glyphosate-isophopylammianium was the least toxic compound as hydroxy（-OH） replaced by glycine isophopylammianium. Toxicity tests demonstrated that the EC-50 concentrations of chlorpyrifos, phoxim, trichlorphon, dichlorovos, dimethoate, glyphosate-isophopylammianium on S. quadricanda were 6.34, 6.62, 59.53, 82.12, 141.37 and 7.25 mg.L1 at 96 h, respectively, while, those on M. macrocopa were 0.20, 0.12, 0.28, 0.17, 1.12 and 5.03 mg.L-1 at 48 h, respectively. The toxicity of the six organophosphorus pesticide to M. macrocopa was generally ordered as -OH 〉=O 〉-O. In conclusion, this study demonstrates the utility of using QSAR with acute toxicity test for the assessment of ecological risks of organophosphorus pesticides to plankton.