中文摘要：

敌敌畏是一类重要的有机磷杀虫剂,但其对水生生态的影响至今研究较少。为了评价其生态风险,构建了淡水水生生物对敌敌畏的物种敏感性分布（species sensitivity distribution,SSD）模型,在此基础上,讨论了影响SSD模型的主要因素;并分析了该模型的不确定性;推导了敌敌畏对不同类别生物的5%危害浓度HC5（hazardous concentration for 5%the species）阈值;整理收集了我国重要流域水体中敌敌畏的环境浓度;结合SSD模型计算了对淡水生物的潜在影响比例（potentially affected fraction,PAF）。结果表明：1）不同模型的选择会影响HC5的结果,且Burr III模型拟合结果较好,推导的HC5值为0.37μg·L-1;2）无脊椎动物在敌敌畏低浓度范围内的敏感性明显高于脊椎动物。甲壳类动物与昆虫和蜘蛛类相似,敏感度较高,鱼类则较低;3）应用Burr III模型构建SSD时,参数k值对HC5最为敏感,蒙特卡罗随机模拟得到HC5变化范围为0.05～40.57μg·L-1,均值为5.07μg·L-1;4）敌敌畏对我国淡水生态影响较小,PAF均低于1%,其中黄河和太湖流域敌敌畏的生态风险高于其他河流湖泊,珠江口和南海北部较低。上述研究结果为评价敌敌畏对全国不同水体水生生物的潜在生态风险提供了科学依据。

英文摘要：

The study of the impact of dichlorvos on the aquatic ecosystem is scarce despite the fact that it is widely used as organophosphate insecticide. In order to assess ecological risk of dichlorvos to freshwater organisms, species sensitivity distribution（SSD） model was applied; the factors and uncertainties affecting the construction and application of SSD were discussed; hazardous concentration for 5% the sensitive species（HC5） was estimated; the en-vironmental concentration of dichlorvos in the water of the aquatic systems around China was primarily reviewed,and potentially affected fraction（ PAF） was computed based on these environmental concentrations. The results show： 1） The outcome of HC5 will be affected by choosing models, while Burr III model is the best fit for the toxicity data, and HC5 value is predicted at 0.37 μg·L^（-1）; 2） The sensitivity of invertebrates in the low concentration range was significantly higher than that of vertebrates. Crustaceans were similar to insects and spiders which were more sensitive in comparison with fishes; 3） parameter k of Burr III model was expected the largest influence factor on the predicted HC5 concentration, and HC5 of dichlorvos was estimated at a range of 0.05 ～ 40.57 μg·L^（-1）with a geometric mean of 5.07 μg·L^（-1）using Monte Carlo method; 4） Generally, dichlorvos posed low risks to freshwater ecosystems of China with PAF value less than 1%. The high risk was investigated in Yellow River and Taihu Lake, while low risk was observed in the Pearl River Estuary and the northern South China Sea. Totally, the results in the present study will provide the scientific information to protect national aquatic ecosystem