粤桂琼区域水源地有机磷农药的生态风险评价

利用气相色谱-质谱检测粤桂琼(广东、广西、海南三省区)区域水源地9个采样点水样中的有机磷农药浓度,构建了淡水生物对有机磷农药的物种敏感性分布,并计算出各类水生生物的HC₅(hazardous concentration for 5% the species)值；采用基于浓度加和模型的混合物风险商值法和商值概率分布法,评价了粤桂琼区域水源地中敌敌畏、内吸磷、阿特拉津、甲基对硫磷、乐果、马拉硫磷和对硫磷7种有机磷农药的的生态风险,同时利用聚类分析法对9个采样点进行了生态风险评价. 结果表明:粤桂琼区域水源地7种有机磷农药的总质量浓度在nd~1 260.95 ng/L之间,平均值为184.68 ng/L,主要以马拉硫磷、甲基对硫磷、对硫磷和乐果为主. 东莞东江南支流、玉林苏烟水库和柳州柳江水源地的生态风险级别相对较高. 敌敌畏、对硫磷、甲基对硫磷的HC₅值均低于0.1 μg/L,这3种物质对生态系统毒性效应较大. 根据风险商结果排序可知,粤桂琼区域水源地预防的重点为甲基对硫磷、对硫磷和马拉硫磷对水生生物的危害,其中甲基对硫磷是对混合风险商贡献最高的污染物,其危害指数达21.313；在95%的置信区间内,甲基对硫磷、对硫磷和马拉硫磷的生态风险较大,风险商超过1的概率为5%,应作为最优先控制的污染物. 

Ecological Risk Assessment of Organophosphorus Pesticides in Water Source Areas of Guangdong, Guangxi and Hainan Provinces

Concentrations of organophosphorus pesticides were determined by using GC-MS. Water samples were collected from different sites of water source areas of Guangdong, Guangxi and Hainan provinces. Species sensitivity distribution (SSD) curves of different freshwater organisms exposed to organophosphorus pesticides were established. Based on organophosphorus pesticides concentrations and SSD models, the hazardous concentration for 5% of the species (HC₅) of organophosphorus pesticides to freshwater organisms were estimated. In addition, the method of risk quotient (RQ) for mixtures and quotient probability distribution, which were based on the concentration addition model and SSD curves, were employed to assess the ecological risks of seven organophosphorus pesticides-dichlorvos, demeton-s, atrazine, methyl parathion, dimethoate, malathion and parathion-in the water source areas of the three provinces. Cluster analysis was subsequently used to assess nine sample sites of water source areas based on the concentration data. The total concentrations of organophosphorus pesticides were detected between nd and 1260.95 ng/L, with average 184.68 ng/L. They were mainly composed of malathion, methyl parathion, parathion and dimethoate. The results showed that the ecological risk of the south branch of Dongjiang River, Liujiang River water source and Suyan Reservoir were higher than other water source areas. The HC₅ values of dichlorvos, parathion and methyl parathion to freshwater organisms were below 0.1 μg/L, which might have large effects on the ecological system. Results based on the risk quotient method revealed that the risk level of methyl parathion was the highest among the seven organophosphorus pesticides in the water source areas, while the hazard index of methyl parathion was 21.313. The results from quotient probability distribution showed that parathion, methyl parathion and malathion posed higher risks at 95% confidential level, and the probability of risk quotient exceeding 1 was 5%. Therefore, parathion, methyl parathion and malathion should be listed as the priority control pollutants in the water source areas.