会仙湿地水体有机磷农药污染特征及生态风险

为系统了解桂林会仙岩溶湿地水环境中有机磷农药(OPs)污染水平、时空分布特征和生态风险,分别于2018年8月至2019年1月3个不同水期在研究区域内采集湿地湖泊和农田沟渠水样共72份,利用固相萃取法结合超高效液相色谱串联质谱仪(UPLC-MS/MS)对16种OPs含量进行检测分析,并通过风险熵值法(RQ)开展生态风险评估。结果表明:湿地湖泊和农田沟渠水体中OPs的残留浓度分别为nd～182.590、nd～146.636 ng·L~(-1),平均浓度分别为11.633、16.813 ng·L~(-1);其中氧乐果、敌百虫和三唑磷为主要污染物,占总残留浓度的65%以上;毒死蜱和对硫磷分别在湿地湖泊水和农田沟渠水中检出率最高,分别为55.5%和44.5%。在时间分布上,OPs残留量呈现季节变化特征,表现为丰水期枯水期平水期,丰水期平均浓度分别是平水期和枯水期的3.73倍和6.74倍;在空间分布上,OPs呈现沿水流方向减少的趋势。OPs混合物生态风险评估表明,在采集的72个水样中,有27.8%的水样RQ值大于1,表现为高风险;44.4%的水样RQ值在0.1～1,表现为中等风险。高风险点位多集中于丰水期和平水期农业活动频繁的农田沟渠水中,而人类活动较少的湿地湖泊水多表现为中低风险,说明人类活动强度可能与OPs污染强度密切相关。研究表明,会仙湿地水体中OPs具有一定的生态风险,对产生中高等风险的农业耕种区应加强OPs的施用管控。

Pollution characteristics and ecological risk assessment of organophosphorus pesticides in Huixian wetland water

The study aims to investigate the pollution level, temporal and spatial distribution characteristics, and ecological risks of organophosphorus pesticides(OPs) in the water of Guilin Huixian karst wetland. During three different water periods from August 2018 to January 2019, 72 water samples were collected from lakes and farmland ditches in the study area. The content of 16 OPs was analyzed using solid-phase extraction combined with ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS). The ecological risks were assessed using risk entropy methods. The results showed that the residual concentrations of OPs in wetland lakes and farmland ditches were nd~182.590 ng·L^-1 and nd~146.636 ng·L^-1, respectively, while the average concentrations were 11.633 ng·L^-1 and 16.813 ng·L^-1, respectively. Omethoate, trichlorfon, and triazophos were the main pollutants, accounting for more than 65% of the total residual concentration. Chlorpyrifos and parathion had the highest detection rates of 55.5% and 44.5% in lakes and farmland ditches, respectively. Regarding time distribution, the OPs residues presented seasonal changes, in the order of high water period> dry period> normal water period. The average concentration in the wet period was 3.73 times and 6.74 times more than in the normal and dry periods, respectively. For spatial distribution, OPs decreased along the water flow direction. The results of the ecological risk assessment of the OPs mixture showed that 27.8% of the water samples had risk quotient(RQ) values greater than 1, indicating high risk; 44.4% had RQ values of 0.1 to 1, indicating medium risk. The high-risk points were mostly concentrated in farmland ditches with frequent agricultural activities during the wet and flat periods, while wetland lakes with less human activities were mostly low-and medium-risk, indicating that the intensity of human activities might be closely related to that of OPs pollution. Studies have shown that OPs in Huixian wetland water bodies have certain ecological risks, and the application and control of OPs should be strengthened in agricultural farming areas that produce medium and high risks.