桂林会仙岩溶湿地水体中有机氯农药分布特征及混合物环境风险评估

Distribution of organochlorine pesticides(OCPs) in the water body of Huixian Karst wetland of Guilin and environmental risk assessment of OCP mixtures

为研究桂林会仙岩溶湿地水体中有机氯农药(OCPs)的残留水平、分布特征、来源和环境风险,分别于2016—2017年四个季节在研究区域采集地表水(湖泊和沟渠水)和浅层地下水样品共88份,利用气相色谱法(GC-ECD)对其中15种OCPs残留量进行检测和相关分析。结果表明,会仙湿地湖泊、沟渠和浅层地下水中总OCPs残留量范围(平均值)分别为68.7~305 ng·L^(-1)(137 ng·L^(-1))、77.4~211 ng·L^(-1)(137 ng·L^(-1))和24.6~76.4 ng·L^(-1)(38.6 ng·L^(-1)),其中六六六(HCHs)是最主要的污染物,占总OCPs的61.7%以上,其次是七氯类OCPs和滴滴涕(DDTs)。与国内外其他地区水体OCPs污染相比,研究区域地表水OCPs污染处于较高水平,浅层地下水OCPs污染处于中等水平,同时夏季OCPs残留浓度高于其他季节。从特征组分比例可确认HCHs主要来自历史残留,但2016年10月可能有新的林丹输入;DDTs降解不完全,可能有持续输入。OCPs混合物风险评估结果表明甲壳类对研究区域水体中15种OCPs最敏感,其次为鱼类和藻类;15种OCPs混合物对浅层地下水水生生态环境具有中等风险,而对地表水水生生态环境具有高风险。

In order to investigate residual levels, distribution characteristics, sources, and environmental risk of organochlorine pesticides（OCPs）in the Huixian Karst wetland of Guilin, 88 water samples were collected from surface waters（lake water and canal water）and shallow groundwater in April, July, and October 2016 and January 2017. Fifteen different species of OCPs were quantitatively determined using a gas chromatography with an electron capture detector（GC-ECD）. Results showed that the residues of OCPs in the lake water, canal water,and shallow groundwater ranged 68.7-305 ng·L^（-1）（mean value：137 ng·L^（-1））, 77.4-211 ng·L^（-1）（mean value：137 ng·L^（-1））, and 24.6-76.4 ng·L^（-1）（mean value：38.6 ng·L^（-1））, respectively. A majority of the OCPs detected were HCHs, accounting for more than 61.7%, followed by heptachlor（heptachlor and heptachlor epoxide）and DDTs. Residual levels of OCPs in the surface water from the Huixian wetland were present at higher levels, whereas moderate levels of residues were observed in the shallow groundwater, compared with respective data. Additionally,the highest residue levels of OCPs were found in summer. Results presented herein indicate that the HCH residues were mainly from a historical source, whereas the source of lindane might be from a new input as of October 2016. The residues of DDTs were most likely due to their persistence against degradation. Environmental risk assessment of the OCP mixture suggested that crustaceans were the most sensitive aquatic species, followed by fish and algae. The mixture of OCPs showed a moderate risk to aquatic organisms living in shallow groundwater,whereas it posed a high risk to living organisms in the surface waters.