固城湖及出入湖河道表层水体、沉积物和鱼体中有机氯农药分布及风险评估

Distribution and Risk Assessment of OCPs in Surface Water, Sediments, and Fish from Lake Gucheng and Inflow and Outflow Rivers

为研究固城湖环境中有机氯农药(organochlorine pesticides,OCPs)时空分布、来源与生态风险,采用GC-μECD定性定量分析了固城湖及其出入湖河道12个监测点夏、冬两季水体、沉积物和鱼类体内19种OCPs的含量.结果表明,固城湖表层水、沉积物和鱼类中(以干重计)有机氯农药总量范围分别是26.74~48.12 ng·L^-1、 9.01~35.34 ng·g^-1和13.39~124.29 ng·g^-1.水中有机氯农药污染特征表现为夏季含量高于冬季,出入湖河道高于养殖塘和湖区;沉积物中季节性污染特征不明显.从组成特征上看,夏、冬两季水体、沉积物和生物体内19种OCPs均有不同程度地检出,均呈现以HCHs和DDTs为主的污染特征,其中,夏冬两季各监测点表层水和沉积物中HCHs以α-HCH为主,占HCHs总含量的21%~42%;表层水中DDTs以p,p′-DDD为主,占DDTs总含量的30%~76%,沉积物中以p,p′-DDT为主,占DDTs总含量的68%~93%.分析固城湖环境中OCPs来源,根据异构体比值,可以推断环境中HCHs和DDTs主要来源于近期新的农药输入,且主要发生厌氧分解.生态风险评价显示,固城湖水体中OCPs的健康风险不大,沉积物中的有机氯农药残留量有一定的生态风险.固城湖各监测点所采生物样均在可接受的潜在致癌风险范围内.

To investigate the distribution, source, and ecological risk of organochlorine pesticides(OCPs) residues in Lake Gucheng, surface water, sediment, and biological samples were collected from 12 sampling sites of Lake Gucheng and its inlets and outlets during summer and winter, and the concentrations of 19 OCPs were analyzed. The results showed that the concentration(dry weight) of OCPs in Lake Gucheng ranged from 26.74 to 48.12 ng·L^-1 in surface water, 9.01 to 35.34 ng·g^-1 in sediment, and 13.39 to 124.29 ng·g^-1 in organisms. The pollution characteristics of OCPs in surface water showed that the concentration was much higher in summer than in winter, and much higher at inflow and outflow rivers than in farming ponds and the central region of Lake Gucheng;the seasonal pollution characteristics in sediment were not obvious. All 19 kinds of OCPs in water, sediment, and organisms were detected in different degrees, and the dominant contaminants were HCHs and DDTs. α-HCH was the main pollutant at all sites in both surface water and sediment, with 21% to 42% of total HCHs in two seasons. p,p′-DDD was the main pollutant in surface water with 30% to 76% of total DDTs, whereas p,p′-DDT was the main pollutant in sediment with 68% to 93% of total DDTs in two seasons. Source analysis based on ratios of HCHs isomers and DDTs isomers indicated that there was a new input of OCPs under anaerobic conditions in the study area. The ecological risk assessment showed that the OCPs in surface water did not lead to significant health risks, but the OCPs in sediments might pose ecological risks to the Lake Gucheng ecosystem. The organisms were within the acceptable potential carcinogenic risk range.