太湖有机氯农药的水平、历史趋势及迁移规律的研究

【作者】 亓学奎；

【导师】 王英；

【作者基本信息】 中央民族大学 ， 环境科学， 2012， 硕士

【摘要】 有机氯农药(OCPs)是一类重要的持久性有机污染物(POPs),具有高毒性、难降解性、半挥发性和生物蓄积性,可在环境中可长期存在,并通过食物链富集,危害生态系统和人体健康。我国是世界上OCPs生产和使用大国,虽然早在20世纪70年代,西方发达国家就已经开始禁用OCPs,而我国也于1983年开始禁止生产和使用,但由于其使用量大,在环境中降解缓慢、滞留时间长,使得OCPs仍然是环境中检出率最高的一类POPs。目前,国内外对于有机氯农药污染的研究主要集中于海湾及河口地带,对湖泊的研究较少,太湖是我国东部沿海地区多功能湖泊,关于太湖的有机氯农药水体-沉积物交换还尚未见报道,探讨太湖水体和沉积物中有机氯农药的来源与归宿,以及沉积物中有机氯农药的重新释放对太湖水质的影响,可以为太湖有机污染的控制与治理提供理论依据。本文系统研究了太湖表层沉积物、柱状样品和水体中OCPs的含量、分布规律、可能来源、潜在的生态风险以及水体-沉积物之间的交换通量,结果如下：采用GC-NCI-MS分析了太湖69个表层沉积物样品中OCPs的含量,OCPs的总含量范围为0.55-11.66ng/g,平均值为4.13ng/g,DDTs、HCHs和HCB的含量分别为0.14-8.53ng/、nd-4.20ng/g、nd-6.24ng/g。其中w(DDTs)占w(OCPs)的40%,是样品中OCPs的主要成份。DDTs的残留以DDTs的降解代谢产物p,p’-DDE为主,HCHs的残留以其长期降解产物β-HCH为主。采用a-HCH/y-HCH、 p,p’-DDT/p,p’-DDE的值对HCHs和DDTs的来源进行分析,发现太湖表层沉积物中γ-HCH主要源于工业品和林丹的使用,近期可能有DDTs源的输入。与国内外不同地区沉积物中有机氯农药残留相比,太湖有机氯农药残留水平属于中等偏下水平。太湖所有沉积物采样点的T-氯丹的含量小于ERL值,大部分采样点DDT、DDE和∑DDTs的含量小于ERL值,含量超过ERL值的区域出现在污染较为严重的竺山湾、梅梁湾地区,不存在含量超过ERM值的采样点。总体来说,太湖水体沉积物中的有机氯农药存在一定的生态风险,可能对生态环境造成危害,OCPs对环境的潜在威胁仍不容忽视。太湖3个柱状沉积物样品中OCPs的测定结果如下：OCPs浓度为0.88-4.73ng/g,平均值为2.i7ng/g；DDTs、HCHs、六氯苯的残留量均较高,其中DDTs为0.35-1.68ng/g,平均值为0.55ng/g；HCHs的浓度为0.25-1.99ng/g,平均值为0.65ng/g；六氯苯为0.50-1.35ng/g,平均值为0.92ng/g。3个湖湾的沉积柱表层DDTs含量最高,有明显的表面富集现象,说明太湖可能着存在着DDTs类物质的输入。对太湖水样中有机氯农药的分析结果如下：p,p’-DDT的含量最高浓度为426.26pg/L,其次是a-HCH和硫丹I,浓度分别为289.99pg/L和215.20pg/L,虽然沉积物中六氯苯和p,p’-DDE的浓度较高,但是因为六氯苯和p,p’-DDE具有很高的辛醇水分配系数(logKow),水溶性差,因此水体中六氯苯和p,p’-DDE的浓度并不高。采用a-HCH/γ-HCH比值对HCHs的来源进行分析,发现太湖水体中的y-HCH污染来源于工业品和林丹的使用,由交换模型得出HCHs的净交换通量为释放通量,全年大约有706.71kg由沉积物释放到水体中,水体中的p,p’-DDT/p,p’-DDE比值远大于1,说明了近期可能有新的污染源的输入,由交换模型得出p,p’-DDT的净交换通量为沉降通量,全年大约有50.74kg由水体沉降到沉积物中,另外全年大约有25.63kg的硫丹I由水体沉降到沉积物中,反映出太湖水体存在较为严重的硫丹I污染,而且近期有DDTs产品的输入。从而造成了水体中DDTs的污染。更多还原

【Abstract】 Organochlorine pesticides (OCPs) are important persistent organic pollutants (POPs), Because of their persistence, half-volatility and high toxicity in the environment and biological accumulation through the food web, OCPs have great harm to the environment and human health. China is the largest user and producer of OCPs in the world. Because they were used largely and are difficult to be degraded, OCPs are still the most widespread POPs in the environment despite ban or restricted use in developed countries and in china since1983.At present, the studies on OCPs are mainly paid attention to bays and estuaries, and very few studies on OCPs in Lake. Taihu Lake is a typical multifunctional Lake in southeast coast of China, However, no date of water-sediment exchange are available for OCPs in Taihu Lake. Through the discussion about the origin, tendency and release of OCPs, we can know the transferring and transforming pathways of OCPs in the water and sediments in Taihu Lake, which may provide theoretical foundation for controlling and treating organic pollution of Taihu Lake.This study systematically researched into the concentration of OCPs in sediments, water and core samples from Taihu Lake, distribution feature, possible sources, potential ecological risk and the water-sediment exchange flux.The results are following: It employed gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) to analysis a total of69sediment samples. The total OCPs concentrations in sediments were0.55-11.66ng/g and the average levels of OCPs were4.13ng/g. Among the OCPs, the concentrations of DDTs (0.14-8.53ng/g dw), HCHs (0.12-4.75ng/g dw) and HCB (nd-6.24ng/g dw) were much higher than other pesticides. DDTs were the most dominant compounds in the sediments, accounting for about40%of the total levels. The dominant compound of DDTs was the residual metabolic products p,p’-DDE and the dominant compound of HCHs was?-HCH. According to component analysis, the ratios of a-HCH/γ-HCH and p,p’-DDT/p,p’-DDE suggested that residues of HCHs and DDTs in surface sediments from Taihu Lake were mainly due to long-term usage in past. But there was still new inpute of some OCPs in recent use. By comparing the concentration of OCPs in surface sediments from Taihu Lake with other regions, the concentration of OCPs in sediments from Taihu Lake were slightly lower than the median level around the world.Less than the ERL value of the content of all sampling points of the T-chlordane in Taihu Lake sediments, most of the sampling points of DDT, DDE and SDDTs, content is less than the ERL value content more than the ERL value of the region in more serious pollution ZhushanBay, Meilianghu Bay region, there is no content to exceed the ERM value of the sampling points. Overall, the organochlorine pesticides in Taihu Lake sediments there is a certain ecological risk, and may cause harm to the ecological environment of OCPs in the potential threat to the environment can not be ignored.Three column sediments were sampled from Taihu Lake, The contents of OCPs in these samples were tested. The results indicated that the total OCPs concentrations in sediments ranging from0.88to4.73ng/g dw (average2.17ng/g dw), Among the different OCPs, hexachlorobenzene(HCB), DDTs and HCHs presented the hightest detection rate and residual level, The average value of HCB, DDTs and HCHs in sediments sample was0.92ng/g,0.55ng/g,0.65ng/g respectively. Three bays of the sedimentary column surface DDTs content of the highest apparent surface enrichment, the composition analysis results showed that there was still new input of DDTs in recent years.It can be seen from the analysis data, among all the organochlorine pesticides in Taihu Lake water samples, the highest concentration of p,p’-DDT was426.26pg/L, followed by a-HCH and endosulfan which concentration were289.99pg/L and215.20pg/L. The concentration of hexachlorobenzene (HCB) and p,p’-DDE in the sediments were slightly higher. But the octanol-water partition coefficient (log Kow) of hexachlorobenzene (HCB) and p,p’-DDE were very high, with poor water solubility, so concentration of HCB and p,p’-DDE in the water were not high.According to ratio of a-HCH/γ-HCH and HCHs source analysis, it can be found that HCHs pollution in Taihu Lake came from the use of industrial lindane. We use exchange model to calculate the net exchange flux of HCHs, the derived release flux of HCHs from sediments to water bodies were about706.71kg throughout the year. The ratio of p,p’-DDT/p,p’-DDE in water bodies is much larger than1, indicating the new sources of input. The exchange model indicated that the net exchange flux of p,p’-DDT were deposition fluxes. The deposition fluxes of p,p’-DDT were about50.74kg throughout the year. Besides there were about25.63kg of endosulfan I from water bodies into sediments, reflecting the endosulfan I pollution in Taihu Lake was very serious and new input of DDTs products, resulting in the DDT pollution of water bodies.更多还原