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环境介质中多氯联苯的检测及光致降解理论研究

The Detection of Polychlorinated Biphenyls in Environmental Media and the Study of Photodegradation Theory

【作者】 王贤

【导师】 孙友敏;

【作者基本信息】 山东建筑大学 , 环境工程, 2011, 硕士

【摘要】 多氯联苯(简称PCBs)是典型的持久性有机污染物,其污染呈现出区域性、多介质性的特点,对人类健康和生态安全构成潜在威胁。中国有长期的PCBs生产和使用历史,集中在七八十年代。虽然今天商业上不再生产多氯联苯,但在世界上许多的电器系统和生态系统中仍然有多氯联苯。由于PCBs相当稳定不易降解,在未来的很多年里,多氯联苯会长期存在于环境中。而目前对环境中PCBs污染状况研究还不是很全面,因此有必要对济南地区环境介质中PCBs组分特征和来源进行分析研究,所得结果有利于准确评价PCBs对济南地区生态环境安全的影响,对探索具体的治理方法和制定相关环境政策具有重要意义。在209种多氯联苯同系物中,我们将具有单邻位或无邻位氯取代的共平面结构PCBs称为类二噁英类多氯联苯(DL-PCBs),属于毒性最强的一组同系物,共包括12种。本论文在济南市区主要道路(高速公路、主要干道、支路)的十字路口区布点,采取道路尘样品10个,选取章丘、济阳、商河、长清、历城和槐荫区12个采样地点,采集表层土壤样品12个。实验室分离提取目标物,用气相色谱-电子捕获器(GC-ECD)方法分析了济南地区道路尘和土壤中毒性较高的12种DL-PCBs的残留情况,分析样品中DL-PCBs的含量、组成以及分布情况检测结果表明:(1)济南市道路尘中12种DL-PCBs中除了同系物PCB189未被检出外,其它11种DL-PCBs在各样品均有检出,样品中可检出的12种DL-PCBs残留总浓度在0.20~22.84 ng/g干重之间,平均浓度为5.069g/g干重。其毒性当量(TEQ)值在0.050-117.100pg/g干重之间。对同系物平均残留百分含量分析可知同系物PCB81百分含量与同系物PCB77百分含量相当,其他同系物检出量大小依次为PCB123>PCB167>PCB156> PCB157>PCB118, PCB81检出率最高。道路尘中DL-PCBs以非邻位氯取代的剧毒类二噁英类PCBs含量相对较大。(2)济南地区采样点土壤中均有DL-PCBs检出,除PCB169和PCB189之外,其它10中PCBs均有检出。残留总量在0.02~0.63ng/g干重之间,平均含量为0.10 ng/g。最高值出现在长清区归德乡。12种DL-PCBs含量检出几率较高的三种分别为PCB114 >PCB77>PCB167。12种DL-PCBs总TEQ在0.0020~0.111 pg/g干重之间。(3)另外,对土壤中四种具有手型结构的阻转类多氯联苯(PCB95、PCB132、PCB149、PCB174)检测结果发现,七氯取代PCB174的两种手性异构体未检测到,其它三种同系物的手性结构同系物均有检出,平均含量为0.49ng/g,残留总量在0.192~1.253ng/g干重之间。四种阻转类手性PCBs含量最高的是PCB95-2,其次是PCB132-2, PCB149-1。由于部分采样点阻转类PCB的两种手性结构异构体差异较大,致使分布两种异构体在土壤中的含量呈现不均衡现象。(4)应用主成分分析法得到土壤和道路尘中DL-PCBs主成分特征曲线,得出土壤中含4个主成分,道路尘含3个主成分。通过对DL-PCBs同系物相对含量和不同氯代数同系物相对含量特征的比较分析,判断济南地区土壤和道路尘中PCBs主要污染类型为Arocforl242,1248,1254,来源可能与电力设备绝缘油以及工业生产有关。(5)本论文采用量子化学的方法对三氯杀螨醇与OH自由基的反应机制进行研究找到可行的反应路径和点位。对前线电子密度和键解离能的分析结果表明,可以利用这两种方法预测OH诱导的光反应的起始点位,并且与实验结果有很好的一致性。同时,找到了三氯杀螨醇与OH自由基反应的两种反应路径。其中,OH取代CCl3的反应势垒很低,反应产物二氯二苯酮为实验中的主要检测产物。

【Abstract】 Polychlorinated biphenyls (PCBs) are typical Persistent organic Pollutants. The pollution of PCBs presents regional and multi-edium charaeteristies, which poses latent threats to human health and the ecological security. PCBs have been used in China area and the surrounding areas for a long time, especially in 70s and 80s. At present, although the business has ceased making PCBs, but in the world, there are lots of PCBs in some the electrical system and ecological system. As PCBs are quite stable and is not easy to break down, in the future many years, many of PCBs will be long existed in the environment. But the research about PCBs pollution in environmental is little. Therefore, the research about components and source of PCBs in the environmental media in jinan area have important significance to evaluate PCBs effect to jinan areas of ecological environment safe and explore management methods and develop the environmental policies.In 209 polychlorinated biphenyl ongeners, the coplanar PCBs which has mono-ortho-substituted or no-ortho-substituted chlorine atoms were named Dioxin-Like Polychlorinated biphenyls (DL-PCBs). They include 12 types and have the highest toxicity.We collected the 10 samples of road dust from the main cross road (freeway, primary road, branch) in Jinan, and collected 12 soil samples from zhangqiu, jiyang, shanghe, changqing, licheng, and huaiyin areas. Using the method of gas chromatography with electron capture detection (GC-ECD), the residues of 12 types of Dioxin-Like Poly-chlorinated biphenyls (DL-PCBs) with higher toxicity were analyzed. The residual concentration and distribution of DL-PCBs were given in details. The results indicated that:(1) The detection and analysis results indicated that except PCB189, the others 11 DL-PCBs were detected in all samples.The average road dust concentration of DL-PCBs in Jinan area was 5.069 ng/g dry weight.∑DL-PCBs are distribution in 0.20~22.84 ng/g dry weight. Compared with other areas, the average concentration of∑PCBs in the area atmosphere was in the middle level. The detectable amount is ortho-position substituted PCB77. in order PCB123>PCB167>PCB156>PCB157>PCB118, The detection ratio of PCB81 is the highest. By the TEQ calculating, the total TEQ of 12 species of DL-PCBs is 0.050~117.100 pg/g dry weight.(2) The detection and analysis results of soil samples indicated that except PCB169 and PCB189, the others 10 DL-PCBs were detected in all samples. The average soil concentration of DL-PCBs in Jinan area was O.lOng/g dry weight.L-PCBs are distribution in 0.02-0.63 ng/g dry wight. The highest concentration was in Changqing Guide town. DL-PCBs was detected in Zhangqi, Jinyang, Pingyin, Changqing, Licheng and Huaiyin area.The three high species of DL-PCBs is PCB114>PCB77> PCB167. The total TEQ of 12 species DL-PCBs is 0.0020~0.111 pg/g dry weight. (3) In addiation, from the inspection results of atropisomeric PCBs which have hand-type structure, we find that:except PCB174, other 3 species of atropisomeric PCBs and their hand-type structures was detected. The average concentration was 0.49 ng/g, and the total concentration was distribution in 0.192~1.253 ng/g dry weight. The highest content is PCB95-2, and then are PCB132-2, PCB149-1. As some hand-type structure isomers of atropisomeric PCBs in the samples was different, the content of isomers in soil are not inequality.(4) By analyzing the characteristics of the relative distributions of DL-PCBs and the characteristies of the relative distributions of PCBs with different Cl atom, it comes to the conclusion that the type of PCBs Pollution was Aroelor 1242, and it was known that the source of PCBs was the Insulating oil in the Power Equipments that had the similar composition with Aroclor 1242. A large number of the Power Equipments ever be used, and may be the main source of PCBs contamination in this area.(5) In this paper, we apply the method of quantum chemistry to research the Reaction mechanism of Dicofol and OH free radical, in order to find practicable Reaction Pathway and point. The analytic results of frontier electron density and bond dissociation energy show that we can use these two methods to predict the initiation sites of initiation sites by OH induced, and the results are agreed with the experimental results. At the same time, we find two reaction pathways between Dicofol and OH free radical. The Rotational Barrier for OH substitude of CCl3 is lower. The product DCBP is the major determination product.

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