【作者】 张庆红；

【导师】 李先国；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2009， 硕士

【摘要】 多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)是一类广泛存在于环境中具有“致癌、致畸、致基因突变”作用的有机污染物,由于其毒性、生物蓄积性和半挥发性并能在环境中持久性存在,而被列入典型持久性有机污染物(Persistent Organic Pollutants,POPs),受到国际上科学界的广泛关注。环境中PAHs的来源很广,但大多是人为污染。大气或水环境中PAHs趋向于在颗粒物上富集,最终沉降于地表或者沉积物中,除对人类健康和陆地生态造成危害外,也对水生生物,尤其是底栖生物造成严重影响。PAHs在环境中可以通过多种途径加以去除,主要包括生物降解、化学降解和光降解。在沉积物环境中,生物降解是最主要的降解途径。蒽(Anthracene,AC)是低分子量PAHs中一种常见的三环芳香化合物。AC和它的降解产物似乎对人体都不具有毒性,但是由于AC的结构单元在致癌性PAHs如苯并[a]芘(BaP)和苯并[a]蒽(BaA)中同样存在,因此经常被用作模型化合物。蒽的甲基取代物是环境中广泛存在的污染物,其一甲基取代衍生物在微生物致突和致癌性评价中具有生物惰性。但是,9,10-二甲基蒽(9,10-DMA)由于生成了有生物活性的含湾区结构的环氧化物,能够增加肿瘤的突变能力和细胞转变性能。本论文选择这三种物质作为模式化合物,以污染较为严重的李村河口区沉积物为培养基质,进行实验室好氧生物微生态培养,以期获得此三种目标污染物的降解速率及其可能中间降解产物。具体内容和结论如下:(1)建立了研究沉积物中有机污染物生物降解的实验室微生态培养装置,为整个好氧生物降解研究提供了必要前提条件。(2)培养实验前对微生态培养基质下的环境条件(包括上覆海水和沉积物孔隙水的相关指标参数)进行了测定。结果表明,采样区海水pH值为7.46,盐度约31.794,溶解氧含量为4.27mg·L-1;孔隙水中电子受体Fe3+,SO42-和NO3-浓度分别为4.26mg·L-1,1156mg·L-1和2.58mg·L-1;沉积物氧化还原电势为-280.4mv,总有机碳含量达1.54%。这些参数充分表明李村河口沉积环境主要为还原环境,沉积物中的有机碳主要来源于人源有机质。(3)优化了气相色谱-氢火焰离子化检测器分析蒽及其取代衍生物的色谱条件。在此最佳条件下,蒽、9-甲基蒽和9,10-二甲基蒽的空白回收率在79.5%~83.79%间,相对标准偏差在4.61%~14.78%之间;基质加标回收率在66.2%~82.95%之间,相对标准偏差在3.34%~6.19%之间。此外还优化了沉积物前处理条件,特别考察了柱色谱净化过程中两种常见淋洗液的净化效率,最终选择了正己烷和甲苯混合溶液,其对目标污染物的洗脱回收率略高于正己烷和二氯甲烷混合溶液。(4)测得李村河口沉积物中蒽的本底值为32.88ng·g-1,9-甲基蒽和9,10-二甲基蒽均未检测到。6个月的好氧生物降解实验结果表明,沉积物中本底蒽由32.88ng·g-1降到32.32ng·g-1,降解率仅为1.70%;而在添加了蒽的沉积物样品中其浓度由170.40ng·g-1降到151.36ng·g-1,降解率高达11.17%;加入的9-甲基蒽和9,10-二甲基蒽的浓度也分别由133.84ng·g-1和144.26ng·g-1减少至120.50ng·g-1和135.18ng·g-1,降解率分别达到8.46%和6.33%。根据蒽的高本底值初步推测李村河口区已经受到较为严重的PAHs污染。相同条件下三种有机污染物的不同降解速率表明,9、10位取代使得蒽在沉积环境中更加持久,自然降解速率更慢。虽然目前实验条件下未能检出任何蒽和甲基蒽的(中间)降解产物,但本论文结果有助于人们进一步关注PAHs的污染问题,对环境污染治理和环保决策部门具有一定的指导意义和参考价值。更多还原

【Abstract】 Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous contaminants in the environment, known for their carcinogenic, teratogenic and mutagenic properties. Because of their toxicity, bioaccumulation, semi-volatility and persistence, PAHs are recognized as Persistent Organic Pollutants (POPs) and received worldwide scientific concerns. The sources of PAHs are very broad, but are mostly anthropogenic. PAHs in atmosphere and water tend to accumulate on the particles, and finally deposit into ground and sediment. In addition to posing threats to human health and terrestrial ecosystem, PAHs can also seriously affect aquatic and benthic organiams. PAHs in the environment can be eliminated by a variety of ways, such as microbial degradation, chemical degradation and photodegradation. In sedimentary environment, biodegradation is the major one, through which PAHs could be transformed, and ideally, completely mineralized to produce CO2, H2O and other inorganic small-molecular compounds, thus to entirely eliminated the pollution of PAHs.Anthracene(AC) is a common three-ring low-molecular-weight PAH. AC and its degradation products usually are nontoxic to human, but due to its structural resemblance to moieties of carcinogenic PAHs, such as BaP and BaA, it is often selected as a model compound. Methyl-substituted anthracene is a widely existing pollutant in the envirnment. Methyl-substituted anthracene is believed to be biologically inactive for mutagenicity and carcinogenicity, while dimethyl-substituted derivative, 9,10-dimethyl anthracene,can be transformed to epoxide with“bay area”structure, which is bioactive for tumor mutation and cell aberrance.In this thesis, AC, 9-methyl anthracene (9-MA) and 9,10-dimethyl anthracene (9,10-DMA) were selected as model compounds, and LiCun esturary sediment, the incubation substrate, to investigate the aerobic biodegradation of these anthracenes using a labotory microcosm system. The aims were to obtain the degradation rates and to determin the possible degradation products (intermediates). Major results and conclusions are as follows:(1) A laboratory microcosm system with controlled oxic or anoxic conditions was set up for investigation of biodegradation of organic pollutants in sediment.(2) The environmental parameters, including those of overlaying seawater and sediment porewater, were determined before incubation experiment. It was shown that pH, salinity and dissolved oxygen concentration of seawater were 7.46, 31.794 and 4.27mg·L-1, respectively, and concentrations of potential electron acceptors such as Fe3+, SO42-and NO3- , in sediment porewater were severally 4.26mg·L-1, 1156mg·L-1and 2.58mg·L-1. The redox potential and the content of total organic carbon in sediment were -280.4mV and 1.54%. These parameters indicated that, LiCun estuary sediment was principally in a reduced environment and the organic matter in this region was chiefly anthropogenic.(3) Gas chromatography-hydrogen flame ionization detection (GC-FID) was chosen to detect targeted pollutants and their possible degradation products in sediment samples. The chromatography conditions were optimized, under which the recoveries of AC, 9-MA and 9,10-DMA for spiked blanks were 79.5~83.79%, with RSD ranged from 4.61 to 14.78%; and the recoveries of AC, 9-MA and 9,10-DMA for spiked matrices were 66.20~82.95%, with RSD ranged from 3.34% to 6.19%. Meanwhile the pretreatment process of the sediment samples was optimized, and the recoveries for column chromatographic purification eluted by hexane/toluene and hexane/dichloromethane were compared with special attention. Mixture of hexane/toluene with equal volume was selected for its higher recovery, although it has a lower volatility and thus harder for solvent replacement.(4) The background value of AC was determined to be 32.88ng·g-1, while no 9-MA and 9,10-DMA was detected. It was shown, from a 6-month aerobic incubation experiment, that the concentration of AC decreased from 32.88ng·g-1 to 32.32ng·g-1 in the control experiment, corresponding to a degradation percentage of 1.70%. However, the degradation percentage of the spiked AC was 11.17%, with concentration reduced from 170.40 ng·g-1 to 151.36 ng·g-1. For spiked 9-MA and 9,10-DMA samples, the concentration were declined from the initial values of 133.84 and 144.26ng·g-1 to 120.50 and 135.18ng·g-1, respectively, accounting for degradation percentages of 8.46% and 6.33% separately. According to the high background of AC, it was inferred that LiCun estuary might has been severely polluted by PAHs. Different degradation percentages of the three targeted pollutants under the same condition indicated that methyl-substitution resulted in higher persistence of AC in sedimentary environment with lower natural attenuation rate.Even though no degradation product or intermediate was detected, the results of this work are helpful for raising awareness to the pollution of PAHs, and may also provide guidance and reference for pollution combating and decision-making for environmental agency.更多还原