【作者】 马万里；

【导师】 孙德智； 李一凡；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 博士

【摘要】 多环芳烃(PAHs),是一类环境中广泛存在的持久性有毒物质,其污染和归趋已成为环境科学领域的研究热点。近年来,我国也陆续开展了环境介质中PAHs的调查和研究,但从目前的研究情况来看,仍存在不足。我国在PAHs的监测和模型研究方面往往都集中在某些小区域,缺少PAHs在全国范围内环境介质中的数据,不利于深入了解大尺度下PAHs的迁移转化规律以及环境归趋。结合我国PAHs研究的现状及不足,本文的研究将通过在全国范围内采集土壤和大气样品,并结合相应的我国大尺度多介质环境模型,研究我国国家尺度土壤和大气中PAHs的时空分布特征和迁移转化规律,这将为我国制定相关政策提供科学依据,同时也为我国履行斯德哥尔摩公约贡献一份力量。对于我国土壤中PAHs的残留和分布特征的研究,本文是通过在全国布设土壤采样点,采集表层土壤,进而分析了我国土壤中PAHs的浓度、组成特征和空间分布特征,并探讨了土壤中PAHs残留的影响因素、毒性评价和污染源。共采集表层土壤样品157个,其中包括28个城市土壤,120个农村土壤和9个背景土壤三种不同类型的土壤样品,采集的土壤样品经过索氏萃取、硅胶柱净化等预处理后,再用气质联用仪测定PAHs的含量。结果表明,16种PAHs在我国土壤中均有不同程度的检出,其中以菲、萘、荧蒽和苯并[b]荧蒽的含量较高;农村土壤样品中总PAHs的含量平均值为340±676 ng/g,小于城市的平均值(617±936 ng/g),而高于背景点(126±74 ng/g),与国外一些典型地区的PAHs含量比较,我国土壤中PAHs的污染处于中等程度。PAHs的空间分布主要受污染源的影响,以经度分布和城市分馏为主。采用比值法和主成分分析-多元线性回归法对我国土壤中的PAHs进行了源解析,我国城市地区土壤中PAHs主要来自于煤燃烧和汽车尾气等高温燃烧源和石油源的混合型污染;农村地区土壤中的PAHs主要来自于煤和生物质燃烧为主的高温燃烧源和石油源的混合型污染;而背景地区土壤中PAHs则主要来自于自然源(野火)和混合源(外来源和未知源)的污染。对于我国大气中PAHs的残留和时空分布特征的研究,本文是通过在全国布设大气采样点,采集大气样品,进一步分析了我国大气中PAHs的浓度、组成特征和季节变化,并对大气中温度的影响和气粒分配行为进行了初探,最后,对大气中PAHs的来源进行了解析。本文选择了10个城市(哈尔滨、北京、石河子、兰州、西安、成都、拉萨、南昌、昆明及广州)作为大气采样点,于2008年8月至2009年7月,利用主动大气采样器进行每周一次、为期一年的大气样品采集,采集的大气样品经过索氏萃取、硅胶柱净化等预处理后,再用气质联用仪测定PAHs的含量。结果表明,16种PAHs在我国城市大气中均有不同程度的检出,其中以菲、荧蒽和芴的含量较高,地区间差异明显,浓度差异在一个数量级内。我国北方5城市大气中PAHs的年平均浓度为251±126 ng/m3,高于南方5城市的均值165±102 ng/m3,与国外一些典型城市大气中的PAHs含量比较,我国城市大气中PAHs的污染处于中等程度。与南方5城市相比,北方5城市大气中PAHs的组成、指纹谱、气粒分配、季节变化和温度的影响等,皆存在明显差异。采用比值法和主成分分析-多元线性回归法对我国大气中PAHs的来源进行了解析,我国城市大气中PAHs的主要污染源为化石燃料的高温燃烧源(煤、石油类产品的燃烧)和石油源。本文通过引入大尺度多介质环境模型,模拟我国土壤和大气中PAHs的残留和时空分布特征,并对源汇关系进行了解析。本文首先建立了1/4经度和1/6纬度网格化的我国1990年至2008年PAHs的排放清单,结合PAHs的物理化学性质和其他环境参数作为模型输入数据,改进并优化多介质环境模型,模拟输出了我国土壤和大气中PAHs的残留。结果表明,1990年至2000年间,我国PAHs的排放量相对稳定,保持在2万吨左右;从2001年开始,排放量逐年递增。多介质环境模型对于我国土壤和大气中PAHs残留的模拟结果与本文的实测结果吻合的很好,且整个模拟过程中模型的输入与输出相对误差为2%,因而,该模型能够用于模拟我国土壤和大气中PAHs的残留。我国土壤和大气中PAHs的残留空间分布特征相似,均表现为东部地区残留浓度高,中西部地区浓度低,青藏高原残留浓度最低的特征。与土壤残留分布特征略有不同,大气中PAHs的空间分布形成了两个明显的高浓度带,分别为贯穿甘肃东部、四川东部、贵州中部的中部高浓度带和贯穿辽宁、河北、山东、江苏的东部高浓度带,这两个高浓度带的形成主要是由于大气在传输过程中受到阻力作用所导致。采用排放清单分离的方法,解析了我国不同地区间的相互影响作用和供暖对于我国不同地区土壤中PAHs的影响。我国不同地区芘的土壤残留均以本地排放源的影响为主,其本地源贡献率几乎大于95%,但地区间的相互影响依然存在,这种地区间的相互影响主要受大气传输的影响。而供暖对于我国不同地区土壤中芘的影响差异较大,其贡献率呈现明显的南北差异,从北到南,贡献率依次降低。更多还原

【Abstract】 Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent toxic substances (PTSs) that widespread in the environments. The environmental pollution and fate of PAHs have become a hot research topic in the environmental science domain. In recent years, some researches and studies have been carried out on PAHs in the environmental matrix in China. However, there is still a long way to go with PAH studies in China. The monitoring and modeling research programs about PAHs often focused on small areas only. The information regarding the current status of PAHs at the national scale is deficient, which makes it difficult to understand the large scale transport, transfer and the environmental fate of PAHs. Based on the present situation of PAH studies in China, in this paper, soil samples and air samples at a national scale were collected, and a corresponding multi-medium environmental model was employed to understand the spatial and temporal trend, transport and transfer of PAHs in China. The results of this study would provide a scientific basis for the development of relevant policies and add new contribution to the Stockholm Convention for China.For the residual and spatial distribution of PAHs in soil in China, soil sampling site were selected and the samples were collected in China. The concentration, composition and spatial distribution characteristic of PAHs in soil were investigated, and the influencing factors, toxicity assessment and sources of PAHs in soil were evaluated. Totally 157 soil samples were collected in China, among which there were three types of soil samples; 28 were city samples, 120 were rural samples and 9 were background samples. The collected soil samples were extracted by Soxhlet and cleaned using silica gel column, and PAHs were determined by gas chromatography with mass spectrometer detector (GC-MSD). Sixteen PAHs were detected with different detection levels in soil samples, among which phenanthrene, naphthalene, fluoranthene and benzo[b]fluoranthene were the most predominant compounds. The average concentrations of 617±936 ng/g, 340±676 ng/g,126±74 ng/g for the city, rural and background soils. The PAHs concentrations were compared with a few typical regions in foreign countries. PAHs concentrations on a national scale showed an obvious longitude distribution and urban fractionation effect resulted from the sources. The selected diagnostic ratios and principal component analysis and the multiple linear regression (PCA-MLR) indicate that there are different sources of PAHs for different types of soil samples. The PAHs were mainly from mixed sources of pyrogenic sources (coal combustion and vehicle exhaust) and petrogenic sources in urban soil samples. For rural areas, the PAHs in soil also come from mixed sources of pyrogenic sources (coal and biomass combustion) and petrogenic sources. The nature sources (wildfire) and mixed source (external sources and unknown sources) were the main sources to background soils.For the residual and spatial distribution of PAHs in air in China, air sampling sites were selected and air samples were collected. The concentrations, composition and seasonal variation of PAHs in air were studied, and the influence of temperature, gas-particle partitioning and sources of PAHs in air were investigated. Based on a year round dataset (from August 2008 to July 2009), air samples were collected by high-volume air sampler on a weekly base in ten cities, i.e. Harbin, Beijing, Shihezi, Lanzhou, Xi’an, Chengdu, Lhasa, Nanchang, Kunming and Guanghzou in China. The collected air samples were extracted by Soxhlet and cleaned using silica gel column, and PAHs were determined by GC-MSD. The results indicate that 16 PAHs were detected with different detection levels in air samples in the cities, among which phenanthrene, fluoranthene and fluorene were the predominant compounds. The atmospheric PAHs concentrations exhibited obvious differences among the different cities, within approximately 1 order of magnitude. The average atmospheric concentration of PAHs in the northern 5 cities was higher than that in the southern 5 cities, which were 251±126 ng/m3 and 165±102 ng/m3, respectively. The atmospheric PAHs concentrations in China were comparable with some typical urban cities outside China. Compared with the southern 5 cities, the PAHs composition, fingerprint, gas-particle partitioning, seasonal variation and the influence of temperature in the northern 5 cities also show obvious differences. The selected diagnostic ratios and PCA-MLR indicate that the atmospheric PAHs in Chinese cities mainly came from incomplete combustion of fossil fuel (coal and oil combustion) and petrogenic sources.A multi-medium model on large scale was employed to simulate the residue of PAHs, the spatial and temporal trend in soil and air, to study the relationship between the sources and the receptors of PAHs in China. Firstly, the emission inventory of PAHs with a 1/4°×1/6°longitude/latitude resolution was established from 1990 to 2008. The physical and chemical properties of PAHs and the environmental parameters were used as the input data of the model. The multi-medium model was then improved and optimized for generating the concentrations of PAHs residue in soil and air. The results indicate that during the period from 1990 to 2000, the emission of PAHs kept relatively stable. From 2001, the emission of PAHs kept increasing. There was generally a good agreement between the estimated and the observed concentrations of PAHs in soil and air, and the relative error between input and output was 2%, which shows that the model can be applied to simulate the residue of PAHs in soil and air in China. The simulated PAHs residue in soil and air displayed similar geographical distributions, with high concentrations in eastern China, low ones in middle and western China and lowest in Qinghai-Tibet Plateau. However, compared with PAHs residue in soil, there was small difference for PAHs residue in air. For geographical distribution of PAHs residue in air, relatively two high concentration strips were found: one was called as the middle high concentration strip through the eastern of Gansu, the eastern of Sichuan, and the middle of Guizhou; and the other was called as the east high concentration strip which covered Liaoning, Hebei, Shandong and Jiangsu. Both the two strips were caused by the atmospheric transport when forced by resistance. By separating the emission inventory, the mutual influence between different regions of China and the influence of space heating on PAHs residue in soil were analyzed by numerical simulation. The results indicate that local sources were the remarkable contributor to Pyr residue in soil, and the contribution of local sources could be above 95%. However, as caused by the atmospheric transport, the mutual influence between different regions still exists. And the influence of space heating on Pyr residue in soil in different regions of our country were quite different. The contribution rate shows significant differences between north and south China: from north to south areas, the contribution rate was decreased.更多还原