大气颗粒物中有机酸的浓度分布特征及来源分析

发布时间：2018-06-27 04:43

本文选题：有机酸 + 大气颗粒物　；参考：《西北大学》2017年硕士论文

【摘要】：有机酸是大气颗粒物中重要的有机组分,其强吸湿性可以改变颗粒物的粒径分布与云凝结核状态进而影响全球气候、大气能见度及人体健康。二元羧酸(DCAs)是大气中挥发性有机物的氧化降解产物,也是二次有机气溶胶(SOA)的重要组分,复杂的形成过程导致其在不同大气环境中的浓度分布存在明显的差异。当前关于SOA来源与形成机制方面的难题尚未解决,基于烟雾箱模拟、模型计算与实际监测结果之间的较大差异,明确大气环境中SOA类二元羧酸的实际组成及分布,对于准确解析雾霾成因具有重要意义。本论文开展了西安市大气颗粒物中有机酸的分析,主要内容如下:(1)综述部分对大气颗粒物中有机酸的环境效应、浓度分布特征、测定方法、形成机制及来源解析做了详尽的阐述,并结合近期大气环境领域SOA类有机酸的研究动态及前沿性问题提出了本论文的研究意义及主要内容。(2)大气颗粒物中二元羧酸的污染特征。以西安市大气颗粒物为研究对象,于2015年7月13-24日,2016年1月8-28日在三个采样点(城区、郊区、乡村)采集PM2.5和PM10样品,并用吸收液同步采集了气相中的有机酸。使用极性溶剂提取样品中的DCAs并将其衍生,建立了 15种二元羧酸丁酯的气相色谱定量分析方法,考察了方法的精密度(3.6-7.3%)、加标回收率(68.2%～119.6%)、最低检出限(36.4-82.5 μg/L),确定该方法可用于颗粒物样品中DCAs的定量分析。主要研究了不同区域、不同季节、不同粒径、不同天气条件下颗粒物中DCAs的浓度分布,结果表明城区DCAs含量冬季高于夏季、雾霾天(2363 ng/m3)高于晴朗天(921 ng/m3)。DCAs总浓度城区郊区乡村,且DCAs易分配到细颗粒物中,其气粒分配比与湿度、臭氧浓度呈负相关。(3)大气颗粒物中一元羧酸(MCAs)的污染特征。用极性较弱的溶剂提取样品中的MCAs,并将其甲酯化,应用气相色谱方法定量分析32种一元羧酸甲酯,方法的RSD值(小于12%)、回收率(69.2%～117.6%)、检出限(23.6-55.8 μg/L)均能满足样品中的MCAs的定量分析。同时研究了颗粒物中MCAs分子的季节、粒径以及在污染事件中的浓度分布特征,结果表明C16的含量最高,其浓度分布与一次排放量直接相关。城区冬季(1193ng/m3)MCAs的含量高于夏季(541ng/m3),雾霾天高于晴朗天。在PM10中的浓度高于PM2.5、较高的气粒分配比是MCAs与DCAs的明显差异。(4)PM2.5中有机酸的来源分析采用DCAs、MCAs化合物间的比值特征分析方法,结合DCAs与前体物、大气氧化性、有机污染物的相关性研究,并将MCAs与有机污染物、臭氧浓度进行相关性分析。结果表明DCAs浓度与前体物浓度、大气氧化剂浓度呈正相关,MCAs浓度与正构烷烃、稠环芳烃呈正相关。得到西安市颗粒物中的MCAs主要来源于一次排放、DCAs主要来源于光化学反应的结论。光化学反应易受光化学氧化剂浓度、光照强度等条件的影响,光照强度、臭氧浓度越高光化学反应越剧烈,生成的DCAs越多。酮酸化合物的液相氧化也是DCAs的重要生成途径,且环境相对湿度是制约氧化反应强弱的关键因素。
[Abstract]:Organic acids are important organic components in atmospheric particles. Their strong hygroscopicity can change the particle size distribution of particles and the state of cloud coagulating tuberculosis and then affect the global climate, atmospheric visibility and human health. The two meta carboxylic acid (DCAs) is the oxidation and degradation product of the volatile organic compounds in the atmosphere, and is also an important component of the two organic aerosol (SOA). The complex formation process leads to the obvious difference in the concentration distribution in different atmospheric environment. The current problems about the source and formation mechanism of SOA have not been solved. Based on the smoke box simulation, the large difference between the model calculation and the actual monitoring results is made, and the actual composition and distribution of the type SOA two meta carboxylic acid in the atmospheric environment are clearly defined. The analysis of organic acids in atmospheric particulates in Xi'an is carried out in this paper. The main contents are as follows: (1) the overview of the environmental effects, concentration distribution characteristics, determination methods, formation mechanism and source analysis of atmospheric particles in atmospheric particulates is described in detail, and the recent atmospheric environment is combined with the atmospheric environment. The research significance and main content of this paper are put forward in the field of research on SOA organic acids in the field. (2) the pollution characteristics of two meta carboxylic acids in atmospheric particles. Taking the atmospheric particulates in Xi'an as the research object, PM2.5 and PM10 samples were collected at three sampling points (urban, suburban and rural) on 13-24 day of July 2015 and 8-28 on January 2016. The organic acids in the gas phase are collected synchronously with the absorption solution. Using the polar solvent to extract the DCAs in the sample and derive it, 15 kinds of gas chromatography quantitative analysis methods for two meta carboxylic butyl ester are established. The precision (3.6-7.3%), the recovery rate (68.2% ~ 119.6%) and the minimum detection limit (36.4-82.5 mu g/L) are investigated. It can be used for quantitative analysis of DCAs in particle samples. The concentration distribution of DCAs in different regions, different seasons, different grain sizes and different weather conditions is mainly studied. The results show that the DCAs content in the urban area is higher in winter than in summer, fog and haze days (2363 ng/m3) is higher than that of clear sky (921 ng/m3).DCAs in urban rural areas, and DCAs is easily distributed. In fine particles, the distribution of gas particles is negatively correlated with the humidity and ozone concentration. (3) the pollution characteristics of the mono carboxylic acid (MCAs) in the atmospheric particles. The MCAs in the sample is extracted with a weak polar solvent, and its methyl ester is methylated. The quantitative analysis of 32 kinds of mono carboxylic acid methyl esters by gas chromatography, the RSD value of the method (less than 12%), and the recovery rate (69.2% ~ 1). 17.6%), the detection limit (23.6-55.8 mu g/L) can satisfy the quantitative analysis of MCAs in the samples. At the same time, the season, particle size and concentration distribution characteristics of MCAs molecules in the particulate matter are studied. The results show that the content of C16 is the highest, and the concentration distribution is directly related to the first emission. The content of the urban winter (1193ng/m3) MCAs is higher than that in the summer. 541ng/m3, the fog and haze is higher than the clear sky. The concentration in PM10 is higher than that of PM2.5, and the higher gas distribution ratio is the obvious difference between MCAs and DCAs. (4) the source analysis of organic acids in PM2.5 uses the analysis method of the ratio characteristic between DCAs, MCAs compound, the correlation of air oxidation and organic pollutants combined with DCAs and precursors, and MCAs. The correlation analysis between the concentration of ozone and organic pollutants shows that the concentration of DCAs is positively correlated with the concentration of precursor and the concentration of atmospheric oxidizer, and the concentration of MCAs is positively related to n-alkanes and polycyclic aromatic hydrocarbons. The main source of MCAs in the particles in Xi'an is the first emission, and the main source of DCAs is the conclusion of photochemical reaction. The effect of the concentration of photochemical oxidant, light intensity and other conditions, the intensity of light and the higher the concentration of ozone, the more intense the photochemical reaction is, the more DCAs is produced. The liquid phase oxidation of ketoacid compounds is also an important way of generating DCAs, and the relative humidity of the environment is the key factor restricting the oxidation reaction strength.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X513

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