南京市大气细颗粒物中碳组分的时空分布特征及来源研究

发布时间：2018-11-17 07:24

【摘要】：碳组分是大气颗粒物的主要组成部分之一,对大气能见度、环境质量、气候变化以及人体健康等均具有重要影响。然而,目前关于大气颗粒物中碳组分的相关认识还很不充分。由于缺乏系统性的观测资料,现有的研究工作大多比较零散、代表性不高。本研究基于南京市多个点位近5年大气细颗粒物(PM2.5)化学组分的观测资料,系统研究了PM2.5中碳组分的时空分布特征、碳组分与其它组分的相关性,分析不同污染天气过程对于碳组分的影响,并对碳组分的来源和控制对策进行了初步探讨。研究结果表明,和2011年、2012年相比,近三年(2013-2015)南京市PM2.5、有机碳(OC)和元素碳(EC)的质量浓度呈下降趋势。全年总碳(Total Carbon,TC)对PM2.5浓度的平均贡献率达到22%,表明碳组分仍是PM2.5的主要化学组分。南京市六个采样点之间OC和EC的年均浓度差异不大,表明碳组分的浓度在空间分布上是均匀的。六个采样点OC/EC的年均比值均大于2.0,表明南京地区明显受到二次气溶胶污染的影响。OC、EC、一次有机碳(POC)及二次有机碳(SOC)的质量浓度有一致的季节变化特征,都是在秋冬较高,春夏较低,其中冬季的均值几乎都超过了夏季的2倍,表明冬季碳气溶胶污染较严重。在春季,OC、EC和s-K+、NO2之间具有显著的相关性,指示春季生物质燃烧和机动车排放对碳组分浓度存在一定的贡献；在夏季,EC和SO42-、NH4+、SO2都有明显的相关性,说明夏季工业燃煤是碳组分的来源之一；在秋季,OC、EC和SO42-、NO2、SO2以及二次无机盐离子之间的相关系数都较高,同时SOC和S02、NO2及O3也存在较显著的相关性,表明秋季不仅存在机动车和燃煤的贡献,二次转化源也是碳组分的主要来源;在冬季,除了03外,碳组分和二次无机盐以及气态污染物的相关性都较其他三个季节显著,说明冬季各污染物之间的同源性增强,存在机动车排放、煤炭燃烧和二次转化的共同贡献。从清洁天到重污染天,EC和POC的增长幅度最大(306.1%和299.5%),SOC的涨幅最小(238.5%),表明重污染天污染物的一次排放对碳气溶胶的贡献要比二次生成的贡献更显著。同时,重污染天OC和EC几乎没有相关性,表明碳气溶胶的污染来源发生了较大的变化。亚青会和青奥会期间实施的临时污染减排和控制措施对PM2.5、碳组分及气态污染物的浓度均有显著的削减效果,说明高强度的污染调控措施降低了工业燃煤、机动车排放以及二次转化对碳组分的贡献。运用比值判断法和碳谱分析法判断识别南京市各个季节碳气溶胶的污染来源。结果表明,冬季二次有机碳气溶胶(SOA)的贡献相较其他三个季节最显著。夏季工业燃煤和机动车排放对碳气溶胶有显著的贡献,而SOA的贡献相对较小。春季生物质燃烧以及扬尘的贡献比较明显。秋季也可能存在明显的二次转化源的贡献。
[Abstract]:Carbon component is one of the main components of atmospheric particulate matter, which has an important impact on atmospheric visibility, environmental quality, climate change and human health. However, the current understanding of carbon components in atmospheric particulates is still inadequate. Due to the lack of systematic observation data, most of the existing research work is scattered and less representative. Based on the observation data of the chemical components of atmospheric fine particulate matter (PM2.5) in Nanjing over the past 5 years, the temporal and spatial distribution characteristics of the carbon components in PM2.5 and the correlation between the carbon components and other components were systematically studied. The effects of different polluted weather processes on carbon components were analyzed, and the source and control measures of carbon components were discussed. The results show that compared with 2011 and 2012, the mass concentrations of PM2.5, organic carbon (OC) and elemental carbon (EC) decreased in Nanjing in recent three years (2013-2015). The average contribution rate of total carbon (Total Carbon,TC) to PM2.5 concentration reached 22%, indicating that the carbon component is still the main chemical component of PM2.5. The average annual concentrations of OC and EC in six sampling sites in Nanjing were not different, which indicated that the concentration of carbon components was uniform in spatial distribution. The average annual ratio of OC/EC in the six sampling sites was more than 2.0, which indicated that the secondary aerosol pollution affected Nanjing area obviously. OC,EC,. The mass concentrations of primary organic carbon (POC) and secondary organic carbon (SOC) have the same seasonal variation characteristics, both of which are higher in autumn and winter and lower in spring and summer. The mean value in winter is almost twice that in summer. The results show that carbon aerosol pollution is serious in winter. In spring, there is a significant correlation between OC,EC and s-K, NO2, indicating that biomass combustion and motor vehicle emissions contribute to the concentration of carbon components in spring. In summer, EC, SO42-,NH4 and SO2 have obvious correlation, indicating that industrial coal burning in summer is one of the sources of carbon components. In autumn, the correlation coefficients between OC,EC, SO42-,NO2,SO2 and secondary inorganic salt ions were higher, and there were significant correlations between SOC and S02 no _ 2 and O _ 3, which indicated that not only the contribution of motor vehicles and coal combustion existed in autumn, but also the correlation between SOC and S02O _ 2 and O _ 3. The secondary conversion source is also the main source of carbon components. In winter, except 03, the correlation between carbon components, secondary inorganic salts and gaseous pollutants was more significant than that in the other three seasons, which indicated that the homology of the pollutants in winter increased and there were motor vehicle emissions. The common contribution of coal combustion and secondary transformation. From clean days to heavily polluted days, EC and POC increased the most (306.1% and 299.5%), SOC) the least (238.5%). The results show that the contribution of primary pollutant emission to carbon aerosol is more significant than that of secondary generation. At the same time, there is almost no correlation between OC and EC in heavily polluted days, which indicates that the source of carbon aerosol pollution has changed greatly. The temporary pollution abatement and control measures implemented during the period of YYC and YOC have significant effect on the reduction of PM2.5, carbon composition and the concentration of gaseous pollutants, indicating that high intensity pollution control measures reduce industrial coal combustion. The contribution of vehicle emissions and secondary conversion to carbon components. The sources of carbon aerosol pollution in different seasons of Nanjing were identified by the ratio judgment method and the carbon spectrum analysis method. The results show that the contribution of secondary organic carbon aerosol (SOA) in winter is more significant than that in the other three seasons. Industrial coal combustion and motor vehicle emissions contribute significantly to carbon aerosols in summer, while SOA contribution is relatively small. The contribution of biomass combustion and dust in spring is obvious. There may also be a significant contribution from secondary transformation sources in autumn.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X513

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