我国大气二次有机气溶胶分布与来源的初步研究

发布时间：2017-12-28 22:08

本文关键词：我国大气二次有机气溶胶分布与来源的初步研究　出处：《中国科学院研究生院(广州地球化学研究所)》2015年硕士论文　论文类型：学位论文

【摘要】：二次有机气溶胶(SOA)源于反应性有机气体的大气氧化产物,在已有气溶胶颗粒上的凝聚以及有机气溶胶的大气演化。SOA是大气细粒子的重要组成部分,对全球气候变化、区域空气质量和人群健康有重要影响。当前在SOA来源与形成机制方面仍有诸多问题尚不清楚,基于现有认识进行的模式计算结果与实际观测之间,仍有1-2个数量级的差别。另一方面,我国目前面临着严峻的细粒子污染问题,而SOA在其中扮演着重要角色,是区域细粒子污染控制的难点。明确SOA分布、组成与来源,对于准确把握其气候环境效应有重要意义。本论文在全国开展SOA观测,通过有机示踪物,以点-面结合的方式,初步分析了我国SOA的时空分布与组成来源。相关结果如下:2012年夏季在中国的6个区域14个城市同时用石英膜采集颗粒物样品,分析生物源前体物(异戊二烯、单萜烯、β-石竹烯)和人为源前体物(苯系物)生成的SOA示踪物。所测13种SOA示踪物的总浓度范围是29.9-371 ng m-3,异戊二烯的示踪物浓度最高(123±78.8 ng m-3),其次是单萜烯(10.5±6.64 ng m-3)、β-石竹烯(5.07±3.99 ng m-3)、苯系物示踪物(2.90±1.52 ng m-3)。生物源示踪物的最高浓度出现在中国东部,苯系物示踪物的最高浓度出现在中国的北方。生物源示踪物的浓度均与温度呈现正相关关系,表明生物源前体物的排放是影响夏季全国范围内生物源SOA空间分布的主要因素。在异戊二烯的示踪物中,低NOx产物2-methyltetrols占主要地位,但是,在某些城市地区,高NOx产物2-methylglyceric acid的贡献升高,表明在城市地区人为源排放对异戊二烯SOA生成有较大影响。对于单萜烯SOA示踪物,其第一代产物(pinonic acid和pinic acid)与后继产物(3-methyl-1,2,3-butanetricarboxylic acid)的比值(P/M)与后继产物浓度之间呈现显著负相关,表明P/M比值可以用来表征单萜烯SOA的老化程度。各站点的P/M比值在0.89-21.0之间,表明夏季单萜烯SOA老化程度相对低。作为典型的人为源SOA示踪物,2,3-dihydroxy-4-oxopentanoic acid(DHOPA)在城镇地区浓度远高于偏远地区。进一步应用SOA示踪物法估算了我国夏季二次有机碳(SOC)和SOA的总量与来源。SOC和SOA的浓度范围分别为0.37-2.47μg C m-3和0.81-5.44μg m-3,且高浓度出现在我国东部地区。异戊二烯和苯系物是我国夏季SOA的主要来源,分别贡献46±14%和27±8%。在华北地区,苯系物是最主要来源。这些结果表明,以苯系物为代表的人为源前体物是我国大气SOA的重要来源。在青藏高原的纳木错站,从2012年7月至2013年7月,开展了为期一年的采样观测,分析了颗粒物样品中生物源前体物(异戊二烯、单萜烯、β-石竹烯)和人为源前体物(苯系物)生成的SOA示踪物。在所测化合物中,异戊二烯SOA示踪物占据主导地位(26.6-44.2 ng m-3)其次是单萜烯(0.97-0.57 ng m-3)、苯系物(DHOPA,0.25-0.18 ng m-3)以及β-石竹烯(0.09-0.10 ng m-3)。异戊二烯示踪物的浓度夏天最高,冬天最低,其变化受温度显著影响,且与异戊二烯排放受温度影响一致,表明纳木错地区的异戊二烯SOA示踪物浓度季节变化受控于异戊二烯排放。由于受温度和相对湿度影响方面的差异,异戊二烯的高NOx和低NOx产物的浓度比值在冬天最高,夏天最低。单萜烯SOA示踪物的浓度变化,受单萜烯排放和示踪物气-粒分配的双重影响,因而在夏季其浓度没有明显的升高。苯系物SOA示踪物DHOPA首次在全球本底区观测到,其浓度比全球城市地区低1-2个数量级。DHOPA高值出现在夏季,气团轨迹反演显示,其主要来自印度东部和孟加拉;在冬季,纳木错地区的气团主要来自印度东北部,DHOPA的浓度虽然降低,但其在示踪物总量中所占比重反而升高。应用SOA示踪物法估算的结果显示,纳木错地区SOC的年均浓度为0.22±0.29μg C m-3,生物源的贡献约占75%。夏季,异戊二烯对SOC贡献超过80%;冬季,极低的温度导致生物源前体物的排放大大减少,苯系物的贡献显著提高。这些结果表明,来自印度半岛的人为源污染物可以被运输到青藏高原地区,并影响该地区的SOC组成。
[Abstract]:The two organic aerosol (SOA) originates from the atmospheric oxidation products of reactive organic gases, the condensation on the existing aerosol particles and the atmospheric evolution of organic aerosols. SOA is an important component of fine particles in the atmosphere. It has an important impact on global climate change, regional air quality and population health. At present, there are still many problems in the origin and formation mechanism of SOA. It is not clear that there are 1-2 orders of magnitude difference between the calculated results based on the existing knowledge and the actual observations. On the other hand, China is facing a serious problem of fine particle pollution, and SOA plays an important role in it. It is the difficulty of controlling the fine particle pollution in the region. The clear distribution, composition and source of SOA is of great significance to accurately grasp the effect of climate and environment. In this paper, SOA observation was carried out throughout the country, and the spatial and temporal distribution and source of SOA in China were preliminarily analyzed through the combination of organic tracers and point to surface. The related results are as follows: in the summer of 2012, 6 regions and 14 cities in China were collected, and quartz particles were used to collect particulate matter samples. The SOA tracers of biological precursors (isoprene, monoterpene, beta carthene) and human precursors (benzene series) were analyzed. The total concentration range of the 13 SOA tracers was 29.9-371 ng M-3, the highest concentration of isoprene tracers was (123 + 78.8 ng M-3), followed by monoterpene (10.5 + 6.64 ng M-3), beta carnation (5.07 + 3.99 ng M-3), and benzene series tracers (2.90 + 1.52 ng ng). The highest concentration of biogenic tracers occurs in eastern China, and the highest concentration of the tracer is in the north of China. The concentration of biological source tracers is positively correlated with temperature, indicating that the emission of biological precursors is the main factor affecting the spatial distribution of biological SOA in summer. In the isoprene tracers, the low NOx product 2-methyltetrols plays a dominant role. However, in some urban areas, the contribution of high NOx product 2-methylglyceric acid increases, indicating that the emission of anthropogenic sources has great influence on the SOA generation of isoprene in the urban area. The monoterpene SOA tracer, the first generation of products (Pinonic acid and pinic acid) and subsequent product (3-methyl-1,2,3-butanetricarboxylic acid) ratio (P/M) and subsequent product concentration showed a significant negative correlation, shows that the aging degree of the P/M ratio can be used to characterize the monoterpene SOA. The P/M ratio at each site was between 0.89-21.0, indicating that the aging degree of monoterpene SOA was relatively low in summer. As a typical anthropogenic SOA tracer, the concentration of 2,3-dihydroxy-4-oxopentanoic acid (DHOPA) in urban areas is far higher than that in remote areas. The total amount and source of two organic carbon (SOC) and SOA in the summer of China were estimated by the SOA tracer method. The concentration range of SOC and SOA is 0.37-2.47 g C M-3 and 0.81-5.44 u g M-3 respectively, and the high concentration appears in the eastern part of China. Isoprene and benzenes are the main sources of SOA in summer in China, contributing 46 + 14% and 27 + 8% respectively. In North China, the benzene series is the most important source. These results indicate that the precursor precursors, represented by the benzene series, are an important source of SOA in the atmosphere in China. In the Nam Co station on Qinghai Tibet Plateau, from July 2012 to July 2013, a year of sampling observation was carried out, and the SOA tracers of biological precursors (isoprene, monoterpene, beta carthene) and human precursor precursors (benzene series) were analyzed. Among the compounds tested, isoprene SOA tracers are dominant (26.6-44.2 ng M-3), followed by monoterpene (0.97-0.57 ng M-3), benzene series (DHOPA, 0.25-0.18 ng M-3), and beta carnation (0.25-0.18). The concentration of isoprene tracer is the highest in summer and lowest in winter. Its change is significantly affected by temperature and is consistent with the temperature of isoprene discharge. It indicates that the seasonal variation of isoprene SOA tracer concentration in Nam Co area is controlled by isoprene emission. Due to the difference in temperature and relative humidity, the concentration ratio of high NOx and low NOx products of isoprene is highest in winter and lowest in summer. The concentration change of monoterpene SOA tracer is influenced by the dual effects of monoterpene emission and tracer gas particle distribution, so the concentration of monoterpene is not significantly increased in summer. The SOA tracer DHOPA of the benzene series was first observed in the global base area, and its concentration was 1-2 orders of magnitude lower than that of the global urban area. DHOPA high value appeared in summer. Air mass trajectory inversion showed that it mainly came from Eastern India and Bangladesh. In winter, the air masses in Nam Co area mainly came from northeastern India, while the concentration of DHOPA decreased, but its proportion in tracers increased. The results of SOA tracer method showed that the annual average concentration of SOC in Nam Co area was 0.22 + 0.29 mu g C M-3, and the contribution of biological sources was about 75%. In summer, the contribution of isoprene to SOC was more than 80%; in winter, the very low temperature caused the emission of precursors to be greatly reduced and the contribution of benzene compounds increased significantly. These results indicate that the anthropogenic pollutants from the India peninsula can be transported to the Qinghai Tibet Plateau and affect the SOC composition of the region.
【学位授予单位】：中国科学院研究生院(广州地球化学研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X513

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