近年来，世界各地大气污染问题频发，严重影响着社会的健康发展和人们的正常生活。研究发现，大气环境中广泛存在的有机气溶胶(organic aerosol, OA)对空气污染和气候变化的贡献十分突出。OA的研究已经成为科学界、政府部门和社会公众关注的热点问题。由于飞速的经济发展和城市化进程的不断加快，以及高密度的人口，中国首都北京和印度首都新德里都经历着日趋严重的大气污染问题。同时，海洋作为最重要的自然气溶胶系统之一，也在遭受着陆地密集人类活动所释放的污染物的影响。陆源污染物能够通过大气的长距离迁移对海洋环境产生影响，进而间接影响全球气候变化、大气化学和生物地球化学循环。因此，开展大城市及海洋大气有机气溶胶的分子组成及浓度变化的研究，对深入理解OA的形成、来源及其对环境的作用机制具有重要意义。 本文选取北京、新德里以及东海大气气溶胶作为研究对象，主要采用有机萃取-衍生化-气相色谱/质谱联用(GC/MS)技术，同时借助源示踪物、因子分析、正定矩阵因子分析(positive matrix factorization, PMF)以及HYSPLIT后向轨迹分析等多种技术手段分析了有机气溶胶中一些特定分子标志物和主要组分的浓度及分子组成特征，讨论了主要贡献源及大气传输的影响。另外，运用大气化学传输模型(如Community Multiscale Air Quality, CMAQ)分析了海洋和陆地气溶胶的分子组成及来源差异。主要结论如下： (1) 糖类和正构烷烃是城市大气可吸入颗粒物(PM2.5)中重要的有机组分。为了更好的认识北京市区有机气溶胶的来源和季节变化，分析了北京2013-2014全年的PM2.5样品中糖类和正构烷烃的分子组成和浓度水平。结果表明，冬季气溶胶中糖类和正构烷烃化合物的浓度最高，夏季最低。这可能与采暖季增加的燃烧源，如煤、生物燃料和农作物秸秆的焚烧等，以及冬季不利于污染物扩散的气象条件有关。左旋葡聚糖，作为生物质燃烧的特征标志物，是四个季节含量最高的糖类化合物。尤其在秋季和冬季两个寒冷季节，含有更多生物质燃烧产生的有机碳(organic carbon, OC)，表明生物质燃烧对北京细粒子有机气溶胶的贡献显著。植物源对正构烷烃的贡献在春季最高(54.5%)，冬季最低(11.6%)；而化石燃料源在冬季最高(385 ng m-3)。冬季正构烷烃分子分布呈现的微弱奇偶优势以及最小的CPI值，说明化石燃料的燃烧是采暖季正构烷烃的主要来源。PMF结果显示，土壤扬尘、化石燃料和生物质的燃烧是北京细粒子中OC的主要来源。分子标志物浓度、分子组成及来源的季节变化说明气象条件也是影响北京PM2.5浓度及分子组成的一个重要因素。而且，研究结果显示，沙尘暴也能够极大的提高北京大气细粒子中有机组分的浓度。 (2) 脂类化合物是环境中化学性质稳定、来源指示性很强的一类化合物，因此是研究OA来源及大气过程的良好模式化合物。通过分析印度新德里气溶胶中脂类化合物，包括正构烷烃(C19–C33)、脂肪酸(C12–C30)和脂肪醇(C16–C32)的分子组成、浓度及粒径分布，发现这些化合物在霾期、沙尘暴期和晴朗天气条件下的浓度水平及粒径分布存在显著差异。这三类化合物的粒径分布均呈现双模态，即分别在细模态0.7–1.1 μm和粗模态4.7–5.8 μm达到浓度最高值。整体上，颗粒物主要存在于粗模态(≥2.1 μm)，且质量分数为64.8–68.5%。灰霾期细模态正构烷烃的几何平均直径(GMD)大于沙尘期和非霾期，可以归因于灰霾期较高的空气湿度及大量生物质燃烧释放的亲水性颗粒物，从而有利于细粒子的吸湿性增长。春季盛行的沙尘暴能够极大丰富大气中OA的浓度，并促使颗粒物的粒径向粗模态转移，与沙尘期样品较大的GMD值一致。本研究表明，化石燃料(如机动车尾气和工业尾气)、生物质燃烧、家庭烹饪和微生物活动可能是新德里城市气溶胶的主要来源。 (3) 海洋气溶胶是全球大气气溶胶的重要组分。本文采集春季东海大气气溶胶样品，并分析了气溶胶样品中生物来源的糖类和二次有机气溶胶组分(biogenic secondary organic aerosol, BSOA)。与远海样品相比，糖类和BSOA均在沿海样品中表现出较高的浓度，说明陆地有机质对海洋大气的影响。葡萄糖(glucose)是含量最丰富的糖类化合物(0.31–209 ng m–3, 18.8 ng m–3)，其次为甘露醇(mannitol)。所有糖类化合物的夜晚浓度均高于白天，可能与夜晚沿海地区盛行的陆风有关。单萜SOA标志物MBTCA是所检测到的浓度最高的BSOA化合物。真菌孢子产生的OC对总OC的贡献最大(0.03–19.8%, 3.05%)，其次为倍半萜烯产生的二次有机碳(secondary organic carbon, SOC)和生物质燃烧产生的OC。生物来源OC和SOC在沿海样品中具有更高的贡献，再次证明陆地生物源一次和二次气溶胶可以通过大气的长距离传输对海洋大气环境产生影响。PMF结果表明，BSOA、生物质燃烧及真菌孢子是东海海洋气溶胶中OC的主要贡献源。 (4) 分析了东海气溶胶中多环芳烃、邻苯二甲酸酯和脂类化合物，从而更好的认识西北太平洋海域大气污染的来源及其相对贡献。与生物来源的糖类和SOA类似，多环芳烃、邻苯二甲酸酯和脂类化合物在受陆地气团控制的样品中表现出较高的浓度。邻苯二甲酸酯的浓度(白天707±401 ng m–3，夜晚313±155 ng m–3)高于多环芳烃、正构烷烃、脂肪酸和脂肪醇，说明沿海地区微塑料污染也可能对海洋大气有显著贡献。大体上，白天样品中多环芳烃、邻苯二甲酸酯和脂类化合物的浓度高于夜晚，说明白天污染更为严重，可能与陆地白天较高的污染物排放量有关。研究结果表明，亚洲陆地排放源是海洋气溶胶中有机组分的重要来源，这些陆源有机质可以通过大气的长距离迁移改变海洋有机气溶胶的分子组成和浓度分布，从而影响海洋大气环境，尤其对沿海海域大气气溶胶的影响更加显著。 (5) CMAQ空气质量模型对中国东部沿海地区及东海大气气溶胶的模拟结果与东海气溶胶外场观测值基本一致，并且与沿海城市空气监测站点的观测也相吻合。模型结果显示陆地气溶胶中PM2.5及其主要组分的浓度高于海洋气溶胶，表明亚洲大陆是海洋大气颗粒物的一个重要贡献源，与前面观测结果得出的结论相一致。研究发现，硫酸盐(SO42-)是东海海域PM2.5中含量最丰富的组分，其平均浓度为5.12 μg m-3，其次为铵盐(NH4+, 1.02 μg m-3)和一次有机气溶胶(primary organic aerosols, POA, 0.92 μg m-3)。工业活动和船舶航运排放是东海大气PM2.5的两个主要贡献源；而工业和农业活动是陆地PM2.5的两个主要来源。另外，船舶和海盐源对海洋气溶胶的贡献大于陆地气溶胶，而其他排放源(如居民活动、陆地交通运输、工业排放、电厂、农业活动、生物质燃烧和二次有机气溶胶)对陆地气溶胶的贡献更大。该研究将有助于更好的理解陆地和海洋气溶胶分子组成和来源的差异，以及陆海交互作用的影响。 综上，本文通过对北京、新德里及东海气溶胶特定分子标志物的浓度和分子组成的分析，探讨了特大城市和海洋有机气溶胶的来源及其相对贡献，同时结合CMAQ模型分析了陆地和海洋气溶胶分子组成及来源的差异，有助于更好的认识城市及海洋气溶胶的分子组成、来源和形成机理，并且为区域大气污染治理提供可靠的基础数据和理论依据。

In recent years, air pollution has become an important issue in many countries because it exerts adverse impacts on social development and public health. Organic aerosol (OA), widely present in the atmosphere, is a significant contributor to air pollution and global climate change. Studies about OA have become hot issues of great concern to scientists, policy makers and the public. Beijing and New Delhi, the capital cities of the two largest developing countries in the world, are suffering increasingly serious air pollution due to rapid economic development and urbanization. Marine aerosol, one of the most important natural aerosol systems, is also influenced by the long-range transported terrestrial OA, further affecting global climate and biogeochemical circles. Therefore, the investigation on the molecular composition and concentrations of urban and marine OA provides a better understanding of formation mechanism and atmospheric process. In this study, we analyzed the molecular composition and concentrations of organic species in the aerosol samples collected at Beijing, New Delhi and East China Sea mainly using gas chromatography/mass spectrometry (GC/MS) after sample extraction and derivatization. Besides, specific tracers, factor analysis, positive matrix factorization (PMF) and HYSPLIT back trajectory analyses were used for identifying major source contributors and impacts of long-range atmospheric transport. Moreover, the Community Multiscale Air Quality (CMAQ) model was applied to investigate the difference of composition and sources between terrestrial and marine aerosols. Main conclusions were listed as below: (1) Sugars and n-alkanes are important organic constituents of atmospheric fine particles. For better understanding the sources and seasonal variations in urban aerosols, sugar compounds (anhydrosugars, sugars and sugar alcohols) and homologs of n-alkanes (C18–C37) were studied in PM2.5 collected from September 2013 to July 2014 at Beijing, China. In general, all measured compounds showed the lowest levels in summer; higher concentrations of sugar compounds and n-alkanes were in winter, probably attributable to elevated combustion emissions (e.g., coal, biofuel and agricultural residue burning) and stable meteorological conditions during heating season. Levoglucosan was the major sugar species in all seasons particularly winter and autumn with much more biomass burning derived organic carbon (OC), highlighting the significant contribution of biomass burning to fine organic aerosols throughout the whole year especially in cold seasons in Beijing. Plant waxes contributed to n-alkanes the most in late spring (54.5%) and the least in winter (11.6%); while fossil fuel combustion had the largest contribution in winter (385 ng m–3). The very weak odd-carbon predominance of n-alkanes in wintertime aerosols also suggests fossil fuel combustion as the important source of organic aerosols in heating season. Soil resuspension, fossil fuel and biomass burning, and secondary formation are the main sources of OC in PM2.5 at Beijing. The seasonal variation in source contributions indicates that meteorological condition is a key factor in controlling PM2.5 levels. Furthermore, our results suggest that dust storms can strongly enhance the atmospheric level of fine organic matter in spring. (2) Aliphatic hydrocarbons (n-alkanes, n-fatty acids and n-alcohols) account for a significant fraction of ambient aerosols. Most of these aliphatic hydrocarbons are chemically stable and long-lived, thus retaining source signatures. Therefore, researches about size-resolved compositions of aliphatic hydrocarbons will help better understand emission sources and atmospheric processes of OA. Size-segregated aerosol samples were collected in New Delhi, India from March 6 to April 6, 2012. Homologous series of n-alkanes (C19–C33), n-fatty acids (C12–C30) and n-alcohols (C16–C32) were measured using GC/MS. Results showed a high-variation in the concentrations and size distributions of these chemicals during non-haze, haze, and dust storm days. In general, n-alkanes, n-fatty acids and n-alcohols presented a bimodal distribution, peaking at 0.7–1.1 μm and 4.7–5.8 μm for fine modes and coarse modes, respectively. Overall, the particulate matter mainly existed in the coarse mode (≥2.1 μm), accounting for 64.8–68.5% of total aerosol mass. During the haze period, large-scale biomass burning emitted substantial fine hydrophilic smoke particles into the atmosphere, which leads to relatively larger GMDs (geometric mean diameter) of n-alkanes in the fine mode than those during the dust storms and non-haze periods. Additionally, the springtime dust storms transported a large quantity of coarse particles from surrounding or local areas into the atmosphere, enhancing organic aerosol concentration and inducing a remarkable size shift towards the coarse mode, which are consistent with the larger GMDs of most organic compounds especially in total and coarse modes. Our results suggest that fossil fuel combustion (e.g., vehicular and industrial exhaust), biomass burning, residential cooking, and microbial activities could be the major sources of lipid compounds in the urban atmosphere in New Delhi. (3) Marine aerosols significantly contribute to the global aerosol system. Molecular composition and abundance of sugars and secondary organic aerosols (SOA) from biogenic sources over the East China Sea (ECS) were investigated based on GC/MS. Biogenic SOA (BSOA) tracers and sugars exhibited higher levels in the samples affected by continental air masses, demonstrating the terrestrial outflows of organic matter (OM) to the ECS. Glucose was the dominant sugar species (0.31–209 ng m–3, 18.8 ng m–3), followed by mannitol. All sugar compounds showed higher concentrations in nighttime than in daytime. 3-Methyl-1,2,3-butanetricarboxylic acid (MBTCA), one tracer of monoterpene SOA, was found to be the most abundant species among measured BSOA markers. According to the tracer-based methods, fungal-spore-derived organic carbon (OC) was found to be the biggest contributor to total OC (0.03–19.8%, 3.1%), followed by sesquiterpene-derived secondary OC (SOC), biomass-burning-derived OC and others. Larger carbon percentages of biogenic primary OCs and SOCs in total OC presented in the terrestrially influenced aerosols indicate significant contributions of continental aerosols through long-range transport. PMF results illustrate that BSOA, biomass burning, and fungal spores could be the main contributors to OC in marine aerosols over the ECS. (4) Lipid compounds, PAHs and phthalates in the total suspended particle (TSP) samples over the ECS were analyzed using GC/MS to better understand the sources of aerosol pollution in the western North Pacific. Higher concentrations were observed in the terrestrially influenced aerosol samples on the basis of five-day air mass backward trajectories, especially for those collected near coastal areas. Phthalates were found to be the dominant species among these measured compound classes (707±401 ng m–3 for daytime and 313±155 ng m–3 for nighttime), followed by fatty acids, fatty alcohols, n-alkanes and PAHs, likely suggesting important contribution of microplastic pollution to marine atmosphere especially in the coastal regions. In general, the daytime abundances for these compounds are higher than nighttime, possibly attributable to more intensive anthropogenic activities during the daytime. This study demonstrates that the East Asian continent can be a natural emitter of biogenic and anthropogenic organics to the marine atmosphere through long-range transport, which controls the chemical composition and concentration of organic aerosols over the ECS. (5) Community Multiscale Air Quality (CMAQ) model was applied to investigate the fine particulate matter (PM2.5) and its chemical components over the ECS and offshore regions. In spite of slight under-predictions, model predictions agree well with observations over the ECS and along the coast. PM2.5 and its major components in the mainland are higher than in marine area, again suggesting Asian continent is a major emitter of marine aerosols. Aerosol phase SO42- is the most abundant component of PM2.5 over the ECS with an average concentration of 5.12 μg m-3, followed by NH4+ (1.02 μg m-3) and primary organic aerosol (POA) (0.92 μg m-3). Industry and ship emissions are the top two contributors to primary (PPM) and total PM2.5 over the ECS, while industry and agriculture are predominant sources of PM2.5 for terrestrial regions. Besides, ship emission and sea salt contribute more to marine aerosols compared to terrestrial aerosols, but other sources (i.e., residential, transportation, industry, power, agriculture, wildfire and SOA) show larger contributions to terrestrial regions. The study would help better understand the difference of chemical composition and major sources between continent and ocean, and provide useful information about impact of land/sea interaction. In summary, this dissertation analyzes the molecular composition and concentrations of OA in Beijing, New Delhi and ECS, and investigates the sources as well as their relative contributions. In addition, the difference and connection between marine and terrestrial aerosols in molecular composition and sources are studied through predicting aerosols over ECS and adjacent regions using the CMAQ model. These results would be helpful for a better understanding of the chemicals, sources and formation mechanism of urban and marine aerosols, and provide valuable information for designing air pollution control policy.