| 1. Fine aerosol samples were collected throughout spring, summer, and winter in 2004-2005 at a major urban traffic junction (BNU) and a suburban location (MY) in Beijing and at a downtown site (SH) in Shanghai, China. Ten of the 16 EPA priority polycyclic aromatic hydrocarbons (PAHs), seven fatty acids, levoglucosan, and cholesterol were identified and quantified. PAHs showed the same seasonal trend in all sampling sites as the highest in winter and the lowest in summer, while fatty acids and levoglucosan showed no pronounced seasonal variation. The aerosol PAH(4)/PAH(5,6) ratio, C18:1/C18 ratio together with the relative mass distribution patterns of individual PAH in ten PAHs, individual fatty acid in seven fatty acids were used to reflect the change in emission sources of the compounds in different sites and seasons. The relative contributions of coal combustion and vehicle exhaust sources to PAHs in fine aerosols were preliminarily estimated to be 1:2 in Beijing and 1:1 in Shanghai by factor analysis, revealing that the air pollution in these mega-cities in China was mainly the mixing of coal combustion with vehicle exhaust. A significant fraction of levoglucosan from cooking with higher concentrations in urban than in suburban area contributed to the ambient atmosphere. Cooking was a stable source of organic aerosols in both Beijing and Shanghai.2. A total of 238 samples of PM2.5 and TSP were analyzed to study the characteristics, sources, and formation pathways of aerosol oxalate (C2O42-) in Shanghai in four seasons of 2007. The mass concentrations of C2O42- in 2007 sampling year were 0.07-0.41?g/m3 in PM2.5 and 0.10-0.48?g/m3 in TSP, respectively. Oxalate concentration displayed a seasonal variation of autumn> summer> winter> spring in both PM2.5 and TSP and was dominantly present in PM2.5 in all samples. A case study was carried out to explore changes in concentration level and coarse/fine particle distribution of oxalate in a dust event. Vehicular emission was found contributing little to the content of oxalate as a primary source, while it was an important secondary source of oxalate in urban atmosphere. Correlation between C2O42- and K+ and high ratio of C2O42-/K+ suggested that biomass burning was also a secondary source of aerosol oxalate in Shanghai, especially in season of autumn. Secondary formation accounted for the majority of aerosol oxalate in Shanghai, which was supported by the high correlation of C2O42- with nss-SO42-, K+ and NO3-, proceeding from different mechanisms. Simultaneous increases in ambient relative humidity and atmospheric cloud cover was found benefiting the secondary formation of aerosol oxalate. The in-cloud process (aqueous-phase oxidation) was suggested to be the major formation pathway of aerosol oxalate in Shanghai. As a major water-soluble organic compound in aerosols, oxalate contributed to the haze pollution and visibility degradation of the local environment. C2O42- concentration showed a distinct negative correlation to the atmospheric visibility, implying that aerosol organic compounds could play an important role in the formation of haze in Shanghai.3. Atmospheric TSP and PM2.5 were collected at two urban sites to explore the influence of vehicle exhausts on the urban air quality in Shanghai. On the background of 7.0% increase in vehicle population, an increase of 56.8% in NO3-concentration in TSP was observed. The ratio of NO3- mass concentration to SO42-mass concentration (NO3-/SO42-) in the aerosol was used to evaluate the contributions from the stable sources (such as coal combustion) and from the mobile sources (such as vehicle exhausts) to the water-soluble pollutants in the urban atmosphere. NO3-/SO42- ratio of nearly 70% of the PM2.5 samples were higher than 0.5, while NO3-/SO42- ratio of nearly 15% of the PM2.5 samples were even higher than 1. Both the ratios in TSP samples got higher values. This phenomenon reflected that vehicle exhausts was a major source of atmospheric pollutants and inorganic nitrogen in Shanghai. During a recorded dust event in Shanghai, obvious increases were observed in atmospheric NOR and SOR comparing to non-dust days. Increase in SOR was more distinct than NOR. The concentration levels of four components which had vehicle emission sources in the aerosol all showed decreases during the traffic ban period in autumn 2007. NO3-/PM2.5, SO42-/PM2.5 and characteristics of atmospheric gaseous NH3 in Yangtze River Delta were discussed. NH3 was found to be one of the controlling factors in the secondary formation of inorganic ions in atmospheric fine particulate in Shanghai.4. Atmospheric particulate samples were collected at four characteristic sites, Tazhong, Yulin, Shanghai, Xiaoyangshan Isle, from the west to the east China in spring 2008. The spatial variations of water-soluble components NO3-, NO2-, NH4+, SO42- and MSA in atmospheric PM2.5 and TSP and the physical-chemical relationships between them were monitored and analyzed to study the air pollution status in quo of China and evaluate the impact of atmospheric particulate transport and deposition on ecosystem of China's eastern coastal zone. Along the elevation of the industrialization and motorization degree of the sites, increases in concentration levels of particulate NO3-, NO2- and NH4+, SO42- in fine particles and MSA in coarse particles were observed. The severity of air pollution over China was raised gradually from the west to the east. The temporal variation of MSA concentration in PM2.5 in Shanghai site showed a good correlation with the ambient gaseous NO2, proving that existence of atmospheric oxidative pollutants is conducive to the formation of MSA. The input of polluted air mass from the inland area brought substantial influence on the concentration level and fine/coarse particle distribution of MSA over the offshore island XYS isle. NO3- and NH4+ as representative compounds of water-soluble inorganic nutrients in atmospheric particulate, their annual dry deposition flux was estimated based on the observation data on XYS isle. It was found that the marine primary productivity created by the dry deposition of atmospheric NO3- and NH4+ could support 1.9% to 6.6% of East China Sea's new production. Atmospheric dry deposition was an effective pathway of external nitrogen input to the coastal ocean. |
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