| Aerosol can change interior energy balance of land, water, atmosphere systems and water circulation through affecting radiation in the atmosphere, atmospheric chemistry, and cloud and precipitation process, further exerts significant impact on the global climate and environmental change. As the largest sources of aerosol, coal combustion and motor vehicle emit a lot of particles, high-concentrated SO2, NOx, and HC, which not only affect regional environment, but also have a profound influence on the global climate and geobiochemical circulation. Long-term and short-term aerosol sampling of PM2.5 and TSP was conducted, analyzing their main chemical composition (water soluble ions, elements, organic carbon and black carbon), getting trace gaseous concentration (SO2 and NOx) and aerosol photochemical parameters (scattering AOD, absorption AOD and single albedo), combing with meteorological conditions and back trajectory analysis, systematically studying the impact of pollutants from coal combustion and motor vehicle emission on the air quality. The main study results are as follows:1. The impact of coal-fired pollutants including direct emission into the atmosphere and resuspended coal ash on the local air quality were quantitatively studied. Through sampling and analysis of aerosol in Shentou Town, Shuozhou City, Shanxi Province, it was found that without any outside pollution source and under favorable diffusion conditions, the average daily concentration of PM2.5 is 101.0μg m-3, and all days exceeded the annual standard of World Health Organization (35μg m-3). The average daily concentration of TSP was 355.7μg m-3, and 3 out of 7 days exceeded the second class national air quality standard(300μg m-3). Coal ash and soil were largely resuspended with wind, significantly increased the particulate concentration. Ionic anlysis indicated that coal ash and soil brought a great deal of SO42- and Ca2+ in coarse mode. The increased wind velocity not only brought large quantity of mineral elements, but also obvious increase of pollution elements. Enrichment factor study spotted 5 pollution elements, P, Cu, Zn, As, S, among which 4 are related with coal combustion, especially the EF of S was>4000, reflectiong the impact of coal combustion.25 elements of soil were also analyzed. It was found only the concentrations of 5 elements, As, P, S, Pb, Sb, were larger than that in crust, among which 4 elements, As, Pb, S, Sb, are related with coal combustion, especially the concentrations of S and Sb is several thousand and even ten thousand times larger than that in crust, thus, it is sufficient to convince that coal combustion had a serious impact on local soil.2.The fact that coal-fired pollutants constantly mix and interact with dust, further transport to downwind areas and exert a significant impact on air quality were revealed. The concentrations of As, Pb, S in aerosol in most of our sampling sites increased several folds, even 10 folds, during DS compared to NDS, indicating the transport of coal combustion pollutants with dust. The ratio of PAH (4)/PAH (5,6) in aerosol in downwind cities is obviously higher during DS compared to NDS, showing dust can absorb and carry coal-fired organic pollutants. The concentrations of As, Se, S in Shanghai increased several times even several tens during DS, verifying the coal-fired pollutants through long-range transport have severe impact on the air quality of coastal mega-cities. On the island, even during weak DS, As and S increased 2-3 times, indicating the coal-fired pollutants carried by dust can affect marine aerosol. What's more, the EFs of As and Pb in aerosol in a majority of our sampling sites reached as high as>100, and the concentrations also exceeded that in the curst, demonstrating coal-fired pollutants have contaminated air and soil of many places in China.3. The contribution of coal combustion and vehicle emission to the formation of haze in big cities of China was elucidated by comprehensive research of atmospheric aerosol and trace gases in Shanghai. The particulate concentrations, pollution gas concentrations, particulate photochemical parameters(scattering AOD and absorption AOD), concentrations of pollution elements(S, As, Cd, Cr, Cu, Ni, Pb, Ti, Zn), EFs of some elements(Cu, Cd, Pb, As, S) and ionic concentrations (SO42- and NO3-) during haze pollution episode (PE) were 2-6 times compared to non-pollution episode(Non-PE). These chemical components are all related to coal combustion and motor vehicle emission. Only EFs of 5 elements (Cd, Pb, Zn, As, S) were>1000, and all are related with coal combustion and vehicle emission. Factor Analysis also recognized coal combustion and vehicle emission. The formation rates of SO42- and NO3- were quite high, with SOR and NOR in the range of 0.3-0.5, indicating that under favorable chemical reaction and bad diffusion conditions, SO2 and NOx emitted from coal combustion and vehicle formed high concentrations of SO42- and NO3- and contributed to the formation of haze. Organic aerosol contributed 27.4% to PM2.5. OC and EC were mainly from vehicle. Organic aerosol, elemental carbon,sulfate, nitrate were the major contributors to light extinction, which accounted for an average of 46%,22%,22% and 20%, respectively, reflecting the important impact of vehicle emission and coal combustion on light extinction.4. The chance to study the effect of control of coal combustion and vehicle emission on air quality is fulfilled when Beijing implemented many special pollution-curbing measures before and during the Olympics to improve its oft-criticized air quality. It was found although the impact of meteorological conditions is significant, by which the effect of the special measures can be almost hidden. However, under the similar meteorological conditions, the special measures did contribute significantly to the decrease of the concentrations of black carbon, most elements and ions in PM2.5, as well as the aerosol mass. However, a few secondary formed ions increased again after the Olympic Games, which were mainly due to the long-range transport from the eastern China, further indicating that the pollutants from coal combustion and vehicle emission can long-range transport. For the better air-quality during the Olympics, the measures for vehicle control played a dominant role with a proportion of 62.3% and the contribution of coal combustion control accounted for 24.7%, that is 87.0% in sum, reflecting the impact of coal combustion and vehicle emission on air quality. |
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