| With the rapid development of economy, air pollution is increasingly serious in China, which has become a larger burben on economy and society. Chongqing is an important industrial city in China, the primary pollutant were PMio and SO2 during 2001-2011, and PM2.5 accounts for a large proportion of PM10.Chongqing has typical mountainous valley topography. The atmospheric circulation is relatively stable and the annual average wind speed is low, which lead to poor air diffusion conditions. Therefore, air pollution inChongqing is severe.This thesis mainly analyzed the spatial and temporal variation characteristics of gaseous pollutants and PM2.5 in Chongqing. The sources of gaseous pollutants and the relationship between gaseous pollutants and PM2.5 were aslo studied. At the same time, based on the the same period of meteorological data, the analysis of the effect of meteorological conditions on PM2.5 concentrations and the cause of the difference pollution characteristic were conducted to provide information for prevention and control of atmospheric pollution in chongqing. Using Trajstat model, the effect of regional transmission on air pollution in Chongqing was analyzed.Results showed that PM2.5 levels have much difference at different regions of Chongqing, but the change trend of pollutants was consistent. The PM2.5 concentration in Gaojiahuayuan and Baishiyi was significantly higher than that in Jinyun Mountain and Konggang. PM2.5 and SO2, NO2, CO, O3 share a similar diurnal variation, both present a "double-dip and three peak" variation characteristics. It achieves the lowest at 04:00, and peaked at 8:00 and 15:00pm. The pollutant concentration was high in winter and achieves highest in December. For the spatial distribution, the high NO2 and PM2.5 concentrations mainly concentrated in the west, SO2 was high in the south and low in the north, O3 featured low values at urban area and high at suburb area.The objective factors that affect the concentration of PM2.5 in Chongqing were gaseous pollutants and meteorological factors. In clean days, the correlation coefficient between PM2.5 and SO2, NO2, CO were weak. In excessive weather, the correlation coefficient between PM2.5 and SO2, NO2, CO increased. During the serious pollution, the correlation coefficient between PM2.5 and SO2, NO2, CO were largest. With the increase of pollution level, the correlation between PM2.5 and PM10 reduced, this may be due to that the PM10 concentration increased faster than PM2.5.In Winter of Chongqig, correlations between PM2.5 and SO2, NO2, O3 were different for urban and suburban. In urban area, the correlation coefficient between PM2.5 and SO2, NO2 was greater than that in suburbs. While the correlation coefficient between PM2.5 and O3 was greater than that in the suburbs. Compared with other cities, we found that the correlation between PM2.5 and gaseous pollutants can explain the secondary pollution. The key factors that affect the PM2.5 concentration in clean area (Jinyun Mountain) was SO2, CO and wind speed. The high SO2 and CO concentration can lead to high PM2.5 concentration, the higher the wind speed, the lower of the PM2.5 concentration. The key factors that affect the PM2.5 concentration in pollution area (Gaojiahuayuan) was NO2, CO and temperature, the higher the temperature, the more conducive to the spread of PM2.5.The main PM2.5 transportation channel in Chongqing are north, south, southeast and local northeast and local western. The free atmosphere transmission height at altitude of 3000m, eastern channel disappeared and northern and western became the main air flow.In winter of Chongqing, the air transported from the north by east and south was with higher PM2.5 concentration. The main orientations sources of PM2.5, SO2, NO2 were local emissions and transportations from surrounding cities represented by Nanning, Guiyang, Zunyi, Dazhou. |
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