Yangtze River Delta, Ozone And Aerosols Numerical Simulation Study

Since the industrial revolution, human activities not only have directly discharged a great dealof particles into atmosphere, but also have discharged SO₂ and NOx into atmosphere. Then SO₂ andNOx could be changed into sulfate and nitrate particles by heterogeneous reactions. Sulfate aerosol( SO₄^2- ) is one of the substances that are important for the energy balance of the earth atmosphere.Sulfate aerosol is one kind of major air pollutants and it is one kind of acid former too. It couldcause a serial number of environment problems such as air pollution, acid rain and so on. In thetroposphere, SO₄^2- mostly come from sulfur dioxide emitted from nature and discharged byhuman activity. Yangtze delta is one of the key centers for economic developing in our country, andthe economy of this region has developed fast, and more and more energy sources are consumedday by day. So, the research on the forming and transforming of the sulfate aerosol over Yangtzedelta could provide scientific suggestions for government to constitute developing targets andimprove air quality.In this thesis, the ozone and sulfate aerosol over Yangtze delta are studied systematically. Themain work includes: the meteorological field was simulated using MM5. The temporal and spatialdistribution of ozone and sulfate aerosol in this region was simulated with the regional air qualitymodel CMAQ. The field observation is explained. The causes of high concentration of ozone andaerosol in this region are analyzed in physics and chemistry aspects. The major factors are foundout that influencing the concentration and distribution of sulfate aerosol in this region. A modelsensitivity test was used in order to study the influence of sulfur dioxide emitted from Shanghai onthe regional concentration of sulfate aerosol.The simulation of photochemical pollution in Yangtze delta region shows the temporal andspatial distribution of ozone and its precursors in this region. The model result shows that the OPE(Ozone Production Efficiency) in Shanghai region was smaller than the circumambient areas. TheNOx and VOC emitted from Shanghai cumulated downwind (such as Sheshan and Jiaxing areas),so the hourly net produce of ozone was higher in these areas. And ozone from circumambient areascongregated in Sheshan and Jiaxing area because of wind convergence, consequently highconcentration of ozone formed in this area. Based on this research, wind field is vital to thedistribution of regional air contaminants and by the proper effects of wind field, the air pollutantsfrom Shanghai could make a great influence on the air quality in the Yangtze delta.Based on the study of sulfate aerosol, it was found that the different aqueous oxidationreactions of sulfur dioxide occurred in different areas. The contribution of aqueous oxidation ofSO2 to sulfate aerosol was greater than that of condensation and nucleation of gas H2SO4. H2O2 andO2 are the two major oxidizers. Sulfate aerosol that produced over Shanghai area and east ofZhejiang accumulated at Hangzhou area by the wind transport. Linan was close to the region ofmaximal concentration, so high concentration of sulfate aerosol was observed. Consequently, highconcentration of aerosol was observed at Linan. The sensitivity test showed that, after shuttingdown the SO2 emission in Shanghai, the decrease of SO2 concentration was larger in Shanghai thanother areas, and it didn't change with the wind;nevertheless the area where sulfate aerosolconcentration decreased mostly changed significantly with the wind. The SO2 emission in Shanghaicould affect the concentration of sulfate aerosol in a large region around Shanghai;and this effectwas made by the wind that convey the sulfate formed over Shanghai to other region far fromShanghai.