The Numerical Simulation Of Sulfur Dioxide Concentration In The Atmospheric Environment Of Chengdu Based On Meteorological Elements

With the acceleration of urbanization and the development of large industrial development zones,economy have developed rapidly while series of environmental problems have arised.The emissions of air pollutants continue to grow and become complex and changeable.Since the last century,the toxic and harmful effects of these pollutants have gradually emerged^[1-3].The prevention and control of air pollution has become a worldwide problem which needs to be solved urgently.To get the pollution level of atmospheric environment that can represent the regional scale,the method of point to surface,spatial interpolation and extrapolation should be applied to the spatial distribution of atmospheric environmental pollution monitoring data based on the thoroughly research of meteorological factors and geographical conditions.In this paper,firstly the collected data was preprocessed.Based on ArcGIS software,the basic simulation material of Chengdu's atmospheric environmental quality was obtained;they are stored in the form which can facilitate the invocation of MATLAB software.Then,based on the Topography-Adjusted Statistical Model,the Surface Pressure Physical Statistical Model and the Wendlell Interpolation method,the spatial distribution of temperature,pressure and wind in the study area were simulated;these distributions in each representative month or a specific date or a time point were compared.On the basis of meteorological and geographical conditions in the study area,SO₂ is taken as an example to explore the distribution of pollutant concentration in the study area.Finally,as the background value of the pollutants in the study area,the atmospheric pollution diffusion of the point source is simulated with the meteorological elements,and the conclusions are as follows:?1?In the view of geography,from north to south the spatial temperature distribution varies with latitude obviously;the temperature distribution characteristics of the mountain area are also quite different from the distribution of other terrains.In February,April and October,the spatial distribution of temperature was significantly influenced by latitude,followed by altitude;and in July,its dominant factor was elevation.Because the main terrain of the study area is plain and hilly area,the simulation values of all grid points submit to skewed distribution,and there is no significant difference in skewness and kurtosis in each month.The indicators show that the simulation accuracy of the warm season is better than the cold season,because the model does not take into account some physical mechanisms and effects.?2?The general spatial distribution of surface air pressure is the same as the temperature distribution,showing the difference in latitude and topography.The reason is that the spatial distribution of surface pressure is mainly determined by temperature and altitude.In study area,the range of air pressure in January was the largest,while in July was the smallest.It was caused by the pressure change of different terrain in different seasons.In study area,the dominant wind direction is southeast and the seasonal variation is not obvious.Its spatial distribution shows that the wind direction in the mountains of Longquan,west near Chengdu hinterland is easy to change.?3?In study area,the atmospheric environment quality in summer Chengdu is better than that in winter,which is determined by weather conditions.The high SO₂ concentration fields in Chengdu mainly focus on three areas:the downtown in Chengdu and its surrounding two areas?Dujiangyan and Pixian in the northwest of Chengdu;Jintang County in the eastern part of Chengdu?.At 12 and 18 o'clock during the day,most of high concentration areas were located in the urban area of Chengdu and its surrounding area.At0 and 6 o'clock in the night,most of high concentration areas were located in the other two regions.This is due to the formation of urban heat island effect in Chengdu City,caused a local circulation between urban and rural areas.The hot air in urban areas rises to the upper level and spreads to the suburbs.When its surrounding temperature is cold,it drops down and returns to the ground of urban areas again.This process brings the pollutants in rural areas to urban areas,caused a rise of pollutant concentration in urban areas.In the night,some enterprises discharge pollutant without permission,caused a suddenly rise of pollutant concentration in the areas where these companies locacted at.?4?In the occasion that pollutants discharged continuously without processed,the pollutants concentration of the grid point near pollution source increase with time,while the value of the areas away from the pollution source is slightly reduced due to the dilution effect of wind.However,when the diffusion effect caused by the concentration difference is less than the dilution effect caused by the wind,the concentration of some grid points near the pollution source and located at the downwind will decrease instead.