The main objective of this study is to investigate the relative contribution of air pollution sources in and outside Beijing to the air quality in Beijing. This objective is accomplished by analyzing the temporal and the spatial characteristics of meteorological conditions associated with air pollution transport in and around Beijing, as well as through the analyses of both observations and model data to quantify the effects of pollution sources in and outside Beijing on the air quality in Beijing in different seasons. Main conclusions are summarized below.In springtime, dust storms originating in the region to the northwest of Beijing will impact the air quality in Beijing. During dust storm events, the PM concentration, especially PM10, increases tremendously, but the concentration of SO2 and NO2 decrease at the same time. In summer, due to high temperatures, the ozone concentration will reaches its maximum annual value. A strong inversion layer occurs in winter and autumn.Most of pollutants can not be dispersed under these atmospheric conditions and thus accumulate in the surface layer during the nighttime. The residents in Beijing use coal combustion for home heating which produces a great deal of SO2.As a consequence, the peak value of PM2.5 will occur during the colder winter months of November-February. PM concentration has been affected by some meteorological factors, such as relative humidity, air pressure, wind speed and wind direction.Based on the observational data, Beijing and surrounding areas can be considered one environmental system. The air quality of surrounding areas impacts the concentration of air pollutants in Beijing. Analysis from the Hysplit model and Satellite imagery shows that in spring the pollutant mainly comes from the inner-Mongolia region and Xinjiang province. In summer, the main source of air pollutants is located to the south of Beijing. The precursor of ozone has been transported from the southern area to northern Beijing. The highest concentration occurs in the northwestern part of the city. In the Beijing area, the O3 concentration has been affected by the combination of local emission and surrounding area emission. From the model output, almost 40% of total PM2.5 and PM2.5 sulfate come from the emission in surrounding area outside Beijing.In autumn and winter, the pollutant comes from the southern and western regions of Beijing, such as Shijiangzhuang and Tianjin. From the spatial interpolation analysis, we can easily find an aerosol transport band from the southern region outside Beijing to in the Beijing area. During high pollution episodes, based on the CMAQ model output, the PM2.5 and PM2.5 sulfate from the surrounding area account for more than 30% of the total PM2.5 and PM2.5 sulfate value in Beijing urban and suburb areas.
【 预 览 】
Spatial-Temporal Characteristic of Meteorological Variables Associated with Air Pollution in Beijing Area