| Abstract: | With a high-resolution SO2 emission inventory categorized by industries and seasons for Beijing city and gridded meteorological data fields from NCEP, the pollution dispersion model, HYSPLIT4 (Hybrid Single Particulate Lagrangian Integrated Trajectory, version 4), is used to determine the day-to-day variation of surface SO2 in Beijing for 2000 and 2001. Furthermore,the contributions of different emission sources in and around Beijing to the surface SO2 are studied. As shown in comparison with observations, the model does well in simulating the daily variation and seasonal distribution. The model computation of the annual source contributions to Beijing surface SO2 indicates that local emissions from the city give the largest contribution and the sources from the surrounding regions contribute only about 20%. During SO2 polluted or unpolluted days, the contribution from the latter can exceed 30%, and depending upon weather conditions, the contribution may exceed 40%. If the emissions from the surrounding sources during the winter heating season are assumed to be doubled in intensity, their contribution to surface SO2 in Beijing increased from 21% to 35% and 25% to 40% in 2000 and 2001, respectively. Evaluation of 7 types of emission sources identified for Beijing for their relative contribution to the concentration of surface SO2 has shown that area emissions by industrial production and furnaces, though discharging relatively small amounts (less than 1/3 of the total), have the largest contribution to the urban surface SO2, which is the key to the mitigation of the pollutant in the city. |
