Characteristics Of PM_2.5 And Its Precursor Pollutants During Haze Pollution In Beijing-Tianjin-Hebei Region

In recent years, heavy haze pollution happened in Beijing-Tianjin-Hebei region remind people that atmospheric pollution in this region has entered a new era. However, compared with abroad, research on haze pollution in China is still insufficient, and much more research is needed. Therefore, study about haze pollution and characteristics of gaseous pollutants is contribute to cognitive about the present situation of pollution in this region, and have great significance to control haze pollution in this area.In order to study the relationship between haze pollution and its gaseous precursor in this region, continuous measurements of NOx, O3, SO2and PM2.5were conducted during2012. The results show as follow:(1) In2012, haze pollution appeared99and84times in Beijing and Tianjin, respectively. And it mostly appeared in winter and fall. PM2.5was the main pollutant during haze days. (2) PM2.5was high in fall and winter, low in spring and summer. The diurnal variation of PM2.5peaking in the morning and evening with the largest diurnal amplitude in winter. PM2.5accounted for60%to80%of PM10in haze days, which means fine particle is the main pollutant. In2012, PM2.5in Beijing, Tianjin and Xinglong exceed the Class II standard for169,111and54days, and their annual average concentrations were83μg/m3,66μg/m3and36μg/m3, respectively. It showed that anthropogenic emissions were the main sources of PM2.5in Beijing and Tianjin.(3) NOx and SO2performed similar seasonal and diurnal variations as PM2.5. Annual average concentration of NO2in Beijing, Tianjin and Xinglong were104μg/m3,83μg/m3and18μg/m3. Annual average concentration of SO2in Beijing, Tianjin and Xinglong are21μg/m3,61μg/m3and26μg/m3. Seasonal and diurnal variations of O3were similar at three sites, the maximum hourly concentration of O3appeared in summer afternoon around15:00, they were66μg/m3,257μg/m3and336μg/m3in Beijing, Tianjin and Xinglong.(4) There was a close relationship between PM2.5and gas pollutants. The correlation coefficient of PM2.5to O3in summer was higher than others, indicated that active photochemical reaction was the main cause. The correlation coefficients of PM2.5to NOx, SO2in winter also were very high, indicated that haze days in winter were closely related to the increase of burning fossil fuels. (5) Meteorological conditions played an important role in the concentration of PM2.5and its gaseous precursors. The haze pollution easily happened in days with high relative humidity and low wind speed, while high wind speed and rain conduced to remove air pollutants.(6) The contribution of atmospheric pollutants in surrounding areas to fine particles in Beijing-Tianjin-Hebei region was investigated by using cluster analysis with Hysplit-4model. The results showed that the air mass arriving in Beijing-Tianjin-Hebei region mainly can be divided into three parts:air mass from the northwest of Inner Mongolia high altitude, air mass from the southwest and local transport. The first one conduced to the removal of pollutants in Beijing-Tianjin-Hebei region, while the others were favor of the formation of haze pollution.