How do experts interpret the heavy pollution process in Beijing, Tianjin and Hebei and its surrounding areas?

Since March 9, Beijing-Tianjin-Hebei and its surrounding areas are experiencing a serious air pollution process. The National Air Pollution Prevention and Control Center organizes an expert meeting every day. This time, Professor Peking University Hu Min, who is in charge of the research project "Causes and Control of Heavy Air Pollution", is invited to interpret it.

Judging from the pollution changes, this pollution process is a typical regional accumulation and transmission process. From the afternoon of March 9, due to adverse meteorological conditions, pollutants in southern Hebei, northwestern Shandong, northern Henan and other places began to accumulate. In the early morning of 10, pollutants gathered in front of Taihang Mountain with weak southerly wind, and the air quality in cities along Shijiazhuang-Zhengzhou reached severe pollution, and Beijing reached moderate pollution all day. 1 1 On the same day, the air quality in Beijing, Tianjin and central Hebei improved, and the air quality in Beijing recovered well. Pollution convergence areas are mainly concentrated in southern Hebei, southwestern Shanxi, northwestern Shandong and central and northern Henan, and most cities in Sanmenxia in the west, Weifang in the east, Xingtai in the north and Xuchang in the south continue to be heavily polluted. In the morning of 12, the air quality in western Shandong was obviously improved due to the influence of strong systematic southeast wind, and the polluted air mass was transported to the former city of Taihang Mountain. In the afternoon, the polluted air mass is transported rapidly from south to north along Taihang Mountain, staying in the south of Yanshan Mountain, and even affecting the northern mountainous areas of Beijing, Tianjin and Hebei. The concentration of PM2.5 in Beijing, Tianjin, Tangshan, Baoding, Langfang, Zhangjiakou and Chengde increased rapidly. 12 at night, the hourly concentration in most cities reached serious pollution level, and some cities even reached serious pollution level.

By March 13 1 1, among the "2+26" cities in Beijing, Tianjin and Hebei and its surrounding areas, 1 1 reached the level of severe pollution and above, and five of them reached the level of serious pollution. The highest hourly concentration of PM2.5 occurred in Tangshan (June 3rd 1 1, 4 14 μ g/m3). The daily average concentration of PM2.5 in Beijing reached moderate pollution (146 μ g/m3), and the hourly concentration of PM2.5 reached 236 μ g/m3 at 1 13.

From the pollution reasons, on the one hand, since the afternoon of March 9, most of the region has been in a state of light wind (wind speed: 60%), and with the regional inversion, the vertical diffusion conditions are obviously reduced, and the environmental capacity is greatly reduced, which is more likely to cause pollution accumulation and secondary transformation, pushing up the concentration of PM2.5. By analyzing the composition of PM2.5, we can also see that the concentration and proportion of nitrate (NO3-) in Beijing are all the same.

Judging from the previous regional heavy atmospheric pollution process, it is usually caused by unfavorable meteorological conditions such as regional large-scale static stability, the local environmental capacity is greatly reduced, and the pollutant discharge quickly accumulates and superimposes the influence of regional transmission, resulting in a more serious pollution process. In this pollution process, the influence of regional transmission is more prominent. Although the environmental capacity of foothill cities is greatly reduced and local emissions are accumulating, they are also significantly affected by regional transmission. Therefore, the industrial structure, energy structure and traffic structure in this area have not been fundamentally changed, and the emission intensity is still at a high level. In this pollution process, the cities in front of Taihang Mountain and Yanshan Mountain may be seriously polluted for a long time.

Judging from the current air quality monitoring data, although the pollution level in some cities has reached severe or serious pollution, the concentration of PM2.5 in the region has not increased explosively in a wide range, and the development of pollution process is relatively stable compared with that under unfavorable meteorological conditions in the same period last year, which is closely related to the comprehensive action of air pollution control in autumn and winter initiated by the Ministry of Environmental Protection in June last year (5438+ 10) and the current measures to deal with heavily polluted weather.

According to the latest air quality forecast results of China National Environmental Monitoring Center, it is predicted that the weather process with unfavorable regional diffusion conditions will continue on March 13- 14. From March 15, cold air will affect the Beijing-Tianjin-Hebei region from north to south, and the regional pollution situation will be alleviated.