What are the causes of autumn and winter pollution in Beijing, Tianjin and Hebei?

There are four reasons for the pollution in Beijing, Tianjin and Hebei in autumn and winter: pollutant discharge exceeds the environmental capacity, the concentration of nitrogen oxides and volatile organic compounds in the atmosphere is high, the regional environmental capacity is reduced due to unfavorable meteorological conditions, and three transmission channels cause transmission in polluted areas.

Cause 1: pollutant discharge exceeds environmental capacity.

The emission of pollutants exceeds 50% of the environmental capacity, which is the fundamental reason for the frequent occurrence of heavily polluted weather.

Zhao Yingmin introduced that Beijing-Tianjin-Hebei and its surrounding areas, which are often called "2+26" cities, have a high concentration of heavy chemical industry. The energy utilization mode mainly based on coal and the freight transportation mode mainly based on road transport in the region lead to high emissions of major air pollutants in the region. The discharge of major pollutants per unit land area is 2-5 times of the national average, and the discharge multiples of different pollutants are different.

Except sulfur dioxide, the emissions of major pollutants in the region all exceed 50% of the environmental capacity, and some cities even exceed 80%- 150%.

In addition, due to heating, the discharge of major pollutants in autumn and winter is about 30% more than usual.

The second reason: the concentration of nitrogen oxides and volatile organic compounds in the atmosphere is high.

The high concentration of nitrogen oxides and volatile organic compounds in the atmosphere increases atmospheric oxidation, which is the key factor for the rapid growth of secondary PM2.5 during heavy pollution.

Some of PM2.5 is directly emitted, but some of it is also due to the emission of gaseous pollutants into the air, such as sulfur dioxide and nitrogen oxides, which form fine particles in the air through secondary transformation. We call this part of the secondary transformation of PM2.5 PM2.5.

With the deepening of air pollution control, the proportion of primary components has obviously decreased, and the proportion of secondary components transformed from pollutants in the air into particulate matter has been increasing. From 20 13, the proportion of secondary components gradually increased from 40% to about 50%. During the period of heavy pollution, secondary pollutants are the main components of particulate matter, and the proportion can reach 60% or even higher.

High concentrations of nitrogen oxides and VOC in the region will lead to rapid photochemical reactions in the atmosphere, leading to high degree of atmospheric oxidation, which is the decisive factor to promote the transformation of gas pollutants in the air into secondary PM2.5

Reason 3: Adverse meteorological conditions lead to the reduction of regional environmental capacity.

Unfavorable meteorological conditions lead to a significant reduction in regional environmental capacity, which is a necessary condition for the formation of heavily polluted weather.

Beijing-Tianjin-Hebei and its surrounding areas are located in the semi-closed terrain on the east side of Taihang Mountain and the south side of Yanshan Mountain, which objectively has a "weak wind zone" and a "warm cover" structure in the troposphere over this area. The "congenital deficiency" of atmospheric diffusion conditions is mainly due to the fact that the diffusion conditions in this place are worse than those in other places, resulting in a small environmental capacity. Affected by climate change, the regional environmental capacity has generally declined since 2000.

In addition, the environmental capacity also shows seasonal and monthly differences. It is well understood that an important reason for good air in summer is good air diffusion conditions. In addition, due to the change of meteorological factors, every month and every year is different. Generally speaking, the environmental capacity in autumn and winter is about 30% smaller than that in spring and summer, and the environmental capacity in June 5438+ 10 is about half that in July.

Reason 4: Three transmission routes cause the spread in polluted areas.

It is found that regional transmission has a significant impact on PM2.5, and the average contribution rate of each city is about 20%-30%, which is further increased to 35%-50% during heavy pollution.

Zhao Yingmin introduced that in the initial stage of air pollution control, due to the relatively large local emissions, local sources often have a greater impact on local environmental quality. With the deepening of pollution control, the proportion of local sources is gradually decreasing, and the external input is gradually increasing.

Starting from 20 13, the key projects analyzed nearly 100 heavy pollution weather processes. It shows that during the period of heavy pollution, the average contribution rate of regional transmission to PM2.5 in Beijing is about 45%, and individual processes can reach 70%.

There are mainly three transport channels for pollutants in the region, which is also the conclusion of this research project through research and observation. One channel is the southwest channel, that is, the northern part of the Henan-Handan and Shijiazhuang-Baoding-Beijing lines. This channel has the highest transmission frequency and maximum transmission intensity. The average contribution rate of heavy pollution process is about 20%, and the individual heavy pollution process can reach 40%.

The second channel is the southeast channel, along the central Shandong-Cangzhou-Langfang-south-central Tianjin. The third passage is the eastward passage, which is the Tangshan-Tianjin North-Beijing line.

Extended data:

Research background: It took three years to tackle key problems, involving 20 academicians and nearly 3,000 researchers.

2065438+The the State Council executive meeting held on April 26th, 2007 decided to set up a research project on the causes and control of heavy air pollution, led by the Ministry of Ecology and Environment, in conjunction with the Ministry of Science and Technology, the Ministry of Agriculture and Rural Affairs, the Health and Wellness Commission, the Chinese Academy of Sciences, the Meteorological Bureau and other departments and units, focusing on the causes of heavy air pollution in autumn and winter, key industries and pollutant emission control technologies, and residents' health protection in Beijing, Tianjin and Hebei and its surrounding areas, so as to promote the continuous improvement of air quality.

According to Zhao Yingmin, since the implementation of key projects, the Ministry of Ecology and Environment and relevant departments have organized 2,903 scientific and technological workers in the field of atmospheric environment, including 295 scientific research units and 20 academicians, and established the National Air Pollution Prevention and Control Joint Center; Send 28 "one city, one policy" stagnation tracking research groups to the regional "2+26" cities; Build a data sharing and management platform to solve the problem of digital sharing.

Ganlong Com- Beijing-Tianjin-Hebei found the causes of heavy pollution in autumn and winter, including four major causes and three major pollution sources.