Seven problems of smog

Recently, Beijing-Tianjin-Hebei and its surrounding areas have experienced frequent severe smog, and the early warning of heavy air pollution initiated from time to time has filled people's hearts with anxiety. So, what is the reason why the smog is so serious? What is the therapeutic effect of smog in recent years? When can I keep breathing clean air? Many people have raised such questions.

In the past few days, the reporter interviewed many experts and scholars in related fields and analyzed the smog problem. Please learn from the following seven smog problems:

1. What caused such a serious smog?

"The main reason is the large amount of pollution emissions, and unfavorable meteorological conditions are also important coordination factors."

He Kebin (Academician of China Academy of Engineering and Dean of Tsinghua University Institute of Environment): Before 1990, there was similar weather with unfavorable diffusion conditions in Beijing, but there was no heavy pollution. After these years of rapid development, the pollutants emitted by coal and motor vehicles in Beijing, Tianjin and Hebei and its surrounding areas have quadrupled. With the increase of pollutant discharge, the meteorological threshold of haze formation decreases year by year. When the meteorological conditions are almost bad, there will be smog, and when it is almost bad, there will be severe smog pollution.

At present, China's emissions of major air pollutants such as sulfur dioxide and nitrogen oxides are nearly 20 million tons, and pollutants are mainly concentrated in the east, Beijing-Tianjin-Hebei and surrounding areas.

Zhang Xiaoye (chief scientist of the national air pollution special project "Research on Two-way Feedback Mechanism between Heavy Air Pollution Accumulation and Weather and Climate in China", chairman of the professional committee of atmospheric composition of China Meteorological Society): The main reason is the large pollution discharge, and unfavorable meteorological conditions are also important coordination factors. The scientific community is still studying the link mechanism between climate change and smog. The mid-term evaluation of the implementation of Atmospheric Decades by China Academy of Engineering shows that the meteorological conditions of pollution in Beijing-Tianjin-Hebei region are worse 17%, 438+04 and 12% than in 2065. Generally speaking, the meteorological conditions are unfavorable. Of course, the main reason is that pollutant emissions have not yet fallen into place. If it can be lowered to a suitable position, the duration and frequency of smog will be reduced even under unfavorable meteorological conditions.

Ouyang Zhiyun (researcher, Center for Ecological Environment Research, Chinese Academy of Sciences): I think man-made pollutant discharge is the main cause of heavy pollution. Weather conditions are the external environment that forms smog. If there are not so many pollutants discharged, the concentration of pollutants will not be so high even if the weather is bad.

2. Does global warming have an impact on the formation of smog?

"The high temperature in winter causes smog."

Zhou Bing (Chief Expert of Climate Service, National Climate Center, China Meteorological Bureau): Weather and climate conditions play an important role in the occurrence, development and dissipation of smog. With global warming, the stability of the atmospheric boundary layer, the number of windy days in winter and the atmospheric environmental capacity have changed, which has certain influence on the formation of haze.

Since 20 14, the global temperature has been breaking records. 20 14 was once the warmest year in the world, but 20 15 broke the record of 20 14, and 20 16 will break the record of 20 15 again, and the record breaking range will be further increased. Meteorological monitoring data show that in recent ten years, the temperature in Beijing-Tianjin-Hebei region has increased, precipitation has decreased and wind speed has decreased. Obviously, the atmospheric environmental capacity of Beijing-Tianjin-Hebei region, that is, the capacity of the atmosphere to accommodate pollutants, is generally declining.

20 16 the past month, 65438+February, was the warmest month in China since 195 1. The national average temperature is 2.6℃ higher than the multi-year average, and Beijing is about 1.6℃ higher. This is a very extreme situation. Such a warm temperature provides an important background for the process of fog and haze, and the high temperature in winter contributes to haze.

Zhang Xiaoye: Meteorological conditions such as temperature, air pressure, wind force and humidity are all related to smog to some extent. At the same time, smog is also affected by climate change. It is international common sense that climate change characterized by global warming will make the atmospheric stratification more stable. In other words, in the context of global warming and climate change, the weather conditions that lead to pollution are generally unfavorable, which is likely to lead to increased smog. Not long ago, some parts of Europe also suffered from air pollution.

3. What is the "inversion layer"?

"Inversion forms pollution, pollution intensifies inversion, and the vicious circle is getting heavier and heavier."

Ma Xuekuan (chief forecaster of the Central Meteorological Observatory): The phenomenon of inversion has always existed in nature. Generally speaking, the atmospheric temperature decreases with the increase of altitude, but in some weather conditions, the atmospheric temperature above the ground will increase with the increase of altitude, which is called "inversion" in meteorology, and the atmosphere with inversion is called "inversion layer".

There are many kinds of inversion, and inversion often refers to radiation inversion, which is formed by the rapid drop of near-surface temperature caused by long-wave radiation at night. Inversion is a typical phenomenon of atmospheric stratification stability, especially in winter.

Air pollutants can not only spread horizontally, but also spread vertically into the sky. If the atmospheric stratification is stable and the temperature is in a state of low before and high after, that is, when an "inversion layer" appears, it will cover the ground like a big quilt, which will hinder the vertical convection movement of air and greatly reduce the height of the mixed layer from several kilometers in the upper layer to hundreds or even tens of meters, thus inhibiting the diffusion of pollutants.

Zhang Xiaoye: Human activities also have an impact on the inversion phenomenon. When pollutants are concentrated in the lower atmosphere and haze occurs, the total effect of aerosol is "cooling effect", which makes the temperature drop in the lower atmosphere higher than that in the upper atmosphere, which will aggravate the inversion and make the atmospheric stratification more stable. Inversion forms pollution, pollution intensifies inversion, and the vicious circle is getting heavier and heavier. Cold air from a weather process is needed to destroy this cycle.

4. What natural conditions are conducive to the dissipation of smog?

"The destruction of inversion stratification and the enhancement of vertical diffusion ability of the atmosphere may play a role in removing smog."

Zhang Hengde (Deputy Director, Environmental Meteorological Center, China Meteorological Bureau): The increase of wind speed, the change of wind direction, the decrease of humidity, the decrease of effective precipitation, the destruction of inversion stratification and the enhancement of atmospheric vertical diffusion capacity may all play a role in eliminating smog. Influenced by factors such as building shielding, sometimes the wind speed is small, but the wind speed near the ground has reached a certain order of magnitude, which has obvious removal effect on pollutants; Another possibility is that the relative humidity in the near-surface layer is significantly reduced and pollutants are gradually diluted and diffused under the action of the persistent weak north wind; In addition, the destruction of the atmospheric inversion layer and the enhancement of the vertical diffusion ability of pollutants may also weaken and dissipate the smog.

5. What is the focus of smog control during heavy air pollution?

"Reducing the emission of nitrogen oxides may be more effective."

He Kebin: Ten Articles of Atmosphere is aimed at the following pollutants: primary particulate matter, sulfur dioxide, nitrogen oxides and volatile organic compounds. This order is also arranged according to the actual emission reduction intensity. Primary particles and sulfur dioxide decreased more, followed by nitrogen oxides, and volatile organic compounds decreased less.

The main sources of nitrogen oxides include coal (coal-fired power plants, industrial boilers, loose coal) and motor vehicles. Nitrogen oxides are not only precursors of nitrates, but also oxidants for forming sulfates. When dealing with heavy PM2.5 pollution in winter, it may be more effective to reduce the emission of nitrogen oxides on the basis of coordinated emission reduction of various pollutants. At present, the power plant has achieved ultra-low emission, and there is little room for further emission reduction. The next step is to intensify efforts to control industrial boilers, loose coal and motor vehicles.

During the Eleventh Five-Year Plan period, some experts suggested that sulfur dioxide and nitrogen oxides should be included in the total control at the same time, but in the end only sulfur dioxide was included. During the Eleventh Five-Year Plan period, the national sulfur dioxide emissions decreased by 14%, and the nitrogen oxide emissions increased by more than 30%. Since the Twelfth Five-Year Plan, nitrogen oxides have been included in the total control. Compared with sulfur dioxide, the time accumulation of nitrogen oxide control technology is relatively short, which is also a challenge for its emission reduction.

At present, volatile organic compounds have not been included in the total amount control, and there is no substantive action to control ammonia, which will have a great impact on the overall atmospheric environment control effect. Ammonia is an important precursor of atmospheric fine particles, and the increase of its emission may offset the emission reduction effect of other measures.

6. When can I always breathe clean air?

"The smog is formed by decades of development and accumulation, and there must be medium-and long-term prevention strategies and scientific measures."

He Kebin: If Beijing-Tianjin-Hebei integration is smoothly promoted, there will be a breakthrough in energy structure and industrial structure, and emission reduction will be accelerated. The concentration of PM2.5 in Beijing and other places dropped to 35 μ g/m3 10 to 15 years, after 2025.

There is no one-size-fits-all treatment of smog, which requires long-term and multi-faceted efforts.

Ouyang Zhiyun: With people's awareness of the hazards of smog and their attention to the control of smog pollution, smog will be gradually controlled by adjusting the industrial structure and improving the technical level and management level.

Chang Jiwen: After treatment, the average annual concentration of PM2.5 in Beijing, Tianjin and Hebei has decreased, but the concentration of PM2.5 precursors is still about 10 times that of developed countries. Generally speaking, in the next 10 year, the emission of major pollutants in China will generally be at the turning point of crossing the peak and entering the downward channel. By the end of the Thirteenth Five-Year Plan and the middle of the Fourteenth Five-Year Plan, the inflection point of the total discharge of major pollutants may come in an all-round way.

To fill the outstanding shortcomings of economic and social development, it is necessary to have a historical sense of urgency to solve environmental problems and the necessary patience in strategic deployment, and to solve environmental problems scientifically, steadily and in stages in a way that is coordinated with economic and social development and combines pollution prevention with ecological construction. Smog is formed by decades of development and accumulation, and it can't be cured in a year or two. There must be long-term preventive strategies and scientific measures.

7. What more powerful measures are needed to control smog?

"emission reduction must make greater efforts in the adjustment of energy structure and industrial structure"

He Kebin: Some achievements have been made in emission reduction in the first three years. However, at present, all localities have made great efforts in terminal treatment, including ultra-low emissions and upgrading. To find new emission reduction points, we must make greater efforts in the adjustment of energy structure and industrial structure. Now the emissions are reduced, but there are still enough pollutants in the air, so the effect is not obvious, and the pollutants must be further greatly reduced.

At present, more than 30 cities are carrying out the pilot work of compiling the list of air pollutant emission sources, and investigating nine pollutants such as sulfur dioxide, nitrogen oxides, volatile organic compounds, PM 10 and PM2.5 from various emission sources to achieve full coverage of air pollutants. This is very important for understanding and controlling pollution sources.

Every time the Ministry of Environmental Protection supervises the heavy air pollution, it can find unruly enterprises. There are emission reduction technologies and equipment. How to ensure the full use of technology and equipment needs to strengthen supervision. It is not reliable to rely entirely on people's "consciousness", and it is not easy to spot check. Supervision needs good technical means, and the state should invest more money to study supervision technology. Pollution emissions always leave traces, which can be traced by technical means to plug loopholes and crooked ways. Otherwise, the statistics on paper may reduce a lot of pollutants, which is actually a big discount.

Chang Jiwen: The Beijing-Tianjin-Hebei region and its surrounding areas should alleviate the smog problem through scientific management. For example, optimize the structure of urban space development and utilization, follow the basic conditions such as geography, meteorology and ecology, carry out "multi-regulation integration", crack down on illegal activities, and form a scientific and sustainable production, living and ecological space; We will implement the border system for urban development and utilization with the most resolute attitude, so as to prevent the scope of the main city, districts and counties from continuing to expand beyond the regional ecological environment capacity.