Difference between smog in Beijing, smog in London and photochemical pollution in Los Angeles

Compare the recent weather in Beijing with the "London fog". "I have been to London this year, obviously it has nothing to do with the fog. Maybe the fog belongs to some of our cities. " This may have touched a sore spot. But careful observation shows that this comparison is inappropriate. This year's air pollution in Beijing and other places is very different from the "London smog" in the 1960s and before, and the "Los Angeles smog" in the 1960s.

"London Haze" is caused by black smoke directly emitted from factory chimneys and civil heating, and it is mainly a primary pollutant, such as sulfur dioxide (SO2) and other gases and smoke. Coupled with exposure to adverse diffusion conditions such as ground inversion and humid meteorological conditions, it caused serious pollution and smog, which did great harm to people's health-1952 caused more than 4,000 deaths in four days. At present, Beijing's heavily polluted factories have been moved away, central heating, chimney height has also increased, dust removal equipment is running well, and ground pollution control has achieved fruitful results.

In my opinion, the smog in Beijing this time is mainly secondary pollution. Its source may be power plants, industrial processes and automobile exhaust emissions, but the main part is likely to be converted from gaseous pollutants such as sulfur dioxide (SO2) and nitrogen oxides (NOX) in the air. This converted nitrate and sulfate are the main components of fine particles (PM2.5, that is, particles with a diameter less than 2.5 microns in the atmosphere, also known as aerosol, whose diameter is less than 65438+ 0/20 of the thickness of human hair), so it is also called "secondary pollutants". Fine particles, mainly composed of nitrate and sulfate, have strong hygroscopicity. When encountering stable atmosphere and humid meteorological conditions, their concentration increases, absorbing water vapor, and their volume increases, which affects the scattering of incident light and causes visibility problems. The more serious the scattering, the darker the scattering area looks, so it is "gray". The recent smog pollution in Beijing mainly affects visibility, and car dealers, aviation and water transport are greatly affected, which may lead to serious traffic accidents. For human health, it is mainly psychological. With the increase of PM2.5 concentration, it may increase the incidence of respiratory diseases, but it will not cause serious health damage and will never cause many deaths. Beijing citizens need not worry.

The number of motor vehicles in Beijing is about 5 million, which is equivalent to the level of Los Angeles in the 1960s, but this time the smog in Beijing is completely different from the smog in Los Angeles. The smog in Los Angeles is photochemical smog, which is mainly caused by photochemical reaction of NOX emitted by automobiles under sunlight. In addition to pollutants such as NOX, photochemical smog mainly contains ozone, aldehydes and fine particles. It also has a direct impact on the human respiratory system: suffocation, eye irritation, etc. Because there are many motor vehicles in Beijing, there are also photochemical smog problems, so we should pay attention. The recent smog in Beijing is not photochemical smog because there is no obvious strong illumination and other necessary conditions.

Satellite remote sensing images show that Beijing-Tianjin-Hebei, East China, North China and Sichuan are among the regions with the most serious distribution of PM2.5 in the world. Note: The remote sensing image is the average from 2005 to 2007, indicating that the problem of fine particulate pollution in Beijing has existed for a long time (there were not so many cars at that time). Then, why has the smog event suddenly formed since June 10 this year? The answer to the question lies in meteorological conditions. Beijing may encounter an unusually high relative humidity process in the near future (which needs the approval of meteorologists), and stable airflow is not conducive to diffusion. The formation is beneficial to the moisture absorption and growth of fine particles, resulting in haze at the end of 10. The fog in recent days may also be related to this: smog can be transformed, enough water vapor may turn haze into fog, and fine particles that absorb moisture may still be the culprit.

Where do sulfate and nitrate, the main hygroscopic components of PM2.5, come from? Many of them are motor vehicles. 5 million in Beijing, 2.3 million in Shanghai and 2 million in Guangzhou. For a wide range of smog and PM2.5 pollution, it is not true that motor vehicle exhaust is the main source of fine particles. For example, some people superimpose the large cities with more than 2 million motor vehicles on the remote sensing PM2.5 concentration distribution map, showing that PM2.5 pollution has only a small relationship with motor vehicle exhaust, mainly not from motor vehicles.

The structure of energy consumption in China can explain the heavily polluted areas of PM2.5 in China. As we all know, China's coal consumption ranks first in the world, accounting for about 70% of the total fossil energy consumption. The investigation results of 20 10 atmospheric pollution sources by the Ministry of Environmental Protection also show that the main sources of SO2 emission are coal-fired power plants and civil use, as well as smelting process. At the same time, the main source of NOX is also coal-fired power plants, and the emissions even exceed those of motor vehicles! SO2 and NOX emitted by coal combustion greatly exceed the contribution of NOX emitted by motor vehicles to fine particle pollution, that is, smog pollution. This can also explain why around 2005, when there were not many motor vehicles, smog occurred very seriously in all parts of China, forming "urban agglomeration pollution"; However, after 2007, due to the rigid requirements of the state for desulfurization, the number of smog in various places gradually decreased. When there was no smog before, Beijing residents also lived under serious PM2.5 pollution, but they were dry and invisible.

China's specific energy structure will continue to burn a lot of coal: natural gas and oil resources are scarce, and hydropower development has almost come to an end. Although nuclear energy has room for development, there are also security problems. It is difficult for us to be as clean as Europe. People mainly burn oil, natural gas and nuclear fuel. As far as the whole country is concerned, the "coal burning" pollution in China will continue for a long time. The country's continuous efforts in pollution control have achieved remarkable results: the pollution problem of PM 10 has been improved, the ground concentration of SO2 has decreased, and the concentration of NO2 is not very serious. This is why the API (the air pollution index we commonly use now) is low, and even if there is serious smog, the API will say "light pollution" or even "good". In other words, it is effective to control the "primary pollutants" directly discharged by pollution sources. In this sense, it can be said that the air quality is improving. Photochemical smog, acid rain and smog all belong to "secondary pollution", which is caused by a large number of coal burning and the increase of motor vehicles. We must strictly strengthen the desulfurization work, strictly implement and implement the requirements of increasing nitrogen oxide emission reduction in the national "Twelfth Five-Year Plan", and at the same time adhere to strict motor vehicle emission control. In recent years, the subway system in Beijing has developed rapidly. I hope to further improve public transportation and reduce the use of motor vehicles, which will naturally help improve air quality.

Ordinary medical masks are low in price and poor in protection, and are basically only suitable for ordinary nurses or cooking at home; Advanced medical masks are adopted by surgeons or dentists, who earn more and pay more attention to the quality of masks rather than the low cost. Advanced medical masks have excellent barrier to particles and liquids, ensuring breathability when worn in precise working environment. It can also deodorize. Sources of toxic particles in cities: first, automobile exhaust, medical masks imported from the United States, and Puwei server, which have good filterability and prevent both particles and fog drops. The filtration efficiency is 99.8% for particles as small as 0. 1 micron, and 99.9% for bacteria or virus carriers as small as 0.3 micron (common in droplets). SecureFit patented technology is adopted to adapt to different face shapes and achieve a high degree of fit. For the health of you and your family, wear a mask when you go out. I wish you happiness and hope to adopt it.