Experts' view | the heavy pollution process has gradually dissipated, and the air quality is expecte

    In the new spring of the new year of the ox, pollution process has appeared in many places in the country, especially in Beijing, Tianjin and Hebei and surrounding areas. On February 9, the Ministry of ecological environment and China Meteorological Bureau jointly discussed that the air diffusion conditions in the early and first half of the Spring Festival were generally poor, and the process of polluted weather would occur in many regions, especially in Beijing, Tianjin, Hebei and surrounding areas, and a serious pollution process would also occur in Beijing. The Ministry of ecological environment issued warning tips, requiring all regions to launch corresponding level emergency plans in time, take measures to jointly prevent and control, and reduce pollution discharge. According to the local emergency plan for heavy pollution weather, emergency emission reduction measures shall be taken in time. Besides Beijing, Tianjin and Hebei and surrounding areas, Jiangsu, Liaoning, Inner Mongolia, Heilongjiang, Sichuan and other places have also started successively, 61 cities have started orange warning and 6 cities start yellow warning. Beijing also launched a yellow warning on February 11. Emergency emission reduction measures have effectively reduced the impact of pollution, and played a role of "cutting peak and reducing speed". Up to now, except for the heavy pollution maintained in the cities in front of Taihang Mountain and Guanzhong, other areas in the country have basically recovered to be excellent, and some cities are light to moderate pollution.

     Due to the adverse weather conditions such as large-scale steady steady wind, high humidity and temperature inversion before the Spring Festival, the initial concentration is high. Since February 10, many cities in Beijing, Tianjin and Hebei and surrounding areas have reached the level of severe pollution. Beijing has reached the level of heavy pollution at noon on New year's Eve and continues to the night. Under this initial concentration, the pollution degree will be aggravated by the influence of fireworks and firecrackers from New Year's Eve to the early morning of the first year. From 19:00 to 6:00 on November 19-12, fireworks and firecrackers were set off intensively. The air quality of 5 cities reached serious pollution, and Langfang City lasted for the longest time, reaching 9 hours. Beijing reached the level of serious pollution in 7 hours from 1 to 7 on December 12. Due to the lack of large-scale strong cold air activity and strong Dongfeng, the area is still in medium to severe pollution. The cities at the junction of Taihang Mountain and Yanshan are affected by transmission, and are in severe pollution, which needs to be improved 13 days and night.

    During the Spring Festival, the level of social activities has declined, and the emission of general industrial enterprises, transportation, construction and other industries has declined significantly. Why is the pollution still frequent? Chaifa, a researcher at the Chinese Academy of Environmental Sciences and deputy director of the National Joint Center for the prevention and control of air pollution, worked together to answer:

    The main reason is that the heavy pollution industry emissions are still high. China's economic operation has been steadily restored. In 2021, the main industries have maintained a rapid growth rate. For example, in January, crude steel production increased by more than 20%, national power generation increased by 25% year-on-year, thermal power generation also increased significantly, and coal consumption increased by about 20% year on year. During the Spring Festival, production activities such as transportation, construction and other activities have been greatly reduced, and some industrial enterprises have also stopped production, and the total pollutant emission of the whole society is reduced compared with that of ordinary times. However, thermal power generation and iron, coking, nonferrous, petrochemical, coal chemical, glass, pharmaceutical, pesticide and other industries, due to production characteristics, process equipment, etc., must be continuously produced, and these industries are also the largest polluters, a large number of non-stop processes continue to produce, and the pollutant discharge is still at a high level.

    The short-term effect of fireworks and firecrackers is great. In this year, the extremely unfavorable weather conditions, the high concentration of pollutants is long. Generally, we can use the concentration ratio of PM2.5 and CO as the index to evaluate the contribution of fireworks and firecrackers to PM2.5 pollution, which can reduce the influence of some meteorological factors. At the same time, the variation of station concentration and PM2.5 tracer component (potassium ion, magnesium ion, etc.) in the peak time of the fire were analyzed. From Beijing, Tianjin, Hebei and its surrounding areas, fireworks in Beijing, Baoding and Shijiazhuang contributed 20% - 40% to PM2.5 from the night of new year's Eve to the early morning of the first day (19:00-12:00 on November 11). The concentration of potassium and magnesium ions in PM2.5 is about 10-30 times of that of non burning period. In the peak period of pollution in some stations in Beijing, the concentration of potassium ion increased 79 times and magnesium ion 17 times in two hours. The concentration of PM2.5% in some cities of China appeared in the early morning. From the observation of historical data, this explosive growth is very obvious from New Year's Eve to early morning of the first day of each year. Although the regulations on the prohibition of fireworks and firecrackers have been issued in all parts of China, the amount of fireworks and firecrackers can not be ignored. According to the noise observation, the 10 hour average noise level of fireworks in Beijing this year (from 18:00 to 4:00 the next day) is 57.6 decibels, which is higher than that of the same period last year, indicating that there are more fireworks in Beijing this year than last year. At the same time, the heating emission in winter is also a rigid demand. In recent years, the clean heating reform in Beijing, Tianjin, Hebei and surrounding areas has been effective, but the cities in Northeast, Inner Mongolia and Northern Shanxi and Hebei have not been included in the scope of transformation. The main heating is still various coal-fired facilities and small coal briquettes and biomass in rural areas, and the overall emission is still large.

    How bad are the weather conditions? Guihailin, chief forecaster of the central meteorological station, came to answer:

    During the Spring Festival, the atmospheric diffusion conditions in Beijing and surrounding areas are the worst year of new year's Eve in recent years. The ground is in low pressure convergence zone, with high humidity and long duration.

    Since the day of February 9, North China has been controlled by weak southerly wind, and the diffusion conditions have turned to be unfavorable, and the pollutants discharged continue to transfer northward and accumulate. At the same time, the relative humidity gradually increased, and by February 11 (New Year's Eve), the daily average relative humidity was more than 60%, which was conducive to the conversion of SO2, NOx and other gaseous pollutants to the secondary components of particles.

    From the night of February 11 to the early morning of 12th, the adverse weather conditions of steady and small wind and high wet fog appeared in many places in China. Especially in Beijing, Tianjin and Hebei and its surrounding areas, Taihang Mountain Yanshan junction has been in the wind field convergence area since February 11. There is strong inversion near the ground to 950 PA, and the atmospheric diffusion conditions are extremely unfavorable. Under the adverse weather conditions, the pollutants in the area converge to the low-pressure convergence area, and the influence of fireworks and firecrackers from New Year's Eve to the early morning of the first morning is superimposed. The air quality maintains the level of heavy pollution and serious pollution in a short time.

    When will air quality improve? Wang Wei, chief forecaster of China environmental monitoring station, said: the third day of the first three is expected to improve, and the overall good at the end of the Spring Festival

    In the northern region, heavy fog and heavy pollution weather are easy to appear due to the meteorological characteristics of low pressure, high humidity and static stability in the winter and spring seasons. At present, Beijing, Tianjin and Hebei and its surrounding areas are in the high wet state before precipitation, and the body sense is poor. Improvements are expected in the third year of the first three.

    Air quality in Beijing is expected to improve from night to day 14 on February 13 (second day), and moderate to severe pollution levels are expected to be maintained on the 13th. With the advent of this cold air, the pollutant removal may also be accompanied by the first precipitation process after the Spring Festival. However, before the cold air and precipitation process arrive, the humidity is close to saturation, there is fog weather, and the influence of high concentration in the early stage is superimposed. The PM2.5 concentration will continue to be at a higher level, and the actual sense is poor. From the 14th to the end of the Spring Festival holiday, the air quality has been basically maintained at a good level.

    The improvement time of Beijing Tianjin Hebei and surrounding areas was later. On the 13th, the central and southern part of the region was still affected by weak wind, high humidity and inversion temperature. Most cities still had medium to severe air pollution, and some cities may have serious pollution in a short time. On the 14th, the pollution situation of Tianjin and central and Eastern Hebei improved due to the cold air in the northeast. The cities in Southern Hebei, western Shandong and Northern Henan were affected by upwind pollution transmission, and moderate to severe pollution may occur. From 15 to 17, the region was affected by air transit, and the overall diffusion conditions were favorable. It is expected that the air quality of most cities in the region is mainly excellent, and some cities in the South and south of the region may have slight pollution.

    From the national perspective, the meteorological conditions were relatively unfavorable from 13 to 14. The major areas of East China, South China, northwest, southwest and North China were mainly good light pollution, the northeast and southwest were mainly light to moderate pollution, and the central and southern parts of North China were mainly medium to heavy pollution. Affected by fireworks and firecrackers, the air quality of the above areas can be improved by 1-2 grades on the original basis. On 15th, the diffusion conditions improved as a whole, with good air quality in the northeast, north, South, South, South and southwest China. The air quality in the south central, northern, northern, northern and northwest parts of North China was mainly good light pollution, and moderate pollution may occur in the north of East China and the two lakes. The local sand dust in Xinjiang may have moderate to severe pollution.

    The Ministry of ecological environment will guide the local governments to respond scientifically and timely release the early warning in accordance with the requirements of the local emergency plan for heavy polluted weather.