Abstract Yesterday, the Ministry of Environmental Protection reported that as of the end of June, the concentration of PM2.5 in the transmission channel of Beijing-Tianjin-Hebei and surrounding areas showed a monthly decline. From March to June in Beijing, the monthly PM2.5 concentration was lower than the historical average. . However, recent monitoring data shows that due to unfavorable weather conditions...
Yesterday, the Ministry of Environmental Protection reported that as of the end of June, the concentration of PM2.5 in the transmission channel city of Beijing-Tianjin-Hebei and surrounding areas showed a monthly decline. From March to June in Beijing, the monthly PM2.5 concentration was the lowest compared with the historical period. However, recent monitoring data show that the level of air pollution in Beijing-Tianjin-Hebei and surrounding areas has increased due to adverse meteorological conditions. The expert group of the Ministry of Environmental Protection said that factors such as “sauna daysâ€, motor vehicles and regional transmissions pushed up the concentration of pollutants in the near future. Reason 1: Sauna Day
According to the expert group, the concentration of PM2.5 in the Beijing-Tianjin-Hebei region and the surrounding areas, especially in the eastern and southeastern regions of the region, including Tangshan, Beijing, Tianjin, Langfang and northwestern Shandong, showed a significant increase in PM2.5 concentration from late June to early July. According to the analysis of the expert group of the Ministry of Environmental Protection, the “sauna days†appeared in the Beijing-Tianjin-Hebei region. Due to this, the pollution diffusion conditions were unfavorable, and regional pollutants continued to accumulate. As the subtropical high center is at sea, the control and influence of the subtropical high ridge area in the eastern and southeastern parts of the Beijing-Tianjin-Hebei region are more obvious, and the atmosphere is more stable. This is also a factor that is more obvious in the recent increase in air pollution levels in the region.
Reason 2: Motor vehicle
In addition to the unfavorable meteorological conditions caused by the “sauna daysâ€, localized motor pollution and transmission properties of coal-fired pollution are the main factors for the recent deterioration of air quality, especially the high concentration of PM2.5. Due to the large amount of motor vehicles in Beijing and the obvious pollution of motor vehicles, it can be seen from the analysis of the composition of PM2.5 in the near future that nitrates closely related to motor vehicle pollution continue to show significant peaks every morning, and in PM2.5. It ranks first in concentration, accounting for about 20%. At the same time, industrial source emissions and freight traffic contribute more to nitrate. From the analysis of the wind direction frequency distribution of the Beijing Observatory, the recent dominant wind direction is the southeast wind, and the regional pollution transmission is particularly evident in the eastern and southeast transmission channels.
Reason 3: Transmission of coal-fired pollution
Due to the difference in air pollution control process and energy structure, the consumption of coal in Beijing is low. The monthly average concentration of sulfur dioxide in summer is as low as 5 μg/m3, but recently, the composition of PM2.5 is analyzed. Salt is the second highest component, accounting for about 15%, second only to nitrate. In the surrounding area, the consumption of coal in summer is still very large. The high temperature, high humidity and weak wind weather are favorable for the formation of sulfate. Under the action of transmission, the coal burning pollution in the region affects the northern part of the region in the form of sulfate, especially in Beijing.
Judging from the recent forecast of climate trends, the surface temperature in the Beijing-Tianjin-Hebei region was relatively high in the first half of July, with southerly winds as the mainstay and lower precipitation frequency. The overall characteristics of weak air pressure and high temperature and low rainfall were maintained in the second half of the month. It is expected that the current unfavorable air pollution diffusion conditions will continue and the air pollution concentration will be high.
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