China News Service, November 13th. According to the website of the Ministry of Ecology and Environment, due to adverse weather conditions, increased pollutant emissions in winter, regional transmission and other comprehensive factors, an incident occurred in Beijing-Tianjin-Hebei and surrounding areas on November 11-12. Contamination process.
After a slight alleviation on the 13th, a pollution process will occur again on the 14-17, and this pollution process will gradually end with the rain on the 17th-18th.
Retrospective analysis of pollution process from 11-12
Basic situation: From 11 to 12, Beijing reached light pollution every day, and some cities in the region experienced heavy pollution.
The daily average levels of PM2.5 were 107 and 83 micrograms/cubic meter for two consecutive days on the 11th and 12th in Beijing. Among them, from 18:00 on the 11th to 9:00 on the 12th, it reached hourly heavy pollution for 16 consecutive hours. Pollution level.
From a regional perspective, 15 cities in the southern part of the region, including Zhengzhou and Kaifeng, first experienced pollution accumulation on the 9th to 10th. Langfang reached heavy pollution on the 11th, Baoding and Shijiazhuang were moderately polluted, and 19 cities were lightly polluted on the 12th. Two cities, Baoding and Shijiazhuang, were heavily polluted, Anyang, Tangshan, and Xingtai were moderately polluted, and 15 cities were slightly polluted.
Reason analysis: With the change of seasons and heating in winter, Beijing-Tianjin-Hebei and surrounding areas will experience one or two heavy pollution processes of varying degrees before and after heating each year.
This pollution process is mainly due to the unfavorable weather conditions, the increase of regional pollution emissions, and the superposition of the three factors of regional transmission.
From the perspective of meteorological conditions, the Beijing-Tianjin-Hebei region and its surrounding areas were affected by the back of the high-pressure system from 9-12. The southerly wind prevailed near the ground, and pollutants continued to gather in the piedmont plain. In addition, there was a strong temperature inversion process in the area. And the high humidity in the early morning is good for the conversion of pollutants.
From the perspective of the increase in regional pollution emissions, the increase in heating emissions in winter, the increase in traffic flow, and the recovery of industrial production activities have led to an overall increase in regional pollution levels.
In terms of heating, Hebei and Tianjin started central heating on November 1st, and Beijing started central heating on November 7th. Self-heating residents also started heating. Pollutants such as nitrogen oxides produced by heating have increased regional pollution. Level.
In terms of traffic flow, in recent months, the national freight volume and traffic flow have both shown an upward trend. From June to September, the year-on-year growth rate of road freight traffic remained at 3.1-7%. In October, the traffic volume of large truck sections increased by 11% year-on-year.
In terms of industry, with the continuous advancement of resumption of work and production, the output of key industries such as steel, cement, coke, non-ferrous metals, automobiles, rubber, plastics, coatings and other key industries and the processing volume of crude oil continued to increase, all exceeding the level of the same period in previous years, and some increased year-on-year Even reaching double-digit rates, the corresponding air pollutant emissions have reached their annual peaks.
From the perspective of regional transmission, under the action of southerly winds near the ground, pollutants in the central and southern regions of the region are transported and accumulated to the northern piedmont plain, forming a pollution convergence zone in Beijing, Langfang, Baoding, and Shijiazhuang.
Schematic diagram of PM2.5 concentration distribution and wind field transmission in "2 26" cities on November 9-12 (Data source: China National Environmental Monitoring Station)
At the same time, PM2.5 component analysis also reflects this feature. The secondary inorganic components (nitrate, sulfate, ammonium ion) account for more than 50% of PM2.5, and some cities account for about 75%. Among them, nitrate ions account for the highest proportion. The conversion of nitrogen oxides from heating, diesel vehicles and industrial sources to nitrate ions dominates the increase in PM2.5 concentration in this process.
Time series of the concentration of the main components of PM2.5 in Beijing from November 10-12 (Data source: China Environmental Monitoring Center)
Future pollution process forecast
There will be another pollution process from November 14-17. Beijing may reach moderate pollution, and some cities in the region are at risk of serious pollution.
Since the pollutants accumulated during the pollution process from November 11 to 12 have not been completely removed, central and southern Beijing, Tianjin and Hebei will be affected by the return of pollution from some cities in northern Henan and central and western Shandong.
On this basis, the region is simultaneously affected by temperature inversion, near-saturation high humidity in the early morning and southeast airflow, and atmospheric diffusion conditions continue to be unfavorable.
It is expected that the Beijing-Tianjin-Hebei region and its surrounding areas will experience a moderate to severe pollution process on the 14th to 17th. The pollution is mainly concentrated in the central and southern parts of the Beijing-Tianjin-Hebei region and the central and western parts of Henan.
Among them, from the night of the 16th to the 17th, affected by long-term stability and wind convergence, individual cities in central Hebei Province are at risk of serious pollution.
Beijing on the 14th is expected to air quality 2-3 good to light pollution; on the 15th is expected to be 3-4 mild to moderate pollution, the peak concentration of evening to night can reach moderate to severe; on the 16th is expected to be 3-4 mild Moderate pollution; Level 3 mild pollution is expected on the 17th.
The pollution process will gradually end with regional precipitation.
From the night of November 17th to 18th throughout the day, a systematic precipitation process affects North my country from west to east. The precipitation time is longer and the amount of rainfall is heavier. The pollution situation will be significantly alleviated. Mainly from good to light pollution.
From the 19th to 20th, due to the comprehensive influence of the rear of the low pressure system and the northwest cold high pressure system, the regional diffusion conditions were significantly improved, and the pollution process was completely ended.
the measures taken
In accordance with the forecast and forecast results, the Ministry of Ecology and Environment printed and sent regional early warning information to the people's governments of Hebei, Shanxi, Shandong, and Henan on November 13, requiring all localities to take timely corresponding emission reduction measures in accordance with the results of air quality forecasts and local emergency plans. , To carry out regional joint prevention and control.
Up to now, a total of 33 cities (including 21 key cities) in the Beijing-Tianjin-Hebei region and surrounding areas have activated the warning, 30 of which have activated the orange warning, and 3 cities have activated the yellow warning.
Each early warning city will adopt differentiated emission reduction measures in accordance with the latest revision of the heavy-polluted weather emergency emission reduction list and the performance level of each enterprise to encourage advanced and spur backwards to achieve “scientific pollution control, precise pollution control, and pollution control according to law. ".
The Ministry of Ecology and Environment dispatched in various cities to strengthen supervision and designated assistance working groups will focus on supervising and inspecting the implementation of emergency emission reduction measures in various regions, tracking and evaluating the effects of emergency emission reduction measures in various regions, and supporting the scientific response to heavy pollution weather in various regions.