Experiencers say

Original title: Accurately fight against air pollution sources, paint a happy background with blue sky and white clouds

Li He, reporter of Science and Technology Daily

In the main building of Beijing Ecological Environment Monitoring Center, a special calendar chart is hung, which shows the daily concentration of fine particulate matter (PM2.5) in Beijing since 2013. "The darker the color, the redder it is, indicating the worse the air quality; the lighter the color, the greener it is, indicating the better the air quality." Liu Baoxian, a representative of the 20th National Congress of the Communist Party of China and director of the Beijing Ecological Environment Monitoring Center, said that it was clear from this calendar chart that the air quality in Beijing had improved significantly in the past decade. "From looking forward to the blue sky in 2013 to now, the blue sky has gradually become the norm, and the blue sky and white clouds have become the happy background of Beijing citizens."

In 2021, Beijing will make a landmark breakthrough in air pollution control, and the air quality will reach the overall standard for the first time. The average annual concentration of PM2.5 decreased by 63.1% compared with that in 2013, with an average annual decrease of 7.9%, far exceeding the decrease rate of cities in developed countries over the same period. In 2021, the number of days with good air quality in Beijing will be 288, 112 days more than that in 2013, nearly four months more.

In 2013, China implemented the new Ambient Air Quality Standard, and Beijing became one of the first cities in China to officially release PM2.5 monitoring data. PM2.5 source resolution is an important support for achieving scientific and accurate pollution control in the atmosphere. Liu Baoxian said that Beijing has carried out three PM2.5 source analyses, and achieved the improvement of air quality step by step through the precise implementation of policies.

From 2012 to 2013, Beijing carried out PM2.5 source analysis for the first time, and the analysis results showed that regional transmission accounted for about 1/3 of the total; Among local emission sources, mobile sources account for 31.1%, coal sources account for 22.4%, and dust sources and industrial sources also exist. Therefore, the Beijing 2013-2017 Clean Air Action Plan focuses on the governance of the four local sources, while taking into account the regional transmission characteristics, participating in the regional joint prevention and control.

From 2017 to 2018, Beijing carried out the second PM2.5 source analysis, and found that the proportion of regional transmission increased; Among local sources, mobile sources still accounted for the largest proportion, up to 45%, fugitive dust sources rose to the second place, accounting for 16%, and coal sources dropped to 3%.

"The source analysis results show that after treatment, all kinds of local air pollution sources in Beijing have shown a significant downward trend, indicating that the clean air action plan is scientific and the measures are accurate." Liu Baoxian said that according to the changes in air pollution sources, especially for local mobile sources, dust sources, industrial sources and living sources in Beijing, Beijing has formulated the Three Year Action Plan for Beijing to Win the Battle of Blue Sky Defense from 2018 to 2020.

From 2020 to 2021, Beijing conducted the third PM2.5 source analysis. The latest source analysis finds that regional transmission has increased, especially in heavily polluted weather, and regional transmission accounts for more than 60%. Among local emission sources, mobile sources are still the main source of air pollution in Beijing, and living sources have gradually risen to the second place. "This shows that the improvement of air quality in Beijing benefits not only from the improvement of air quality in the whole region, but also from scientific and accurate action plans, and pollution control increasingly relies on regional joint prevention and control," Liu Baoxian said.

In September 2012, Beijing released the distribution map of PM2.5 monitoring stations, with 35 stations in total. Three years later, Beijing is faced with more refined management needs. "With the deepening of air pollution control, large fixed emission sources such as factories have basically met the requirements, but mobile sources, dust sources and living sources are still widespread and highly mobile." Liu Baoxian said that this requires further matching monitoring means to the corresponding pollution source areas to improve the spatial resolution of monitoring. The original monitoring can only reach the district level, and now it is necessary to extend the monitoring network to more than 300 streets, towns and other management terminals.

Therefore, Liu Baoxian led the team to use the Internet of Things to associate all monitoring equipment for easy management and application. At the same time, AI is used to extend the traditional algorithm to each site, establish a cloud quality control system, and improve data quality. "For example, we have established a local high value recognition algorithm, which can eliminate the impact of transmission and meteorology after having massive data, to characterize the characteristics of local pollution, so as to carry out precise governance." Liu Baoxian said that this monitoring method has been promoted to the whole country at present.

During this year's Beijing Winter Olympic Games, in order to serve the Winter Olympic Games well, Liu Baoxian led the team to specially build a set of refined air quality prediction and forecasting system, so that the forecast can be refined from day to hour, and the forecast of the whole region can be refined to kilometer level, supporting Beijing's air quality to reach the daily standard.

"Although the air quality in Beijing has improved significantly, the prevention and control of air pollution is characterized by long-term, complexity and difficulty. To achieve long-term and stable standards in Beijing, we need to persevere and work hard for a long time." Liu Baoxian said that with the joint efforts of all of us, "we have the confidence to harvest more and more blue sky".