Guide
On September 25, 2021, the 2020/2021 China Urban Planning Annual Conference and the 2021 China Urban Planning Academic Quarter (hereinafter referred to as the Planning Annual Conference) opened in Chengdu, and the theme of this year's Planning Annual Conference is "Spatial Governance for High-quality Development". Professor Tao Shu, academician of the Chinese Academy of Sciences and school of urban and environmental sciences of Peking University, delivered a conference report entitled "Assessment of Air Pollution and Hazard Trends in China".
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Tao Shu
Academician of the Chinese Academy of Sciences, Professor of the School of Urban and Environmental Sciences, Peking University
Air pollution is closely linked to the theme of this year's annual meeting, "Space for High-Quality Development.". A city with high-quality development should not be a polluting city. This report provides a scientific basis for national policy decision-making by assessing air pollution and its hazards in China.
#1
Background analysis of air pollution research in China
The most serious health hazards are environmental problems. As we all know, air pollution has a great impact on the environment, and in previous years PM2.5 was the primary factor for severe air pollution in northern cities. In addition to outdoor air pollution, indoor air pollution also has a big problem. The indoor air pollution mentioned here does not refer to problems such as formaldehyde pollution, but to indoor air pollution caused by solid fuels (i.e. burning coal and burning firewood).
According to the World Health Organization's Burden of Disease report, premature deaths caused by air pollution accounted for about 17% in China in 2019, which is a high proportion, indicating that air pollution has a great impact on health. Among them, PM2.5 particulate matter pollution is the main part, accounting for 16.4%. PM2.5 particulate pollution includes not only outdoor air pollution (13.4%), but also household air pollution. The source of life refers to the health hazards caused by the use of pollutants emitted from various solid fuels.
Since 2007, we have begun to pay attention to the problem of air pollution, based on the geological background, to carry out large-scale work, to develop a research roadmap: first list the emissions of atmospheric pollutants, use this list to make an atmospheric transport model, simulate the ins and outs of pollutants, and then detect its impact on human health and climate. On this basis, policy analysis and evaluation are carried out, and the specific content and related measures for pollution control are proposed by exploring the impact process of air pollution on health and climate, so as to provide a scientific basis for government decision-making.
In recent years, China has carried out air pollution control actions, invested a lot of money and done a lot of work, and the air quality has been significantly improved. By reviewing the improvement process, we summarize the measures taken and assess the effectiveness of the representative measures.
Data analysis shows that from 2013 to 2018, the average annual PM2.5 concentration in China's major cities decreased significantly, but individual cities rebounded in individual years (as shown by the red arrow in the figure), which is mainly caused by meteorological factors. Specifically, air pollution comes from two drivers, one is emissions, the more pollutants are emitted, the more pollution is more serious, and the other is atmospheric transmission conditions, such as pollution stains will accumulate in static weather, causing serious pollution. Together, they form a pollution profile at a certain location at a certain time. Taking 2014 as an example, although the peak year of emissions has passed that year, there was still serious pollution weather, which was because there were meteorological conditions that were very unfavorable to the spread of pollutants that year, and the entire North China region was shrouded in severe haze for a long time, which was not conducive to the spread of atmospheric pollutants and led to serious air pollution.
Based on the previously established global air pollutant emission inventory, we analyze the trend of China's atmospheric pollutants since 1960, and we can see that since the 1950s and 1960s, pollutant emissions have gradually increased, and after the reform and opening up, they have increased rapidly; but since 2000, most of the pollutant emissions have begun to decline, which means that the peak of emissions has passed. At the same time, it can be found that emissions of most pollutants are declining, but emissions of volatile organic compounds (VOCs) have not declined, and have only stopped the upward trend so far.
Our general approach to assessing the drivers is as follows: first design scenarios, then construct pollutant emission inventories for different scenarios, construct atmospheric transport models using meteorological data, calculate its exposure to populations and health effects, and finally analyze differences between different scenarios to analyze the effectiveness of control measures. Time-limited, the following examples omit the intermediate analysis process and directly introduce the relevant results.
#2
Rural living energy transition and its health benefits
First, the transition to living energy in rural areas is discussed. Through the analysis of energy data, it is found that in China, commercial fuels (such as fuels used in industry, power plants, and transportation) have a relatively complete record, but data on the source of life is very scarce. In response to the uncertainty of existing statistics, in order to obtain first-hand information, we launched a nationwide large-scale rural household survey in 2012 in order to obtain the energy structure of rural residents. The survey included the type of fuel, the length of time each fuel was used, and even the weight of the fuel used within 24 hours, yielding a lot of invaluable first-hand data. Based on the results of these data, it was found that the source of life is quite important in China's air pollutant emissions, and this importance has long been ignored. Based on this result, we recommend that the relevant departments add surveys of domestic energy and emissions in the second national survey of pollution sources in 2017.
In the figure below, pink is electricity, blue is gas, they are called clean energy; black is coal, orange is biomass, they are called solid fuels, and solid fuels emit many pollutants. Through the analysis, it can be seen that between 1992 and 2012, China's rural living energy consumption has undergone a rapid transformation, and the proportion of clean energy used in cooking has risen rapidly from 8% to nearly 60%, an increase of 7 times; the clean energy used for heating has increased from 2% to 15%, although the growth rate is very fast, but due to the low starting point, so by 2012, the proportion of clean heating in the country is still very low. The main driver of energy consumption transformation is an increase in living standards. When the people are rich, they will spontaneously be willing to use clean methods to cook. Although there is such a trend, heating is very slow and fluctuates a lot because the cost of clean heating is too high and therefore requires government intervention.
According to the communiqué of the second national pollution source census in 2017, the contribution of living sources to pollutant emissions is very high. Specifically, living sources account for 18% of SO2 emissions; 22% of primary PM2.5 emissions; 29% of VOCs emissions; and 4% of NOx emissions. Therefore, it is visible that the control of the source of life is very important.
In urban areas, emissions of major pollutants from domestic sources have also changed significantly, thanks to clean energy replacing coal burning, central heating, power plant dust removal and other measures. Among them, the amount of coal burning has dropped sharply, and the amount of clean energy is rising, but the total amount has not changed much. This is because although the proportion of clean energy is increasing, with the process of urbanization, a large number of rural people have entered the city, and the energy use structure of this part of the population is different from the original urban population, and more coal is used, resulting in a total change that is not significant. In 2014, for example, emissions from domestic sources contributed about 23% to outdoor atmospheric PM2.5, which is one of the main factors contributing to air pollution. There are obvious urban-rural and spatial differences in emissions from living sources, and seasonal changes are also obvious, with significant increases in the heating period in winter. In previous years, Beijing had severe winter smog, which was closely related to the heating of residents in the surrounding areas.
#3
The environmental effects of double substitution in the northern region
In view of the high cost of clean heating, the state has made great efforts to promote clean heating, and 10 ministries and commissions have jointly issued a document to adopt the method of "coal to electricity and coal to gas" in Beijing, Tianjin and 26 surrounding prefecture-level cities to achieve 60% clean heating by the end of 2020 and alleviate winter air pollution in northern China, especially in the Beijing-Tianjin-Hebei region.
Through simulation and analysis, it can be seen that clean heating has a significant effect on improving outdoor air quality, and the contribution of living sources to outdoor PM2.5 concentration has decreased by more than half, but more importantly, the indoor PM2.5 concentration of rural residents in the area and the overall exposure level of the population have been greatly reduced, indicating that government intervention has greatly improved health benefits.
After that, the state continued to launch the "Northern Clean Heating Action", which plans to achieve 40% clean heating replacement in 128 prefecture-level cities (in addition to the above 2+26 areas). Based on the model established according to the actual progress of "2+26", it can be seen that promoting clean heating in the entire heating area should be adapted to local conditions and avoid "one-size-fits-all". Specifically, according to the actual progress of the 2+26 area, the topography, economic conditions and population density factors should be mainly considered. Strengthen clean heating in relatively developed and densely populated plains. This adaptation to local conditions can reduce costs and improve environmental and health benefits.
#4
The health benefits of soil coking are prohibited
The coking industry has always been an important source of industrial emissions. The soil method of coking is a very special phenomenon, the people build their own kilns, in a very primitive way to produce coke, the emission is extremely high, and there are no control measures. Causes serious contamination. In this regard, the state promulgated the "Coal Law", which stipulates that from December 1, 1996, the production of soil coke is prohibited. Due to the various obstacles encountered in the implementation, after more than ten years of legislation, the production of soil coke completely disappeared.
In this study, we traced the historical trajectory of the prohibition of soil coke, used remote sensing information to reconstruct the spatio-temporal distribution of soil coke over the past 82 years, and simulated the emission of pollutants produced by soil coke and its impact on health. Comparative analysis shows that after the implementation of the Coal Law, the situation of lung cancer caused by soil coke pollutants has been significantly reduced, the risk of exposure of the population has been greatly reduced, and the health situation has been significantly improved. At the same time, it has been proved that if the coal law is not implemented, the health hazard will be greatly increased. In the same way, if tujiao could be completely banned from the end of 1996, it would protect the health of more people. It can be seen that both legislation and law enforcement are very important for protecting the environment and health.
#5
Indoor air pollution and health hazards
In urban areas, indoor air pollution comes from the following sources. (1) Outdoor infiltration: indoor air and outdoor air are synchronous in the rise and fall, when the outdoor pollution is serious, pollutants will easily penetrate indoors, even if the doors and windows are closed in winter, it is inevitable; (2) cooking: even if natural gas is used for cooking, indoor air pollution will increase significantly in a short period of time. Smoking, incense burning, and other man-made activities such as cleaning and living can also contribute to indoor air pollution. In rural areas, the use of solid fuels (coal, fuelwood and straw) is a major source of indoor air pollution. Indoor pollution caused by the use of solid fuels is far more serious than other activities. Therefore, vigorous efforts should be made to clean cooking and clean heating.
In rural and urban areas, how to reduce indoor air pollution is a matter of great concern to us. In terms of health, indoor pollution is far more important than outdoor pollution. In smoggy weather, wearing a mask when going out and equipping an air purifier at home can effectively block the harm of pollution sources to the body. At the same time, relevant data show that the impact of living sources on air pollution is gradually increasing. Pollutants emitted by domestic sources enter the indoor air and partly into the outdoor air, while pollutants emitted by other sources enter the outdoor air directly. As a result, indoor air is more affected by sources of life. The average time Chinese adults spend indoors is about 86%, so indoor air has a greater impact on health. Considering the relationship between the source of life and indoor air, controlling the source of life is crucial to improving indoor air quality. Clean heating actions are very timely and should be vigorously promoted. In addition to clean heating, we also call for clean cooking. When the government is helping the poor and building beautiful rural areas, it should pay more attention to how to improve indoor air quality, especially the fuel structure of poor households.
In summary, it can be seen that the factors that lead to the decline in the degree of air pollution include socio-economic development, legislation and law enforcement, and emission reduction measures. Through the analysis of the above factors, it is hoped to provide a scientific basis for the government's policy decision to control pollution and reduce emissions.
Report finisher: Li Caige
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