News Release 

On the causes of regional haze

Science China Press

The ravages of smog have caused concern about its causes. In terms of macroscopic causes, the "meteorological conditions", "combustion, industrial pollution", "influence around the city" and "atmospheric passage transportation" and other theories only give superficial or qualitative expressions. A recent study has given a quantitative theory of the physical and lumped chemical origin of secondary fine particles in haze. The paper entitled " The macroscopic mechanisms and associated atmospheric precursor environmental capacities that lead to secondary fine particle pollution" was Published in SCIENCE CHINA Earth Sciences recently. The authors were Xu Dahai and Chen Junming, researchers at the Chinese academy of meteorological sciences.

Currently, the management and control methods of secondary fine particles, the main components of haze, can be roughly divided into two categories in terms of academic knowledge: responsible source tracking and total emission control. The primary control of air pollution by the method of liability source tracing has achieved good results? however, due to the uncertainty of atmospheric flows and the complexity of pollution scenarios, it is very difficult to further accurately track the source of responsibility, and when the emission sources in some areas are treated with simplified tracing method, the problem of "one size fits all" is easy to appear.

Total emission control of air pollutants has long been an important control method. If the total allowable emissions are below the atmospheric capacity, the possibility of large-scale, high-intensity pollution is very small, but unfortunately the current definition of atmospheric capacity is not very clear. With defined atmospheric capacity as the total allowable emissions, the capacity determined by the baseline meteorological conditions, a given monitoring point, a specified list of sources and a simulation tool with chemical processes is related to the above four conditions, so its climate statistical characteristics are difficult to be objectively estimated. If the atmospheric capacity is thought to be determined by the ability of the atmosphere to remove pollutants from it, then the given capacity is only related to climate characteristics, and its statistical parameters can be easily determined. However, how to define the self-cleaning ability of the atmosphere and express the process of air pollution together with other characteristic parameters of air pollution, such as source intensity, concentration and polluting species, has not been an effective solution, thus limiting the development of this idea of air quality control. This paper solves this problem on the level of mechanism analysis.

In this paper, the researchers defined the atmospheric physical self-purification ability and the overall chemical conversion ability as the driving force, established the atmospheric chemical dynamics equations, theoretical analysis of the key factors forming secondary fine particles, and clarified the macro mechanism of each factor and its synergistic effect. The solution of the equations expresses the variation law of the concentration of secondary fine particles and their precursors under the action of atmospheric self-purification force and chemical transformation, and can also be used to calculate the atmospheric environmental capacity of the precursors forming secondary fine particles. The solution of the equation also reveals the dependence of the concentration of secondary fine particles on the size of the polluted area or urban built-up area. The irrational expansion of urban area will sharply reduce the atmospheric self-purification capacity per unit area, and lead to the sharp increase of secondary pollutants under the condition of quiet and small wind.

In addition, the paper gives the atmospheric environmental capacity of lumped precursors (including conventional pollutants SO2, NOx and NH3) with different recurrence periods in different regions by using the time-by-time records distributed in meteorological stations for 40 years and various relevant data collected at present. At the same time, the distribution of the clearance rate of precursors per unit area with different recurrence periods is given.

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This research result is of certain scientific significance and of great reference value for the formulation of air pollution control and environmental protection policies.

The research was supported by the science and technology development fund of Chinese academy of meteorological sciences (no. 2018KJ026).

See the article: Xu D, Chen J. 2019. The macroscopic mechanisms and associated atmospheric precursor environmental capacities that lead to secondary fine particle pollution. Science China Earth Sciences, 62, https://doi.org/10.1007/s11430-018-9378-1 http://engine.scichina.com/doi/10.1007/s11430-018-9378-1

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