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Harbin is a northmost megacity in the cold regions of China and experiences severe PM2.5 pollution. However, comprehensive investigations for severe haze formation are few. In this study, we simultaneously measured aerosol composition in real time to assess the sources apportionment, regional transport and its interaction with meteorology from 1 October 2018 to 1 May 2019 by using the single particle aerosol mass spectrometer (SPAMS). The daily average PM2.5 concentration was 51.21 µg/m3 with the hourly maximum of 900.45 µg/m3. Winter coal combustion was the largest source of PM2.5 aerosols during this period. Open straw burning from surrounding and adjacent areas by short-distance transport could aggravate air quality deterioration in Harbin. Three extreme haze events (i.e., Ep1, Ep2 and Ep3) were observed in this study, showing the typical characteristics of local winter pollution. The pollutants of PM2.5 and SO2 emitted from coal combustion played an important role in haze episode during Ep1, whereas Ep2 was caused by the joint effect of coal combustion and straw burning. Ep3 was characterized by long-distance transport of windblown dust from southeast Inner Mongolia and northwest Harbin. Real-time source apportionment of fine particulate matter highlights the importance of joint control of coal and straw burning from the surrounding cities of Harbin. [ABSTRACT FROM AUTHOR]

The "Joint Prevention and Control of Regional Air Pollution in China" has been put forward to solve serious regional air pollution. However, there is no geographical division covering the whole country that could reveal the similarities and differences among regions to support implementing this policy. This paper applied an air quality model and a multiregional input-output model to analyze the impacts and patterns of atmospheric transmission and trade transfer of regional air pollution, then compared the differences among typical provinces in the northern, central and southern regions. The social network analysis method was used to analyze the interacting pattern of regional atmospheric transmission and trade transfer, and 31 provinces in mainland China were divided into 5 clusters to reveal the interprovincial relationship of atmospheric transmission; then, the 31 provinces were divided into 3 clusters to reveal the interprovincial relationship of trade transfer. Based on these results, the provincial geographical division of "Nine Atmospheric Environmental Transmission Zones" covering mainland China was carried out. In addition, the key regions linking atmospheric transmission and trade transfer were also found. For example, Inner Mongolia is a typical key linkage region. From an atmospheric transmission perspective, it is linked to the northeast area. However, from a trade transfer perspective, it has a close relationship with the southern provinces. The linkage among provinces provides support for the interregional interaction mechanism of air pollution and the formulation of "Joint Prevention and Control of Regional Air Pollution in China". Image 1 • The impact of atmospheric and trade transfer on regional pollution were discussed. • The atmospheric transmission is location-sensitive and trade transfer is not. • The social network analysis was used in air atmospheric environmental zoning. • The 31 provinces were classified into 9 atmospheric environmental transmission zones. • There are four provinces being nodes connecting atmosphere and trade transfer. [ABSTRACT FROM AUTHOR]