Atmos. Chem. Phys., 20, 5355–5372, 2020 https://doi.org/10.5194/acp-20-5355-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Exploring wintertime regional haze in northeast China: role of coal and biomass burning Jian Zhang1, Lei Liu1, Liang Xu1, Qiuhan Lin1, Hujia Zhao2, Zhibin Wang3, Song Guo4, Min Hu4, Dantong Liu1, Zongbo Shi5, Dao Huang1, and Weijun Li1 1Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou, 310027, China 2Institute of Atmospheric Environment, China Meteorological Administration, Shenyang, 110016, China 3Research Center for Air Pollution and Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China 4State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China 5School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK Correspondence: Weijun Li ([email protected]) Received: 6 November 2019 – Discussion started: 8 January 2020 Revised: 18 March 2020 – Accepted: 1 April 2020 – Published: 7 May 2020 Abstract. As one of the intense anthropogenic emission 223 µg m−3) with predominantly OM (98–133 µg m−3) and regions across the relatively high-latitude ( > 40◦ N) areas unexpectedly high KC (3.8 µg m−3). TEM also showed that on Earth, northeast China faces the serious problem of re- K-rich particles internally mixed with OM (named K-OM) gional haze during the heating period of the year. Aerosols increased from 4 %–5 % by number to 50 %–52 %. The re- in polluted haze in northeast China are poorly understood sults indicate that there were different sources of aerosol compared with the haze in other regions of China such as particles causing the Haze-I and Haze-II formation: Haze-I the North China Plain. Here, we integrated bulk chemi- was mainly induced by accumulation of primary OM emitted cal measurements with single-particle analysis from trans- from residential coal burning and further deteriorated by sec- mission electron microscopy (TEM), nanoscale secondary ondary aerosol formation via heterogeneous reactions; Haze- ion mass spectrometry (NanoSIMS), and atomic force mi- II was caused by long-range transport of agricultural biomass croscopy (AFM) to obtain morphology, size, composition, burning emissions. Moreover, abundant primary OM parti- aging process, and sources of aerosol particles collected dur- cles emitted from coal and biomass burning were considered ing two contrasting regional haze events (Haze-I and Haze- to be one typical brown carbon, i.e., tar balls. Our study high- II) at an urban site and a mountain site in northeast China lights that large numbers of light-absorbing tar balls signifi- and further investigated the causes of regional haze forma- cantly contribute to winter haze formation in northeast China tion. Haze-I evolved from moderate (average PM2:5: 76– and they should be further considered in climate models. 108 µg m−3) to heavy pollution (151–154 µg m−3), with the dominant PM2:5 component changing from organic mat- ter (OM) (39–45 µg m−3) to secondary inorganic ions (94– 101 µg m−3). Similarly, TEM observations showed that S- 1 Introduction rich particles internally mixed with OM (named S-OM) in- creased from 29 % to 60 % by number at an urban site and Haze pollution is mainly caused by high levels of fine partic- 64 % to 74 % at a mountain site from the moderate Haze- ulate matter (PM2:5), and it has spread widely over the globe I to heavy Haze-I events, and 75 %–96 % of Haze-I parti- to places such as Mexico City (Adachi and Buseck, 2008), cles included primary OM. We found that change of wind Paris, France (Fortems – Cheiney et al., 2016), north India direction caused Haze-I to rapidly turn into Haze-II (185– (Chowdhury et al., 2019), north China (Huang et al., 2014), and the Arctic (Frossard et al., 2011). In the past 20 years, Published by Copernicus Publications on behalf of the European Geosciences Union. 5356 J. Zhang et al.: Exploring wintertime regional haze regional haze events with high concentrations of PM2:5 have under high relative humidity (RH) mainly elevates haze lev- frequently occurred in China following rapid economic de- els and causes regional hazes (X. Li et al., 2019; Y. Liu et al., velopment. Various studies on regional haze in China have 2017; G. Wang et al., 2016; Xing et al., 2019). The two-way been conducted by many scientists (e.g., Bennartz et al., feedback between accumulation of air pollutants and depres- 2011; Guo et al., 2014; Li and Shao, 2009; Lin et al., 2017; sion of the atmospheric boundary layer also aggravate haze M. Liu et al., 2017; Ren et al., 2016; Shi et al., 2017; Zhang et pollution (Wang et al., 2014; Zhong et al., 2019). Moreover, al., 2018b). Current hot issues on haze pollution concentrate regional transport of air pollutants is one of the important on the formation processes of regional haze in various atmo- factors for the long duration of regional haze (Li et al., 2015; spheric environments and their potential optical and health Tao et al., 2014; G. J. Zheng et al., 2015). These studies re- influences (J. Chen et al., 2017; Gao et al., 2017). vealed formation mechanisms of regional winter hazes in the Many of these studies reported that haze particles can ad- NCP well. versely affect human health, ecological environments, and Among different regions or cities in China, the haze for- regional climate (Ding et al., 2016; Huang et al., 2013; mation mechanisms would most likely differ due to different Lelieveld et al., 2015; W. Li et al., 2017; Liu et al., 2019, emissions and meteorological conditions (M. Li et al., 2019; 2016; Mahowald et al., 2018; Shi et al., 2019; Xie et Zhang et al., 2017; G. J. Zheng et al., 2015). The air quality al., 2019; Zhang et al., 2013). For example, exposure to in northeast China, a region with a long heating period (mid- high levels of ambient PM2:5 cause or contribute to a va- October to mid-April), is mainly influenced by abundant in- riety of human diseases (e.g., stroke, ischemic heart dis- efficient combustion activities (e.g., coal and biomass burn- ease, chronic obstructive pulmonary disease, and lung can- ing in residential stoves and coal burning in small boilers for cer) (Chen et al., 2019; Liu et al., 2016) and lead to ∼ household heating and cooking) (Yang et al., 2017; Zhang et 1:3 million premature deaths per year in China (Lelieveld et al., 2017). Extremely high concentrations of organic aerosols al., 2015). Abundant anthropogenic metal, ammonium, and have been observed in northeast China during winter haze phosphorus-containing particles are transported into remote that coincides with crop growing and harvest periods (Cao et regions of oceans, where they promote plankton growth and al., 2017; Chen et al., 2015; Zhang et al., 2017). Because of further influence ocean ecology (W. Li et al., 2017; Ma- the influences of the regional haze in winter, annual aerosol howald et al., 2018; Shi et al., 2019). High concentrations optical depth in urban areas was ∼ 3:7 times higher than that of fine aerosols suspended in haze layers not only influence in rural areas in northeast China (H. Zhao et al., 2018). In regional climate through absorbing (e.g., black carbon (BC) the past 5 years, some studies have focused on the physic- and brown carbon (BrC)) and scattering (e.g., sulfates and ochemical properties of haze particles collected in northeast nitrates) solar radiation (Huang et al., 2013; Liu et al., 2019; China (Cao et al., 2017; Chen et al., 2015; X. Li et al., 2017; Xie et al., 2019), but also depress the planetary boundary Miao et al., 2018; Zhang et al., 2017; H. Zhao et al., 2018). layer development (Ding et al., 2016; Z. Li et al., 2017; However, studies on regional haze evolution and haze for- Zhang et al., 2013) and reduce crop yields (Tie et al., 2016) in mation mechanisms in northeast China are rare. This limited China. Therefore, understanding haze formation mechanisms information precludes the comparison of regional hazes in and sources of haze particles in different regions of China is northeast China with other regions in China. Furthermore, it crucial to provide feasible control strategies for reducing re- is difficult to adopt some reasonable regional haze pollution gional PM2:5 concentration and protecting ecosystems. control strategies from the NCP to apply to the air pollution In China, regional heavy haze events frequently occur in northeast China. in the North China Plain (NCP) (Zhao et al., 2013) and Northeast China is only one intense anthropogenic emis- northeast China (Ma et al., 2018) during winter. In the past sion region in addition to Mongolia across the relatively decades, the regional haze formation mechanisms in the NCP high-latitude (> 40◦ N) areas on Earth (van Donkelaar et al., have been intensely investigated (S. Chen et al., 2017; Cheng 2016). This region is significantly influenced by the Siberian et al., 2016; Li et al., 2015; Y. Liu et al., 2017; Tao et al., cold, high-pressure systems in winter. The Siberian anticy- 2014; Tian et al., 2015; G. Wang et al., 2016, 2019, 2014; clone transports air pollutants from northeast China to South Xing et al., 2019; G. J. Zheng et al., 2015; Zhong et al., Korea, Japan, and even the Arctic and further exerts large- 2019). Adverse meteorological conditions (e.g., low wind scale influence in the global climate (Jung et al., 2015; Rodo speeds and stable atmospheric boundary layer) can induce et al., 2014; Sobhani et al., 2018; Zhang et al., 2016).