Vertically resolved characteristics of air pollution during two severe winter haze episodes in urban Beijing, China

Wang, Qingqing; Sun, Yele; Xu, Weiqi; Du, Wei; Zhou, Libo; Tang, Guiqian; Chen, Chen; Cheng, Xueling; Zhao, Xueyan; Ji, Dongsheng; Han, Tingting; Wang, Zhe; Li, Jie; Wang, Zifa

doi:10.5194/acp-18-2495-2018

Cited by 83 publications

(55 citation statements)

References 66 publications

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“…As demonstrated by Li et al (2011), the probability of O 3 peaks greater than 120 ppbv increased dramatically with the removal of aerosol from their simulations, and the response of OH concentrations was shown to be roughly proportional to changes in J [O 1 D]. Therefore, under the recent reductions in PM 2.5 in Beijing through emissions controls implemented as part of China's clean-air plans (Wang et al, 2015;Liu et al, 2016), the resultant increases in J [O 1 D] could lead to enhanced O 3 concentrations, where summer levels are already very high (Wang et al, 2006;Xue et al, 2014;Ni et al, 2018). Enhanced near-surface photolysis rates would also increase NO 2 photolysis and enhance levels of NO, which sub- sequently react with RO 2 , leading to a rise in O 3 production.…”

Section: Photochemical Impacts Of Haze Pollution and Implications Formentioning

confidence: 97%

Photochemical impacts of haze pollution in an urban environment

et al. 2019

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Abstract. Rapid economic growth in China over the past 30 years has resulted in significant increases in the concentrations of small particulates (PM2.5) over the city of Beijing. In addition to health problems, high aerosol loading can impact visibility and thus reduce photolysis rates over the city, leading to potential implications for photochemistry. Photolysis rates are highly sensitive not only to the vertical distribution of aerosols but also to their composition, as this can impact how the incoming solar radiation is scattered or absorbed. This study, for the first time, uses aerosol composition measurements and lidar optical depth to drive the Fast-JX photolysis scheme and quantify the photochemical impacts of different aerosol species during the Air Pollution and Human Health (APHH) measurement campaigns in Beijing in November–December 2016 and May–June 2017. This work demonstrates that severe haze pollution events (PM2.5 > 75 µg m−3) occur during both winter and summer, leading to reductions in O3 photolysis rates of 27 %–34 % (greatest in winter) and reductions in NO2 photolysis of 40 %–66 % (greatest in summer) at the surface. It also shows that in spite of much lower PM2.5 concentrations in the summer months, the absolute changes in photolysis rates are larger for both O3 and NO2. In the winter, absorbing species such as black carbon dominate the photolysis response to aerosols, leading to mean reductions in J[O1D] and J[NO2] in the lowest 1 km of 24 % and 23 %, respectively. In contrast, in the summer, scattering aerosol such as organic matter dominate the response, leading to mean decreases of 2 %–3 % at the surface and increases of 8 %–10 % at higher altitudes (3–4 km). During these haze events in both campaigns, the influence of aerosol on photolysis rates dominates over that from clouds. These large impacts on photochemistry can have significant implications for concentrations of important atmospheric oxidants such as the hydroxyl radical. Idealized photochemical box model studies show that such large impacts on photochemistry could lead to a 12 % reduction in surface O3 (3 % for OH) due to haze pollution. This highlights that PM2.5 mitigation strategies could have important implications for the oxidation capacity of the atmosphere both at the surface and in the free troposphere.

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Section: Photochemical Impacts Of Haze Pollution and Implications Formentioning

confidence: 97%

Photochemical impacts of haze pollution in an urban environment

et al. 2019

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“…For example, Wu et al 2015 , and OC increased with height. The 325-m meteorological tower in Beijing has been used to study the vertical distribution of PM 2.5 (Sun et al 2013;Wang et al 2018b;Zhou et al 2018), and the Amazon Tall Tower Observatory (ATTO) has proven useful for studying atmospheric composition and physical properties (Andreae et al 2015). Finally, long-term studies have been undertaken using the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia (Chi et al 2013).…”

Section: The Advantage Of Meteorological Masts Over Other Tower Typesmentioning

confidence: 99%

“…Xie et al (2019) studied the light absorption vertical profile in Beijing during winter using the Beijing meteorological mast. Wang et al (2018b) found that constant BC profiles accounted for 37% of all profiles during winter haze episodes in Beijing. Recent studies have suggested that the interactions between BC and the boundary layer can cause a "dome effect" that leads to air pollutant accumulation (Wendisch et al 2008;Ding et al 2016).…”

Section: Introductionmentioning

confidence: 96%

Time-resolved black carbon aerosol vertical distribution measurements using a 356-m meteorological tower in Shenzhen

Sun

et al. 2020

Theor Appl Climatol

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Black carbon (BC) is an essential climate forcer in the atmosphere. Large uncertainties remain in BC's radiative forcing estimation by models, partially due to the limited measurements of BC vertical distributions near the surface layer. We conducted time-resolved vertical profiling of BC using a 356-m meteorological tower in Shenzhen, China. Five micro-aethalometers were deployed at different heights (2, 50, 100, 200, and 350 m) to explore the temporal dynamics of BC vertical profile in the highly urbanized areas. During the observation period (December 6-15, 2017), the average equivalent BC (eBC) concentrations were 6.6 ± 3.6, 5.4 ± 3.3, 5.9 ± 2.8, 5.2 ± 1.8, and 4.9 ± 1.4 μg m −3 , from 2 to 350 m, respectively. eBC temporal variations at different heights were well correlated. eBC concentrations generally decreased with height. At all five heights, eBC diurnal variations exhibited a bimodal pattern, with peaks appearing at 09:00-10:00 and 19:00-21:00. The magnitudes of these diurnal peaks decreased with height, and the decrease was more pronounced for the evening peak. eBC episodes were largely initiated by low wind speeds, implying that wind speed played a key role in the observed eBC concentrations. eBC wind-rose analysis suggested that elevated eBC events at different heights originate from different directions, which suggested contributions from local primary emission plumes. Air masses from central China exhibited much higher eBC levels than the other three backward trajectory clusters found herein. The absorption Ångström exponent (AAE 375-880) showed clear diurnal variations at 350 m and increased slightly with height.

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“…Beijing have shown that aerosol properties between these heights can significantly differ, depending on meteorological conditions (Du et al, 2017;Wang et al, 2018). This indicates that ML in Beijing is not always well-mixed, which may cause us to over-or underestimate particle emissions, depending on the structure of boundary layer and the height of the particle sources.…”

Section: Mixing Of Boundary Layermentioning

confidence: 99%

Size-resolved particle number emissions in Beijing determined from measured particle size distributions

Kontkanen¹,

Deng²,

Fu³

et al. 2020

Preprint

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Abstract. The climate and air quality effects of aerosol particles depend on the number and size of the particles. In urban environments, a large fraction of aerosol particles originates from anthropogenic emissions. To evaluate the effects of different pollution sources on air quality, knowledge of size distributions of particle number emissions is needed. Here we introduce a novel method for determining size-resolved particle number emissions based on measured particle size distributions. We apply our method to data measured in Beijing, China, to determine the number size distribution of emitted particles in diameter range from 2 to 1000 nm. The observed particle number emissions are dominated by emissions of particles smaller than 30 nm. Our results suggest that traffic is the major source of particle number emissions with the highest emissions observed for particles around 10 nm during rush hours. At sizes below 6 nm, clustering of atmospheric vapors contributes to calculated emissions. The comparison between our calculated emissions and those estimated with an integrated assessment model GAINS shows that our method yields clearly higher particle emissions at sizes below 60 nm, but at sizes above that the two methods agree well. Overall, our method is proven to be a useful tool for gaining new knowledge of size distributions of particle number emissions in urban environments.

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Vertically resolved characteristics of air pollution during two severe winter haze episodes in urban Beijing, China

Cited by 83 publications

References 66 publications

Photochemical impacts of haze pollution in an urban environment

Photochemical impacts of haze pollution in an urban environment

Time-resolved black carbon aerosol vertical distribution measurements using a 356-m meteorological tower in Shenzhen

Size-resolved particle number emissions in Beijing determined from measured particle size distributions

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