The formation mechanism of air pollution episodes in Beijing city: Insights into the measured feedback between aerosol radiative forcing and the atmospheric boundary layer stability

Zhao, Dandan; Xin, Jinyuan; Gong, Chongshui; Quan, Jiannong; Liu, Guangjing; Zhao, Wenpeng; Wang, Yuesi; Liu, Zan; Song, Tao

doi:10.1016/j.scitotenv.2019.07.255

Cited by 57 publications

(23 citation statements)

References 55 publications

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“…This implied that a very stable lower layer defined as the nocturnal stable boundary layer (NSBL) had formed with an ABLH of ∼ 0.3 km. Due to the notable radiation effect of the already high aerosol loading during the daytime, the surface solar radiation was greatly blocked and reduced, which promoted stable stratification at midnight (Zhao et al, 2019;Zhong et al, 2017). In such a thermally stable state, the buoyancy transport heat flux in the atmosphere continuously consumes turbulent energy, suppressing the development of turbulence.…”

Section: B Extremely Stable Abl Structures Are a Prerequisite For Pomentioning

confidence: 99%

“…As no wet deposition process occurred, the Haze II diffusion stage was different from that of Haze I. Generally, the arrival of strong and clean air masses from the south is the main factor dissipating air pollution in Beijing (Zhong et al, 2017(Zhong et al, , 2018Zhao et al, 2019). Calm and light winds in the lower layer dominated during the outbreak stage, while sudden increased southeastern winds persisted in the 0-2 km layer after 08:00 LT on 27 July, with a wind speed of 6-9 m s −1 (Figs.…”

Section: The Diffusion Stagementioning

confidence: 99%

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Haze pollution under a high atmospheric oxidization capacity in summer in Beijing: insights into formation mechanism of atmospheric physicochemical processes

et al. 2020

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Abstract. Under a high atmospheric oxidization capacity, the synergistic effect of the physicochemical processes in the atmospheric boundary layer (ABL) caused summer haze pollution in Beijing. The southern and southwestern areas, generally 60–300 km away from Beijing, were seriously polluted in contrast to Beijing, which remained clean. Southerly winds moving faster than 20–30 km h−1 since the early morning primarily caused haze pollution initiation. The PM2.5 (particulate matter with a dynamic equivalent diameter smaller than 2.5 µm) level increased to 75 µg m−3 over several hours during the daytime, which was simultaneously affected by the ABL structure. Additionally, the O3 concentration was quite high during the daytime (250 µg m−3), corresponding to a high atmospheric oxidation capacity. Much sulfate and nitrate were produced through active atmospheric chemical processes, with sulfur oxidation ratios (SORs) up to ∼0.76 and nitrogen oxidation ratios (NORs) increasing from 0.09 to 0.26, which further facilitated particulate matter (PM) level enhancement. However, the increase in sulfate was mainly linked to southerly transport. At midnight, the PM2.5 concentration sharply increased from 75 to 150 µg m−3 over 4 h and remained at its highest level until the next morning. Under an extremely stable ABL structure, secondary aerosol formation dominated by nitrate was quite intense, driving the haze pollution outbreak. The PM levels in the southern and southeastern areas of Beijing were significantly lower than those in Beijing at this time, even below air quality standards; thus, the contribution of pollution transport had almost disappeared. With the formation of a nocturnal stable boundary layer (NSBL) at an altitude ranging from 0–0.3 km, the extremely low turbulence kinetic energy (TKE) ranging from 0 to 0.05 m2 s−2 inhibited the spread of particles and moisture, ultimately resulting in elevated near-surface PM2.5 and relative humidity (∼90 %) levels. Due to the very high humidity and ambient oxidization capacity, NOR rapidly increased from 0.26 to 0.60, and heterogeneous hydrolysis reactions at the moist particle surface were very notable. The nitrate concentration steeply increased from 11.6 to 57.8 µg m−3, while the sulfate and organics concentrations slightly increased by 6.1 and 3.1 µg m−3, respectively. With clean and strong winds passing through Beijing, the stable ABL dissipated with the potential temperature gradient becoming negative and the ABL height (ABLH) increasing to ∼2.5 km. The high turbulence activity with a TKE ranging from 3 to 5 m2 s−2 notably promoted pollution diffusion. The self-cleaning capacity of the atmosphere is commonly responsible for air pollution dispersion. However, reducing the atmospheric oxidization capacity, through strengthening collaborative control of nitrogen oxide (NOx) and volatile organic compounds (VOCs), as well as continuously deepening regional joint air pollution control, is urgent.

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Section: B Extremely Stable Abl Structures Are a Prerequisite For Pomentioning

confidence: 99%

Section: The Diffusion Stagementioning

confidence: 99%

Haze pollution under a high atmospheric oxidization capacity in summer in Beijing: insights into formation mechanism of atmospheric physicochemical processes

et al. 2020

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“…8n-m was formed with ABLH of ~0.3 km. By the strong radiation effect of already-existing high aerosol loading at daytime, the surface solar radiation could be strongly blocked and reduced, conducive to a stable stratification formed at midnight (Zhao et al, 2019;Zhong et al, 2017). In such a thermally stable state, the buoyancy transport heat flux in the atmosphere will continuously consume turbulent energy, suppressing the development of turbulence.…”

Section: A the Contribution Of Southerly Transport Was Almost Gonementioning

confidence: 99%

“…As no wet deposition process existed, the diffusion stage of Haze II was different from that of Haze I. Generally, the arrival of strong and clean air mass from the south is the main factor that dissipates the air pollution in Beijing (Zhong et al, 2017;Zhong et al, 2018;Zhao et al, 2019). Calm/light winds in the lower layer were dominated in the outbreak stage, while sudden increased southerly winds blew in the 0-2 km layer since 8:00 on the 27 th , with a wind speed of ~6-9 m s -1 (Fig.…”

Section: The Diffusion Stagementioning

confidence: 99%

The haze pollution under strong atmospheric oxidization capacity in summer in Beijing: Insights into the formation mechanism of atmospheric physicochemical process

Zhao¹,

Liu²,

Xin³

et al. 2020

Preprint

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Abstract. Under strong atmospheric oxidization capacity, haze pollution in the summer of Beijing was the result of the synergistic effect of physicochemical process in the atmospheric boundary layer (ABL). The south/southwest areas generally ~&#8201;60&#8211;300&#8201;km far away from Beijing were seriously polluted, in contrast to a clean situation in Beijing. The southerly winds moving more than ~&#8201;20&#8211;30&#8201;km&#8201;h&#8722;1 since early morning primarily caused the initiation of haze pollution. The PM2.5 level increased to 75&#8201;&#956;g&#8201;m&#8722;3 in several hours at daytime, which was simultaneously affected by the ABL structure. Additionally, the O3 concentration was quite high at daytime (250&#8201;&#956;g&#8201;m&#8722;3), corresponding to a strong atmospheric oxidation capacity. Numerous sulfate and nitrate were formed through active atmospheric chemical processes, with sulfur oxidation ratio (SOR) up to ~&#8201;0.76 and nitrogen oxidation ratio (NOR) increasing from 0.09 to 0.26, which further facilitated the particulate matter (PM) level rising. Even so, the increase in sulfate was mainly linked by southerly transport. At midnight, the PM2.5 concentration sharply increased from 75&#8201;&#956;g&#8201;m&#8722;3 to 150&#8201;&#956;g&#8201;m&#8722;3 in 4 hours and stayed the highest level till the next morning. With the premise of an extremely stable ABL structure, the formation of secondary aerosols dominated by nitrate was quite intense, driving the outbreak of haze pollution. PM levels in the south/southeast of Beijing were significantly lower than that in Beijing over this time, even below air quality standards, thus, the contribution of pollution transport was almost gone. With the formation of nocturnal stable boundary layer of 0&#8211;0.3&#8201;km altitude, the extremely low turbulence kinetic energy (TKE) of 0&#8211;0.05&#8201;m2&#8201;s&#8722;2 inhibited the spread of particles and moisture, ending up with elevated levels of PM2.5 and relative humidity (~&#8201;90&#8201;%) near the surface. Under quite high humidity and strong ambient oxidization capacity, the NOR rapidly increased from 0.26 to 0.60 and heterogeneous hydrolysis reactions at the moist particle surface were very significant. The nitrate concentration explosively increased from 11.6&#8201;&#956;g&#8201;m&#8722;3 to 57.8&#8201;&#956;g&#8201;m&#8722;3, while the concentrations of sulfate and organics slightly increased by 6.1&#8201;&#956;g&#8201;m&#8722;3 and 3.1&#8201;&#956;g&#8201;m&#8722;3, respectively. With clean & strong winds passing through Beijing, the stable ABL was broken with potential temperature gradient turning to negative and ABL heights increasing to ~&#8201;2.5&#8201;km. The strong turbulence activity with TKE of ~&#8201;3&#8211;5&#8201;m2&#8201;s&#8722;2 notably promoted the pollution diffusion. The self-cleaning capacity of the atmosphere is always responsible for the dispersion of air pollution. Even so, reducing atmospheric oxidization capacity such as strengthening the collaborative control of nitrogen oxide (NOx) and volatile organic compounds (VOCs) was urgent, as well as continuously deepening regional joint control of air pollution.

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“…The formation of HW needs to satisfy two basic conditions: the first is the source that can continuously transport sufficient PM to the atmosphere; the second is the meteorological conditions that are unfavorable to the diffusion and dilution of these PM and make them suspended at low altitude and near the ground, which can provide favorable conditions for the formation of secondary pollution sources and the interaction between chemical species with meteorology [35][36][37]. These two factors work together to bring about the concentration of these PM in the atmosphere reaches or exceeds the limit of the atmosphere self-purification capacity, thereby forming HW [38,39].…”

Section: Main Causes Of Hw Formationmentioning

confidence: 99%

Research Progress of HP Characteristics, Hazards, Control Technologies, and Measures in China after 2013

Wei

Wang

2019

Atmosphere

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In recent years, hazy weather (hazy weather (HW) has frequently invaded peoples’ lives in China, resulting in the disturbance of social operation, so it is urgent to resolve the haze pollution (HP) problem. A comprehensive understanding of HP is essential to further effectively alleviate or even eliminate it. In this study, HP characteristics in China, after 2013, were presented. It was found that the situation of HP is getting better year by year while it has been a pattern of high levels in the north and low levels in the south. In most regions of China, the contribution of a secondary source for HP is relatively large, and that of traffic is greater in the regions with rapid economic development. Hazards of HP were then summarized. Not only does HP cause harm to human health, but it also has effects on human production and quality of life, furthermore, property and atmospheric environment cannot be ignored. Next, the source and non-source control technologies of HP were first reviewed to recognize the weakness of HP control in China. This review provides more systematic information about HP problems and the future development directions of HP research were proposed to further effectively control HP in China.

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The formation mechanism of air pollution episodes in Beijing city: Insights into the measured feedback between aerosol radiative forcing and the atmospheric boundary layer stability

Cited by 57 publications

References 55 publications

Haze pollution under a high atmospheric oxidization capacity in summer in Beijing: insights into formation mechanism of atmospheric physicochemical processes

Haze pollution under a high atmospheric oxidization capacity in summer in Beijing: insights into formation mechanism of atmospheric physicochemical processes

The haze pollution under strong atmospheric oxidization capacity in summer in Beijing: Insights into the formation mechanism of atmospheric physicochemical process

Research Progress of HP Characteristics, Hazards, Control Technologies, and Measures in China after 2013

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