Composited analyses of the chemical and physical characteristics of co-polluted days by ozone and PM<sub>2.5</sub> over 2013–2020 in the Beijing–Tianjin–Hebei region

Dai, Huibin; Liao, Hong; Li, Ke; Yue, Xu; Yang, Yang; Zhu, Jia; Jin, Jianbing; Li, Baojie; Jiang, Xingwen

doi:10.5194/acp-23-23-2023

Cited by 18 publications

(4 citation statements)

References 46 publications

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“…O 3 concentrations generally increased during 2014-2020, with a slower increasing rate after 2017, and the highest O 3 concentrations primarily occurred during summer in northern China, and during autumn or spring in southern China [56]. Moreover, co-polluted days by ozone (O 3 ) and PM 2.5 were frequently observed in the Beijing-Tianjin-Hebei (BTH) region in the North China Plain in the warm seasons (April-October) of 2013-2020 [57]. In summary, O 3 pollution, as well as PM 2.5 , has become the challenge of air pollution prevention and control in Chinese mega cities.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of Atmospheric Pollution in a Chinese Megacity: Insights from Three Different Functional Areas

Yang

Qiao

et al. 2023

Sustainability

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The most important atmospheric pollutants include PM2.5, PM10, SO2, NO2, CO and O3. Characteristics of atmospheric pollution were investigated by analyzing daily and hourly concentrations of the six key pollutants in three different functional areas (urban, suburban, and rural) of Shanghai during 2019–2021. Results show that O3, exceeding PM2.5, has become the primary pollutant determining air quality in Shanghai. The frequency of O3 as a primary pollutant ranged from 40% in an urban area to 71% in a rural area, which was much higher than that of PM2.5 (14–21%). NO2 and SO2, precursors of PM2.5, presented a clear weekend effect, whereas PM2.5 at weekends seems higher than that on weekdays. In the warm season, O3 at weekends was higher than that on weekdays in the three different functional areas, whereas no significant difference was observed between O3 on weekdays and at weekends in the cold season. Potential source contribution function analysis indicated that air pollution in Shanghai was impacted by inter-regional and intra-regional transport. The potential source areas of PM2.5 and O3 were different, which brought challenges to the coordinated control of PM2.5 and O3 in Shanghai. This study emphasizes the prominent O3 pollution in Shanghai, and argues that the prevention and control of O3 pollution requires regional joint prevention and control strategy.

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Section: Discussionmentioning

confidence: 99%

Characteristics of Atmospheric Pollution in a Chinese Megacity: Insights from Three Different Functional Areas

Yang

Qiao

et al. 2023

Sustainability

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“…We also see that both high daytime and nighttime ozone concentrations are linked to high PBLH. High PBLH is typically coincident with high air temperature that favors ozone chemical production in NOx-rich environment (Fu and Tian, 2019;Lu et al, 2019a), and also features vigorous atmosphere turbulence that enhances the vertical mixing of ozone (Dai et al, 2023), allowing ozone-rich air at higher altitudes to mix with air in the lower boundary layer.…”

Section: Nighttime Ozone In the Residual Layer And Affecting Factorsmentioning

confidence: 99%

Nighttime ozone in the lower boundary layer and its influences on surface ozone: insights from 3-year tower-based measurements in South China and regional air quality modeling

Wang

et al. 2023

Preprint

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Abstract. Nighttime ozone in the lower boundary layer regulates atmospheric chemistry and surface ozone air quality, but our understanding of its vertical structure and impact is largely limited by the extreme sparsity of direct measurements. Here we present 3-year (2017–2019) measurements of ozone in the lower boundary layer (up to 500 m) from the Canton Tower at Guangzhou, the core megacity in South China, and interpret the measurements with a one-month high-resolution chemical simulation from the Community Multiscale Air Quality (CMAQ) model. Measurements are available at 10 m, 118 m, 168 m, and 488 m, with the highest 488 m measurement platform higher than the typical height of nighttime stable boundary layer that allows direct measurements of ozone in the nighttime residual layer (RL). We find that ozone increases with altitude in the lower boundary layer throughout the day, with nighttime (daytime) ozone at the 488 m height being 2.4–5.4 (1.5–2.4) times as that at the 10 m height. This indicates a persistent high ozone level and oxidation capacity aloft the surface. The ozone vertical gradient between the 10 m and 488 m height (∆O3/∆H10–488 m) is 3.6–6.4 ppbv/hm in nighttime and 4.4–5.8 ppbv/hm daytime. We identify a strong ozone residual capacity, defined as the ratio of the ozone concentration averaged over nighttime to that in the afternoon (14:00–17:00 LT), of 67 %–90 % in January, April and October, remarkably higher than that in the other three layers (29 %–51 %). Ozone in the afternoon convective mixing layer provides the source of ozone in the RL, and strong temperature inversion facilitates the ability of RL to store ozone from the daytime convective mixing layer, by constraining the exchange of RL ozone with ozone inside the nocturnal stable boundary layer that is subject to strong chemical destruction and deposition. The tower-based measurement also indicates that nighttime surface Ox (Ox=O3+NO2) level can be an effective indicator of RL ozone if direct measurement is not available. We further find significant influences of nocturnal RL ozone on both nighttime and the following day’s daytime surface ozone air quality. During the surface nighttime ozone enhancement (NOE) event, we observe significant decrease in ozone and increase in NO2 and CO at the 488 m height, in contrast to their changes at the surface, a typical feature of enhanced vertical mixing. The enhanced vertical mixing leads to NOE event by introducing ozone-rich air in the RL to enter the nighttime stable boundary layer and weakens the titration effect by diluting NOx concentrations. The CMAQ model simulations also demonstrate enhanced positive contribution of vertical diffusion (ΔVDIF) to ozone at the 10 m and 118 m and negative contribution at the 168 m and 488 m during the NOE event. We also observe strong correlation between nighttime RL ozone and the following day’s surface MDA8 ozone. This is tied to enhanced vertical mixing with the collapse of nighttime RL and the development of convective mixing layer, which is supported by the CMAQ simulated increase in positive ΔVDIF of +50 ppbv·hr−1 at the 10 m and negative ΔVDIF of -10 ppbv·hr−1 at 488 m at early morning (08:00–09:00 LT), suggesting that the mixing of ozone-rich air from nighttime RL downward to surface via the entrainment is an important mechanism to aggravate ozone pollution in the following day. We find that the bias of CMAQ simulated surface MDA8 ozone in the following day shows a strong correlation coefficient (r=0.74) with the bias in nighttime ozone in the RL, highlighting the necessity to correct air quality model bias in the nighttime RL ozone for accurate prediction of daytime ozone. Our study thus highlights the value of long-term tower-based measurements for understanding the coupling between nighttime ozone in the RL, surface ozone air quality, and boundary layer dynamics.

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“…Air pollution is a global environmental concern that can pose substantial adverse impacts on climate change and human health. − In China, severe PM 2.5 pollution has been considerably alleviated due to rigorous emission control measures but remains a significant concern. − This is especially evident in the North China Plain (NCP), where severe PM 2.5 pollution events continue to occur frequently. − Additionally, O 3 levels have continued to show a steady upward trend on a global scale in recent years, gradually replacing PM 2.5 as the most important air pollutant. − The frequent occurrence of double-high level pollution events, where both PM 2.5 and O 3 concentrations exceeded the national air quality standards simultaneously, have been observed in the NCP. − Hence, there is an urgent need to address such pollution issues by reducing both PM 2.5 and O 3 pollution synergistically.…”

Section: Introductionmentioning

confidence: 99%

Unexpected Trade-Offs of Fossil Fuel Reduction on PM_2.5 and O₃ Pollution Regulation Can Be Offset by Synergistic Control of VOCs Source

Shi,

Yu,

et al. 2024

ACS EST Air

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Particulate matter (PM2.5) and ozone (O3) are typical air pollutants that require effective simultaneous control. Current PM2.5 and O3 co-mitigation strategies are primarily focused on the emission optimization of nitrogen oxides (NO x ) and volatile organic compounds (VOCs); however, fundamental mechanisms underlying these co-mitigation efforts remain largely unanswered. Here, utilizing an atmospheric chemistry model combined with machine learning technique, we extend the scope of coordinated control efforts beyond just precursors by identifying and controlling common sources of PM2.5 and O3, which are fossil fuel combustion sources including coal combustion, industrial emission, and vehicle exhausts. We conducted further sensitivity simulations and found that reducing fossil fuel combustion emissions significantly lowers PM2.5 levels but has trade-off effects on O3 control, which is attributable to the suppressed aerosol sink of hydroperoxyl radicals and the enhanced atmospheric oxidizing capacity. Furthermore, this unexpected enhancement of O3 can be offset by synergistically controlling certain other specific VOCs sources. For example, during days with high levels of both PM2.5 and O3 pollution, a 40% reduction of VOCs sources at the corresponding level of coal combustion reduction is predicted to lead to an ∼13 ppb (∼14%) reduction in O3 concentration. Our results provide the scientific evidence and theoretical framework for mitigating PM2.5 and O3 pollution through joint control of fossil fuel combustion sources and specific VOCs sources.

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Composited analyses of the chemical and physical characteristics of co-polluted days by ozone and PM_2.5 over 2013–2020 in the Beijing–Tianjin–Hebei region

Cited by 18 publications

References 46 publications

Characteristics of Atmospheric Pollution in a Chinese Megacity: Insights from Three Different Functional Areas

Characteristics of Atmospheric Pollution in a Chinese Megacity: Insights from Three Different Functional Areas

Nighttime ozone in the lower boundary layer and its influences on surface ozone: insights from 3-year tower-based measurements in South China and regional air quality modeling

Unexpected Trade-Offs of Fossil Fuel Reduction on PM_2.5 and O₃ Pollution Regulation Can Be Offset by Synergistic Control of VOCs Source

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Composited analyses of the chemical and physical characteristics of co-polluted days by ozone and PM2.5 over 2013–2020 in the Beijing–Tianjin–Hebei region

Cited by 18 publications

References 46 publications

Characteristics of Atmospheric Pollution in a Chinese Megacity: Insights from Three Different Functional Areas

Characteristics of Atmospheric Pollution in a Chinese Megacity: Insights from Three Different Functional Areas

Nighttime ozone in the lower boundary layer and its influences on surface ozone: insights from 3-year tower-based measurements in South China and regional air quality modeling

Unexpected Trade-Offs of Fossil Fuel Reduction on PM2.5 and O3 Pollution Regulation Can Be Offset by Synergistic Control of VOCs Source

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Composited analyses of the chemical and physical characteristics of co-polluted days by ozone and PM_2.5 over 2013–2020 in the Beijing–Tianjin–Hebei region

Unexpected Trade-Offs of Fossil Fuel Reduction on PM_2.5 and O₃ Pollution Regulation Can Be Offset by Synergistic Control of VOCs Source