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The increasingly serious surface ozone (O 3 ) pollution in North China Plain (NCP) has received wide attention. However, the contribution of the changes for each emission source to the elevated O 3 concentration, as well as the direct and indirect effect of meteorological condition variation on increased O 3 level have not been comprehensively analyzed. This study applied the Community Multiscale Air Quality (CMAQ) model coupled with the integrated source apportionment method (ISAM) to quantify changes in daily maximum 8-h average O 3 concentration (MDA8 O 3 ) under different air pollutants emissions and meteorological conditions during summertime 2012-2017. The results showed that incoordinate NOx/VOC emission control sustainably increased MDA8 O 3 by 2.2-36.2 μg/m 3 in the NCP, of which emission changes from industrial and transportation sectors were the predominant contributors (-0.6-19.5 μg/m 3 for industrial sector and 1.2-18.1 μg/m 3 for transportation, respectively). In contrast, MDA8 O 3 decreased by 2.5-9.2 μg/m 3 for the power plants. The effect of changes in meteorological condition on MDA8 O 3 exhibited significantly spatial and temporal variation and unfavorable meteorological fields were shown in 2014, 2016, and 2017, which enhanced MDA8 O 3 by -2.5-23.1, -5.3-20.7, and -7.2-25.8 μg/m 3 , respectively. In addition, the changed meteorological factors indirectly affected the biogenic emission thus prompting the increases of MDA8 O 3 by -3.9-4.9 μg/m 3 in the NCP during 2012-2017. The sensitive simulations suggested that more aggressive control measures about VOC reduction in industrial and transportation sectors should be implemented to further mitigate the O 3 pollution under unfavorable meteorological condition., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Oxygenated volatile organic compound (OVOC) emissions play a critical role in tropospheric ozone (O3) formation. This paper aims to establish an emission inventory and source profile database for OVOCs in Beijing, utilizing revised and reconstructed data from field measurements and existing literature. The study also assesses their potential impact on the O3 base on the ozone formation potential (OFP). Results indicate that OVOC emissions in Beijing predominantly originate from natural and residential sources, encompassing commercial solvent usage, cooking, residential combustion, construction adhesives, and construction coatings. OVOCs contributed 5.6% to OFP, which is significantly less than their emission contribution of 20.1%. Major OFP contributors include plant sources (26.2%), commercial solvent use (21.0%), cooking (20.5%), and construction adhesives (8.4%). The primary OVOC species contributing to OFP for OVOCs are acetaldehyde, methanol, hexanal, ethanol, and acetone, collectively contributing 59.0% of the total OFP. Natural sources exhibit significant seasonal variability, particularly in summer when plant emissions peak, constituting 78.9% of annual emissions and significantly impacting summer ozone pollution (OFP of 13,954 t). Conversely, emissions from other OVOC sources remain relatively stable year-round. Thus, strategies to mitigate summer ozone pollution in Beijing should prioritize plant sources while comprehensively addressing residential sources in other seasons. District-specific annual OVOC emissions are from Fangshan (3967 t), Changping (3958 t), Daxing (3853 t), and Chaoyang (3616 t), which reflect year-round forested areas in these regions and high populations. [ABSTRACT FROM AUTHOR]

Multiphase chemistry of chlorine is coupled into a 3D regional air quality model (CMAQv5.0.1) to investigate the impacts on the atmospheric oxidation capacity, ozone (O 3), as well as fine particulate matter (PM 2.5) and its major components over the Yangtze River Delta (YRD) region. The developed model has significantly improved the simulated hydrochloric acid (HCl), particulate chloride (PCl), and hydroxyl (OH) and hydroperoxyl (HO 2) radicals. O 3 is enhanced in the high chlorine emission regions by up to 4% and depleted in the rest of the region. PM 2.5 is enhanced by 2–6%, mostly due to the increases in PCl, ammonium, organic aerosols, and sulfate. Nitrate exhibits inhomogeneous variations, by up to 8% increase in Shanghai and 2–5% decrease in most of the domain. Radicals show different responses to the inclusion of the multiphase chlorine chemistry during the daytime and nighttime. Both OH and HO 2 are increased throughout the day, while nitrate radicals (NO 3) and organic peroxy radicals (RO 2) show an opposite pattern during the daytime and nighttime. Higher HCl and PCl emissions can further enhance the atmospheric oxidation capacity, O 3 , and PM 2.5. Therefore, the anthropogenic chlorine emission inventory must be carefully evaluated and constrained. [Display omitted] • Anthropogenic chlorine enhances O 3 and PM 2.5 in the Yangtze River Delta region by up to 4% and 6%, respectively. • Changes in the secondary pollutants were due to changes in the HO x and RO 2 radicals during the day and NO 3 radical at night. • Anthropogenic chlorine emissions were underestimated by a factor of 10 based on the observations in Taizhou. [ABSTRACT FROM AUTHOR]

Increasing ambient ozone pollution in China has caused widespread concern. It is necessary to strengthen ozone pollution control and promote PM 2.5 and ozone's coordinated management in China. This study assessed the PM 2.5 - and ozone-related health impacts of 100 major Chinese cities in fourteen seasons of 2017 (60 cities studied), 2018, 2019, and the first half of 2020. We found 6.68 × 107 disability-adjusted life years (DALYs) and 3.72 × 107 DALYs attributable to ambient PM 2.5 and ozone pollution in the 100 major cities. High PM 2.5 -related health impacts mostly appeared in winter and north, while high ozone-related mostly in summer and south. In the winter of 2019, the total PM 2.5 -related health impact of 100 major cities accounted for 98.67% of the sum of PM 2.5 - and ozone-related. The proportion in the summer of 2019 was only 23.15%. We also found a north-south differentiation of PM 2.5 - and ozone-related health impacts in spring and autumn. Taking the Yangtze River Basin as the dividing zone, PM 2.5 was generally the primary attribution of health impacts in the north in spring and autumn. To the south of the Yangtze River, ozone-related health impacts were generally dominant. The attempt to introduce seasonal population data in the health impact assessment provided a reference. Population movements relatively influenced the seasonal health impacts of developed urban agglomerations. The present study could help in the policy implementation of PM 2.5 - and ozone-related health risk prevention. [Display omitted] • PM 2.5 -related health impacts of China's major cities are assessed at the season-level. • Ozone-related health impacts of China's major cities are assessed at the season-level. • We attempt to introduce seasonal population data in health impact assessment. • We conduct a comparative analysis of health impacts at the season-city level. [ABSTRACT FROM AUTHOR]