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Simultaneous measurements of atmospheric volatile organic compounds (VOCs), conventional gases and meteorological parameters were performed at an urban site in Jinan, East China, in June 2021 to explore the formation and evolution mechanisms of summertime ozone (O3) pollution events. O3 Episode Ⅰ, O3 Episode II, and non-O3 episodes were identified based on the China Ambient Air Quality Standards and the differences in precursor concentrations. The O3 concentrations in Episode I and Episode II were 145.4 μg/m3 and 166.4 μg/m3, respectively, which were significantly higher than that in non-O3 episode (90 μg/m3). For O3 precursors, VOCs and NOx concentrations increased by 48% and 34% in Episode I, and decreased by 21% and 27% in Episode II compared to non-O3 episode days. The analysis of the m,p-xylene to ethylbenzene ratio (X/E) and OH exposure demonstrated that the aging of the air masses in Episode II was significantly higher than the other two episodes, and the differences could not be explained by localized photochemical consumption. Therefore, we speculate that the high O3 concentrations in Episode II were driven by the regional transport of O3 and its precursors. Backward trajectory simulations indicated that the air masses during Episode II were concentrated from the south. In contrast, the combination of high precursor concentrations and favorable meteorological conditions (high temperatures and low humidity) led to an excess of O3 in Episode I. Positive matrix factorization (PMF) model results indicated that increased emissions from combustion and gasoline vehicle exhausts contributed to the elevated concentrations of VOCs in Episode I, and solvent usage may be an important contributor to O3 formation. The results of this study emphasize the importance of strengthening regional joint control of O3 and its precursors with neighboring cities, especially in the south, which is crucial for Jinan to mitigate O3 pollution. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) undergo substantial photochemical losses during their transport from emission sources to receptor sites, resulting in serious implications for their source apportionment and ozone (O 3) formation. Based on the continuous measurements of VOCs in suburban Jinan in August 2022, the effects of photochemical losses on VOC source contributions and O 3 formation were evaluated in this study. The observed and initial concentrations of total VOCs (TVOC) were 12.0 ± 5.1 and 16.0 ± 7.4 ppbv, respectively. Throughout the observation period, alkenes had the most prominent photochemical losses (58.2%), followed by aromatic hydrocarbons (23.1%), accounting for 80.6% and 6.9% of the total losses, respectively. During high O 3 episodes, the photochemical loss of VOCs was 6.9 times higher than that during the cleaning period. Alkene losses (exceeding 67.3%), specifically losses of isoprene, propylene, ethylene, and n-butene, dominated the total losses of VOCs during the O 3 increase period. Eight sources of VOCs were identified by positive matrix factorization (PMF) based on the observed and initial concentration data (OC-PMF and IC-PMF, respectively). Concentrations of all emission sources in the OC-PMF were underestimated by 2.4%–57.1%. Moreover, the contribution of each emission source was over- or underestimated compared with that in case of the IC-PMF. The contributions of biogenic and motor vehicle exhaust emissions were underestimated by 5.3 and 2.8 percentage points, respectively, which was associated with substantial oxidation of the emitted high-reactive species. The contributions of coal/biomass burning and natural gas were overestimated by 2.4 and 3.9 percentage points, respectively, which were related to the emission of low-reactive species (acetylene, ethane, and propane). Based on our results, the photochemical losses of VOCs grossly affect their source apportionment and O 3 formation. Thus, photochemical losses of VOCs must be thoroughly accounted to establish a precise scientific foundation for air-pollution control strategies. [Display omitted] • Photochemical losses contributed 58.2% of initial alkenes and 23.1% of initial aromatics. • Photochemical loss of VOCs during high ozone period was 6.9 times higher than that during cleaning period. • Source apportionment based on measured VOCs might lead to biased conclusions. [ABSTRACT FROM AUTHOR]

Based on the continuous online measurements of volatile organic compounds (VOCs) at a suburban site in Jinan, Shandong province in the wintertime of 2021, characteristics, chemical transformations and sources of VOCs were analyzed. The total mixing ratio of VOCs was 30.35 ± 19.9 ppbv, with alkanes being the most abundant species. Alkenes and aromatics were the major contributors to the hydroxyl radical loss rate (L OH) and the ozone formation potential (OFP), accounting for 44.9% and 32.7% to L OH , and 43.2% and 33.4% to OFP, respectively. Aromatics had the primary contribution (98.1%) to the secondary organic aerosol potential (SOAP), and the high correlation between SOAP and PM 2.5 concentrations (R = 0.70) suggested that VOCs were critical precursors of PM 2.5. Coal/biomass burning and motor vehicle emissions were the main sources of VOCs (24.6% and 23.8%, respectively), followed by petrochemical and fuel evaporation (19.9%), industrial sources (16.9%), and liquefied petroleum gas/natural gas use (14.8%). Backward trajectories and the potential source contribution function (PSCF) analysis results suggested that short-range transport from the southeast was the primary potential source of VOC concentrations in suburban Jinan. The results can provide theoretical support for local governments to develop VOC emission control strategies in suburban areas. • Daytime VOCs were significantly influenced by strong localized emissions. • SOAP of VOCs and PM 2.5 were highly correlated. • Coal/biomass burning and vehicle emissions were the most significant sources of VOCs. • Short-distance transport from the southeast was important for VOCs control. [ABSTRACT FROM AUTHOR]