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1. Examining the Summertime Ozone Formation Regime in Southeast Michigan Using MOOSE Ground-Based HCHO/NO2 Measurements and F0AM Box Model

   Huang, Y; Xiong, Y; Chai, JC; Mao, H; Mariscal, N; Yacovitch, TI; Lerner, BM; Majluf, F; Canagaratna, MR; Olaguer, EP (December 2023, American Geophysical Union)

   The summertime surface ozone (O3) concentrations over Southeast Michigan (SEMI) often exceed 70 ppbv. However, the associated O3 formation regime is still not well known. In this study, we examined the chemical drivers of O3 exceedances in SEMI, based on the Michigan-Ontario Ozone Source Experiment (MOOSE) field campaign during the period of May 20 – June 30, 2021. We employed a zero-dimensional (0-D) box model, which was constrained by measurements of meteorology and trace gas concentrations during MOOSE. Our model simulations demonstrated that the formaldehyde to nitrogen dioxide ratio (HCHO/NO2) for the transition between the VOC- and NOx-limited O3 production regimes was 3.0 ± 0.3 (mean ± 1σ) in SEMI. The midday (12:00-16:00) averaged HCHO/NO2 ratio during MOOSE was 1.62 ± 1.03, suggesting that O3 production in SEMI was likely limited by VOC emissions. Our study has significant implications for air quality policy and the design of effective O3 pollution control strategies through ground-based HCHO/NO2 measurements and model simulations. 

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2. The Michigan–Ontario Ozone Source Experiment (MOOSE): An Overview

   https://doi.org/10.3390/atmos14111630  

   Olaguer, Eduardo P; Su, Yushan; Stroud, Craig A; Healy, Robert M; Batterman, Stuart A; Yacovitch, Tara I; Chai, Jiajue; Huang, Yaoxian; Parsons, Matthew T (November 2023, Atmosphere)

   The Michigan–Ontario Ozone Source Experiment (MOOSE) is an international air quality field study that took place at the US–Canada Border region in the ozone seasons of 2021 and 2022. MOOSE addressed binational air quality issues stemming from lake breeze phenomena and transboundary transport, as well as local emissions in southeast Michigan and southern Ontario. State-of-the-art scientific techniques applied during MOOSE included the use of multiple advanced mobile laboratories equipped with real-time instrumentation; high-resolution meteorological and air quality models at regional, urban, and neighborhood scales; daily real-time meteorological and air quality forecasts; ground-based and airborne remote sensing; instrumented Unmanned Aerial Vehicles (UAVs); isotopic measurements of reactive nitrogen species; chemical fingerprinting; and fine-scale inverse modeling of emission sources. Major results include characterization of southeast Michigan as VOC-limited for local ozone formation; discovery of significant and unaccounted formaldehyde emissions from industrial sources; quantification of methane emissions from landfills and leaking natural gas pipelines; evaluation of solvent emission impacts on local and regional ozone; characterization of the sources of reactive nitrogen and PM2.5; and improvements to modeling practices for meteorological, receptor, and chemical transport models. 

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3. Photochemistry of Volatile Organic Compounds in the Yellow River Delta, China: Formation of O ₃ and Peroxyacyl Nitrates

   https://doi.org/10.1029/2021JD035296  

   Lee, Y.; Huey, L. G.; Wang, Y.; Qu, H.; Zhang, R.; Ji, Y.; Tanner, D. J.; Wang, X.; Tang, J.; Song, W.; et al (December 2021, Journal of Geophysical Research: Atmospheres)

   Abstract An extensive set of primary and secondary pollutants was measured at a ground site in a remote location in the Yellow River Delta, China during the Ozone Photochemistry and Export from China Experiment (OPECE) from March to April 2018. The measurements include volatile organic compounds (VOCs), peroxyacyl nitrates (PANs), ozone (O₃), particulate species, nitrogen oxides (NO_x), and SO₂. Observed VOC mixing ratios were comparable to those measured in heavily polluted cities in the U.S. and China. The VOC source signatures suggest a strong influence from Oil and Natural Gas (O&NG) emissions with potentially large contributions from Liquified Petroleum Gas (LPG) sources as well. Consistently elevated concentrations of O₃, PAN, and its rarely measured homologs peroxybenzoylic nitric anhydride (PBzN) and peroxyacrylic nitric anhydride (APAN) at the OPECE site indicate complex photochemistry in a heterogeneous VOC environment. Diagnostic 0‐D box model simulations are used to investigate the budgets of RO_x(OH + HO₂ + RO₂), and the rate and efficiency of O₃production. Model sensitivity calculations indicate that O₃production at OPECE site is VOC limited in spring. This suggests that reduction in VOCs should be a priority for reducing O₃, where production and fugitive emissions from O&NG provide an attractive target. While initial reductions in NO_xmight increase O₃production, reduction of NO_xalong with VOCs will be a necessary step to achieve long‐term ozone reduction. 

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4. Sensitivity of Ozone Production to NOx and VOC along the Lake Michigan Coastline

   Vermeuel, Michael P; Novak, Gordon A; Alwe, Hariprasad D; Hughes, Dagen D; Kaleel, Rob; Dickens, Angela F; Kenski, Donna; Czarnetzki, Alan; Stone, Elizabeth A; Stanier, Charles O; et al (September 2019, Journal of geophysical research. Atmospheres)

   We report on the sensitivity of enhanced ozone (O3) production, observed during lake breeze circulation along the coastline of Lake Michigan, to the concentrations of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs). We assess the sensitivity of O3 production to NOx and VOC on a high O3 day during the Lake Michigan Ozone Study 2017 (LMOS 2017) using an observationally-constrained chemical box model that implements the Master Chemical Mechanism (MCM v3.3.1) and recent emission inventories for NOx and VOCs. The MCM model is coupled to a backward air mass trajectory analysis from a ground supersite in Zion, IL where an extensive series of measurements of O3 precursors and their oxidation products, including hydrogen peroxide (H2O2), nitric acid (HNO3), and particulate nitrates (NO3-) serve as model constraints. We evaluate the chemical evolution of the Chicago-Gary urban plume as it advects over Lake Michigan and demonstrate how modeled indicators of VOC- vs. NOx- sensitive regimes can be constrained by measurements at the trajectory endpoint. Using the modeled ratio of the instantaneous H2O2 and HNO3 production rates (PH2O2 / PHNO3), we suggest that O3 production over the urban source region is strongly VOC-sensitive and progresses towards a more NOx-sensitive regime as the plume advects north along the Lake Michigan coastline on this day. We also demonstrate that ground-based measurements of the mean concentration ratio of H2O2 to HNO3 describe the sensitivity of O3 production to VOC and NOx as the integral of chemical production along the plume path. 

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5. Extending Ozone‐Precursor Relationships in China From Peak Concentration to Peak Time

   https://doi.org/10.1029/2020JD033670  

   Qu, Hang; Wang, Yuhang; Zhang, Ruixiong; Li, Jianfeng (November 2020, Journal of Geophysical Research: Atmospheres)

   Abstract High ozone concentrations have become the major summertime air quality problem in China. Extensive in situ observations are deployed for developing strategies to effectively control the emissions of ozone precursors, that is, nitrogen oxides (NO_X = NO + NO₂) and volatile organic compounds (VOCs). The modeling analysis of in situ observations often makes uses of the dependence of ozone peak concentration on NO_Xand VOC emissions, because ozone observations are among the most widely available air quality measurements. To extract more information from regulatory ozone observations, we extend the ozone‐precursor relationship to ozone peak time in this study. We find that the sensitivities of ozone peak time and concentration are complementary for regions with large anthropogenic emissions such as China. The ozone peak time is sensitive to both VOC and NO_Xemissions, and the sensitivity is nearly linear in the transition regime of ozone production compared to the changing ozone peak concentration sensitivity in this regime, making the diagnostics of ozone peak time particularly valuable. The extended ozone‐precursor relationships can be readily applied to understand the effects on ozone by emission changes of NO_Xand VOC and to assess potential biases of NO_Xand VOC emission inventories. These observation constraints based on regulatory ozone observations can complement the other measurement and modeling analysis methods nicely. Furthermore, we suggest that the ozone peak time sensitivity we discussed here to be used as a model evaluation measure before the empirical kinetic modeling approach (EKMA) diagram is applied to understand the effectiveness of emission control on ozone concentrations. 

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