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

Abstract

Ambient ozone (O3) concentrations in Southeast Michigan (SEMI) can exceed the U.S. National Ambient Air Quality Standard (NAAQS). Despite past efforts to measure O3 precursors and elucidate reaction mechanisms, changing emission patterns and atmospheric composition in SEMI warrant new measurements and updated mechanisms to understand the causes of observed O3 exceedances. In this study, we examine the chemical drivers of O3 exceedances in SEMI, based on the Phase I MOOSE (Michigan‐Ontario Ozone Source Experiment) field study performed during May – June 2021. A zero‐dimensional (0‐D) box model is constrained with measurement data of meteorology and trace gas concentrations. Box model sensitivity simulations suggest that the formaldehyde to nitrogen dioxide ratio (HCHO/NO2) for the transition between the volatile organic compounds (VOC)‐ and nitrogen oxides (NOx)‐limited O3 production regimes is 3.0 ± 0.3 in SEMI. The midday (12:00‐16:00) averaged HCHO/NO2 ratio during the MOOSE Phase I study is 1.62 ± 1.03, suggesting that O3 production in SEMI is limited by VOC emissions. This finding implies that imposing stricter regulations on VOC emissions should be prioritized for the SEMI O3 nonattainment area. This study, through its use of ground‐based HCHO/NO2 ratios and box modeling to assess O3‐VOC‐NOx sensitivities, has significant implications for air quality policy and the design of effective O3 pollution control strategies, especially in O3 nonattainment areas.

Summertime Ozone Production at Carlsbad Caverns National Park, New Mexico: Influence of Oil and Natural Gas Development

“…Box models can reasonably capture observed O 3 concentrations when a large fraction of O 3 at a given site is produced by in situ chemistry (Edwards et al, 2013(Edwards et al, , 2014McDuffie et al, 2016;Ninneman & Jaffe, 2021;Xiong et al, 2023). O 3 in photochemically aged air masses depleted of NO x and primary VOCs is likely to be underestimated by a box model, as substantial O 3 production occurs upwind of the location of interest (Xue et al, 2013).…”

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

“…Based on prior analyses of satellite column and ground-based monitoring data, ozone modeling and trend assessments, and weekday-weekend differences, the Lake Michigan Air Directors Consortium (LADCO) had previously identified SEMI as in a transitional regime evolving away from VOC sensitivity towards NO x sensitivity ( [22] and references therein). Xiong et al [23], however, used the observed ratio of formaldehyde (HCHO) to nitrogen dioxide (NO 2 ) in near-surface ambient air measured by the AML during MOOSE and a zero-dimensional (0-D) photochemical box model, F0AM (the Framework for 0-D Atmospheric Modeling), utilizing an extensive set of contemporaneous speciated VOC, NO x , and O 3 measurements to analyze the sensitivity of local ozone in SEMI to VOC and NO x controls. F0AM model sensitivity simulations by Xiong et al [23] suggest that the HCHO/NO 2 ratio for the transition between the VOC-and NO x -limited O 3 production regimes is 3.0 ± 0.3 in SEMI.…”

“…Xiong et al [23], however, used the observed ratio of formaldehyde (HCHO) to nitrogen dioxide (NO 2 ) in near-surface ambient air measured by the AML during MOOSE and a zero-dimensional (0-D) photochemical box model, F0AM (the Framework for 0-D Atmospheric Modeling), utilizing an extensive set of contemporaneous speciated VOC, NO x , and O 3 measurements to analyze the sensitivity of local ozone in SEMI to VOC and NO x controls. F0AM model sensitivity simulations by Xiong et al [23] suggest that the HCHO/NO 2 ratio for the transition between the VOC-and NO x -limited O 3 production regimes is 3.0 ± 0.3 in SEMI. The midday (12:00-16:00) averaged HCHO/NO 2 ratio during the MOOSE intensive campaign was 1.6 ± 1.0, implying that local O 3 production in SEMI is limited by VOC emissions.…”

Inferring Near-Surface Ozone Production Regimes: Challenges with using Satellite Retrievals over the Contiguous US

“…O 3 /(NO y -NO x ) and HCHO/NO y were proposed and tested as a means to assess whether tropospheric ozone production was NO x or VOC-limited (Kleinman et al, 2001;Sillman, 1995;Sillman & He, 2002;Tonnesen & Dennis, 2000). Chemical box models often use the ratio of LRO x (radical loss rates of self-reaction) to LNO x (reaction rate loss of OH with NO 2 ) to estimate OPRs, although the transition point between regimes is still debated (Kleinman et al, 2001;Roberts et al, 2022;Schroeder et al, 2017;Sebol et al, 2024;Xiong et al, 2023).…”