Were Wildfires Responsible for the Unusually High Surface Ozone in Colorado During 2021?

Abstract

The adverse impacts of wildfires on ambient air quality and human health have grown in recent years as climactic shifts and long-standing fire suppression practices have increased fire activity across the western U.S. and Canada (Bryant & Westerling, 2014;Westerling et al., 2016). Wildfires generate large quantities of carbon monoxide (CO) and carbon dioxide (CO 2 ) in addition to primary and secondary fine particulates (PM 2.5 ), and also produce a variety of other gaseous compounds including the reactive nitrogen oxides (NO + NO 2 = NO x ) and volatile organic compounds (VOCs) that are the photochemical precursors of ozone (O 3 ). The negative health effects of CO, O 3 , NO 2 , and PM 2.5 have long been recognized, and these pollutants comprise four of the six "criteria" air pollutants regulated by the U.S. Clean Air Act (CAA) and are subject to National Ambient Air Quality Standards (NAAQS) (Karstadt et al., 1993). Ozone and PM 2.5 both impair lung and cardiovascular function (Brown et al., 2008;Reid et al., 2016) and recent studies (Kalashnikov et al., 2022) suggest that exposure to wildfire smoke containing both O 3 and PM 2.5 can have more severe health impacts than exposure to either pollutant alone.The production of O 3 by wildfires depends on many factors (Jaffe et al., 2018;Jaffe & Wigder, 2012) that affect the NO x and VOC precursor emissions (e.g., fuel type and moisture content), the photochemical reaction rates (e.g., plume height and density), or both (e.g., meteorology) (Xu et al., 2021). Ozone concentrations

Mobile Observations of Ozone and Aerosols in Alabama: Southeastern US Summer Pollution and Coastal Variability

“…This assumes a conversion ratio of 10 5 μg m −2 , which is close to the results by Langford et al. (2023) after accounting for the laser wavelength and lidar ratio differences. The lidar aerosol curtain in Figure 2b presents some elevated aerosols around Huntsville below 2.5 km with reducing AOD toward the south.…”

Measuring Coupled Fire–Atmosphere Dynamics: The California Fire Dynamics Experiment (CalFiDE)

“…The exact makeup of fire emissions depends on a multitude of factors including fuel type and fire intensity (Sekimoto et al 2018), but all wildfires emit large amounts of volatile organic compounds (VOCs), nitrogen oxides (NO x ), and particulate matter (PM). The VOCs and NO x lead to rapid and prolonged ozone formation (Robinson et al 2021;Xu et al 2021), contributing to ozone exceedances in populated areas across continents and influencing ozone at global scales (Bourgeois et al 2021;Gong et al 2017: Langford et al 2023Rickly et al 2023). PM is also an air quality concern at regional and continental scales (Kalashnikov et al 2022;Sarangi et al 2023), especially when stagnant conditions near a fire result in dangerous concentrations, e.g., smoke-filled valleys (Childs et al 2022).…”