Investigation of Ozone Formation Chemistry during the Salt Lake Regional Smoke, Ozone, and Aerosol Study (SAMOZA)

Matthew Ninneman, Seth Lyman, Lu Hu, Emily Cope, Damien Ketcherside, Daniel Jaffe

Research output: Contribution to journalArticlepeer-review

Abstract

Salt Lake City (SLC), UT, is an urban area where ozone (O3) concentrations frequently exceed health standards. This study uses an observationally constrained photochemical box model to investigate the drivers of O3 production during the Salt Lake Regional Smoke, Ozone, and Aerosol Study (SAMOZA), which took place from August to September 2022 in SLC. During SAMOZA, a suite of volatile organic compounds (VOCs), oxides of nitrogen (NOx), and other parameters were measured at the Utah Technical Center, a high-NOx site in the urban core. We examined four high-O3 cases: 4 August and 3, 11, and 12 September, which were classified as a nonsmoky weekday, a weekend day with minimal smoke influence, a smoky weekend day, and a smoky weekday, respectively. The modeled O3 production on 4 August and 3 September was highly sensitive to VOCs and insensitive to NOx reductions of ≤50%. Box model results suggest that the directly emitted formaldehyde contributed to the rapid increase in morning O3 concentrations on 3 September. Model sensitivity tests for September 11-12 indicated that smoke-emitted VOCs, especially aldehydes, had a much larger impact on O3 production than NOx and/or anthropogenic VOCs. On 11 and 12 September, smoke-emitted VOCs enhanced model-predicted maximum daily 8 h average O3 concentrations by 21 and 13 parts per billion (ppb), respectively. Overall, our results suggest that regionwide VOC reductions of at least 30-50% or NOx reductions of at least 60% are needed to bring SLC into compliance with the national O3 standard of 70 ppb.

Original languageEnglish
Pages (from-to)2521-2534
Number of pages14
JournalACS Earth and Space Chemistry
Volume7
Issue number12
DOIs
StatePublished - Dec 21 2023

Keywords

  • box model
  • nitrogen oxides
  • ozone
  • smoke
  • volatile organic compounds
  • wildfires

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