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Examining the sensitivity of ozone to NOx and VOCs in the Salt Lake City urban region from spatiotemporal patterns observed using stationary and mobile observations collected from a light-rail public transit platform
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2024
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Source: Atmospheric Environment, 334, 120686
[PDF-8.66 MB]
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Journal Title:Atmospheric Environment
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Description:Ozone (O3) is a secondary atmospheric pollutant that can adversely impact human health, with production rates dependent on chemical precursors such as nitrogen oxides (NOx), Volatile Organic Compounds (VOCs), as well as meteorological variables such as incoming solar radiation, temperature, and humidity. NOx concentrations in Salt Lake City, UT (SLC), have decreased significantly since 2000 (−60%). However, during this time minimal declines in O3 were observed. To better understand the drivers behind O3 trends in SLC, we leveraged air quality measurements from sites maintained by the Utah Division of Air Quality, along with mobile O3 measurements collected on top of a light-rail train that traverses the Salt Lake Valley (SLV). Analyses were carried out from March 15th through April (spring) and June through August (summer) for 2019, 2020, and 2021 and focused on the afternoon when O3 was typically at the highest concentrations (1–4 p.m. MST). Overall, there were large differences in O3 between the spring and summer months, with the latter being higher by ∼10 ppb. However, there were relatively small differences in O3 between weekday and weekend. For the spring, differences in afternoon O3 concentrations were higher during weekends (<12%), while during the summer, the differences were smaller (1–2%) and higher during weekdays. While weekday vs weekend differences in NOx emissions are usually large (∼20%) due to changes in traffic activity, there were relatively minimal differences in O3 between weekday and weekends. There were minimal differences at point locations such as downtown SLC, and along multiple points along the TRAX train line. The analyses carried out in this study suggests that cities such as SLC are primarily under the influence of VOC-limited chemical regimes, meaning that there is limited O3 sensitivity to changes in NOx. These results suggest that reducing VOC emissions, would be the most effective approach for reducing O3 pollution in cities like SLC.
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Source:Atmospheric Environment, 334, 120686
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ISSN:1352-2310
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Rights Information:CC BY-NC
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Compliance:Submitted
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