Summertime spatiotemporal patterns of nitrogen oxides (NOx) in Salt Lake City and implications for ozone (O3) production

Salt Lake City, UT exceeds the National Ambient Air Quality Standard (NAAQS) for ozone (O₃). In addition to substantial local emissions of O₃ precursors from vehicular traffic and industrial activities, this region is also impacted by wildfire smoke and long range pollutant transport. High pressure systems, low wind speeds, and hot temperatures support high O₃ periods, thus predicting the spatiotemporal distribution of O₃ in the region remains a challenge. During the 2024 Salt Lake City-Summer Ozone Study (SLC-SOS), we used a Mobile Lab to make mobile and stationary measurements of O₃ and its precursors throughout the Salt Lake Valley. Our initial analysis of this data quantifies regional gradients in nitrogen oxides (NO_x = NO + NO₂) measured with an Aerodyne dual channel Cavity Attenuated Phase Shift Monitor (CAPS). We discuss NO_x variability between regulatory monitoring sites, daily variability, weekend-weekday differences in O₃ and NO_x, and gradients up the canyons. These measurements will help develop strategies to mitigate high O₃ levels and improve air quality in the region.