New paper explores relationships between PM, ozone, and nitrogen oxides during urban smoke events

Claire Buysse at Mt. Bachelor Observatory, July 29, 2019

Claire Buysse installing equipment at Mt. Bachelor Observatory, July 29, 2019. Photo credit: Mark Stone.

A newly published paper by Claire Buysse and coauthors Aaron Kaulfus, Udaysankar Nair, and Dan Jaffe explores the the impact of wildfire smoke on urban air quality. The paper, published in Environmental Science & Technology, describes the authors’ study of ozone (O3) impacts from smoke on 18 western US cities during July–September 2013–2017. They used monitoring data from ground-based sites and identified smoke using the satellite-based hazard mapping system (HMS) fire and smoke product provided by the National Oceanic and Atmospheric Administration.

Their findings include the following:

  • O3 and particulate matter <2.5 μm in diameter (PM2.5) are elevated at most sites on days influenced by smoke, while nitrogen oxides (NOx) are not consistently elevated at all sites.
  • PM2.5 and O3 exhibit a nonlinear relationship: O3 increases with PM2.5 at low to moderate PM2.5 and then O3 decreases at higher PM2.5.
  • On days influenced by smoke, the rate of increase of morning O3 is higher and the NO/NO2 ratios are lower.
  • The HMS product is useful for identifying smoke. However, because O3 and PM2.5 are elevated on days before and after HMS-identified smoke events, some smoke events are not being detected.

Read the full paper here.