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Weekend‐Weekday Implications and the Impact of Wildfire Smoke on Ozone and Its Precursors at Boulder Reservoir, Colorado Between 2017 and 2019
Author(s) -
Pollack Ilana B.,
Helmig Detlev,
O'Dell Katelyn,
Fischer Emily V.
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2021jd035221
Subject(s) - smoke , environmental science , ozone , air quality index , atmospheric sciences , cigarette smoke , hydrology (agriculture) , environmental chemistry , meteorology , chemistry , geography , geology , toxicology , geotechnical engineering , biology
Abstract The Northern Front Range of Colorado regularly exceeds the ozone (O 3 ) National Ambient Air Quality Standard. This region is unique because it is impacted by emissions from urban activities (i.e., traffic and light industry) as well as from oil and natural gas production. Here, we summarize three years of observations from a new O 3 monitoring site at the western edge of the region, located at the Boulder Reservoir. There were 41 days at the Boulder Reservoir in 2017, 2018, and 2019 when the maximum daily 8‐hour average O 3 mixing ratio (MDA8 O 3 ) exceeded 70 ppbv. Of these 41 high O 3 days, 40 occurred between May and September, two were influenced by stratospheric intrusion events, one was influenced by a local industrial fire, and 13 of the days were impacted by wildfire smoke. Within the smoke‐free subset of data, weekend‐weekday differences in O 3 versus nitrogen oxides (NO x ) during 2018 and 2019 suggest NO x ‐limited O 3 production. Enhanced nonmethane volatile organic compounds (NMVOC) to NO x ratios are also observed on weekend days and are driven by weekend reductions in NO x . An analysis of 13 NMVOCs on days that had MDA8 O 3 > 70 ppb showed that NMVOC abundances and their relative source contributions are variable at this location. Finally, we compare smoke‐impacted with smoke‐free conditions. At a given temperature, smoke‐impacted days have higher expected O 3 mixing ratios than smoke free‐days. On average, benzene, toluene, and hexane are also elevated during smoke‐impacted periods.