Evaluating our understanding of smoke from wild and prescribed fires can benefit from downwind measurements that include inert tracers to test production and transport and reactive species to test chemical mechanisms. We characterized smoke from fires in coniferous forest fuels for >1,000 hr over two summers (2017 and 2018) at our Missoula, Montana, surface station and found a narrow range for key properties. ΔPM2.5/ΔCO was 0.1070 ± 0.0278 (g/g) or about half the age‐independent ratios obtained at free troposphere elevations (0.2348 ± 0.0326). The average absorption Ångström exponent across both years was 1.84 ± 0.18, or about half the values available for very fresh smoke. Brown carbon (BrC) was persistent (~50% of absorption at 401 nm) in both years, despite differences in smoke age. ΔBC/ΔCO doubled from 2017 to 2018, but the average across 2 years was within 33% of recent airborne measurements, suggesting low sampling bias among platforms. Switching from a 1.0 to a 2.5 micron cutoff increased the mass scattering and mass absorption coefficients, suggesting often overlooked supermicron particles impact the optical properties of moderately aged smoke. O3was elevated ~6 ppb on average over a full diurnal period when wildfire smoke was present, and smoke‐associated O3increases were highest (~9 pbb) at night, suggesting substantial upwind production. NOxwas mostly local in origin. NO
- Award ID(s):
- 1748266
- NSF-PAR ID:
- 10127271
- Date Published:
- Journal Name:
- Atmospheric Chemistry and Physics
- Volume:
- 19
- Issue:
- 6
- ISSN:
- 1680-7324
- Page Range / eLocation ID:
- 3905 to 3926
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract x spurred high rates of NO3production, including in the presence of wildfire smoke (up to 2.44 ppb hr−1) and at least one nighttime BrC secondary formation event that could have impacted next‐day photochemistry. -
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/acp-19-3905-2019
