On the contribution of nocturnal heterogeneous reactive nitrogen chemistry to particulate matter formation during wintertime pollution events in Northern Utah

E. E. McDuffie; E. E. McDuffie; E. E. McDuffie; E. E. McDuffie; C. C. Womack; C. C. Womack; D. L. Fibiger; D. L. Fibiger; D. L. Fibiger; W. P. Dube; W. P. Dube; A. Franchin; A. Franchin; A. M. Middlebrook; L. Goldberger; L. Goldberger; B. H. Lee; J. A. Thornton; A. Moravek; A. Moravek; J. G. Murphy; M. Baasandorj; M. Baasandorj; S. S. Brown; S. S. Brown

doi:10.5194/acp-19-9287-2019

Atmospheric Chemistry and Physics (Jul 2019)

On the contribution of nocturnal heterogeneous reactive nitrogen chemistry to particulate matter formation during wintertime pollution events in Northern Utah

E. E. McDuffie,
E. E. McDuffie,
E. E. McDuffie,
E. E. McDuffie,
C. C. Womack,
C. C. Womack,
D. L. Fibiger,
D. L. Fibiger,
D. L. Fibiger,
W. P. Dube,
W. P. Dube,
A. Franchin,
A. Franchin,
A. M. Middlebrook,
L. Goldberger,
L. Goldberger,
B. H. Lee,
J. A. Thornton,
A. Moravek,
A. Moravek,
J. G. Murphy,
M. Baasandorj,
M. Baasandorj,
S. S. Brown,
S. S. Brown

Affiliations

E. E. McDuffie: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
E. E. McDuffie: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
E. E. McDuffie: Department of Chemistry, University of Colorado, Boulder, CO, USA
E. E. McDuffie: now at: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
C. C. Womack: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
C. C. Womack: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
D. L. Fibiger: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
D. L. Fibiger: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
D. L. Fibiger: now at: California Air Resources Board, Sacramento, CA, USA
W. P. Dube: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
W. P. Dube: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
A. Franchin: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
A. Franchin: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
A. M. Middlebrook: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
L. Goldberger: Department of Atmospheric Science, University of Washington, Seattle, WA, USA
L. Goldberger: now at: ARM Aerial Facility, Pacific Northwest National Laboratory, Richland, WA, USA
B. H. Lee: Department of Atmospheric Science, University of Washington, Seattle, WA, USA
J. A. Thornton: Department of Atmospheric Science, University of Washington, Seattle, WA, USA
A. Moravek: Department of Chemistry, University of Toronto, Toronto, ON, Canada
A. Moravek: now at: Department of Chemistry, York University, Toronto, ON, Canada
J. G. Murphy: Department of Chemistry, University of Toronto, Toronto, ON, Canada
M. Baasandorj: Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT, USA
M. Baasandorj: now at: Chevron Corporation, Houston, TX, USA
S. S. Brown: Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
S. S. Brown: Department of Chemistry, University of Colorado, Boulder, CO, USA

DOI: https://doi.org/10.5194/acp-19-9287-2019
Journal volume & issue: Vol. 19
pp. 9287 – 9308

Abstract

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Mountain basins in Northern Utah, including the Salt Lake Valley (SLV), suffer from wintertime air pollution events associated with stagnant atmospheric conditions. During these events, fine particulate matter concentrations (PM2.5) can exceed national ambient air quality standards. Previous studies in the SLV have found that PM2.5 is primarily composed of ammonium nitrate (NH4NO3), formed from the condensation of gas-phase ammonia (NH3) and nitric acid (HNO3). Additional studies in several western basins, including the SLV, have suggested that production of HNO3 from nocturnal heterogeneous N2O5 uptake is the dominant source of NH4NO3 during winter. The rate of this process, however, remains poorly quantified, in part due to limited vertical measurements above the surface, where this chemistry is most active. The 2017 Utah Winter Fine Particulate Study (UWFPS) provided the first aircraft measurements of detailed chemical composition during wintertime pollution events in the SLV. Coupled with ground-based observations, analyses of day- and nighttime research flights confirm that PM2.5 during wintertime pollution events is principally composed of NH4NO3, limited by HNO3. Here, observations and box model analyses assess the contribution of N2O5 uptake to nitrate aerosol during pollution events using the NO3- production rate, N2O5 heterogeneous uptake coefficient (γ(N2O5)), and production yield of ClNO2 (φ(ClNO2)), which had medians of 1.6 µg m−3 h−1, 0.076, and 0.220, respectively. While fit values of γ(N2O5) may be biased high by a potential under-measurement in aerosol surface area, other fit quantities are unaffected. Lastly, additional model simulations suggest nocturnal N2O5 uptake produces between 2.4 and 3.9 µg m−3 of nitrate per day when considering the possible effects of dilution. This nocturnal production is sufficient to account for 52 %–85 % of the daily observed surface-level buildup of aerosol nitrate, though accurate quantification is dependent on modeled dilution, mixing processes, and photochemistry.

Published in Atmospheric Chemistry and Physics

ISSN: 1680-7316 (Print); 1680-7324 (Online)
Publisher: Copernicus Publications
Country of publisher: Germany
LCC subjects: Science: Physics; Science: Chemistry
Website: http://www.atmospheric-chemistry-and-physics.net/

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