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Volume 16, issue 21 | Copyright

Special issue: Uintah Basin Winter Ozone Studies (ACP/AMT inter-journal SI)

Atmos. Chem. Phys., 16, 13837-13851, 2016
https://doi.org/10.5194/acp-16-13837-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 09 Nov 2016

Research article | 09 Nov 2016

The magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USA

Maria Zatko1, Joseph Erbland2,3, Joel Savarino2,3, Lei Geng1,a, Lauren Easley4,b, Andrew Schauer5, Timothy Bates7, Patricia K. Quinn6, Bonnie Light8, David Morison8,c, Hans D. Osthoff9, Seth Lyman10, William Neff11, Bin Yuan11,12, and Becky Alexander1 Maria Zatko et al.
  • 1Department of Atmospheric Sciences, University of Washington, Seattle 98195, USA
  • 2Université Grenoble Alpes, LGGE, 38000 Grenoble, France
  • 3CNRS, LGGE, 38000 Grenoble, France
  • 4Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
  • 5Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA
  • 6Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, Washington 98115, USA
  • 7Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, Washington 98195, USA
  • 8Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, Washington 98195, USA
  • 9Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
  • 10Bingham Entrepreneurship and Energy Research Center, Utah State University, 320 Aggie Boulevard, Vernal, Utah 84078, USA
  • 11Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, Colorado 80309, USA
  • 12Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado 80305, USA
  • anow at: Université Grenoble Alpes, LGGE, 38000 Grenoble, France, CNRS, LGGE, 38000 Grenoble, France
  • bcurrent address: DSG Solutions, LLC, Shoreline, WA, 98133, USA
  • cnow at: Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA

Abstract. Reactive nitrogen (Nr = NO, NO2, HONO) and volatile organic carbon emissions from oil and gas extraction activities play a major role in wintertime ground-level ozone exceedance events of up to 140ppb in the Uintah Basin in eastern Utah. Such events occur only when the ground is snow covered, due to the impacts of snow on the stability and depth of the boundary layer and ultraviolet actinic flux at the surface. Recycling of reactive nitrogen from the photolysis of snow nitrate has been observed in polar and mid-latitude snow, but snow-sourced reactive nitrogen fluxes in mid-latitude regions have not yet been quantified in the field. Here we present vertical profiles of snow nitrate concentration and nitrogen isotopes (δ15N) collected during the Uintah Basin Winter Ozone Study 2014 (UBWOS 2014), along with observations of insoluble light-absorbing impurities, radiation equivalent mean ice grain radii, and snow density that determine snow optical properties. We use the snow optical properties and nitrate concentrations to calculate ultraviolet actinic flux in snow and the production of Nr from the photolysis of snow nitrate. The observed δ15N(NO3) is used to constrain modeled fractional loss of snow nitrate in a snow chemistry column model, and thus the source of Nr to the overlying boundary layer. Snow-surface δ15N(NO3) measurements range from −5 to 10‰ and suggest that the local nitrate burden in the Uintah Basin is dominated by primary emissions from anthropogenic sources, except during fresh snowfall events, where remote NOx sources from beyond the basin are dominant. Modeled daily averaged snow-sourced Nr fluxes range from 5.6 to 71 × 107moleccm−2s−1 over the course of the field campaign, with a maximum noontime value of 3.1 × 109moleccm−2s−1. The top-down emission estimate of primary, anthropogenic NOx in Uintah and Duchesne counties is at least 300 times higher than the estimated snow NOx emissions presented in this study. Our results suggest that snow-sourced reactive nitrogen fluxes are minor contributors to the Nr boundary layer budget in the highly polluted Uintah Basin boundary layer during winter 2014.

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This manuscript presents chemical and optical observations collected in the air and snow during UBWOS2014 in eastern Utah. These observations are used to calculate fluxes of reactive nitrogen associated with snow nitrate photolysis. Snow-sourced reactive nitrogen fluxes are compared to reactive nitrogen emission inventories to find that snow-sourced reactive nitrogen is a minor contributor to the reactive nitrogen budget, and thus wintertime ground-level ozone formation, in the Uintah Basin.
This manuscript presents chemical and optical observations collected in the air and snow during...
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