Preprints
https://doi.org/10.5194/acp-2017-671
https://doi.org/10.5194/acp-2017-671

  28 Aug 2017

28 Aug 2017

Review status: this preprint was under review for the journal ACP. A revision for further review has not been submitted.

Evolution of NOx in the Denver Urban Plume during the Front Range Air Pollution and Photochemistry Experiment

Carlena J. Ebben1, Tamara L. Sparks1, Paul J. Wooldridge1, Teresa L. Campos2, Christopher A. Cantrell3, Roy L. Mauldin3, Andrew J. Weinheimer2, and Ronald C. Cohen1,4 Carlena J. Ebben et al.
  • 1Department of Chemistry, University of California Berkeley, Berkeley, California 94720, USA
  • 2National Center for Atmospheric Research, Boulder, Colorado 80301, USA
  • 3Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, Colorado 80309, USA
  • 4Department of Earth and Planetary Sciences, University of California Berkeley, Berkeley, California 94720, USA

Abstract. As NOx (NOx ≡ NO + NO2) is transported away from cities, it undergoes photochemical oxidation to peroxynitrates (RO2NO2, ΣPNs), alkyl nitrates (RONO2, ΣANs), and nitric acid (HNO3). These higher oxide species each have different lifetimes to permanent removal or conversion back to NOx, resulting in nitrogen oxide chemistry that evolves as plumes are transported away from cities. Here, observations from the Front Range Air Pollution and Photochemistry Experiment (FRAPPÉ) are used to describe the evolution of NOx and NOy (NOy ≡ NOx + ΣPNs + ΣANs + HNO3 + …) as the Denver urban plume flows outward from the city center. We evaluate the chemistry, dilution, and deposition rates in the plume to provide numerical constraints on the NOx and NOy,i lifetimes. We find that plume dilution with background air occurs with a lifetime of 3.5 hours. NOx concentrations decrease more rapidly with a lifetime to chemical loss and dilution of 2 hours in the near field of the city center. NOy has an effective lifetime of 3 hours and due to a combination of HNO3 deposition and dilution. The results provide a useful test of conceptual and numerical models of chemistry during the evolution of urban plumes.

Carlena J. Ebben et al.

 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Carlena J. Ebben et al.

Carlena J. Ebben et al.

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Short summary
We use observations from the FRAPPÉ campaign to examine the evolution of reactive nitrogen as it is transported from Denver. We provide estimates for dilution rates, chemical lifetimes, and deposition rates. While dilution is the primary loss process in the immediate outflow from Denver, chemically, a majority of NOx is converted to HNO3 and is subsequently deposited. Understanding the evolution of reactive nitrogen informs how urban emissions affect air quality in the surrounding regions.
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