Preprints
https://doi.org/10.5194/acp-2017-671
https://doi.org/10.5194/acp-2017-671
28 Aug 2017
 | 28 Aug 2017
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. Ebben, Tamara L. Sparks, Paul J. Wooldridge, Teresa L. Campos, Christopher A. Cantrell, Roy L. Mauldin, Andrew J. Weinheimer, and Ronald C. Cohen

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.

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Carlena J. Ebben, Tamara L. Sparks, Paul J. Wooldridge, Teresa L. Campos, Christopher A. Cantrell, Roy L. Mauldin, Andrew J. Weinheimer, and Ronald C. Cohen
 
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, Tamara L. Sparks, Paul J. Wooldridge, Teresa L. Campos, Christopher A. Cantrell, Roy L. Mauldin, Andrew J. Weinheimer, and Ronald C. Cohen
Carlena J. Ebben, Tamara L. Sparks, Paul J. Wooldridge, Teresa L. Campos, Christopher A. Cantrell, Roy L. Mauldin, Andrew J. Weinheimer, and Ronald C. Cohen

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Latest update: 23 May 2024
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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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