Heterogeneous formation of nitryl chloride and its role as a nocturnal NOx reservoir species during CalNex‐LA 2010. Issue 18 (24th September 2013)

• Record Type: Journal Article
• Authors: Mielke, L. H.; Stutz, J.; Tsai, C.; Hurlock, S. C.; Roberts, J. M.; Veres, P. R.; Froyd, K. D.; Hayes, P. L.; Cubison, M. J.; Jimenez, J. L.; Washenfelder, R. A.; Young, C. J.; Gilman, J. B.; de, J. A.; Flynn, J. H.; Grossberg, N.; Lefer, B. L.; Liu, J.; Weber, R. J.; Osthoff, H. D.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 18(2013)
• Page Start: 10, 638
• Page End: 10, 652
• Publication Date: 2013-09-24
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/jgrd.50783
• Languages: English
• ISSNs: 2169-897X

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>[1] The nocturnal conversion of dinitrogen pentoxide (N<sub>2</sub>O<sub>5</sub>) to nitryl chloride (ClNO<sub>2</sub>) on chloride‐containing aerosol can be a regionally important NO<italic><sub>x</sub></italic> (= NO + NO<sub>2</sub>) recycling and halogen activation pathway that affects oxidant photochemistry the following day. Here we present a comprehensive measurement data set acquired at Pasadena, California, during the CalNex‐LA campaign 2010 that included measurements of odd nitrogen and its major components (NO<italic><sub>y</sub></italic> = NO<italic><sub>x</sub></italic> + NO<sub>3</sub> + 2N<sub>2</sub>O<sub>5</sub> + ClNO<sub>2</sub> + HNO<sub>3</sub> + HONO + peroxyacyl, alkyl, and aerosol nitrates) and aerosol size distribution and composition. Nitryl chloride was present during every night of the study (median mixing ratio at sunrise 800 pptv) and was usually a more significant nocturnal NO<italic><sub>x</sub></italic> and odd oxygen (O<italic><sub>x</sub></italic> = O<sub>3</sub> + NO<sub>2</sub> + 3N<sub>2</sub>O<sub>5</sub> + ClNO<sub>2</sub>) reservoir species than N<sub>2</sub>O<sub>5</sub> (whose concentrations were calculated from its equilibrium with NO<sub>2</sub> and NO<sub>3</sub>). At sunrise, ClNO<sub>2</sub> accounted for 21% of NO<italic><sub>z</sub></italic> (=NO<italic><sub>y</sub></italic> − NO<italic><sub>x</sub></italic>), 4% of NO<italic><sub>y</sub></italic>, and 2.5% of O<italic><sub>x</sub></italic>, respectively (median values). Kinetic parameters for the N<sub>2</sub>O<sub>5</sub> to ClNO<sub>2</sub> conversion were estimated by relating ClNO<sub>2</sub> concentrations to their time‐integrated heterogeneous production from N<sub>2</sub>O<sub>5</sub> and were highly variable between nights. Production of ClNO<sub>2</sub> required conversion of N<sub>2</sub>O<sub>5</sub> on submicron aerosol with average yield (φ) and N<sub>2</sub>O<sub>5</sub> reactive uptake probability (γ) of γφ = 0.008 (maximum 0.04), scaled with submicron aerosol chloride content, and was suppressed by aerosol organic matter and liquid water content. Not all of the observed variability of ClNO<sub>2</sub> production efficiency could be rationalized using current literature parameterizations.</p> </abstract>