Spatial and diurnal variability in reactive nitrogen oxide chemistry as reflected in the isotopic composition of atmospheric nitrate: Results from the CalNex 2010 field study. Issue 18 (17th September 2013)

• Record Type: Journal Article
• Authors: Vicars, W. C.; Morin, S.; Savarino, J.; Wagner, N. L.; Erbland, J.; Vince, E.; Martins, J. M. F.; Lerner, B. M.; Quinn, P. K.; Coffman, D. J.; Williams, E. J.; Brown, S. S.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 18(2013)
• Page Start: 10, 567
• Page End: 10, 588
• Publication Date: 2013-09-17
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/jgrd.50680
• Languages: English
• ISSNs: 2169-897X

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>[1] Here we present measurements of the size‐resolved concentration and isotopic composition of atmospheric nitrate (NO<sub>3</sub><sup>−</sup>) collected during a cruise in coastal California. Significant differences in air mass origin and atmospheric chemistry were observed in the two main regions of this cruise (South and Central Coast) with corresponding differences in NO<sub>3</sub><sup>−</sup> concentration and isotope ratios. Measurements of the <sup>17</sup>O‐excess (<italic>Δ</italic><sup>17</sup>O) of NO<sub>3</sub><sup>−</sup> suggest that nocturnal chemistry played an important role in terms of total NO<sub>3</sub><sup>−</sup> production (~ 50%) in the coastal Los Angeles region (South Coast), where NO<sub>3</sub><sup>−</sup> concentrations were elevated due to the influence of sea breeze / land breeze recirculation and <italic>Δ</italic><sup>17</sup>O(NO<sub>3</sub><sup>−</sup>) averaged (25.3 ± 1.6)‰. Conversely, <italic>Δ</italic><sup>17</sup>O(NO<sub>3</sub><sup>−</sup>) averaged (22.3 ± 1.8)‰ in the Central Coast region, suggesting that the daytime OH + NO<sub>2</sub> reaction was responsible for 60–85% of NO<sub>3</sub><sup>−</sup> production in the marine air sampled in this area. A strong diurnal signal was observed for both the <italic>Δ</italic><sup>17</sup>O and <italic>δ</italic><sup>15</sup>N of NO<sub>3</sub><sup>−</sup>. In the case of <italic>Δ</italic><sup>17</sup>O, this trend is interpreted quantitatively in terms of the relative proportions of daytime and nighttime production and the atmospheric lifetime of NO<sub>3</sub><sup>−</sup>. For <italic>δ</italic><sup>15</sup>N, which had an average value of (0.0 ± 3.2)‰, the observed diurnality suggests a combined effect of isotopic exchange between gas‐phase precursors and variability in reactive nitrogen sources. These findings represent a significant advance in our understanding of the isotope dynamics of nitrate and its precursor molecules, with potentially important implications for air quality modeling.</p> </abstract>