Nitrate chemistry in the northeast US – Part 1: Nitrogen isotope seasonality tracks nitrate formation chemistry

Abstract δ 15 N)) to investigate atmospheric nitrate spatiotemporal trends in the northeastern US from samples collected at three US EPA Clean Air Status and Trends Network (CASTNET) sites from December 2016–2018. For the considered sites, similar seasonal patterns in nitric acid (HNO3) and particulate nitrate (pNO3) concentrations were observed with spatial differences attributed to nitrogen oxide (NOx) emission densities in source contributing regions that were typically ≤ δ 15 N) variabilities in HNO3 and pNO3 were observed with higher values during winter relative to summer, like previous reports from CASTNET samples collected in the early 2000s for our study region. In the early 2000s, δ 15 N) of atmospheric nitrate in the northeast US had been suggested to be driven by NOx emissions; however, we did not find significant spatiotemporal changes in the modeled NOx emissions by sector and fuel type or δ 15 N, NOx) for the source regions of the CASTNET sites. Instead, the seasonal and spatial differences in the observed δ 15 N) of atmospheric nitrate were driven by nitrate formation pathways (i.e., homogeneous reactions of NO2 oxidation via hydroxyl radical or heterogeneous reactions of dinitrogen pentoxide on wetted aerosol surfaces) and their associated δ 15 N) fractionation. Under the field conditions of low NOx relative to O3 concentrations and when δ 15 N, NOx) emission sources do not have significant variability, we demonstrate that δ 15 N) of atmospheric nitrate can be a robust tracer for diagnosing nitrate formation.

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch

References and Relationships

• Bibliographic citation: Nitrate chemistry in the northeast US – Part 1: Nitrogen isotope seasonality tracks nitrate formation chemistry ; volume:23 ; number:7 ; year:2023 ; pages:4185-4201 ; extent:17 ; Atmospheric chemistry and physics ; 23, Heft 7 (2023), 4185-4201 (gesamt 17)

Contributors, Places and Time

• Creator: Bekker, Claire ; Walters, Wendell W. ; Murray, Lee T. ; Hastings, Meredith G.

Further information

• DOI: 10.5194/acp-23-4185-2023
• URN: urn:nbn:de:101:1-2023041305200011656218
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 24.08.2025, 11:55 AM CEST