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Published September 25, 2015 | Supplemental Material + Published
Journal Article Open

Influence of crustal dust and sea spray supermicron particle concentrations and acidity on inorganic NO_3^- aerosol during the 2013 Southern Oxidant and Aerosol Study

Abstract

Inorganic aerosol composition was measured in the southeastern United States, a region that exhibits high aerosol mass loading during the summer, as part of the 2013 Southern Oxidant and Aerosol Study (SOAS) campaign. Measurements using a Monitor for AeRosols and GAses (MARGA) revealed two periods of high aerosol nitrate (NO_^3−) concentrations during the campaign. These periods of high nitrate were correlated with increased concentrations of supermicron crustal and sea spray aerosol species, particularly Na^+ and Ca^(2+), and with a shift towards aerosol with larger (1 to 2.5 μm) diameters. We suggest this nitrate aerosol forms by multiphase reactions of HNO_3 and particles, reactions that are facilitated by transport of crustal dust and sea spray aerosol from a source within the United States. The observed high aerosol acidity prevents the formation of NH_4NO_3, the inorganic nitrogen species often dominant in fine-mode aerosol at higher pH. Calculation of the rate of the heterogeneous uptake of HNO_3 on mineral aerosol supports the conclusion that aerosol NO_3^− is produced primarily by this process, and is likely limited by the availability of mineral cation-containing aerosol surface area. Modeling of NO_3^− and HNO_3 by thermodynamic equilibrium models (ISORROPIA II and E-AIM) reveals the importance of including mineral cations in the southeastern United States to accurately balance ion species and predict gas–aerosol phase partitioning.

Additional Information

© Author(s) 2015. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 28 Feb 2015 – Published in Atmos. Chem. Phys. Discuss.: 13 May 2015. Revised: 21 Aug 2015 – Accepted: 02 Sep 2015 – Published: 25 Sep 2015. The authors would like to thank Annmarie Carlton, Jose-Luis Jimenez, and everyone who helped organize the SOAS field campaign. We would also like to thank Metrohm Applikon for use of the MARGA instrument, and in particular J. T. Stanton for invaluable instrument troubleshooting advice. Chuck Brock, Greg Frost, and Stu McKeen provided a useful NEI emissions mapping tool that aided our analysis. Tran Nguyen, Alex Teng, John Crounse, Jason St. Clair, and Paul Wennberg provided HNO_3 data from their CIMS instrument. Weiwei Hu, Pedro Campuzano-Jost, Brett Palm, Doug Day, and Jose Jimenez provided PM_1 inorganic NO

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August 20, 2023
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