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Volume 18, issue 14
Atmos. Chem. Phys., 18, 10237-10254, 2018
https://doi.org/10.5194/acp-18-10237-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: NETCARE (Network on Aerosols and Climate: Addressing Key Uncertainties...

Atmos. Chem. Phys., 18, 10237-10254, 2018
https://doi.org/10.5194/acp-18-10237-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 18 Jul 2018

Research article | 18 Jul 2018

High gas-phase mixing ratios of formic and acetic acid in the High Arctic

Emma L. Mungall1, Jonathan P. D. Abbatt1, Jeremy J. B. Wentzell2, Gregory R. Wentworth1,3, Jennifer G. Murphy1, Daniel Kunkel4, Ellen Gute1, David W. Tarasick2, Sangeeta Sharma2, Christopher J. Cox5,6, Taneil Uttal5, and John Liggio2 Emma L. Mungall et al.
  • 1Department of Chemistry, University of Toronto, Toronto, Canada
  • 2Air Quality Processes Research Section, Environment and Climate Change Canada, Toronto, Ontario, Canada
  • 3Environmental Monitoring and Science Division, Alberta Environment and Parks, Edmonton, Alberta, Canada
  • 4Institute for Atmospheric Physics, Johannes Gutenberg University of Mainz, Mainz, Germany
  • 5NOAA Earth Systems Research Laboratory (ESRL), Physical Sciences Division (PSD), Boulder, CO, USA
  • 6Cooperative Institute for Research in Environmental Sciences (CIRES), Boulder, CO, USA

Abstract. Formic and acetic acid are ubiquitous and abundant in the Earth's atmosphere and are important contributors to cloud water acidity, especially in remote regions. Their global sources are not well understood, as evidenced by the inability of models to reproduce the magnitude of measured mixing ratios, particularly at high northern latitudes. The scarcity of measurements at those latitudes is also a hindrance to understanding these acids and their sources. Here, we present ground-based gas-phase measurements of formic acid (FA) and acetic acid (AA) in the Canadian Arctic collected at 0.5Hz with a high-resolution chemical ionization time-of-flight mass spectrometer using the iodide reagent ion (iodide HR-ToF-CIMS, Aerodyne). This study was conducted at Alert, Nunavut, in the early summer of 2016. FA and AA mixing ratios for this period show high temporal variability and occasional excursions to very high values (up to 11 and 40ppbv respectively). High levels of FA and AA were observed under two very different conditions: under overcast, cold conditions during which physical equilibrium partitioning should not favor their emission, and during warm and sunny periods. During the latter, sunny periods, the FA and AA mixing ratios also displayed diurnal cycles in keeping with a photochemical source near the ground. These observations highlight the complexity of the sources of FA and AA, and suggest that current chemical transport model implementations of the sources of FA and AA in the Arctic may be incomplete.

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We measured gas-phase formic and acetic acid at Alert, Nunavut. These acids play an important role in cloud water acidity in remote environments, yet they are not well represented in chemical transport models, particularly in the Arctic. We observed high levels of formic and acetic acid under both cold, wet, and cloudy and warm, sunny, and dry conditions, suggesting that multiple sources significantly contribute to gas-phase concentrations of these species in the summer Arctic.
We measured gas-phase formic and acetic acid at Alert, Nunavut. These acids play an important...
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