22 Jan 2021

22 Jan 2021

Review status: this preprint is currently under review for the journal ACP.

Acidity and the multiphase chemistry of atmospheric aqueous particles and clouds

Andreas Tilgner1, Thomas Schaefer1, Becky Alexander2, Mary Barth3, Jeffrey L. Collett Jr.4, Kathleen M. Fahey5, Athanasios Nenes6,7, Havala O. T. Pye5, Hartmut Herrmann1, and V. Faye McNeill8 Andreas Tilgner et al.
  • 1Leibniz Institute for Tropospheric Research (TROPOS), Atmospheric Chemistry Department (ACD), Leipzig, 04318, Germany
  • 2Department of Atmospheric Science, University of Washington, Seattle, WA, 98195, USA
  • 3National Center for Atmospheric Research, Boulder, CO, 80307, USA
  • 4Department of Atmospheric Science, Colorado State University, Fort Collins, CO, 80523, USA
  • 5Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC, 27711, USA
  • 6School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
  • 7Institute for Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Patras, GR-26504, Greece
  • 8Departments of Chemical Engineering and Earth and Environmental Sciences, Columbia University, New York, NY, 10027, USA

Abstract. The acidity of aqueous atmospheric solutions is a key parameter driving both the partitioning of semi-volatile acidic and basic trace gases and their aqueous-phase chemistry. In addition, the acidity of atmospheric aqueous phases, e.g. deliquesced aerosol particles, cloud and fog droplets, is also dictated by aqueous-phase chemistry. These feedbacks between acidity and chemistry have crucial implications for the tropospheric lifetime of air pollutants, atmospheric composition, deposition to terrestrial and oceanic ecosystems, visibility, climate, and human health. Atmospheric research has made substantial progress in understanding feedbacks between acidity and multiphase chemistry during recent decades. This paper reviews the current state of knowledge on these feedbacks with a focus on aerosol and cloud systems, involving both inorganic and organic aqueous-phase chemistry. Here, we describe the impacts of acidity on the phase partitioning of acidic and basic gases and buffering phenomena. Next, we review feedbacks of different acidity regimes on key chemical reaction mechanisms and kinetics, as well as uncertainties and chemical subsystems with incomplete information.

Finally, we discuss atmospheric implications and highlight needs for future investigations, particularly with respect to reducing emissions of key acid precursors in a changing world, and needs for advancements of field and laboratory measurements and model tools.

Andreas Tilgner et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on acp-2021-58', Krzysztof Rudzinski, 09 Feb 2021
  • RC1: 'Comment on acp-2021-58', Anonymous Referee #1, 27 Feb 2021
  • RC2: 'Comment on acp-2021-58', Anonymous Referee #2, 21 Apr 2021

Andreas Tilgner et al.

Andreas Tilgner et al.


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Short summary
Feedbacks of acidity and atmospheric multiphase chemistry in deliquesced particles and clouds are crucial for the tropospheric composition, depositions, climate, and human health. This review synthesizes the current scientific knowledge on these feedbacks involving both inorganic and organic aqueous-phase chemistry. Finally, this review outlines atmospheric implications and highlight needs for future investigations with respect to reducing emissions of key acid precursors in a changing world.