11 Mar 2022
11 Mar 2022
Status: this preprint is currently under review for the journal ACP.

Sulfuric acid in the Amazon Basin: Measurements and evaluation of existing sulfuric acid proxies

Deanna C. Myers1, Saewung Kim2, Steven Sjostedt3, Alex B. Guenther2, Roger Seco4, Oscar Vega Bustillos5, Julio Tota6, Rodrigo A. F. Souza7, and James N. Smith1 Deanna C. Myers et al.
  • 1Department of Chemistry, University of California, Irvine, USA
  • 2Department of Earth System Science, University of California, Irvine
  • 3Morgan Community College, Fort Morgan, CO, USA
  • 4Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Catalonia, Spain
  • 5Instituto de Pesquisas Energéticas e Nucleares, Cidade Universitaria, São Paulo, Brazil
  • 6Universidade Federal do Oeste do Pará, Santarém, Brazil
  • 7Escola Superior de Tecnologia, Universidade do Estado do Amazonas, Manaus, Brazil

Abstract. Sulfuric acid is a key contributor to new particle formation, though measurements of its gaseous concentrations are difficult to make. Several parameterizations to estimate sulfuric acid exist, all of which were constructed using measurements from the Northern Hemisphere. In this work, we report the first measurements of sulfuric acid from the Amazon Basin. These measurements are consistent with concentrations measured in Hyytiälä, Finland, though unlike Hyytiälä there is no clear correlation of sulfuric acid with global radiation. There was a minimal difference in sulfuric acid observed between the wet and dry seasons in the Amazon Basin. We also test the efficacy of existing proxies to estimate sulfuric acid in this region. Our results suggest that nighttime sulfuric acid production is due to both a stabilized Criegee intermediate pathway, and oxidation of SO2 by OH, the latter of which is not currently accounted for in existing proxies. They also illustrate the drawbacks of the common substitution of radiation for OH concentrations. None of the tested proxies effectively estimate sulfuric acid measurements at night. For estimates at all times of day, a recently published proxy based on data from the boreal forest should be used. If only daytime estimates are needed, several recent proxies that do not include the Criegee pathway are sufficient. More investigation of nighttime sulfuric acid production pathways is necessary to close the gap between measurements and estimates with existing proxies.

Deanna C. Myers 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 Myers er al. by Meinrat O. Andreae', Meinrat O. Andreae, 11 Mar 2022
  • RC1: 'Comment on acp-2022-166', Anonymous Referee #1, 22 Apr 2022
  • RC2: 'Comment on acp-2022-166', Anonymous Referee #2, 09 May 2022

Deanna C. Myers et al.

Deanna C. Myers et al.


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Short summary
We present the first measurements of gas phase sulfuric acid from the Amazon Basin and evaluate the efficacy of existing sulfuric acid parameterizations in this under-studied region. Sulfuric acid is produced during daytime and nighttime, though current proxies underestimate nighttime production. These results illustrate the need for better parameterizations of sulfuric acid and its precursors that are informed by measurements across a broad range of locations.