Photochemical reactions on aerosols at West Antarctica: A molecular case-study of nitrate formation among sea salt aerosols

Sérgio J Gonçalves Jr; Johannes Weis; Swarup China; Heitor Evangelista; Tristan H Harder; Simon Müller; Marcelo Sampaio; Alexander Laskin; Mary K Gilles; Ricardo H M Godoi

doi:10.1016/j.scitotenv.2020.143586

Photochemical reactions on aerosols at West Antarctica: A molecular case-study of nitrate formation among sea salt aerosols

Sci Total Environ. 2021 Mar 1:758:143586. doi: 10.1016/j.scitotenv.2020.143586. Epub 2020 Nov 11.

Authors

Affiliations

¹ Environmental Engineering Department, Federal University of Paraná, Curitiba, PR, Brazil; LARAMG, Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ, Brazil.
² Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Chemistry, University of California, Berkeley, CA 94720, USA; Physikalisches Institüt, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
³ William R. Wiley Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
⁴ LARAMG, Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ, Brazil.
⁵ Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Chemistry, University of California, Berkeley, CA 94720, USA.
⁶ Brazilian National Space Institute - INPE, São José dos Campos, SP, Brazil.
⁷ William R. Wiley Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA; Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
⁸ Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁹ Environmental Engineering Department, Federal University of Paraná, Curitiba, PR, Brazil. Electronic address: rhmgodoi@ufpr.br.

PMID: 33218800
DOI: 10.1016/j.scitotenv.2020.143586

Abstract

Environmental implications of climate change are complex and exhibit regional variations both within and between the polar regions. The increase of solar UV radiation flux over Antarctica due to stratospheric ozone depletion creates the optimal conditions for photochemical reactions on the snow. Modeling, laboratory, and indirect field studies suggest that snowpack process release gases to the atmosphere that can react on sea salt particles in remote regions such as Antarctica, modifying aerosol composition and physical properties of aerosols. Here, we present evidence of photochemical processing in West Antarctica aerosols using microscopic and chemical speciation of individual atmospheric particles. Individual aerosol particles collected at the Brazilian module Criosfera 1 were analyzed by scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) combined with computer-controlled scanning electron microscopy (CCSEM) with energy-dispersive X-ray (EDX) microanalysis. The displacement of chlorine relative to sodium was observed over most of the sea salt particles. Particles with a chemical composition consistent with NaCl-NO₃ contributed up to 30% of atmospheric particles investigated. Overall, this study provides evidence that the snowpack and particulate nitrate photolysis should be considered in dynamic partition equilibrium in the troposphere. These findings may assist in reducing modeling uncertainties and present new insights into the aerosol chemical composition in the polar environment.

Keywords: Antarctica aerosols; Molecular speciation; Nitrates aerosol; Photochemical reactions; Single particles; Snowpack.