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

• Published in: The Science of the total environment Vol. 758; no. C; p. 143586
• Main Authors: Gonçalves, Sérgio J., Weis, Johannes, China, Swarup, Evangelista, Heitor, Harder, Tristan H., Müller, Simon, Sampaio, Marcelo, Laskin, Alexander, Gilles, Mary K., Godoi, Ricardo H.M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2021; Elsevier
• Subjects: Antarctica aerosols; Molecular speciation; Nitrates aerosol; Photochemical reactions; Single particles; Snowpack; Molecular speciation; Photochemical reactions; Antarctica aerosols; Single particles; Snowpack; Nitrates aerosol
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.143586

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. [Display omitted] •Trends of aerosol transformation in West Antarctica by photochemical reactions•Particles analyzed by synchrotron technology (NEXAFS) with CCSEMEDX analysis•Displacement of Cl- relative to Na+ was observed over most of sea salt particles.•New insights into NaCl/NO3 core/shell particle type in the Antarctica environment•Findings may assist in reducing modeling uncertainties of radiative effects.