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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L05810, doi:10.1029/2005GL025164, 2006

Isotopic constraints on non-photochemical sulfate production in the Arctic winter

Justin R. McCabe

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA


Joel Savarino

Laboratoire de Glaciologie et Geophysique de l'Environnement CNRS/UJF, St. Martin d'Heres, France


Becky Alexander

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA


Sunling Gong

Air Quality Research Branch (ARQM), Atmospheric Environment Service, Toronto, Ontario, Canada


Mark H. Thiemens

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA


Abstract

The oxygen isotopic composition (Δ17O) of non-seasalt sulfate (NSS) aerosol was measured in samples from Alert, Canada over one year (July 1999–June 2000) and used to quantify the S(IV) oxidants. Measurements of Δ17O in NSS are used to evaluate the relative contributions of O3, H2O2, and OH oxidation leading to the formation of SO4 2− compared to a model of Feichter et al. (1996). The isotopic values suggest that there is a twofold overestimate of ozone oxidation in the model during winter. The isotopic composition is consistent with 10 to 18% contribution from a non-photochemical oxidation pathway, likely Fe3+/Mn2+-catalyzed O2 oxidation, during the dark Arctic winter. Isotopic evidence also invokes a 3 to 10% contribution of a mass dependent oxidant during springtime Arctic ozone depletion events.

Received 15 November 2005; accepted 2 February 2006; published 9 March 2006.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 1041 Geochemistry: Stable isotope geochemistry (0454, 4870); 1615 Global Change: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912).

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Citation: McCabe, J. R., J. Savarino, B. Alexander, S. Gong, and M. H. Thiemens (2006), Isotopic constraints on non-photochemical sulfate production in the Arctic winter, Geophys. Res. Lett., 33, L05810, doi:10.1029/2005GL025164.