Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 6 1 2006 10.5194/acpd-6-615-2006 http://www.atmos-chem-phys-discuss.net/6/615/2006/ http://www.atmos-chem-phys-discuss.net/6/615/2006/acpd-6-615-2006.html http://www.atmos-chem-phys-discuss.net/6/615/2006/acpd-6-615-2006.pdf 615 648 2006-01-17 Small HONO emissions from snow surfaces at Browning Pass, Antarctica H. J. Beine A. Amoroso F. Dominé M. D. King M. Nardino A. Ianniello J. L. France C.N.R. – IIA, Via Salaria Km 29,3, 00 016 Monterotondo Scalo (Roma), Italy CNRS – LGGE, BP 96, 54 rue Molière, 38 402 Saint Martin d’Hères, France Department of Geology, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK C.N.R. – IBIMET, Sezione di Bologna, via Gobetti 101, 40 129 Bologna, Italy Measured Fluxes of nitrous acid at Browning Pass, Antarctica were very low, despite conditions that are generally understood as favorable for HONO emissions, including: acidic snow surfaces, an abundance of NO₃^− anions in the snow surface, and abundant UV light for NO₃^− photolysis. Photochemical modeling suggests noon time HONO fluxes of 5–10 nmol m^−2 h^−1; the measured fluxes, however, were close to zero throughout the campaign. The analysis of soluble mineral ions in snow reveals that the NO₃^− ion is probably present in aged snows as NaNO₃. This is peculiar to our study site, and we suggest that this may affect the photochemical reactivity of NO₃^−, by preventing the release of products, or providing a reactive medium for newly formed HONO. In fresh snow, the NO₃^− ion is probably present as dissolved or adsorbed HNO₃ and yet, no HONO emissions were observed. We speculate that HONO formation from NO₃^− photolysis may involve electron transfer reactions of NO₂ from photosensitized organics and that fresh snows at our site had insufficient concentrations of adequate organic compounds to favor this reaction.