Surprisingly small HONO emissions from snow surfaces at Browning Pass, Antarctica

Article (PDF Available)inAtmospheric Chemistry and Physics 6(9) · July 2006with10 Reads
DOI: 10.5194/acp-6-2569-2006 · Source: DOAJ
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 NO<sub>3</sub><sup>-</sup> anions in the snow surface, and abundant UV light for NO<sub>3</sub><sup>-</sup> photolysis. Photochemical modeling suggests noon time HONO fluxes of 5–10 nmol m<sup>-2</sup> h<sup>-1</sup>; the measured fluxes, however, were close to zero throughout the campaign. The location and state of NO<sub>3</sub><sup>-</sup> in snow is crucial to its reactivity. The analysis of soluble mineral ions in snow reveals that the NO<sub>3</sub><sup>-</sup> ion is probably present in aged snows as NaNO<sub>3</sub>. This is peculiar to our study site, and we suggest that this may affect the photochemical reactivity of NO<sub>3</sub><sup>-</sup>, by preventing the release of products, or providing a reactive medium for newly formed HONO. In fresh snow, the NO<sub>3</sub><sup>-</sup> ion is probably present as dissolved or adsorbed HNO<sub>3</sub> and yet, no HONO emissions were observed. We speculate that HONO formation from NO<sub>3</sub><sup>-</sup> photolysis may involve electron transfer reactions of NO<sub>2</sub> from photosensitized organics and that fresh snows at our site had insufficient concentrations of adequate organic compounds to favor this reaction.