Small Antarctic HONO emissions

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 − 3 anions in the snow surface, and abundant UV light for NO − 3 photolysis. Photochemical modeling suggests noon time HONO fluxes 5 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 NO − 3 ion is probably present in aged snows as NaNO 3. This is peculiar to our study site, and we suggest that this may affect the photochemical reactivity of NO − 3 , by preventing the release of products, or providing a reactive medium for newly formed HONO. In 10 fresh snow, the NO − 3 ion is probably present as dissolved or adsorbed HNO 3 and yet, no HONO emissions were observed. We speculate that HONO formation from NO − 3 photolysis may involve electron transfer reactions of NO 2 from photosensitized organics and that fresh snows at our site had insufficient concentrations of adequate organic compounds to favor this reaction.