Observation of coinciding arctic boundary layer ozone depletion and snow surface emissions of nitrous acid

Measurements of snow surface—atmosphere exchange fluxes of nitrous acid at Ny-Ålesund, Svalbard during springtime confirmed earlier findings that no significant emissions occurred from alkaline snow surfaces at this marine high Arctic location. On 29 April 2004 air arriving from the North Pole brought both ozone depleted air and significant snowfall. On that day we observed HONO emission fluxes of up to 40 nmol m−2 h−1. These emissions were made possible by the combination of two independent phenomena. The acidic snow allowed the transport of NO3− ions to photochemically reactive areas and the release of produced HONO from the snow interstitial air; while the absence of ozone likely increased the HONO/NO fraction over that of NO2 in the snow interstitial air.