Sources and Mobility of Nitrates in European High Arctic Snow

Measurements of atmospheric and snow mixing ratios of nitrates and nitrites and their fluxes above the snow surface were made during two intensive campaigns during spring time 2001 in the high Arctic at Ny-Ålesund, Svalbard as part of the EU project "The NItrogen Cycle and Effects on the oxidation of atmospheric trace species at high latitudes" (NICE). Of the measured nitrogen species only HNO₃ showed a significant flux above the snow surface, a mean deposition of -8.7 nmol h^-1m^-2 was observed in late April / early May 2001. During snowfall periods dry deposition of HNO₃ may contribute up to 10% of the N budget in the snow; however, the main source for N is wet deposition in falling snow. The surface snow at Ny-Ålesund showed very complex stratigraphy; the NO₃^- mixing ratio in snow varied between 65 and 520 ng g^-1, the total NO₃^- content of the snowpack was on the order of 2700 ng cm^-2. In comparison the atmospheric boundary layer column showed a NO₃^- content of only 8 ng cm^-2. The limited exchange, however, between the snow and the atmosphere was attributed to low mobility of NO₃^- in the observed snow.