Fluxes of nitrates between snow surfaces and the atmosphere in the European high Arctic

[摘要] Measurements of atmospheric and snow mixing ratios of nitrates and nitrites and their fluxesabove the snow surface were made during two intensive campaigns during spring time 2001 atNy-Ålesund, Svalbard as part of the EU project"`The NItrogen Cycle and Effects on the oxidation ofatmospheric trace species at high latitudes" (NICE).

At this coastal site close to the unseasonably unfrozen fjord, of the measured nitrogen species, onlyHNO₃ showed a significant flux on to the snow surface; a mean deposition of-8.7 nmol h^-1 m^-2 was observed in late April / early May 2001. These fluxes may be due to the reaction ofHNO₃ with sea salt, and especially NaCl, or may be simply uptake ofHNO₃ by ice, which is alkaline because of the sea salt in our marineenvironment.During snowfall periods dry deposition of HNO₃ may contribute up to10% 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 variedbetween 65 and 520 ng g^-1, the total NO₃^- content of the snowpack was on the order of2700 ng cm^-2.In comparison the atmospheric boundary layer column showed aNO₃^- content of only 8 ng cm^-2.The limitedexchange, however, between the snow and the atmosphere was attributed to low mobility ofNO₃^- in the observed snow.

Contrary to other Arctic sites (i.e. Alert, Nunavut or Summit, Greenland) deposition of sea salt and crustalaerosols in this marine environment made the surface snow alkaline; snowNO₃^- was associated with heavier cations and was not readily available for physical exchange or photochemical reactions.

[学科分类] 大气科学