CHEMICAL-CONSTITUENTS IN THE AIR AND SNOW AT DYE-3, GREENLAND .1. SEASONAL-VARIATIONS

Chemical constituent concentrations in air and snow from the Dye 3 Gas and Aerosol Sampling Program show distinct seasonal patterns. These p atterns are different from those observed at sea-level sites throughou t the Arctic. Airborne SO42- and several trace metals of crustal and a nthropogenic origin show strong peaks in the spring, mostly in April, Some species also have secondary maxima in the fall. The spring peaks are attributed to transport over the Pole from Eurasian sources, as we ll as transport from eastern North America and western Europe. The fal l peaks are attributed primarily to transport from North America, and less frequent transport from Europe. Airborne Be-7 and Pb-210 show str ong peaks in both spring and fall, suggesting that vertical atmospheri c mixing is favored during these two seasons. Several other airborne c onstituents peak at other times. For example, Na peaks in winter due t o transport of seaspray from storms in ice-free oceanic areas, while M SA peaks in summer due to biogenic production in the oceans nearby. Ma ny trace gases such as freons and other chlorine-containing species sh ow roughly uniform concentrations throughout the year. CO and CH4 show weak peaks in February-March. Concentrations of chemical constituents in fresh snow at Dye 3 also show distinct seasonal patterns. SO42- an d several trace metals show springtime maxima, consistent with the aer osol data. Na shows a winter maximum and MSA shows a summer maximum in the snow, also consistent with the aerosols. Be-7 and Pb-210 in the s now do not show any strong variation with season. Similarly, soot and total carbon in snow do not show strong variation. When used with dry deposition models, these air and snow concentration data suggest that dry deposition of submicron aerosol species has relatively minor influ ence on constituent levels in the snowpack at Dye 3 compared to wet de position inputs(including scavenging by fog); crustal aerosol, on the other hand, may have a more significant input by dry deposition. Overa ll, the results suggest that gross seasonal patterns of some aerosol s pecies are constistent in the air and in fresh snow, although individu al episodes in the air are not always reflected in the snow. The diffe rences in data reported here compared with data sets for sea-level arc tic sites demonstrate the need for sampling programs on the Ice Sheet in order to properly interpret Greenland glacial record data.