Seasonal variations in heavy metals concentrations in present day Greenland snow

Thirty-six snow samples collected from a 1.6 m snow pit in central Greenland, have been analysed for Pb, Cd, Zn, Cu and other species using ultraclean analytical procedures. They cover continuously a 2 year time period from summer 1992 to spring 1990, with sub-seasonal resolution. Pronounced seasonal variations of the concentrations are observed for all four heavy metals, with low values in winter, and much higher concentrations not only in spring but also in summer. The factors of variations are 75 for Pb, 31 for Cd, 22 for Zn and 48 for Cu. Estimates of the contributions from natural sources show that anthropogenic contributions are dominant for Pb, Cd and Zn while a significant fraction of Cu derives from rock and soil dust in part of the samples. Our data confirm that the high altitude central areas of the Greenland ice sheet remain isolated from the highly polluted air masses of the Arctic basin in winter. The enhanced concentrations observed in the summer layers are attributed to inputs from pin point sources in high latitude continental areas.