THE OCCURRENCE OF ZINC IN ANTARCTIC ANCIENT ICE AND RECENT SNOW

Concentrations of zinc (Zn) have been measured in various sections of the Dome C and Vostok deep Antarctic ice cores, whose ages range from 3850 to 155,000 years BP, and in several large-size surface Antarctic snow blocks collected in Adelie Land and at the geographic South Pole. All the samples were mechanically decontaminated, and detailed outside-inside variation profiles were drawn for most of them then allowing us to clearly establish the accuracy of the data obtained from the analysis of the most central parts of each individual core section or snow block. Natural Zn concentrations are found to have strongly varied in Antarctic ice during the past 155,000 years, the highest values (up to about 100 pg Zn/g) being observed during the Last Glacial Maximum and possibly during the end of the next to last ice age. Wind-blown dust from crustal rock and soil appears to be the main natural source of Zn during the glacial periods, especially the Last Glacial Maximum. Zn concentrations in present-day Antarctic snow from central East Antarctica, about 5 pg Zn/g, are found to be comparable with those in Holocene ice several thousand years old, which evidences that the Antarctic tropospheric cell is still little affected by anthropogenic Zn.