ANTHROPOGENIC LEAD ISOTOPES IN ANTARCTICA

We report the first measurements of Pb isotopes in Antarctic snow, whi ch show that even recent snow containing 2.3 pg/g is highly polluted w ith anthropogenic Pb. This follows from a comparison of isotope abunda nces of Pb in surface snow and terrestrial dust extracted from ancient Antarctic ice (Dome C, depth 308 m, approximate age 7,500 a BP), the latter being distinctly more radiogenic. This result is independent of geochemical arguments based on measurements of Al, Na and SO4. South America is suggested as a likely source of this anthropogenic Pb. The presence of significantly less radiogenic Pb in the snow adjacent to t wo Antarctic base stations indicates that there is contamination from station emissions, although emission from Australia is an alternative explanation for a site 33 km from Dumont d'Urville.