Preliminary data on changes of lead concentrations in Antarctic ice from 155,000 to 26,000 years BP

Abstract

Concentrations of lead (Pb) have been measured by ultraclean Isotope Dilution Mass Spectrometry in six sections of the 2083 m Vostok deep Antarctic ice core which integrates some 155,000 years. Lead contamination of 15,000–32,000 pg Pb g^(−1) existed on the outside of the cores, but measured concentrations decreased abruptly along a radius from the outside to the center of the cores, establishing interior values in the 2–40 pg Pb g^(−1) range. These interior data show that natural concentrations of Pb have varied strongly in Antarctic ice during the last 155,000 years: Pb values were high during the end of the ice age (Illinois) which proceeded the last interglacial and during the Last Glacial Maximum; they were low during the last interglacial and most of the last ice age (Wisconsin). Soil dust appears to be the major source of natural Pb, but the volcanic contribution is found to be significant during low Pb time periods.