A 50-YEAR RECORD OF LEAD ISOTOPES IN ANTARCTIC SNOW FROM DOME FUJI, EAST ANTARCTICA

초록

We report here the first record of Pb and Ba concentrations and Pb isotopic composition in snow from a remote site in central East Antarctica. The snow samples were recovered at a site close to Dome Fuji in Dronning Maud Land, East Antarctica (77°18´S, 39°47´E, 3785 m a.s.l.), on December 10, 2007, during the Japanese-Swedish IPY Antarctic expedition. Great precautions were taken during the collection of samples in the field to prevent the possibility of contaminating the snow. A continuous series of 80 snow samples were collected at a 5 cm depth interval from a 4-m deep snow pit, covering the period from 1956 to 2007. The Pb and Ba concentrations and the isotopic composition of Pb were determined by means of thermal ionization mass spectrometry (TIMS). Our results show well-defined variations in Pb and Pb isotopic ratios, which is obviously linked to the rise and fall in the use of leaded gasoline in the Southern Hemisphere as previously reported from different locations in Antarctica. The changing Pb isotopic composition documents the predominent sources of anthropogenic Pb with time during the past 50 years. Pb concentrations remain at very low level with a mean concentration of 3.6 pg g-1 during recent years. Despite this low level of Pb, however, the isotopic signature reveals that significant input of anthropogenic Pb to central Antarctica is currently underway.