A methodology for simultaneous determination of Pb, In and Ba, and Pb isotopes at the picogram per gram level using thermal ionization mass spectrometry and its application for Greenland NEEM ice core

초록

Changes in Pb isotopic compositions provide a time-integrated record of fingerprinting regional and global patterns of atmospheric dust transport. We developed an analytical methodology for simultaneous determination of Pb, In and Ba, and Pb isotopes at the picogram per gram level in polar snow and ice using thermal ionization mass spectrometry (TIMS). Lead isotopic compositions were measured by TIMS (TRITON, Thermo Scientific), and the concentrations of each element were simultaneously determined by isotope dilution mass spectrometry (IDMS) using 113In, 137Ba, and 205Pb spike. Ultra-clean procedures were adopted during the whole treatment of the samples in a clean room. Our methodology is applied for analyzing Pb, In and Ba, and Pb isotopes in a 2,540-m-long NEEM (North Greenland Eemian Ice Drilling) Greenland ice core which was retrieved from North-West Greenland during 2008-2012. The major purpose of this study is to reconstruct the first high-resolution ice record of a shift of mineral dust sources in response to dramatic climate transition between the Last Glacial Maximum (~25,000 yr BP) and the Holocene (8000 yr BP).