I. Ancient Arctic Ice Does Not Contain Large Excesses of Natural Lead. II. Chronological Variations in Lead and Barium Concentrations and Lead Isotopic Compositions in Sediments of Four Southern California Off-Shore Basins

• Main Author: Ng, Chihang Amy
• Format: Thesis
• Language: English
• Published: 1982
• Subjects: Arctic; Antarctic; Greenland; Byrd; Byrd Station; Lorius; Antarc*; Antarctica; ice core
• Online Access: https://thesis.library.caltech.edu/3203/; https://thesis.library.caltech.edu/3203/3/ng_ca_1982.pdf; https://resolver.caltech.edu/CaltechETD:etd-08232006-143453

Part I This study settled the dispute and proved beyond doubt that excess lead today is 300-fold instead of the 5-fold, as proposed by other investigators, greater than prehistoric time. And, virtually all of the present-day excess of lead above natural levels was shown to be caused by industrial lead emissions to the atmosphere. Concentrations of lead and potassium were determined in a series of ice samples taken in sequence from the outside to the interior of several >2000 year old ice cores drilled from the Greenland and Antarctic ice sheets. Concentrations of lead and potassium were observed to decrease continuously in going from the exterior to the interior of the cores, which indicated that surface contamination had penetrated to the interior of the core, making it impossible to determine the original concentration of lead in the ice. Concentrations measured at the centers of these cores must therefore represent upper limits of lead concentration originally present in the ice. There are l.6 ng Pb/kg ice in 5000 year old Greenland ice and l.4 ng Pb/kg in 2000 year old Antarctic ice. These data verified the earlier findings reported by Murozumi et al. (1969) of <1 ng Pb/kg ice in 800 B.C. Greenland ice near Camp Tuto and also at New Byrd Station. Our findings also support their observation of a continual progressive increase of lead concentration with time even before 1900 A.D. These new data refuted the high concentration values of 45 ng Pb/kg ice and 70 ng Pb/kg ice reported by Herron et al. (1977) and Cragin et al. (1975) in pre-1900 Greenland ice and their claims of no concentration change with time before 1900. These new data also refute the lead concentration values of 26 ng Pb/kg ice reported by Boutron and Lorius (1979) in snow strata of Dome C, Antarctica for the period 1914 to 1974 and their claims that this high lead concentration is natural and has been present since ancient times. Potassium concentrations at the center of the ice core are 2 x 10 3 ng K/kg ice in 5000 year old Greenland ice ...