J. Phys. IV France 107 (2003) 1157
DOI: 10.1051/jp4:20030505

Pb and Sr isotopes from an ice-core provides evidence for changing atmospheric conditions at the Sajama icecap, South America

K.J.R. Roman¹, S. Hong², G. Bulion¹, L. Burn¹, C.F. Boutron³, C.P. Ferrari³, L.G. Thompson⁴, L. Maurice-Bourgoin⁵ and B. Francou<sup>5

1</sup>  Department of Applied Physics, Curtin University of Technology, G.P.O. Box U1987, Perth 6845, Australia
²  Polar Sciences Laboratory, Korea Ocean Research & Development Institute, Ansan, P.0. Box 29, Seoul 425-600, South Korea
³  Laboratoire de Glaciologie et Géophysique de l'Environnement du CNRS, 54 rue Molière, BP. 96, 38402 Saint-Martin-d'Hères, France
⁴  Byrd Polar Research Center, Department of Geological Sciences, Ohio State University, Columbus, OH 43210, U.S.A.
⁵  Institut de Recherche pour le Développement Bolivie, CP. 9214 La Paz, Bolivia

Abstract
Measurements of Ph and Sr isotopes and Pb, Sr, Ba and Rb concentrations in ice-core samples from the Sajama icecap in Bolivia were made to investigate the changing environmental conditions in the region over the past 22 ky.. The Pb isotopic measurements indicate there has been a significant change in the ²⁰⁶Pb/ ²⁰⁷Pb ratio in the ice by 1700 AD which can be attributed to human activity. This change was also accompanied by increasing Pb/Ba ratios that reach ~10 times natural values by the beginning of the 20th century, confirming an increase of anthropogenic Pb levels. Sr and Rh concentrations are highly enhanced in 3 ky and 0.5 ky BP ice relative to the upper-crustal rock indicating a different origin for a significant proportion of the dust in these samples. Likely sources of this dust are dry lake beds that occur on the Altiplano as a result of changing climatic conditions. This dust adds to the background level of dust accumulating on the Sajama icecap.

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