J. Phys. IV France 107 (2003) 633
Changes in the occurrence of heavy metals in the tropical atmosphere during the past 22,000 years as recorded in Bolivian ice coreS. Hong1, J.K. Park1, L.G. Thompson2, C.F. Boutron3, 4, C.P. Ferrari3, 5, B. Franco6 and L. Maurice-Bourgoin6
1 Polar Sciences Laboratory, Korea Ocean Research and Development Institute, Ansan, P.O. Box 29, Seoul 425-600, Korea
2 Byrd Polar Research Center, Department of Geological Sciences, The Ohio State University, Columbus, OH 43210, U.S.A.
3 Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS, BP. 96, 38402 Saint-Martin-d'Hères cedex, France
4 Observatoire des Sciences de l'Univers et Unité de Formation et de Recherche de Physique, Université Joseph Fourier de Grenoble, Institut Universitaire de France, BP. 68, 38041 Grenoble, France
5 Institut des Sciences et Techniques, Université Joseph Fourier de Grenoble, 28 avenue Benoît Frachon, BP. 53, 38041 Grenoble, France
6 Institut de Recherche pour le Développement Bolivie, 9214 La Paz, Bolivia
Nine sections from the Sajama ice core recovered from the summit of an extinct Andean volcano in Bolivia were analysed for various heavy metals to assess anthropogenic changes in the tropical upper troposphere over South America. Tnese samples include two sections dating from 14,100 to 19,200 years BP, corresponding to the Last Glacial Stage (LGS), one section dating from 2800 years BP (the late Holocene), and six sections dating from AD 790 to 1988. Our preliminary data, combined with data reported elsewhere, demonstrate that the heavy metal concentrations since the late Holocene are higher than in the period from the LGS to the early Holocene. The enrichment factors calculated by normalizing for crustal abundance using the metal/AI ratio in the mean upper continental crust indicate that a significant input of heavy metals attributed to anthropogenic contributions has occurred since the beginning of the 19th century for Pb and from the last century for Cd, Cu, and Zn.
© EDP Sciences 2003