Historical record of trace elements in aerosols from Western Amazon Basin during 20th century (1919-1999) from Illimani ice core, Bolivian Andes
Alexandre
Correia, Institute of Physics, University of Sao Paulo, LGGE, CNRS and Universite Joseph Fourier, acorreia@if.usp.br
(Presenting)
Robert
J
Delmas, LGGE, CNRS and Universite Joseph Fourier, delmas@lgge.obs.ujf-grenoble.fr
Remi
Freydier, UMR5563, LMTG, CNRS and Universite Paul Sabatier, freydier@lmtg.ups-tlse.fr
Jean-Denis
Taupin, LGGE, IRD, jdtaupin@inamhi.gov.ec
Paulo
Artaxo, Institute of Physics, University of Sao Paulo, artaxo@if.usp.br
Bernard
Dupre, UMR5563, LMTG, CNRS and Universite Paul Sabatier, dupre@lmtg.ups-tlse.fr
A 137 m ice core drilled in 1999 from the summit of Nevado Illimani (16°37' S, 67°46' W, 6350 m asl, Bolivian Andes) allows to study the chemical composition of aerosols from the Western Amazon Basin during the 20th century. The ice core extraction site is downwind from the Amazon Basin. Dating shows the upper 50 m of the ice core correspond to about 80 years of record (1919-1999). Elemental concentrations were determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) for 45 chemical species (from Li to U) in 744 ice and snow samples along the 50-m ice core section, providing a database with sub-annual to annual resolution. Several statistical methodologies were used to yield a full chemical characterization of aerosol deposits, their seasonality and long term trends. During austral winter (dry season) elemental concentrations usually reach their highest values, due to reduced removal processes (wet deposition). Average Aluminum concentration was 965 ng/g during dry season and 18.1 ng/g during wet season. Potassium averages range from 388 ng/g in the dry season to 14.3 ng/g in the wet season. Heavy metal concentrations measured in the beginning of the 20th century are generally in accordance with results reported by other authors for the same region. Excess (non-terrigenous) concentrations for several heavy metals show high (4 to 10-fold) enrichments after the second half of 20th century, most probably due to increasing mining exploitation in South America.
Submetido por Alexandre Lima Correia em 18-MAR-2004