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| Titel |
Trace elements in South America aerosol during 20th century inferred from a Nevado Illimani ice core, Eastern Bolivian Andes (6350 m asl) |
| VerfasserIn |
A. Correia, R. Freydier, R. J. Delmas, J. C. Simões, J.-D. Taupin, B. Dupré, P. Artaxo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 3, no. 5 ; Nr. 3, no. 5 (2003-09-11), S.1337-1352 |
| Datensatznummer |
250001248
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| Publikation (Nr.) |
 copernicus.org/acp-3-1337-2003.pdf |
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| Zusammenfassung |
| A 137 m ice core drilled in 1999 from Eastern Bolivian Andes at the summit of
Nevado Illimani (16º 37' S, 67º 46' W, 6350 m asl) was analyzed at high temporal resolution,
allowing a characterization of trace elements in Andean aerosol trapped in the ice during
the 20th century. The upper 50 m of the ice core were dated by multi-proxy analysis of stable
isotopes (d18O and
d2H),
137Cs and Ca+2 content, electrical conductivity, and insoluble
microparticle content, together with reference historical horizons from atmospheric
nuclear tests and known volcanic eruptions. This 50 m section corresponds to a record of
environmental variations spanning about 80 years from 1919 to 1999. It was cut in 744
sub-samples under laminar flow in a clean bench, which were analyzed by Ion Chromatography
for major ionic concentration, by a particle counter for insoluble aerosol content, and by
Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for the concentration of 45
chemical species from Li to U. This paper focuses on results of trace element concentrations
measured by ICP-MS. The high temporal resolution used in the analyses allowed classifying
samples as belonging to dry or wet seasons. During wet season elemental concentrations are
low and samples show high crustal enrichment factors. During dry seasons the situation is
opposite, with high elemental concentrations and low crustal enrichments. For example, with
salt lakes as main sources in the region, average Li concentration during the 20th century is
0.035 and 0.90 ng g-1 for wet and dry seasons, respectively. Illimani average seasonal
concentration ranges cover the spectrum of elemental concentration measurements at another
Andean ice core site (Sajama) for most soil-related elements. Regional crustal dust load in the
deposits was found to be overwhelming during dry season, obfuscating the contribution of
biomass burning material. Marked temporal trends from the onset of 20th century to more
recent years were identified for the concentrations of several trace species of anthropic origin,
especially for Cu, As, Zn, Cd, Co, Ni and Cr. Among these elements, Cu shows average wet
season crustal enrichment factors above 103, while the others range between
102 to about 5x102. P and K show moderate average wet season enrichment factors, suggesting an impact of
natural biogenic emissions from the Amazon Basin. Pb has multiple anthropic sources in the
region, from mining activities in the beginning of 20th century to automotive fuel after 1950s.
From the large number of samples analyzed from Illimani, it was possible to derive an
effective chemical characterization of the deposited background Andean soil dust aerosol
during 20th century. |
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