 |
| Titel |
Sediment records of highly variable mercury inputs to mountain lakes in Patagonia during the past millennium |
| VerfasserIn |
S. Ribeiro Guevara, M. Meili, A. Rizzo, R. Daga, M. Arribére |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 7 ; Nr. 10, no. 7 (2010-04-14), S.3443-3453 |
| Datensatznummer |
250008341
|
| Publikation (Nr.) |
 copernicus.org/acp-10-3443-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
High Hg levels in the pristine lacustrine ecosystems of the Nahuel Huapi
National Park, a protected zone situated in the Andes of Northern Patagonia,
Argentina, have initiated further investigations on Hg cycling and source
identification. Here we report Hg records in sedimentary sequences to
identify atmospheric sources during the past millennium. In addition to
global transport and deposition, a potential atmospheric Hg source to be
considered is the local emissions associated with volcanic activity, because
the Park is situated in the Southern Volcanic Zone. Two sediment cores were
extracted from Lake Tonček, a small, high-altitude system reflecting mainly
direct inputs associated with atmospheric contributions, and Lake Moreno
Oeste, a much larger and deeper lake having an extended watershed covered
mostly by native forest.
The sedimentary sequences were dated based on both 210Pb and 137Cs
profiles. In addition, tephra layers were identified and geochemically
characterized for chronological application and to investigate any
association of volcanic eruptions with Hg records. Hg concentrations in
sediments were measured along with 32 other elements, as well as organic
matter, subfossil chironomids, and biogenic silica. Observed background Hg
concentrations, determined from the sequence domains with lower values,
ranged from 50 to 100 ng g−1 dry weight (DW), whereas the surficial
layers reached 200 to 500 ng g−1 DW. In addition to this traditional
pattern, however, two deep domains in both sequences showed dramatically
increased Hg levels reaching 400 to 650 ng g−1 DW; the upper dated to
the 18th to 19th centuries, and the lower around the 13th
century. These concentrations are not only elevated in the present profiles
but also many-fold above the background values determined in other fresh
water sediments, as were also the Hg fluxes, reaching 120 to
150 μg m−2 y−1 in Lake Tonček . No correlation was observed between Hg
concentrations and the contents of organic matter, subfossil chironomids,
biogenic silica, or the other elements determined. However, distinctly
increased Hg concentrations were observed immediately above some tephra
layers, suggesting a link to volcanic events. Extended fires might be
another potential atmospheric source because the earlier Hg peaks coincide
with reported charcoal peaks, whereas the upper Hg peaks coincide with
evidences of extended forest fires from tree-ring data and historical
records. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|