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| Titel |
Biogeochemistry of sulfur in the Vienna Woods: Study of sulfur stable isotope ratios by MC-ICP-MS as indicator of biogeochemical S cycling |
| VerfasserIn |
Ondrej Hanousek, Torsten W. Berger, Thomas Prohaska |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090575
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| Publikation (Nr.) |
 EGU/EGU2014-4828.pdf |
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| Zusammenfassung |
| Sulfur entering forest ecosystems originates mainly from combustion of fossil fuels. This
source of sulfur has been strongly (by more than 95 %) reduced in last decades and recently,
higher sulfur output (in soil solution or stream water) than sulfur input (in rain water) in an
ecosystem was registered in many monitored forest ecosystems. This unbalance may be
caused by weathering of sulfur-bearing rocks, desorption of sulfur adsorbed in soil in the past
or (re)mineralization of organic sulfur compounds. This ‘negative’ balance leads to
mobilization of base cations along with SO42- and as such to an acidification of soils. As
hypothesis, δ34S/32S depletion in stream water will be observed if a considerable
proportion of atmospherically deposited sulfate is cycled through the organic S
pool.
Rain water and soil solutions samples were collected for this study at 3 sites (beech
stands) in the Vienna Woods, Austria twice a month from May 2010 to April 2012. Due to the
expected sulfate concentration gradient with respect to the distance from a tree, sampling
was carried out at 5 intervals from a stem. The sulfur concentration in the samples
was determined by ion chromatography. Sulfur isotope ratios (δ34S/32SV CDT)
were analyzed by multicollector inductively coupled plasma mass spectrometry
(MC-ICP-MS) in edge-resolution mode. The method was validated using IAEA-S-1 and
IAEA-S-2 isotopic certified reference materials. The combined standard uncertainty
of the measurement (uc = 0.10 %, k = 1) proves the suitability of the developed
method.
The concentration of sulfur in rain water showed expected behavior, with a seasonal
maximum in winter months, in contrast to the corresponding δ34S/32SV CDT isotope ratios,
where no or low seasonal trends were observed. The sulfur isotope ratios in soil solution
samples show a dependence on the distance from a tree stem and the sampling depth with
lower δ34S/32SV CDT ratios as compared to the precipitation. The measured isotopic
fractionation in soil solution samples might be ascribed to aforementioned biogeochemical
redistribution of organic sulfur. |
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