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| Titel |
Stable isotopes of soil water are affected by clay minerals: A post
correction approach for dry soils based on physicochemical soil properties |
| VerfasserIn |
Marcel Gaj, Stephan Kaufhold, Paul Koeniger, Matthias Beyer, Thomas Himmelsbach |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250125863
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| Publikation (Nr.) |
 EGU/EGU2016-5513.pdf |
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| Zusammenfassung |
| The cryogenic vacuum extraction is commonly used to access soil water that will be
subsequently analyzed for stable isotopes (18O and 2H). However, the analytical error
associated with this method is high compared to that of stable isotopes measured directly
from water samples. Additionally, the accuracy of data derived from soil water
extractions decreases with the increasing presence of fine compounds such as silt
and clay. To overcome these limitations an extended applicability of the cryogenic
vacuum extraction method is demonstrated. This study proposes two new methods to
improve isotope values using the cryogenic vacuum extraction method. First, by
showing that the extraction temperature of 205 ˚ C improves the precision and the
accuracy for all tested soil types. Secondly, that the post correction of data based on
physicochemical soil properties and common extraction temperature will reduce
errors.
Results show a reduction in error of d-values of soil water derived from soils with clay
content between 0.1 to 48 %. The analytical error could be significantly reduced
compared to previous studies by increasing the extraction temperature even for soils
with high clay content. Soil water extractions from sandy soils are improved by
halving the analytical error. If soil material is available, the proposed correction
scheme can be applied to past isotope data and will improve comparability between
studies and heterogeneous soils. It is recommended to conduct spike experiments
prior to unsaturated zone isotope studies. We encourage future experiments with
extraction temperatures above 205 ˚ C. If previously oven dried substrate is used for
standard preparation old water might remain in soil with a fine texture (i.e., high clay
content) after oven drying at 105 ˚ C and that this old water will enrich any added
calibration water resulting in the enrichment of all samples normalized using it. |
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