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| Titel |
Stable isotope signatures in bulk samples from two soils with contrasting characteristics. What do they tell about ongoing pedogenic processes? |
| VerfasserIn |
Nicasio T. Jiménez-Morillo, Otávio dos Anjos Leal, Heike Knicker, Deborah Pinheiro Dick, Francisco J. González-Vila, José A. González-Pérez |
| 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 |
250098201
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| Publikation (Nr.) |
 EGU/EGU2014-13854.pdf |
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| Zusammenfassung |
| Isotopic ratio mass spectrometry (IRMS) has been proven as a promising tool for the
monitoring of biogeochemical processes in soil. In this work, stable isotope
signatures of light elements δ15N, δ13C, δ18O and δD were determined for two soils
with contrasting characteristics in terms of climate, vegetation, land use and
management.
The studied soils were a Cambisol from a subtropical area (Paraná region, South
Brazil) and an Arenosol from a Mediterranean climate (Andalusia, South Spain). A
Flash 2000 HT (N, C, S, H and O) elemental analyzer (Thermo Scientific) coupled to a
Delta V Advantage IRMS (Thermo Scientific) was used. Isotopic ratios are reported as
parts per thousand (o ) deviations from appropriate standards recognized by the
international atomic energy agency (IAEA).
In a first approach we took advantage of the well-known different δ13C signature
between plants using either the C4 or C3 carbon fixation pathway (O´Leary, 1981). The
Arenosol (Spain) revealed a δ13C signature which is clearly in the range of C3 plants
(-26 to -30 o ). Different plant canopies (tree, shrubs or ferns) caused only slight
variations δ13C (STD= 0.98). In contrast, the Cambisol (Brazil) showed less depletion of
the heavier carbon isotope corresponding to C4 predominant vegetation. In addition an
increase from -19 oin the soil surface (0 – 5 cm) to -16 oin the subsoil (20 – 30 cm)
was observed in line with a recent (2 years old) shift of the land use from the
predominant C4 grassland to eucalypt (C3) cultivation. Crossplots of δ15N vs. δ18O
may provide information about nitrate (NO3-) sources and N cycling (Kendall,
1998). In the Mediterranean Arenosol this signal (δ18O = 30o δ15N = 2o )
was found compatible with a predominant nitrate atmospheric deposition,
whereas the signal in the Brazilian Cambisol pointed to the use of a mineral
N fertilization with signs of denitrification processes (δ18O = 13o δ15N =
9o ).
No conclusive results could be obtained from the δD isotopic signature probably due
to overlapping of the δD signals from the organic and the mineral fractions. For a more
detailed analysis steps allowing their separation are necessary (Ruppenthal et al. (2013)
and references therein).
Kendall, C. 1998. Tracing nitrogen sources and cycling in catchments. In Isotopes
Tracers in Catchments Hydrology (C. Kendall and J. J. McDonnell, Eds). Elsevier
Science B. V., Amsterdam, 519–576.
O´Leary, M.H. 1981. Carbon isotope fraction in plants. Phytochemistry 20:
553-567.
Ruppenthal, M., Oelmann, Y., Wilcke, W. 2013. Optimized demineralization
technique for the measurement of stable isotope ratios of nonexchangeable H
in soil organic matter. Environmental Science and Technology 47: 949-957. |
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