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| Titel |
Solid-state NMR and IRMS characterization of smouldered peat from ombrotrophic cores |
| VerfasserIn |
Claudio Zaccone, Guillermo Rein, Paola Gioacchini, Heike Knicker, Claudio Ciavatta, Teodoro M. Miano |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080863
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| Zusammenfassung |
| Smouldering fires are slow, low temperature, flameless and the most persistent form of
combustion of organic matter (OM) in porous form.
Although smouldering fires of peatlands represent a large perturbation of the atmospheric
chemistry, to date, most studies on smouldering focused on ignition, carbon (C) losses or
emissions, whereas the literature still lacks understanding of the OM evolution following
these events.
The potential to track OM changes able to serve as new proxies for the identification of
past fire events along peat cores is extremely important, especially considering that bogs are
often used as natural archives of paleoenvironmental changes.
In the present work we show preliminary results about solid-state Nuclear Magnetic
Resonance (NMR) and Isotope-Ratio Mass Spectroscopy (IRMS) characterization of peat
OM along three Sphagnum peat columns (26 cm deep) having different initial moisture
contents (MC): 50% MC, 100% MC, and 200% MC.
The 15N spectrum of fresh peat (FP) used as control shows, as expected, only an amide
signal, which is in agreement with the 13C NMR spectrum where mainly signals of
carbohydrates and alkyl C can be observed. Further signals can be observed in the aromatic
region, most probably due to lignin derivatives. Following the smouldering event, selected
peat samples from both the 50% and 100% MC series show, as expected, signals
supporting the occurrence of fire. In detail, the 15N-signals between -200 and -250 ppm
are typical for pyrrole or indole type N. This is in accordance with the 13C NMR
spectra showing considerable intensity in the aromatic region, most likely from char
residues.
Isotopic signatures (i.e., δ13C and δ15N) show a very interesting behaviour. In detail,
δ13C seems to be slightly affected by smouldering, although the information about
vegetational changes are preserved, whereas the δ15N shows a trend positively correlated
with the relative N enrichment observed in smouldered peat samples, as also supported by
15N NMR.
While further research is in progress to find reliable proxies allowing reconstruction of
ancient smouldering events along peat profiles, our data provide an additional important
insight towards assessing palaeoenvironmental conditions and highlighting that smouldering
fires may have been overlooked as the cause of molecular and chemical variations observed in
peat cores.
The present research was financed by the Italian PRIN program 2009 (2009NBHPWR -
Project title: “Chemical and biomolecular indicators for reconstructing environmental
changes in natural archives”) |
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