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| Titel |
Black carbon characterization in Quebec black spruce forests |
| VerfasserIn |
Laure Soucemarianadin, Sylvie Quideau, Roderick Wasylishen, M. Derek MacKenzie |
| 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 |
250097393
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| Publikation (Nr.) |
 EGU/EGU2014-12969.pdf |
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| Zusammenfassung |
| Black carbon (BC), an important component of the global soil carbon pool, is a major
by-product of wildfires in Quebec black spruce forests. However, BC characteristics vary
depending on the environmental conditions under which it is formed and this may further
affect its resistance to degradation. The objective of this study was to characterize the
chemical and physical properties of BC formed under variable fire severity to assess
its potential for recalcitrance as a passive carbon pool. Samples (n = 267) of BC
produced by early season wildfires in 2005–2007 were collected from the surface
of black spruce forest floors to cover the range of severity encountered in these
fire-affected forests. Representative samples (n = 33) were then analyzed using
elemental analysis, solid-state 13C nuclear magnetic resonance (NMR) spectroscopy,
scanning electron microscopy and surface area analysis (BET method). Properties of
BC sampled in the field were compared with those of samples produced under
a range of controlled formation conditions in the laboratory. The NMR spectra
of the BC collected on sites affected by low fire severity showed a distribution
of total intensity between the different spectral regions very similar to those of
unburned fuels, and were dominated by peaks indicative of cellulose, while spectra for
BC from higher fire severity sites were dominated by a broad peak assigned to
aromatic carbons. Atomic H/C and O/C ratios decreased along the fire severity
gradient, confirming that increasing severity was associated with an increase in
condensation. By comparing field- to laboratory-produced samples, we concluded
that the temperature of formation in the field ranged between 75 and 250°C. In
all analyzed BC samples, the fraction of aromatic carbon:total carbon was low,
suggesting that the freshly produced BC in this boreal forest environment may be
susceptible to rapid physical alteration and chemical degradation. Nevertheless, it is
important to highlight that the BC we investigated was characteristic of early season
fires. These early season fires are typical in eastern Canada, and also present in
regional and global scenarios of future fire regimes associated with climate change. |
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