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| Titel |
2H/1H composition of soil n-alkanes along two altitudinal transects in East Africa |
| VerfasserIn |
Sarah Coffinet, Arnaud Huguet, Nikolai Pedentchouk, Christine Omuombo, David Williamson, Laurent Bergonzini, Thomas Wagner, Sylvie Derenne |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102632
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| Publikation (Nr.) |
 EGU/EGU2015-2022.pdf |
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| Zusammenfassung |
| Long chains n-alkanes are components of terrestrial plant leaf waxes that are ubiquitously
found in geological archives. They have been extensively used to track environmental and
ecological variations in the past, notably changes in vegetation communities. Recent
analytical developments led to the possibility of measuring their deuterium to hydrogen
isotopic ratio (δ2Hwax). This parameter is suggested to be linked to hydrogen isotope ratio of
precipitations (δ2Hp). In 2008, Jia et al. proposed to use soil derived δ2 Hwax as a
paleoelevation proxy since precipitations are known to get more depleted in deuterium with
altitude. They found a linear correlation (R2 0.73) between δ2Hwax in surface
soils and altitude along Mt. Gongga (China). Since then, the correlation between
δ2Hwax and δ2Hp was shown for several other altitudinal transects. Contrary to these
previous observations, however, no trend with altitude was observed in East Africa
along an altitudinal gradient in Mt. Kilimanjaro (North eastern, Tanzania, Peterse et
al., 2009 and Zech et al., 2014). What is the reason for this absence of trend? Is it
because of a difference between African and Asian soils? Or is it specific to Mt.
Kilimanjaro?
To get an insight into this problem, we determined δ2Hwax in 41 surface soils sampled along
two altitudinal transects: from 500 to 2800 m in Mt. Rungwe (South-western Tanzania) and
from 1897 to 3268 m in Mt. Kenya (Central Kenya). The goal of the study was to
further investigate the conditions of applicability of this proxy in East Africa. A
correlation between soil derived δ2Hwax and altitude was observed along Mt. Kenya
(δ2Hwax=20.2*ALT-88.0, R2=0.51) but not along Mt. Rungwe - similarly to Mt. Kilimanjaro
(Peterse et al., 2009; Zech et al., 2014). This contrast between Mt. Kenya on one
hand and Mts. Rungwe and Kilimanjaro on the other hand may be explained by
differences in topography. These results highlight the complexity of the signal recorded
by δ2H, and particularly soil δ2Hwax with regard to its use as a paleoelevation
proxy.
References:
Jia, G., et al. 2008, Geochimica et Cosmochimica Acta 72.
Peterse, F., 2009, Biogeosciences 6.
Zech, M. et al., 2014, Biogeosciences Discussions 11. |
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