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| Titel |
Low temperature accumulation of hydrogen through incubation of forsterite in buffered water. |
| VerfasserIn |
Anna Neubeck, Nguyen Thanh Duc, David Bastviken, Nils G. Holm |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039684
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| Zusammenfassung |
| Abstract
In order to test whether or not methane producing archaea may survive solely on the
products forming through the hydration of olivine, we have analyzed the products formed
from the low temperature incubation of natural forsterite sand in buffered water. Already after
one month of incubation, the molecular hydrogen concentration was high enough to
theoretically sustain the survival of methanogenic archaea at temperatures above 30Ë C.
Also, many important trace elements were present as well as a low enough redox
potential.
Introduction
Hydrocarbons are known to be formed through the reduction of CO2 by H2 in the so
called Fischer-Tropsch Type or Sabatier reaction in hydrothermal systems (Charlou 2002;
Holm 1998; Rushdi A. 2001), but the temperatures used are often higher than at
least 100Ë C. (McCollom 2009). Hydrocarbon and/or hydrogen formation in lower
temperature environments would expand the plausible sites for the existence and
growth of microbial communities and possibly also the abiotic formation of organic
compounds. Therefore we have tested the potential abiotic H2 and CH4 production in a
mixture of forsterite and buffered water at temperatures ranging from 30Ë C to 70Ë
C.
Discussion
We have analyzed the methane and hydrogen formation coupled to the hydration of
forsterite in three different temperatures, 30Ë C, 50Ë C and 70Ë C. In all temperatures, there
is a consistent and temperature dependent release of methane into the headspace of
the reaction cells. Even at temperatures as low as 30Ë C there is a clear methane
and hydrogen release already after one month of incubation. This indicates that
reactions coupled to the hydration of natural forsterite are forming or releasing
methane and hydrogen at very low temperatures. Therefore, environments in which
methane and hydrogen may be released and thus also sustain the growth or survival of
certain microorganisms, might be more widespread than previously thought. Also,
reactions such as the Fischer-Tropsch type or Sabatier reaction may have a great
potential for hydrocarbon formation in natural, forsterite-rich systems at near surface
conditions.
Implications
This study shows that interactions between water and olivine result in the release of
significant amounts of hydrogen and methane, the latter corresponding to olivine dissolution
rates, at temperatures ranging from 30 to 70 ºC. This has important implications regarding
several aspects. First, regarding questions about early life on Earth this study shows that high
quality electron donors (H2 and CH4) can be released when water interacts with very
common minerals also at temperatures suitable for living cells, and not just at temperatures
above 100 ºC as previously reported. This substantially expands the range of environments
suitable for chemosynthetic organisms on the early Earth and there may be a much more
widespread and extensive subsurface biogeochemical cycling of hydrogen and methane than
previously believed.
References
Charlou JL, Donval, J.P., Jean-Baptiste, P., and Holm, N. (2002) Geochemistry of high H2
and CH4 vent fluids issuing from ultramafic rocks at the Rainbow hydrothermal field (36Ë
14’, MAR).
Holm NGaA, E.M. (1998) Organic molecules on the primitive Earth: Hydrothermal
systems. In: A. B (Ed) The Molecular Origins of Life: Assembling Pieces of the Puzzle.
Cambridge University Press, Cambridge
Rushdi A. SBRT (2001) Lipid formation by aqueous Fischer-Tropsch-Type synthesis over
a temperature range of 100 to 400Ë C. Origins of Life and Evolution of the Biosphere 31:
103-118
McCollom TMaB, W (2009) Thermodynamic constraints on hydrogen generation during
serpentinization of ultramafic rocks. . Geochimica et Cosmochimica Acta 73: 856-875 |
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