 |
| Titel |
Biogeochemical constraints on the origin of methane in an alluvial aquifer:
evidence for the upward migration of methane from underlying coal measures. |
| VerfasserIn |
Charlotte P. Iverach, Sabrina Beckmann, Dioni I. Cendón, Mike Manefield, Bryce F. J. Kelly |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137357
|
| Publikation (Nr.) |
 EGU/EGU2017-34.pdf |
|
|
|
|
|
| Zusammenfassung |
| Geochemical and microbiological indicators of methane (CH4) production, oxidation and
migration processes in groundwater are important to understand when attributing sources of
gas. The processes controlling the natural occurrence of CH4 in groundwater must be
characterised, especially when considering the potential impacts of the global expansion of
unconventional gas production on groundwater quality and quantity. We use geochemical
and microbiological data, along with measurements of CH4 isotopic composition
(δ13C-CH4), to determine the processes acting upon CH4 in a freshwater alluvial aquifer
that directly overlies coal measures targeted for unconventional gas production in
Australia.
A combination of geochemical and microbiological groundwater samples were collected
from private irrigation boreholes. The groundwater was analysed for the major ions, water
stable isotopes (δ2H and δ18O), the isotopic composition of dissolved organic carbon
(δ13CDOC) and dissolved inorganic carbon (δ13CDIC). Quantitative real-time PCR was used
to determine abundances of bacterial and archaeal 16S rRNA gene targets and functional
gene targets in the groundwater.
Measurements of CH4 indicate that there is biogenic CH4 in the aquifer, however
microbial community analysis indicates that there are no methanogenic archaea in the
groundwater. In addition, geochemical data, particularly the isotopes of DIC and, as well as
the concentration of SO42−, indicate limited potential for methanogenesis in-situ.
Microbial community analysis also showed that aerobic oxidation of CH4 is occurring
in the alluvial aquifer despite the absence of a microbial pathway to produce the
CH4.
The combination of microbiological and geochemical indicators suggests that the most
likely source of CH4, where it was present in the freshwater aquifer, is the upward migration
of CH4 from the underlying coal measures. |
|
|
|
|
|
|