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| Titel |
An experimental study of basaltic glass-H2O-CO2 interaction at 22 and 50 Ë C: Implications for subsurface storage of CO2 |
| VerfasserIn |
Iwona Galeczka, Domenik Wolff-Boenisch, Eric H. Oelkers, Sigurður R. Gíslason |
| 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 |
250092633
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| Publikation (Nr.) |
 EGU/EGU2014-6991.pdf |
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| Zusammenfassung |
| A novel high pressure column flow reactor (HPCFR) was used to investigate the evolution of
fluid chemistry along a 2.3 meter flow path during 37-104 days of pure water- and
CO2-charged water- (0.3 M CO2(aq)) basaltic glass interaction experiments at 22 and 50 Ë
C. The scale of the HPCFR, the ability to sample a reactive fluid at discrete spatial intervals
under pressure and the possibility to measure the dissolved inorganic carbon and pH in situ
all render the HPCFR unique in comparison with other reactors constructed for studies of
CO2-charged water-rock interaction.
During the pure water-basaltic glass interaction experiment, the pH of the injected water
evolved rapidly from 6.7 to 9-9.5 and most of the dissolved iron was consumed by secondary
mineral formation, similar to natural basaltic groundwater systems. In contrast to natural
systems, however, the dissolved aluminium concentration remained relatively high along the
entire flow path. The reactive fluid was undersaturated with respect to basaltic glass
and carbonate minerals, but supersaturated with respect to zeolites, clays, and Fe
hydroxides.
Basaltic glass dissolution in the CO2-charged water was closer to stoichiometry than
in pure water. The mobility of metals increased significantly in the reactive fluid
and the concentration of some metals, including Mn, Fe, Cr, Al, and As exceeded
the WHO (World Health Organisation) allowable drinking water limits. Iron was
mobile and the aqueous Fe2+/Fe3+ ratio increased along the flow path. Basaltic glass
dissolution in the CO2-charged water did not overcome the pH buffer capacity of the
fluid. The pH rose only from an initial pH of 3.4 to 4.5 along the first 18.5 cm of
the column, then remained constant during the remaining 2.1 meters of the flow
path.
Increasing the temperature of the CO2-charged fluid from 22 to 50 °C increased the
relative amount of dissolved divalent iron along the flow path. After a significant initial
increase along the first metre of the column, the dissolved aluminium concentration decreased
consistent with its incorporation into secondary minerals. The dissolved chromium
concentration evolution mimicked that of Al at 50 °C, suggesting substitution of trivalent Cr
for Al in secondary phases. According to PHREEQC calculations, the CO2-charged fluid was
always undersaturated with respect to carbonate minerals within the column, but
supersaturated with respect to clays and Fe hydroxides at 22 °C and with respect to clays
and Al hydroxides at 50 °C.
Substantial differences were found between modelled and measured dissolved element
concentrations in the fluids during the experiments. These differences underscore the
need to improve computational models before they can be used to predict with
confidence the fate and consequences of carbon dioxide injected into the subsurface. |
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