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| Titel |
Effect of atmospheric conditions on soil diffuse degassing |
| VerfasserIn |
Antonio Pio Rinaldi, Fátima Viveiros, Jean Vandemeulebrouck, Micol Todesco |
| 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 |
250033343
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| Zusammenfassung |
| Secondary manifestations of volcanism in the Azores archipelago include low temperature
fumaroles (maximum temperature around 100 -C), hot springs, CO2 cold springs and several
diffuse degassing areas. Continuous monitoring of hydrothermal soil CO2 flux started at
Furnas volcano (S. Miguel island) in October 2002 with the installation of a permanent gas
station coupled also with several meteorological sensors (barometric pressure, air
temperature, wind speed and direction, air relative humidity, rainfall, soil temperature and
soil water content). In October 2004, a second station was installed in this volcanic system.
Both stations perform measurements by the accumulation chamber method. Daily
and seasonal cycles have been observed in the soil CO2 flux time series. From
all the monitored variables, air temperature and barometric pressure are the ones
that best correlate with the soil CO2 flux cycles. Air temperature and soil CO2
flux behave in an inverse way: the higher soil CO2 flux values are registered early
in the morning (lower air temperature) while lower soil CO2 flux values in the
afternoon (higher air temperature). Barometric pressure shows higher correlation with
the CO2 cycles during winter months and in bad weather conditions. In order to
understand the influence of soil conditions on the gas release, several simulations with
TOUGH2 geothermal simulator were performed. We used different TOUGH modules to
describe multi-component (water, CO2 and air) and multi-phase (liquid and gas)
fluids. Using a 1D model, a parametric study was performed to understand the
physical mechanisms producing the observed variations. In this simplified model,
only the air temperature was changed. Numerical results, in agreement with the
observed data, show that the CO2 are strongly dependent on domain permeability,
gas saturation and temperature changes at the surface. Amplitude of the thermal
oscillations influences the amplitude of the observed variations in soil degassing but does
not affect their temporal evolution. A main role is played by rock permeability. |
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