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  • Titill er á ensku Gas emissions from the Krýsuvík high-temperature geothermal system, Iceland
  • Meistara
  • Útdráttur er á ensku

    A high temperature geothermal system is located within the Krýsuvík volcanic system on the Reykjanes Peninsula. Since 2009 episodes of uplift followed by subsidence have been observed in the area by continuous GPS measurements and InSAR. In April 2013, near-real time monitoring of gas emissions was started in Krýsuvík using a MultiGAS sensor system which collects a semi-continuous time series of gas composition. This monitoring method is relatively new in Iceland, with the first station installed on the summit of Mt. Hekla volcano in 2012.
    In this thesis, gas emissions at Krýsuvík are examined and correlated with crustal deformation and seismicity. The dataset comprises the semi-continuous MultiGAS time series (April-November 2013); quantification of diffuse CO2 gas flux from three areas of high surface activity within the system (Seltún, Hveradalir and Austurengjar); direct samples from fumaroles of dry gas and condensates; seismic records (April-November 2013); and GPS dataset (all of 2013).
    The results from the MultiGAS dataset as well as the fumarole samples indicate that the gas emissions from the Krýsuvík system are H2O dominated with CO2 as the most abundant dry gas species, followed by lesser amounts of H2S. These results are comparable with previous studies in Krýsuvík. In addition, the semi-continuous MultiGAS dataset reveals higher variations of gas composition than previously reported by spot sampling.
    The diffuse CO2 soil flux is variable ranging from 10.9-70.9 T/day from the three observation areas with the highest flux in Hveradalir, the location of the MultiGAS station. The total flux was calculated as 101.4 T/day.
    Correlation of the MultiGAS data with the geophysical data shows that peaks of H2O-rich emissions follow events of crustal movements. Coinciding with the H2O-rich peaks, SO2 is detected in minor amounts (~0.6 ppmv) but this is the first time it has been detected in the Krýsuvík area. The high variations in H2O/CO2 and H2O/H2S ratios measured by MultiGAS are considered to be related to the intensity of degassing activity in the fumarole. The activity of the fumarole is apparently lower during intervals of low or no recorded seismic events. H2O/CO2 and H2O/H2S ratios are lower due to condensation processes affecting the H2O concentration before the steam reaches the inlet tube. Improved sampling set-up may help the detection during periods of low fumarole activity.
    This study is the first to provide a critical evaluation on the suitability of the MultiGAS method in Iceland. It is concluded that a simple setup for the station does generally not suit Icelandic climate because of cold and variable weather conditions. For the station to operate efficiently and reliably during possible future measurements it is necessary to pay close attention to local topographical and climatic conditions and devise the most appropriate station set-up based on that. This is the first time a semi-continuous MultiGAS station has been operated in a highly active geothermal field at high latitude (64°N).

  • 9.10.2014

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