Past and present students (from 1996 -) 

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Post docs
Dr Paul Christian Frogner- Kockum (Sweden) from 1999 - 2001.
Dr Domenik Wolff-Boenisch (Germany) from 2001 - 2004.
Dr Domenik Wolff-Boenisch (Germany) from 2007 - 2011.
Dr Morgan Tomas Jones (United Kingdom) from 2011 - 2013.
Dr Iwona Monica Gałeczka (Poland) from 2013 - 2016.
Dr Eydís Salome Eiríksdóttir (Iceland) from 2016 - 2016.
Dr Sandra Ósk Snæbjörnsdóttir (Iceland) from 2017 - 2017.
Dr Martin Voigt (Germany) 2018 - present.
Dr Marie-Anne Ancellin (France) 2018-2021.
Dr Deirdre Elizabeth Clark (USA and Canada) 2019-2020.

Dr. Elizabeth Jane Phillips (Canada) 2021-2022
 

PhD Students 
Marin Ivanov Kardjilov (Bulgaria) from 2000 - 2008.
Josh Wimpenny (United Kingdom) from 2004 - 2009.
Bergur Sigfússon (Iceland) from 2005 - 2009.
Therese Kaarbø Flaathen (Norway) 2006 - 2009.
Gabrielle Jarvik Stockmann (Denmark) from 2007 - 2012.
Iwona Monica Gałeczka (Poland) from 2009 - 2013.
Snorri Guðbrandsson (Iceland) from 2007 - 2013.
Jonas Olsson (Denmark) from 2010 - 2014.
Helgi Alfreðsson (Iceland) from 2007 - 2015.
Eydís Salome Eiríksdóttir (Iceland) from 2012 - 2016.
Sandra Ósk Snæbjörnsdóttir (Iceland) from 2012-2017.
Rebecca Anna Neely (United Kingdom) from 2012-2017. 
Deirdre Elizabeth Clark (USA and Canada) from 2014-2019.

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Current PhD students
Tobias Linke, (Germany) from 1. November 2016.

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MSc students 
Andri Stefánsson (Iceland) from 1996 - 1998.
Matthildur Bára Stefánsdóttir (Iceland) from 1997 - 1999.
Ingunn María Þorbergsdóttir (Iceland) from 1999 - 2002.
Bergur Sigfússon (Iceland) from 2002 - 2003.
Eydís Salome Eiríksdóttir (Iceland) from 2005 - 2007.
Sigríður Magnea Óskarsdóttir (Iceland) from 2006 - 2007.
Mahnaz Rezvani Khalilabad (Iran) from 2007 - 2008.
Sylviane L. G. Lebon (Belgium) from 2008 - 2009.
Anja Leth (Denmark ) from 2010 - 2012.

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Description of postdoctoral students (from 1996 -)

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Dr. Paul Christian Frogner- Kockum 1999 -2001.

Paul measured the fertilization and toxic potential of pristine volcanic ash by single flow ambient pressure plug flow reactors. 

 

Frogner P., Gislason S. R. and Oskarsson N. (2001). Fertilizing potential of volcanic ash in ocean surface water. Geology 29, 487-490.

Paul C. Frogner, Kockum, Roger B. Herbert, Sigurdur R. Gislason (2006). A diverse ecosystem response to volcanic aerosols. Chemical Geology 231, 57–66. This work was supported by the Nordic Council of Ministers through Nordvolk, the Nordic Volcanological Institute in Iceland. 

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Dr. Domenik Wolff-Boenisch 2001 - 2004, 2007-2011.

Domenik measured the dissolution rate of volcanic glasses of different compositions in various water compositions at 25° to 74 °C, and the effect of crystallinity on the dissolution rate of rocks. For these experiment he used mixed flow through reactors. Domenik came back in 2007 to become a project manager of the University of Iceland’s part of CarbFix until 2011. This work was financed by the European Union through a Research Training Network entitled “Quantifying the dissolution and precipitation of solid solutions in natural and industrial processes” within the 5th framework programme (contract number: HPRN-CT-2000-00058).

Wolff-Boenisch, D., Gislason, S.R. and Oelkers, E.H. (2006). The effect of crystallinity on dissolution rates and CO2 consumption capacity of silicates. Geochimica et Cosmochimica Acta, 70, 858-870. 

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Wolff-Boenisch, D., Gislason, S. R., and Oelkers, E. H. (2004). The effect of fluoride on the dissolution rates of natural glasses at pH 4 and 25°C. Geochim. Cosmochim. Acta 68, 4571-4582. 

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Wolff-Boenisch, D., Gislason, S. R., Oelkers, E. H., and Putnis, C. V. (2004). The dissolution rates of natural glasses as a function of their composition at pH 4 and 10.6, and temperatures from 25 to 74°C. Geochim. Cosmochim. Acta 68, 4843-4858. 

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Dr. Morgan Tomas Jones 2011 - 2013.

Morgan studied the reactivity of river suspended matter in the oceans and its role in the various element cycles on the Earth. In the second half of his postdoc he tested the use of osmotic samplers for river monitoring. The research was supported by the European Union through the Funding Scheme: FP7-PEOPLE-2009-IEF, Grant Agreement number: 254495 Project acronym: VOLCANIC WEATHERING and the Seventh Framework Programme “FutureVolc”, EC project number: 308377. 

Morgan T. Jones, Christopher R. Pearce, Catherine Jeandel, Sigurdur R. Gislasona, Eydis S. Eiriksdottir, Vasileios Mavromatis, Eric H. Oelkers (2012).   Riverine particulate material dissolution as a significant flux of strontium to the oceans. Earth and Planetary Science Letters 355-356, 51–59.

Jones MT, SR Gislason, KW Burton, CR Pearce, V Mavromatis, P AE Pogge von Strandmann, EH Oelkers (2014).  Quantifying the impact of riverine particulate dissolution in seawater on ocean chemistry. Earth and Planetary Science Letters 395, 91-100.

Jones MT, IM Gałeczka, A Gkritzalis-Papadopoulos, MR Palmer, MC Mowlem, K Vogfjörð, Þ Jónsson and Gislason (2015). Monitoring of jökulhlaups and element fluxes in proglacial Icelandic rivers using osmotic samplers.  Journal of Volcanology and Geothermal Research 291, 112-124

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Dr. Iwona Monica Gałeczka 2013 - 2016. 

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Iwona worked with and modified the high pressure plug flow reactor that she build during her PhD study, continued working on “jökulhlaup”, tested the use of osmotic samplers for river monitoring with Morgan Jones, and applied them successfully for monitoring Jökulsá á Fjöllum river chemistry during and following the Bárðarbunga eruption in 2014-2015 and in collaboration with Eydís S. Eiríksdóttir after the eruption in the direct runoff river Fellsá which catchment is about 100 km east of the eruption site. Furthermore she ran a huge sampling campaign on the Vatnajökull glacier to define the pollution form the Bárðarbunga eruption. These projects have been funded by The European Union through the Collaborative project (generic) FP7-ENERGY-2011-1, Grant Agreement Number 283148, CarbFix  creating the technology for safe, long-term carbon storage in the subsurface, Nordic Innovation, through the Top Level Initiative the 11029-NORDICCS – The Nordic CCS Competence Centre and SPI-Cooperation, the Icelandic government by funding through the Civil Protection related to the eruption of the Bárðarbunga volcano 2014-15 and the Icelandic research Fund RANNÍS (Grant # 163531-051 og 163531-052).

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Galeczka I. M., D. Wolff-Boenisch, E. H. Oelkers, S. R. Gislason (2014). An experimental study of basaltic glass–H2O-CO2 interaction at 22 and 50° C: Implications for subsurface storage of CO2. Geochimica et Cosmochimica Acta 126, 123-145.

Galeczka IM, ES Eiriksdottir, J Hardardottir, EH Oelkers, P Torssander, and SR Gislason (2015). The effect of the 2002 glacial flood on dissolved and suspended chemical fluxes in the Skaftá river, Iceland.  Journal of Volcanology and Geothermal Research 301, 253–276.

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Iwona Galeczka, Gunnar Sigurdsson, Eydis Salome Eiriksdottir, Eric H. Oelkers, Sigurdur R. Gislason (2016). The chemical composition of rivers and snow affected by the 2014/2015 Bárðarbunga eruption, Iceland.  Journal of Volcanology and Geothermal Research, 316,101-119. http://www.sciencedirect.com/science/article/pii/S0377027316000615

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Galeczka, Iwona M., Eydis Salome Eiriksdottir, Finnur Pálsson, Eric Oelkers, Stefanie Lutz, Liane G. Benning, Andri Stefánsson, Ríkey Kjartansdóttir, Jóhann Gunnarsson-Robin, Shuhei Ono, Rósa Ólafsdóttir, Elín Björk Jónasdóttir, Sigurdur R. Gislason (2017). Pollution from the 2014–15 Bárðarbunga eruption monitored by snow cores from the Vatnajökull glacier, Iceland. Journal of Volcanology and Geothermal Research, 347, 371-396.

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Iwona Galeczka, Eydís Salome Eiríksdóttir, Finnur Pálsson, Rósa Ólafsdóttir, Elín Björk Jónasdóttir & Sigurður R. Gíslason (2017). Pollution from the 2014/2015 Bárðarbunga eruption monitored by snow cores from Vatnajökull glacier, Iceland. Í; Áhrif Holuhraunsgossins á umhverfi og heilsu. Ritstjórar Bjarni Diðrik Sigurðsson og Gerður Stefánsdóttir bls. 41 –45. Rit LbhÍ nr. 83, Desember 2017. Landbúnaðarháskóli Íslands og Veðurstofa Íslands, ISSN 1670-5785, ISBN 978-9979-881-54-4.

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Iwona Galeczka, Gunnar Sigurdsson, Eydís Salome Eiríksdóttir, Eric H. Oelkers & Sigurður R. Gíslason (2017). The chemistry of rivers and snow affected by the 2014/2015 Bárðarbunga eruption, Iceland. Í; Áhrif Holuhraunsgossins á umhverfi og heilsu. Ritstjórar Bjarni Diðrik Sigurðsson og Gerður Stefánsdóttir bls. 46 –56. Rit LbhÍ nr. 83, Desember 2017.

Landbúnaðarháskóli Íslands og Veðurstofa Íslands, ISSN 1670-5785, ISBN 978-9979-881-54-4.

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Dr. Eydís Salome Eiríksdóttir, post doc in 2016.

Eydís studied the environmental impact of the Holuhraun 2014-2015 eruption on the direct runoff river Fellsá. The catchment is located about 100 km east of the eruption site.  The study was done in collaboration with Iwona Galeczka using osmotic samplers which provided continuous daily average river composition monitoring for the entire first snowmelt period following the end of the eruption. The Icelandic government funded the study through the Civil Protection related to the eruption of the Bárðarbunga volcano 2014-15, and the Landsvirkjun Power Company, Iceland, also provided funding.  

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ES Eiriksdottir, IM Galeczka & SR Gislason (2020). Continuous measurements of riverine chemical constituents reveal the environmental effect of the 2014–2015 Bárðarbunga eruption in Iceland. Journal of Volcanology and Geothermal Research 392, 106766.

Eydís Salome Eiríksdóttir, Iwona M. Gałeczka & Sigurður Reynir Gíslason (2017). Áhrif eldgossins í Bárðarbungu 2014–2015 á efnasamsetningu og framburð Fellsár í Fljótsdal. Í; Áhrif Holuhraunsgossins á umhverfi og heilsu. Ritstjórar Bjarni Diðrik Sigurðsson og Gerður Stefánsdóttir bls. 57 –64. Rit LbhÍ nr. 83, Desember 2017. Landbúnaðarháskóli Íslands og Veðurstofa Íslands, ISSN 1670-5785, ISBN 978-9979-881-54-4.

 

Dr Sandra Ósk Snæbjörnsdóttir, post doc 2017.

Sandra gathered published and unpublished data, some of it from her own MSc thesis on the stratigraphy, porosity, chemical composition of rock, minerals and glasses at the CarbFix2 injection site at Hellisheidi Iceland. Injection of a CO2-H2S gas mixture started in June 2014. This short project was funded by the Research Fund of University of Iceland. 

Snæbjörnsdóttir, Sandra Ó, Sigrún Tómasdóttir, Bergur Sigfússon, Edda Sif Aradóttir, Gunnar Gunnarsson, Auli Niemi, Farzad Basirat, Benoît Dessirier, Sigurdur R Gislason, Eric H Oelkers, Hjalti Franzson (2018). The geology and hydrology of the CarbFix2 site, SW-Iceland, Energy Procedia 146, 146-157.

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Dr. Martin Voigt, post-doc from January 2018.

Martins work at University of Iceland will mainly focus on low-temperature (5°-150°C) basalt-seawater interactions, both to look at natural ocean-floor processes and at the fate of added CO2 to such systems. 

 

About Martin: Martin did his BSc in Freiburg Germany, MSc in Victoria Canada, where he studied magmatic processes at oceanic ridges and finally he got his PhD in geochemistry from Paul Sabatier in Toulouse France in 2017.  There he used experiments in the laboratory, for example, to study Mg- and Sr-isotope fractionation during seawater-basalt interactions at elevated temperature and pressure to simulate processes at oceanic ridges.

M Voigt, C Marieni, DE Clark, SR Gíslason, EH Oelkers (2018). Evaluation and refinement of thermodynamic databases for mineral, Energy Procedia (2018) 146, 81-91. 

This study is a part of the CarbFix2 project: https://www.or.is/carbfix2 and funded by the European Union grant 764760 - CarbFix2- H2020-LCE-2017-RES-CCS-RIA.
 

Dr. Marie-Anne Ancellin, post-doc from September 2018.

The last IPCC report stressed the importance to use Carbon capture and storage (CCS) to reduce the effects of anthropogenic greenhouse gases. The goal of Marie-Anne’s study is to investigate the utility of metal stable isotopes to monitor geochemical reactions induced by injection of CO2 and H2S in  basaltic aquifers. The isotope work is done at Durham University (UK) in collaboration with Kevin Burton. Marie-Anne has analysed Fe, Cu, Zn and St isotopes in water samples from the low temperature (20° - 50°C) CarbFix1 injection site Hellisheiði, Iceland to complement existing Ca and Mg isotope data.  And the same isotopes from the high temperature (80°-270°C) Carbfix2 injection site to complement existing Mg isotope data. Here below is her latest abstract from the Goldschmidt 2020 conference, which focused on the low-temperature Carbfix1 site. Tracing CO2 and H2S sequestration in a basaltic aquifer using stable isotopes at CarbFix, Iceland.

 

The last IPCC report stressed the importance to use Carbon capture and storage (CCS) to reduce the effects of anthropogenic greenhouse gases. The goal of our study is to investigate the utility of metal stable isotopes to monitor geochemical reactions induced by injection of CO2 and H2S in a basaltic aquifer. We have analysed Fe, Cu, Zn and Sr isotopes in water samples from the CarbFix site (Hellisheiði, Iceland) to complement exisiting Ca and Mg isotope data. Pilot injections of (1) 175 tons of CO2 and (2) 73 tons CO2+H2S gas mixture into a deep aquifer were undertaken in 2012. Previous studies have shown that the mobilisation of cations (Ca, Mg, Fe) related to the arrival of the carbonenriched, low-pH waters, was caused by dissolution of the formation basaltic rock. These element concentrations decreased rapidly after this intitial dissolution, being trapped in carbonates, clays, zeolites and hydroxydes. We observe substantial variations in δ56Fe (>1.8 ‰) and δ66Zn (>1.4 ‰) water compositions through the injections and the following monitoring period. Stable Sr, Mg and Zn do not correlate with any specific mineral saturation index, suggesting a multi-mineral influence on their isotopic compositions. Indeed, these isotopes will be fractionated by zeolite, clay, sulfide and carbonate precipitation, for which individual influence are challenging to disentangle. However, Fe and Ca isotope compositions covary when pure CO2 is injected, along with pH variations. Co-injection with H2S at the second injection decouples Fe and Ca isotope fractionation. Ca isotopes are shown to be controlled by calcite dissolution/precipitation at the CarbFix site. Fe isotope fractionation may then be primarly controlled by carbonate precipitation when pure CO2 is involved while being also affected by other phases, in particular sulfides, when H2S is co-injected with CO2. This study demonstrates that Ca and Fe isotopes are the best candidates to quantify carbon capture in carbonates. 

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Funding: This post-doc work was financially supported from the European Commission through the projects S4CE (EC Project 764810).

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About Marie-Anne: After a 2-years preparatory class in Lycée Henri IV (Paris), Marie-Anne did a 3-years geology engineering school in ENSG, Nancy (France) and obtain her M.Sc in 2014. Her end-of-studies internship was completed for ThermoFischer in INGV (Palermo, Italy) to calibrate and monitore the performance of  some ThermoFisher instruments on the field. In parallel, she did a second M.Sc in CRPG (Nancy, France) called “Earth and Planets” and studied the geochemistry of Afar depression lavas for her thesis. Then, she did her PhD (2014-2017) in Laboratoire Magmas et Volcans (Clermont-Ferrand, France) where she was investigating the origin of the geochemical diversity of Ecuadorian magmas at different scales, from the Ecuadorian arc down to single minerals in hand-sized samples. 

 

1Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland – ancellin@hi.is 2Reykjavik Energy, Reykjavik, Iceland 3 Department of Earth Sciences, Durham Univ., Durham, UK 4 Department of Earth Sciences, UCL, London, UK 5GET, CNRS, Toulouse, France. 

ANCELLIN M.-A.1, GISLASON S. R.1, SNAEBJORNSDOTTIR S.2, SIGFUSSON B. 2, , NOWELL G.3, POGGE VON STRANDMANN P.4, OELKERS E.4,5, ALFREDSSON H.A., ARADOTTIR E.2 , MESFIN K.1 , BURTON K. W.3,1 
 

Deirdre Elizabeth Clark 2019-2020.

Industrial-scale testing of a CO2-H2S gas mixture injection commenced in 2014 at the Hellisheiði geothermal power plant in Iceland. By the end of 2017, 23,200 metric tons of CO2 and 11,800 metric tons of hydrogen sulfide (H2S) had been injected to a depth of 750 m into fractured, hydrothermally altered basalts at > 250 °C. Deirdre and collaborators collected over 80 water and gas samples from monitoring and injection wells, before and during injection up to the end of year 2017. Major, minor, and trace element geochemical data were compiled to assess the magnitude of carbon and sulfur mineralization in the subsurface in relation to relevant primary and secondary minerals in the geothermal reservoir and to evaluate the potential scavenging and mobility of trace metals.    

Funding: This post-doc work was financially supported from the European Commission through the projects S4CE (EC Project 764810).

About Deirdre: Deirdre Elizabeth Clark was born on 8 April 1988. Her parents are Deanna Borchers and Paul Chudleigh Clark. She grew up in Calgary, AB, Canada and Scotch Plains, NJ, USA. In 2010 she obtained her BSc in geology and BA in environmental studies from the George Washington University in Washington, D.C., USA. She then completed an MSc degree in geochemistry and hydrology from Utrecht University in the Netherlands in 2013. She finished her doctoral studies at the University of Iceland in 2019.
 

Description of PhD students (from 1996 -)

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Marin Ivanov Kardjilov 2000 - 2008.

Riverine and terrestrial Carbon fluxes in Iceland. Supervisors: Guðrún Gísladóttir Professor at the University of Iceland and Sigurður Reynir Gíslason, research Professor at the University of Iceland. Marin Ivanov Kardjilov defended his doctoral thesis in geography in June 2008 at University of Iceland, in Askja, room 132.  Opponents were: Dr. Rattan Lal, School of Environment and Natural Resources, Ohio State University, Columbus, Ohio, USA, and Dr. Bjarni Didrik Sigurdsson, Faculty of Environmental Sciences, Agricultural University of Iceland, Hvanneyri, Iceland. The members of the doctoral committee were the supervisors and Dr. Björn Birnir, Department of Mathematics, University of California, Santa Barbara, USA. The defence was chaired by Guðrún Marteinsdóttir the Head of Faculty of Life and Environmental Sciences, University of Iceland.

 

PhD granted by: The Department of Geography and Tourism, Faculty of Life and Environmental Sciences, University of Iceland. The research was supported by the Icelandic Research Council; RANNÍS, the Research Fund of the University of Iceland, the Science Institute and later the Institute of Earth Sciences.

Abstract: Carbon, organic and inorganic, is one of the fundamental materials of Earth and is of special interest because of its involvement in continuous and complex exchanges between the atmosphere, the land and the ocean. The effect of increased atmospheric CO2 concentration on global climate change calls upon better understanding and quantification of the different carbon fluxes and analyses of how they interact and how they respond to climate change. The aim of this dissertation was to improve knowledge of carbon fluxes in complex geographical, geological and hydrological settings and under different climate conditions and different measurement scales. The research presents the estimation and comparison of the CO2 sequestration rates of the terrestrial carbon fluxes in vegetation and soil and weathering of rocks represented by riverine fluxes in Iceland, and particularly in the northeast for different periods of time during 1998 to 2006. The Geographic Information Systems (GIS) were used to quantify and analyze satellite data, digitized vegetation, soil, and geological maps, and hundreds of river water and river-suspended matter samples, along with continuous monitoring of climate and water discharge over the study period. Temporal carbon fluxes of vegetation were estimated by using MODIS satellite sensor data. MODIS satellite sensor data were used to measure and quantify the carbon fluxes by area on a catchment scale and for the whole of Iceland. All relations between the studied fluxes were analysed. The largest riverine flux was the dissolved inorganic carbon, stemming from chemical weathering. This flux was larger than those for vegetation for the sparsely vegetated areas dominated by young basaltic rocks. In the more vegetated catchments the vegetation fluxes were significantly larger than the riverine fluxes. The annual average temperature of the river catchments in the northeast during this research rose by 2°C over the first 5 years of the study, and the annual river runoff increased by a factor of ~2 for the same period. The Icelandic vegetation responded with a one year time lag to these climate changes. This research results estimated the total amount of carbon fixed by vegetation, respired and exported out of the environment by the rivers as dissolved and particulate organic carbon. This has been the first attempt to quantify and analyse the relationship between riverine and terrestrial carbon fluxes, and to study their response to climate and climate change.

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Josh Wimpenny 2004 - 2009.

Chemical weathering and erosional transport in an ancient shield terrain. Supervisors were Kevin Burton and Rachael James Professors at The Open University, the United Kingdom and Sigurður Reynir Gíslason research Professor at the University of Iceland. 

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PhD granted by the Department of Earth and Environmental Sciences, Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Walton Hall, Milton Keynes, the United Kingdom.

Research focus was on characterising the behaviour of non-traditional stable isotope systems during weathering. Comparing laboratory experiments to field observations focusing on glacial rivers in Greenland. Josh spent a winter at University of Iceland performing experiments on Mg and Li isotope fractionering during weathering of basaltic glass and olivine.

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Bergur Sigfússon 2005 - 2009. 

Reactive transport of Arsenic through basaltic media. Supervisors were Andy Meharg, University of Aberdeen, Scotland and Sigurður Reynir Gíslason at the University of Iceland. Majority of the work was carried out at the University of Iceland.

PhD granted by University of Aberdeen, Scotland. This study was supported by the Icelandic Research Council; RANNÍS, the Icelandic Governmental Fund for Graduate Education, Orkuveitu Reykjavíkur and Landsvirkjun. 

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Abstract: This thesis studied the volcanic and geothermal source of arsenic (As) and its fate in shallow ground waters and upon entering the ocean by means of experimental and field measurements combined with geochemical modelling. Arsenic enters the atmosphere and hydrosphere from degassing magmas and during volcanic eruptions.  The November 2004 eruption within the Vatnajökull Glacier, Iceland, provided an opportunity to study elemental fluxes from volcanic eruptions into the environment. According to geochemical modelling, lowering of pH due to magma gases during the eruption led to rapid tephra dissolution with corresponding change in flood water chemistry. Geochemical modelling of floodwater/seawater mixing indicated localised decrease in dissolved arsenic and sulphur due to adsorption on the suspended floodwater materials. As the floodwater was diluted the As desorbed and limited effect of the floodwater was predicted after thousand fold dilution. Laboratory experiments were carried out to generate and validate sorption coefficients for arsenite and arsenate in contact with basaltic glass at pH 3 to 10. The mobility of arsenite decreased with increasing pH. The opposite was true for arsenate, being nearly immobile at pH 3 to being highly mobile at pH 10. A 1D reactive transport model constrained by a long time series of field measurements of chemical composition of geothermal effluent fluids from a power plant was constructed.  Thioarsenic species were the dominant form of dissolved As in the waters exiting the power plant but converted to some extent to arsenite and arsenate before feeding into a basaltic lava field.  Chloride, moved through the basaltic lava field (4100 m) in less than 10 yrs but arsenate was retarded considerably due to surface reactions and has entered a groundwater well 850 m down the flow path in accordance to prediction by the 1D model, which further predicted a complete breakthrough of arsenate in the year 2100 while arsenite will be retained for about 1000 yrs.

 

Therese Kaarbø Flaathen 2006 - 2009.

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Water rock interaction during CO2 sequestration in basalt The supervisors were Sigurður Reynir Gíslason, University of Iceland and Eric Oelkers, CNRS Toulouse France. Therese Kaarbø Flaathen defended her thesis Thursday, September 3, 2009 in the University Aula in Reykjavík.  The Opponents were Dr. Yousif Kharaka, US Geological Survey, USA and Dr. Luigi Marini, University of Genova, Italy and representing Université de Toulouse III; Dr. Halldór Ármannsson, Icelandic GeoSurvey,  Dr. Kevin Burton, Université de Toulouse III – Paul Sabatier, France and Dr. Pierre Agrinier, Institue de Physique de Globe de Paris, France. The defence was chaired by Magnús Tumi Guðmundsson, Head of the Faculty of Earth Sciences. Joint degree from: Faculty of Earth Science, School of Engineering and Natural Sciences, University of Iceland & Université de Toulouse, Universitée III Toulouse – Paul Sabatier, Géosciences Environment Toulouse, France, September 2009

This research was funded by the Nordic Council of Ministers through NORDVULK and The European Union through The MIN-GRO Research and Training Network (MRTN-CT-2006-035488). 

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Abstract: The potential dangers with increased concentration of CO2 in the atmosphere, such as climate changes and sea level rise, have led to an interest in CO2 sequestration in geological formations. The thermodynamically most stable way to store carbon is as carbonate minerals. Carbonate mineral formation, however, requires divalent cations originating from a noncarbonated source. One such source is basaltic rocks which contain high concentrations of Ca2+, Mg2+ and Fe2+.  The aim of this thesis was to help optimize carbonate mineral precipitation in basalts during CO2 injection through a series of related field and laboratory studies. A detailed study of the chemical composition of the groundwater surrounding the Mt.
Hekla volcano in south Iceland was performed to assess fluid evolution and toxic metal mobility during CO2-rich fluid basalt interaction. These fluids provide a natural analogue for evaluating the consequences of CO2 sequestration in basalt. The concentration of dissolved inorganic carbon in these groundwaters decreases from 3.88 to 0.746 mmol/kg with increasing basalt dissolution while the pH increases from 6.9 to 9.2. This observation provides direct evidence of the potential for basalt dissolution to sequester CO2. The concentrations of toxic metals in these waters are low and reaction path modelling suggests that calcite and Fe(III) (oxy)hydroxides scavenges these metals as the fluid phase is neutralized by further basalt dissolution. The rate limiting step of mineralization of CO2 in basalt is thought to be the release of divalent cations to solution through basaltic glass dissolution. The dissolution rate of basaltic glass can be enhanced by adding ligands which complex aqueous Al3+. Aqueous SO42- can complex Al3+ and the effect of SO42- on the dissolution rate of basaltic glass where performed using mixed flow reactors at 3 < pH < 10 at 50 °C. Moreover, sulphur is often present in the flue gases of power plants and their disposal also poses an environmental challenge. If possible, co-injection of sulphur with CO2 could provide a novel cost effective disposal method for industrial generated sulphur. Consistent with current models describing basaltic glass dissolution with aqueous solution composition, results show that SO42- enhances the dissolution rate of the glass in acidic conditions, while no effect was found in alkaline solutions. These results suggest both that 1) co-injection of sulphate may accelerate CO2 mineralization in basalts, and 2) existing kinetic models provide an accurate description of basaltic glass dissolution. 

To further assess the potential effect of SO42- on the precipitation rate of carbonates, steady-state rates of calcite precipitation were measured in mixed flow reactors at 25 °C and pH ~9.1. The results show that 0.005 M Na2SO4 decreases the precipitation rate of calcite with ~40%. This result suggests that co-injected sulphate could slow calcite precipitation at the pH conditions typical of calcite precipitation in the subsurface. Further experiments are planned to completely define these effects at conditions expected at subsurface CO2 injection sites.

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Gabrielle Jarvik Stockmann 2007 - 2012. 

Experimental Study of Basalt Carbonisation. The supervisors were Dr. Sigurður Reynir Gíslason at the University of Iceland‘s Institute of Earth Sciences and Eric Oelkers, CNRS Toulouse France.
Gabrielle Jarvik Stockmann defended her thesis Wednesday, May 16, 2012 in the University Aula, Reykjavík.  The Opponents were Prof. Benedicte Menez, Institut de Physique du Globe de Paris, and Prof. Liane G. Benning, University of Leeds.  The defence was chaired by Magnús Tumi Guðmundsson, Head of the Faculty of Earth Sciences. Joint degree from: Faculty of Earth Science, School of Engineering and Natural Sciences, University of Iceland & Université de Toulouse, Universitée III Toulouse – Paul Sabatier, Géosciences Environment Toulouse, France, May 2012.

The Ph.D. project was supported by Reykjavik Energy, the Research Fund of the University of Iceland, the Nordic Council of Ministers through NORDVULK, and the European Community through the MIN-GRO Research and Training Network (MRTN-CT-2006-035488) and the ERASMUS student mobility program.

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Abstract:  The increasing levels of CO2 in the atmosphere and the potential dangers this pose to the Earth through climate change, ocean acidification and sea-level rise has lead to a substantial number of projects attempting to find a safe and benign way to capture and store CO2 in geological formations, also referred to as the CCS (Carbon Capture and Storage) technology. One of these CCS attempts is currently taking place in Iceland at the geothermal power plant Hellisheidi, located close to the capital Reykjavik (the CarbFix project). CO2 and other gasses (H2S, N2, H2, CH4) are waste products of the geothermal energy exploitation and the aim is with time to store all of this anthropogenic-made CO2 in the basaltic formations underlying Hellisheidi. The CO2 is dissolved in groundwater as it is pumped down to 350 meters depth and then injected into mixed horizons of basaltic glass and crystalline basalt. The basaltic rocks are characterized by high contents of divalent cations like Mg2+, Fe2+ and Ca2+ and relatively fast dissolution rates. The acidic CO2-loaded water will dissolve the basalt thereby releasing cations, which can react with the aqueous carbonate ions to form carbonate minerals (magnesite, siderite, calcite, ankerite and Ca-Mg-Fe solid solutions). The rate-limiting step of this carbon sequestration process is thought to be the dissolution of basaltic rocks, thus any effect that could potentially limit basalt dissolution would be detrimental to the overall CO2 sequestration process. My part of the CarbFix project has been to look at the effects the formation of calcium carbonate coatings would have on the dissolution of the primary phase, in this case basaltic glass and the clinopyroxene diopside, so there would be a glass phase to compare with the results of a mineral phase. Furthermore, a series of experiments were conducted where we tested the primary mineral structure’s effect on calcite nucleation. This was done in order to test if different silicate structures would lead to different extent of calcite nucleation and growth. Finally, extensive series were conducted on the dissolution of basaltic glass in the presence of dead and live heterotrophic bacteria, Pseudomonas reactans in order to determine the potential effect of bacteria on the carbon storage effort at the Hellisheidi site.
The basaltic glass and diopside dissolution experiments were run at 25 and 70 °C and pH 7-8 in mixed-flow reactors connected to solutions containing CaCl2 ± NaHCO3 with ionic strengths > 0.03 mol/kg. Two sets of experimental series were run simultaneously, one series called the “precipitation” experiments in which the solution inside the reactor was supersaturated with respect to calcite, and the other series called the “control” experiments, where PHREEQC modeling foretold no major secondary mineral formation. By this, it was possible to compare dissolution rates of basaltic glass and diopside at 25 ºC with and without calcium carbonate and other secondary mineral formation in order to deduce the effect on their dissolution rates. Scanning electron microscope images showed substantial amounts of calcium carbonate had precipitated in the ”precipitation” experiments, but in the case of basaltic glass the primary growth appeared as big, discrete cluster of calcite and aragonite with no growth on the glass itself. Opposed to this, several of the diopside crystals were extensively overgrown by calcite coatings and no aragonite was found. In neither cases did the presence of calcite/aragonite have an effect on the dissolution rates of basaltic glass and diopside when compared to the “control’ dissolution rates. It appears the discontinuous cover of the carbonate allows the ions of the primary phases to continue to diffuse through the secondary layer unhindered.

To further assess the effect of silicate surface on the nucleation of calcite, the dissolution rates of six selected silicate minerals and rocks were measured in mixedflow reactors in solutions supersaturated with respect to calcite at 25 ºC and pH ~9.1. The silicate phases were: Mg-rich olivine, enstatite, augite, labradorite, basaltic glass and peridotite. The results show different onset time of calcite nucleation and thus different extent of carbonate coverage with elapsed time depending on silicate phase. Within the same timeframe olivine, enstatite and peridotite (mainly composed of Mgrich olivine) were the most covered by calcite precipitations, followed by augite, labradorite and finally basaltic glass. All calcite growth took place on the silicate surface including on the basaltic glass. Kinetics favor calcite nucleation growth on the orthorhombic minerals (enstatite and olivine) over the monoclinic and triclinic minerals. Least calcite was found on the glass, which has no ordered silicate structure. 

Heterotrophic bacteria, Pseudomonas reactans was extracted from one of the monitoring wells at Hellisheidi, and then separated, purified and cultured in the laboratory. Its optimal growth conditions were found to be 5-37 ºC and pH 7.0-8.2 on Brain Heart Broth nutrient. Being a common water- and soil bacteria it offered a good candidacy to test what could be expected of heterotrophic bacteria in general when storing CO2 in a natural aquifers like the one at the Hellisheidi site, in Iceland. Basaltic glass dissolution rates were measured at 25 °C in newly developed Bacterial Mixed-Flow reactors (BMFR) in buffer solutions carrying 0.1–0.4 g/L of dead bacteria and 0.9–19 g/L of live bacteria at 4 ≤ pH ≤10. The results show that the presence had either no or a slightly rate-limiting effect. The overall conclusion is that neither the carbonate coatings nor the bacteria had major impact on the measured dissolution rates of the primary silicate phases, thus their effect are expected to be negligible on the CO2 sequestration process in basalt. Crystalline basalt might be faster covered by calcium carbonate, but also basaltic glass can act as a nucleation platform for calcite nucleation.

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About Gabrielle: Gabrielle Jarvik Stockmann was born 1969 in Copenhagen, Denmark and grew up in Denmark and Greenland. She received a B.Sc. degree in Chemistry in 1996 and a M.Sc. degree in Geology in 1998 from the University of Copenhagen, Denmark. Her Master’s study took place in Southern Greenland, where she studied rare submarine tufa columns made of the mineral ikaite (CaCO3x6H2O). Following graduation she worked for four years at the Danish Polar Center as an academic employee, one year as information worker at the Geological Institute, University of Copenhagen and finally two years as Head of Section at Universities Denmark before moving to Iceland in 2007. She wrote a book about the Greenlandic ikaite columns together with another geologist, Uffe Wilken in 2007, and this book is now frequently used for teaching in primary and high schools in Denmark. Gabrielle is married to Erik Sturkell, Professor in Applied Geophysics at the University of Gothenburg, Sweden. 

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Iwona Monica Gałeczka 2009 - 2013. 

Experimental and field studies of basalt-carbon dioxide interaction 
The supervisors were Sigurður Reynir Gíslason, University of Iceland, Domenik Wolff-Boenisch Department of Applied Geology, Curtin University, Australia, & Eric Oelkers, CNRS Toulouse France. Iwona Galeczka defended her doctoral thesis in geochemistry Friday, September 27th, 2013 at 15:00, at University of Iceland, in Askja, room 132.  Opponents were: Prof. Per Aagaard, Department of Geosciences, University of Oslo, and Prof. Alessandro Aiuppa, Dipartimento di Scienze della Terra e del Mare, Palermo University. The defence was chaired by Magnús Tumi Guðmundsson, Head of the Faculty of Earth Sciences.

PhD degree from: Faculty of Earth Science, School of Engineering and Natural Sciences, University of Iceland, September 2013. This PhD study was funded by the European Union through the European Marie Curie network Delta-Min (Mechanisms of Mineral Replacement Reactions; Grant PITN-GA-2008-215360) and SP1-Cooperation (FP7-ENERGY-2011-1; Grant 283148), The Environmental Fund of Reykjavík Energy, University of Iceland and RANNíS, Icelandic Fund for Research Equipment; Grant 10/0293 and 121071-0061, Hitaveita Suðurnesja and Nordurál.

Abstract: The main aim of this study was to design, build, and test a large scale laboratory high pressure column flow reactor (HPCFR) enabling experimental work on water-rock interactions in the presence of dissolved gases, demonstrated here by CO2. The HPCFR allows sampling of a pressurized gas charged fluid along the flow path within a 2.3 m long titanium column filled with mineral, and/or glass particles. In this study, series of experiments were carried out using a carbonated aqueous solution (0.3-1.2 M CO2(aq)) and basaltic glass grains. The scale of the HPCFR, the possibility to sample a reactive fluid at discrete spatial intervals under pressure, and the possibility to monitor the evolution of the dissolved inorganic carbon and pH in-situ all render the HPCFR unique in comparison with other columns constructed for studies of water-rock interactions. Experimental results at ambient temperature showed that the pH of injected pure water evolved from 6.7 to 9-9.5 and most of the dissolved iron was consumed by secondary minerals, similar to natural meteoric water-basalt systems. As CO2-charged water replaced the alkaline fluid within the column, the fluid became supersaturated with respect to carbonates for a short time, but once the entire column was filled with the CO2-charged water and the pH decreased to 4.5, the fluid remained undersaturated with respect to all carbonates. The mobility and concentration of several metals increased significantly in the CO2-fluid phase and some of the metals, including Mn, Fe, Cr, Al, and As exceeded allowable drinking water limits. Iron became 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 reactive fluid. The pH rose from an initial pH of 3.4 to 4.5 during the first 40 minutes of CO2-charged water-basaltic glass interaction along the first 18.5 cm of the column but remained constant during the remaining 2.1 meters of the flow path. 

In volcanic terrains at high latitude and/or altitude, sub-glacier reservoirs are formed within glaciers by geothermal activity and perhaps small eruptions at the base of ice caps. The reservoirs are periodically drained in glacier floods, called jökulhlaups. Some of these floods, especially those associated with large volcanic eruptions can be disastrous because of their size which is comparable to that of the Amazon River (>200,000 m3/s). In July 2011 two floods  ̴ 2,000 m3/s emerged from Icelandic glaciers (Mýrdalsjökull, Vatnajökull). Sub-glacier reservoirs and the geological basement can be looked upon as a laboratory column flow reactor filled up with rocks of a given chemical composition and surface area, where percolating fluid and external gas source react with each other and with the solid material. The fluid represents melt water and external gas source can represent magmatic gases such as CO2, SO2, HCl and HF. 

Water samples collected during both floods had neutral to alkaline pH and conductivity up to 900 µS/cm. Alkalinity present mostly as HCO3- was ~9 meq/kg during the flood peak but stabilized at around 1 meq/kg. Small amount of H2S (up to 1.5 µmol/kg) was detected. Concentrations of most of dissolved constituents including magmatic volatiles Cl-, F- and SO42- in flood water were comparable to the annual concentrations variation of these elements in considered rivers. Comparison of the flood water with Icelandic groundwaters and simple reaction path modelling of fluid chemical evolution suggest that the dissolved element composition of the flood waters developed due to long-time (at least two years) water-rock interaction in presence of limited amount of gases without direct contact of water with magma. This suggests that the origin of the heat source for glacier melting and causing these floods to emerge was geothermal rather than volcanic.
About Iwona: Iwona Galeczka was born 1984 in Tarnowskie Gory, Poland. She received a M.Sc. degree in Hydrogeology and Engineering Geology in 2008 from the University of Science and Technology, Krakow, Poland. Following graduation she worked for one year at the Polish Geological Institute as a junior geologist before moving to Iceland in 2009.  

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Snorri Guðbrandsson 2007 - 2013.

Experimental weathering rates of aluminium-silicates. Dissolution of crystalline basalt and plagioclase, and precipitation of aluminium rich secondary minerals. The supervisors were Dr. Sigurður Reynir Gíslason, at the University of Iceland‘s Institute of Earth Sciences, Eric Oelkers, CNRS Toulouse France Domenik Wolff-Boenisch, Curtin University, Australia. 

 

Snorri Guðbrandsson defended his doctoral thesis for a joint degree in geochemistry from University of Iceland and Paul Sabatier University, Toulouse, France, on Wednesday, October 30th at 15:00 in Hátíðarsalur Háskóla Íslands, Main Building.  Opponents were Dr. Marguerite Godard, Research director at Geosciences Montpellier, CNRS, Montpellier, France, Professor Per Aagaard, Department of Geosciences, University of Oslo, and Professor Kevin Burton from the Paul Sabatier University, Toulouse, France. The defence was chaired by Magnús Tumi Guðmundsson, Head of the Faculty of Earth Sciences. 

Joint degree from: Faculty of Earth Science, School of Engineering and Natural Sciences, University of Iceland & Université de Toulouse, Universitée III Toulouse - Paul Sabatier, Géosciences Environment Toulouse, France, October 2013.
This work was funded by the Environmental Fund of Reykjavík Energy through the CarbFix Project, Delta-Min (Mechanism of Mineral Replacement Reactions: Grant PITN-GA-2008-215360) and the CarbFix (Collaborative Project-FP7-469 ENERGY-2011-1-283148),  the Nordisk Mineralogical Network and the travel fund of the Earth Science Institute, University of Iceland. 

Abstract: The chemical weathering of primary rocks and minerals in natural systems has a major impact on soil development and its composition. Chemical weathering is driven to a large extent by mineral dissolution. Through mineral dissolution, elements are released into groundwater and can readily react to precipitate secondary minerals such as clays, zeolites, and carbonates. Carbonates form from divalent cations (e.g. Ca, Fe and Mg) and CO2, and kaolin clay and gibbsite formation is attributed to the weathering of aluminium-rich minerals, most notably the feldspars. The CarbFix Project in Hellisheiði SW-Iceland aims to use natural weathering processes to form carbonate minerals by the re-injection of CO2 from a geothermal power plant back into surrounding basaltic rocks. This process is driven by the dissolution of basaltic rocks, rich in divalent cations, which can combine with injected CO2 to form and precipitate carbonates. 

 

This thesis focuses on the dissolution behaviour of Stapafell crystalline basalt, which consists of three major phases (plagioclase, pyroxene, and olivine) and is rich in divalent cations. Steady-state element release rates from crystalline basalt at far-from-equilibrium conditions were measured at pH from 2 to 11 and temperatures from 5° to 75° C in mixedflow reactors. Steady-state Si and Ca release rates exhibit a U-shaped variation with pH, where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Silicon release rates from crystalline basalt are comparable to Si release rates from basaltic glass of the same chemical composition at low pH and temperatures ≥25°C but slower at alkaline pH and temperatures ≥50°C. In contrast, Mg and Fe release rates decrease continuously with increasing pH at all temperatures. This behaviour is interpreted to stem from the contrasting dissolution behaviours of the three major minerals comprising the basalt: plagioclase, pyroxene, and olivine. Element release rates estimated from the sum of the volume fraction normalized dissolution rates of plagioclase, pyroxene, and olivine are within one order of magnitude of those measured in this study. In addition, these experimental results show that during injection of CO2- charged waters with pH close to 3.6, crystalline basalt preferentially releases Mg and Fe relative to Ca to the fluid phase. The injection of acidic CO2-charged fluids into crystalline basaltic rocks may therefore favour the formation of Mg and Fe carbonates rather than calcite at acidic to neutral conditions. Plagioclase is the most abundant phase in crystalline basalts and thus influences strongly its reactivity. Plagioclase dissolution rates based on Si release show a common U-shaped behaviour as a function of pH where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Constant pH plagioclase dissolution rates increase with increasing anorthite content at acid conditions, in agreement with literature findings. Interpretation and data fitting suggests that plagioclase dissolution rates are consistent with their control by the detachment of Si-rich activated complexes formed by the removal of Al from the mineral framework. Most notably, compared with previous assumptions, plagioclase dissolution rates are independent of plagioclase composition at alkaline conditions, e.g. anorthite-rich plagioclase dissolution rates increase with increasing pH at alkaline conditions. At such conditions rapid plagioclase dissolution rates likely dominate divalent metal release from crystalline basalts to the fluids phase dueto its high Ca content. Gibbsite is commonly the first mineral formed during low temperature dissolution of plagioclase. Gibbsite is an aluminium-hydroxide that is found in various soils as well as the dominant phase in many bauxite ores. Gibbsite precipitation rates were measured in closed system reactors at alkaline condition, both at 25 °C and 80 °C as a function of fluid saturation state. Analyses of the solids demonstrate that gibbsite precipitation occurred in all experiments. The comparison of gibbsite precipitation to the dissolution rates of plagioclase at pH 11 shows that the rates are close to equal. The precipitation rates of gibbsite, however, decrease faster with decreasing pH than plagioclase dissolution rates. As such it seem likely that plagioclase dissolution is faster than gibbsite precipitation at near to neutral pH, and the relatively slow rate of gibbsite precipitation influences plagioclase weathering in many Earth surface systems. Kaolinite is commonly the second secondary mineral formed during low temperature dissolution of plagioclase. Kaolinite precipitation rates were measured in mixed flow reactors as a function of fluid saturation state at pH=4 and 25 °C. In total eight long-term precipitation experiments were performed in fluids mildly supersaturated with respect to kaolinite, together with a known quantity of cleaned low defect Georgia Kaolinite as seeds. Measured kaolinite precipitation rates are relatively slow compared with plagioclase dissolution rates. This observation suggests that kaolinite formation during weathering is limited by its precipitation rates rather than by the availability of aqueous species sourced from plagioclase dissolution. Taken together the results of this study provide some of the fundamental scientific basic for predicting the rates and consequences of crystalline basalt and plagioclase dissolution at both the Earth’s surface and during the near surface injection of CO2 as part of carbon storage efforts. Results indicate that although gibbsite precipitation rates are relatively rapid, the relatively slow precipitation rates of kaolinite may be the process controlling the formation of this mineral at the Earth’s surface. This observation highlights the need to further quantify this secondary mineral precipitation rates at conditions typical at the Earth’s surface. Moreover, as the composition of divalent metals released from crystalline basalts varies significantly with pH, CO2 carbonation in basalt should yield a systematic variation in the identity of carbonate and zeolite minerals precipitated with distance from the injection site. This latter conclusion can be tested directly as part of the currently on-going CarbFix project in Hellisheiði, Iceland.

About Snorri: Snorri Guðbrandsson was born in 1976 in Reykjavík, Iceland. He started geology studies at the University of Iceland in 2003 and received a B.Sc. in 2007. During his undergraduate studies he worked at the Icelandic Institute of Natural History and later at the Iceland Geosurvey. The PhD research has been carried out at the Institute of Earth Sciences, University of Iceland and GET-CNRS, Midi-Pyrenees laboratory in Toulouse, France, along with a short stint at the NanoGeoScience Institute at the University of Copenhagen.

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Jonas Olsson 2010 - 2014.

The formation of carbonate minerals and the mobility of heavy metals during water-CO2-mafic rock interactions. Instructors were Dr. Sigurður Reynir Gíslason, Research Professor, Institute of Earth Sciences, University of Iceland and Professor Susan Luise Svane Stipp, University of Copenhagen, Denmark.

On Monday May 26th 2014 Jonas Olsson introduced his Ph.D thesis in Geochemistry at University of Iceland in Askja. This is a double PhD degree from the University of Iceland and the University of Copenhagen.  The main defence took place at University of Copenhagen Wednesday, 21 May 2014. The opponents were Prof. Bjørn Jamtveit, Department of Geosciences, University of Oslo, Konrad Herbst, Principal Research Chemist, Chemical Catalyst Department, Haldor Topsøe, Denmark and Hans Christian Bruun Hansen, Professor, Plant Science, University of Copenhagen, Denmark. Doctoral Committee; Professor Susan S. Stipp, University of Copenhagen,  Dr. Sigurður Reynir Gíslason, University of Iceland  Dr. Emil Makovicky, University of Copenhagen. Double degree in Geochemistry from the University of Iceland and the University of Copenhagen, May 2014

The project was funded by the Nordic Council of Ministers through the Nordic Volcanological Institute (NORDVULK), Institute of Earth Sciences, University of Iceland and the NanoGeoScience Group, Department of Chemistry, Copenhagen, Denmark.

Abstract: CarbFix is a pilot project in Iceland created to lock away CO2 through in-situ mineralization in the subsurface. The goal is to dissolve CO2 from the geothermal power plant, Hellisheiði, in water and inject it into basaltic rock formation for permanent storage. The carbonated water dissolves the basaltic host rock and liberates cations. Ideally, the cations react with the dissolved CO2 and form long time stable carbonate minerals. However, dissolution of the basaltic rock can lead to mobility of toxic metals, which is a potential threat to groundwater supplies and surface waters. Besides carbonate minerals, the reaction products are known to be manifold and reflect the complex composition of the basaltic materials and glass. Formation of secondary products, such as iron (hydr)oxides and clays, are considered undesirable, because (1) they consume the cations that could be used to sequester CO2, thus compete with the process of carbonation, and (2) they can form a passivating layer, which inhibit dissolution of the basaltic material and slow down the carbonation process. The purpose of this thesis was to identify formation products, relevant to CarbFix, and assess their ability to immobilize toxic metals released from basaltic material. The work was divided into four projects.

In the first project, basaltic material in form of fresh volcanic ash from the 2011 Grímsvötn eruption was classified as glassy tholeiitic basalt with <10 mass% of plagioclase and pyroxene. The ash was exposed water and the effluent analysed for 74 elements. The effluent was alkaline and high release rates of mainly S, Na, Ca, Mg, F and Cl were observed during the first 10 minutes. After 12 hours, the most abundant element released was Si. Secondary phases of Al and Fe precipitated on the ash surfaces and these were suspected of scavenging As, Ba, Cr, Co, Cu, Ga, Mn, Mo, Ni, P, Te, V and Zn. This study has also other implications: the small particle size of the ash means that they can travel long distances and this can impact air traffic and the chemical balance of surface waters close to and far away from the volcanic eruption.

In the second study, I investigated natural calcium carbonate precipitation in the Hvanná River, Iceland. A decrease of the concentrations of Cd, Co, Cu, Mg, Mn and Sr with distance downstream the river correlated with calcium. Partition coefficients derived from the precipitating calcite in the Hvanná River are consistent with values of controlled laboratory experiments from the literature for Ba, Cd, Co, Cu, Mg, Mn, Na, Ni, Sr and Zn. The calcium carbonates also scavenge other elements, including rare earth elements (REE) and the toxic metals As and Pb. This and the next study can be considered natural analogues to the carbonate precipitation in CarbFix project.

In the third study, water and solid samples from two hyper-alkaline springs in Oman were examined. The elements detected in the spring waters in order of abundance were Na, Cl, DIC, Ca, Mg, SO4, K, Br, Si, F, B, Sr, Al, Fe, Mo, Zn, Ni, Cu, Mn, V, Ba, Cr, Co, Ti, Hg and Pb. The carbonate samples were identified as aragonite needles and calcite rosettes with traces of serpentine and dypingite. The average concentration in μmol per gram CaCO3 of the carbonates were: Mg(430) > Na(81) > Si(46) > Sr(11) > K(1) > Al(0.95) > P(0.39) > Fe(0.26) > Ba(0.22) > Mn(0.13) > Zn(0.08) > Ni(0.07) > V(0.005) > Cr, Cu, Ti (0.003) > As, Ce(0.001) > Pb, Nd, La, Mo, Pr, Sm, Gd, Dy, Er, Cd, Yb, Eu, Th, Ho, Tb, Lu, Tm(<0.001). This suggests active scavenging of REE and toxic metals such as As, Ba, Cd and Pb by carbonate minerals but Hg was not removed from solution.

In the last project, the basaltic mineral, olivine ((Mg,Fe)2SiO4), was reacted with water and CO2 to form iron and magnesium carbonates both at aerobic and anaerobic conditions. Experiments were carried out in pure water equilibrated with CO2 at total pressures up to 80 bars, at temperatures 25 °C and 120 °C. Within days olivine crystals dissolved and secondary minerals formed when exposed to water only at room temperature. Within 4 days, a red precipitate formed when olivine was reacted at increased temperatures and CO2 partial pressures. The precipitate was identified as goethite, hematite, silica, and clay and carbonate minerals. My experiments suggest that supercritical CO2 is a key factor for the formation of magnesite. At 120 °C, iron did not precipitate as carbonate minerals but rather as iron oxides, independent of the oxygen level.

About Jonas: Jonas was born in 1983.  He finished a MSc in Nanosciences from University of Copenhagen in 2009.  After that he worked in the NanoGeoScience Group at the same university, and groundwater studies at University of Waterloo, Ontario, Canada. After that, he worked on his PhD at both Univerity of Copenhagen and University of Iceland, from 2010 to 2014.