Doctoral defense in Geology - Tobias Linke

Doctoral candidate: Tobias Linke

Title of thesis: Effect of basaltic particles and iron-containing minerals in wetland soils and reservoirs on CO2 drawdown: An analogue for Enhanced Rock Weathering

Opponents:
Dr. Heather Buss, Associate Professor at the School of Earth Sciences, University of Bristol, UK
Dr. Jens Hartmann, Professor at the Institute for Geology, Center for Earth System Research and Sustainability (CEN), University of Hamburg, Germany

Advisor: Dr. Sigurður Reynir Gíslason, Research Professor, Institute of Earth Sciences, University of Iceland

Other members of the doctoral committee:
Dr. Eric Herman Oelkers, Visiting Adjunct Professor at the Institute of Earth Sciences, University of Iceland
Dr. Knud Dideriksen, Geochemist, Geological Survey of Denmark & Greenland (GEUS), Copenhagen, Denmark
Dr. Bergur Sigfússon, Chief System Development Officer at Carbfix, Reykjavík, Iceland 

Chair of Ceremony: Dr. Guðfinna Th Aðalgeirsdóttir, Professor and Vice Head of the Faculty og Earth Sciences, University of Iceland

Abstract

Battling climate change and rising temperatures is one of the major tasks of this century. To achieve current climate goals, large-scale removal of carbon dioxide from the atmosphere is needed. Enhanced Rock Weathering, ERW, is one of the most promising methods to draw down carbon dioxide from the atmosphere, but it has been challenging to demonstrate. It involves fine grained reactive rocks and spreading them on land or over the ocean. This Ph.D. study focuses on the soil water chemistry, mineralogy and carbon balance in a basaltic dust-rich Icelandic Andosol formed during the last 3300 years, providing opportunity to quantify the rates and long-term consequences of Enhanced Rock Weathering. Alkalinity generation is promoted by continuous dust dissolution, while toxic trace metals are scavenged at depth or adsorbed to iron minerals in surface waters. Some carbon dioxide is mineralized as siderite FeCO3. The scavenged elements and mineralised carbon might be remobilized upon interaction with seawater. This study validates the ability of soil amendments containing fine-grained mafic minerals to attenuate increasing atmospheric CO2 by alkalinity export. Nevertheless, the soil organic carbon storage likely dominates the net CO2 drawdown of Enhanced Rock Weathering efforts. The estimated CO2 drawdown via alkalinity export from the studied soil is comparable in size to the estimated CO2 drawdown from the atmosphere by glacier meltwater-fed reservoirs in NE-Iceland. These waters are loaded with suspended basaltic particles, but poor in organic carbon. Water-rock interactions in the reservoirs and their catchments result in an alkalinity generation and a direct CO2 drawdown from the atmosphere, or less emission in reservoirs with high CO2 partial pressure, after addition of river waters loaded with inorganic suspended matter. While the partial pressure gradient between the atmosphere and the water bodies is the main driving force for the direction and magnitude of CO2 fluxes, it is highly affected by wind speeds but less by temperature variations.

About the doctoral candidate

Tobias was born and raised in Leipzig, Germany. He obtained his BSc and MSc in Applied Geosciences from the Martin-Luther University of Halle-Wittenberg, Germany. Tobias started his Ph.D. at the Faculty of Earth Sciences, University of Iceland 1st of November 2016. His Ph.D. was originally funded by a European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie action, as part of a project named Metal-Aid, looking for redox active iron minerals. Over the course of his Ph.D. study, he went for several laboratory and modelling training sessions and collaboration stays abroad, for example at the Nano-Science Center of the University of Copenhagen, GFZ Potsdam, GIR-QUESCAT University of Salamanca, and Ampos21 Barcelona, cooperating with various researchers leading to joint publications. Additionally, he aided various visiting guest researchers at the University of Iceland. He presented his work at international conferences, including the international Goldschmidt conference in written form and as talks.