During his PhD studies, Martin Reinhard Rasmussen has explored the use of optical sensors and chemical imaging to investigate dynamic microenvironments in soils and sediments. Chemical imaging enables two-dimensional visualization of key parameters for microbial activity, such as oxygen and pH, in complex soil samples. As part of his research, Martin Reinhard Rasmussen developed a novel, low-cost imaging system for long-term field applications in soils and multiparameter imaging techniques to simultaneously measure microscale oxygen and pH dynamics.

This research contributes to the understanding of biogeochemical fluxes and the formation of so-called hotspots and hot moments associated with elevated greenhouse gas production in soils, thereby supporting strategies for sustainable land management.

The PhD study was completed at Department of Agroecology - Center for Landscape Research in Sustainable Agricultural Futures (Land-CRAFT) & Department of Biology - Microbiology, Faculty of Natural Sciences, Aarhus University

This summary was prepared by the PhD student.

Time: Wednesday, 7 January 2026 at 14:00
Place: Building 1532, room G2, Department of Mathematics, Aarhus University, Ny Munkegade 118, 8000 Aarhus C
Title of PhD thesis: Chemical Imaging of Soils – Development and Application of Optical Sensor Systems for Laboratory and Field Studies
Contact information: Martin Reinhard Rasmussen, e-mail: martinreinhard@bio.au.dk, tel.: +45 23295804
Members of the assessment committee:
Associate Professor Torsten Mayr, Analytical Chemistry, Graz University of Technology, Germany
Professor Jakob Santner, Department for Plant Nutrition, University Giessen, Germany
Professor Kai Finster (chair), Department of Biology - Microbiology, Aarhus University, Denmark
Main supervisor: Associate Professor Klaus Koren, Department of Biology - Microbiology, Aarhus University, Denmark
Co-supervisor: Professor Klaus Butterbach-Bahl, Department of Agroecology - Center for Landscape Research in Sustainable Agricultural Futures (Land-CRAFT), Aarhus University, Denmark
Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Natural Sciences/GSNS, Ny Munkegade 120, building 1521, 8000 Aarhus C