Isotope Biogeoscience research group

The Isotope Biogeoscience research group is led by Prof. Dr. Eliza Harris in the Climate and Environmental Science Division at the University of Bern. Our research focusses on using isotopic composition to understand the production of trace gases from natural and anthropogenic sources, the emission of these gases into the atmosphere, and their chemistry, lifetime and impact in the troposphere.

Trace gases in the atmosphere

Trace gases make up less than 1% of the atmosphere. Despite their low abundance, they play a key role in climate, biosphere-atmosphere exchange, human and ecosystem health, and many other issues.

Trace gases make up a small part of the atmosphere, but their influence is felt through all biogeochemical cycles. LHS: Trace gases, based on a visualization from the Deutsche Wetterdienst. GHG data is for June 2021 from the NOAA HATS program. RHS: Biogeochemical cycles, from NASA Earth Observatory.

Measurement techniques

The development of novel measurement techniques is a key focus of our research. Isotopic signatures can be used to trace the production and consumption of trace gases. Laser spectroscopy allows direct measurement of the isotopic composition of trace gases based on the specific absorption lines for different isotopocules. Coupling of laser spectroscopy with different peripharies as well as advanced data analysis and modelling techniques will produce new and exciting datasets in the coming years.

a) Microbial sources of N₂O can be distinguished using isotopic composition. AOBs = Ammonia Oxidizing Bacteria. b) Simulated and measured spectra for dual-laser QCLAS monitoring of the four major isotopocules of N₂O. Blue points indicate the laser measurements and the red line shows the fitted spectrum used to determine mixing ratios of the isotopomers.

Field applications

We engage in fieldwork in a number of our research projects. This part of our work centers on the emission of N₂O from soils and the monitoring of N₂O in the troposphere. We are currently measuring N₂O emissions at an experimental agricultural site in Kenya. Future campaigns will include:

• Measurement of N₂O in the soil profile using low-cost sensors developed in the CRAN project

• Monitoring of N₂O mixing ratio and isotopic composition at background sites, particularly the Jungfraujoch high altitude research station.

Data science and modelling

Data science and modelling are key to all parts of our research. We are interested in using data science for raw data processing, to achieve higher precision and accuracy for spectroscopic isotopic measurements. Modelling approaches are also required to interpret this data: We have developed the TimeFRAME package to facilitate robust and reproducible quantification of pathways from isotopic datasets. At the global scale, we apply models such as IsoTONE to understand large-scale changes in N₂O emissions and consumption.