Current research and/or projects
My research uses the stable isotopes of Hydrogen, Carbon, Nitrogen, Oxygen, Sulphur, and chlorine to address a wide variety of problems within environmental science. In general, the stable isotope ratios in animals, rocks, water, and plants (and even consumer products) vary depending on their geographic origin around the world. This allows researchers to use isotopes as a kind of forensic tracer of origin. The applications here are numerous, ranging from food adulteration, fingerprinting of oil spills, migratory animal tracking, to tracking the source of contaminants.
- Stable isotope hydrology and aqueous geochemistry.
- Analytical geochemistry.
- Stable isotope tracing of environmental contaminants.
- Stable isotope ecology.
- Stable isotope forensics.
Education and awards
B.Sc. Adv. 1988.. Saskatchewan. Geological Sciences
Ph.D. 1997. Saskatchewan. Stable Isotope Geochemistry.
Soto, D.X., Koehler, G. and Hobson, K.A., 2015. Combining Denitrifying Bacteria and Laser Spectroscopy for Isotopic Analyses (δ15N, δ18O) of Dissolved Nitrate. Analytical chemistry, 87(14), pp.7000-7005.
Hobson, K.A. and Koehler, G., 2015. On the use of stable oxygen isotope (δ18O) measurements for tracking avian movements in North America. Ecology and evolution, 5(3), pp.799-806.
Koehler, G., Wassenaar, L.I. and Hendry, J., 2013. Measurement of stable isotope activities in saline aqueous solutions using optical spectroscopy methods. Isotopes in environmental and health studies, 49(3), pp.378-386.
Koehler, G. and Wassenaar, L.I., 2012. Determination of the hydrogen isotopic compositions of organic materials and hydrous minerals using thermal combustion laser spectroscopy. Analytical chemistry, 84(8), pp.3640-3645.
Koehler, G. and L.I. Wassenaar. 2010. The stable isotopic compositions (37Cl/35Cl) of dissolved chloride in rainwater. Applied Geochemistry 25: 91-96.
L. I. Wassenaar, J. J. Venkiteswaran, S. L. Schiff, G. Koehler. 2010. Aquatic community metabolism response to municipal effluent inputs in rivers quantified using diel d18O values of dissolved oxygen. Canadian Journal of Fisheries and Aquatic Sciences, 67:1232-1246, 10.1139/F10-057
Wassenaar, L.I. and Koehler, G. 2004. An on-line technique for the determination of the d37 Cl of inorganic and total organic chloride in environmental samples. Anal. Chem 76: 6384-6388
JM. Culp, NE. Glozier, M Medding, LI Wassenaar, FJ Wrona, G Koehler and D Halliwell. 2003. Dissolved oxygen relationships of water column and pore water habitat: Implications for guideline improvements. Northern Rivers Ecosystem Initiative. Final Report
Koehler, G., Wassenaar, L.I., and M. J. Hendry. 2000. An automated technique for measuring dD andd18 O values of porewater by direct CO2- and H2- equilibration. Analytical Chemistry 72: 5659-5664.
Wassenaar, L and Koehler, G. 1999. An on-line technique for the determination of the d18 O and d17 O of gaseous and dissolved oxygen. Analytical Chemistry. 71:4965-4968.
Koehler, G., T.K.Kyser, R. Enkin, and E. Irving. 1997. Paleomagnetic and geochemical evidence for the diagenesis of evaporites in the Elk Point Basin, Saskatchewan, Canada. Canadian Journal of Earth Sciences. 34: 1619-1629.
Koehler, G. and T.K.Kyser 1996. The significance of hydrogen and oxygen stable isotope fractionations between carnallite and brine at low temperature: experimental and empirical observations. Geochimica et Cosmochimica Acta. 60: 2721-2726.
Koehler, G., Chipley, D. B. L., and Kyser, T.K. 1991. Measurement of the hydrogen and oxygen isotopic compositions of concentrated chloride brines and fluid inclusion brines in halite. Chemical Geology (Isotope Geoscience Section). 90:45-55.
Koehler, G. and Kyser, T.K. 1991. Fluid events as recorded in the hydration water of carnallite from the Elk Point Basin of Western Canada. Proceedings of the International Williston Basin Symposium, Oct. 1991.
Koehler, G., Kyser, T.K., and Danyluk, T. 1990. Stable isotope evidence for the petrogenesis of carnallite in the Middle Devonian Prairie Evaporite Formation, Saskatchewan. In Summary of Investigations 1990, Saskatchewan Geological Survey. Sask Energy and Mines Misc. Report 90-4.
Hendry, M. Jim, Novakowski, Kent, Smith, Laura, Koehler, Geoff, & Wassenaar, L.I. (2012). Long-term solute transport through thick Cretaceous shale in the Williston Basin Canada using naturally-occurring tracer profiles. Clays in natural and engineered barriers for radioactive waste confinement - 5 International meeting Book of abstracts, (p. 923). France
Koehler, G. 2011. Hydrogen isotopic compositions of organic materials measured by combustion of the organics to water, ASITA 2011 Kingston On.
Koehler, G. 2010. A flow-through water liquid-vapour equilibrator for continuous measurement of the stable isotopic compositions of natural waters by WS-CRDS laser spectroscopy. CFIRMS-2010, Montreal, QC.
Gibson, J.J., Prowse, T.D., Pietroniro, A., Wassenaar, L.I., Koehler, G., 2003 Isotope tracing of water balance and climatic variability along the Mackenzie River, Isotope hydrology and integrated water resources management, 40th Anniversary International Symposium, 19-23 May 2003, IAEA, Vienna Austria.
Wassenaar L.I., and Koehler, G. 2002. The stable oxygen isotopic composition (18O/17O/16O) of dissolved oxygen in aquatic ecosystems. 3rd International conference on Applications of Stable Isotope Techniques to Ecological Studies, Flagstaff, AZ, April 2002.
Wassenaar L.I., and Koehler, G. 2001. A rapid on-line technique for the determination of the d d18O of molecular and dissolved oxygen in natural waters. 7th Continuous Flow Isotope Ratio Mass Spectrometry Conference, Calgary, August 2001.
Wassenaar L.I., and Koehler, G. 1999. A rapid on-line technique for the determination of the d18O of molecular and dissolved oxygen in natural waters. International Atomic Energy Agency SM-361, Vienna.
Kelln, C.J., Hendry, M.J., Wassenaar, L.I., Koehler, G. and Shaw, R.J., 1999. Stable isotope contents of porewaters in clay-rich aquitards, Saskatchewan, Canada: A comparison and evaluation of measurement techniques.
Koehler, G. and Kyser, T. K. 1990. Stable isotope geochemistry of carnallite. (abstract) GSA abstracts with programs. v22, no7.
Adjunct Professor, School of Environment and Sustainability, University of Saskatchewan.