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The Stable Isotope Hydrology and Ecology Research Laboratory conducts applied research and new methods development in the areas of stable isotope hydrology and ecology, and provides light isotope analytical services to NWRI and Environment Canada researchers in support of national research programs. The facility is located in the National Hydrology Research Centre located at the University of Saskatchewan in Saskatoon. Analytical services may be made available to other government departments and the private sector on a cost-recovery basis.
Stable Isotope Lab at NWRI.
Stable isotopes of elements are not radioactive. They are naturally occurring forms of the same element that have different numbers of neutrons, and so have a slightly different atomic mass: for example, carbon-12, carbon-13.
Much of the hydrosphere (water) and biosphere (plants, animals) is made up of several key elemental building blocks, and these include the elements and the stable isotopes of hydrogen (H), oxygen (O), nitrogen (N), carbon (C), and sulfur (S). While there are many isotopes of elements found in the periodic table, these five "light isotopes" are the most abundant and useful.
Why do scientists use light stable isotopes in environmental research?
The ratios of stable isotopes (e.g., 18O: 16O ratio) may vary or change in nature due to chemical and biological processes - this is known as isotope fractionation.
As an example, the stable isotopes of oxygen in rainfall "fractionate" spatially across continents as a result of well-known meteorological processes such as temperature, and factors such as elevation and distance from the sea. Hence, scientists studying ground water and surface water use the stable isotopes of water (O,H) to determine water sources and age, and to quantify physical processes like evaporation.
Light isotope ratios in animals, rocks, water, and plants (and even consumer products) vary depending on their geographic origin around the world. This often 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.
How do scientists measure stable isotopes?
Scientists measure stable isotopes using an instrument called a stable isotope-ratio mass-spectrometer (SIRMS). Samples are generally converted by high temperature combustion to a simple gas. For example, all 13C: 12C determinations are made on 100% CO2 gas, and so any carbon bearing sample is burned and converted to pure CO2 before mass spectrometric analysis.
For further reading:
- Hobson, K.A. and L.I. Wassenaar (ed.). 2008. Tracking Animal Migration with Stable Isotopes, 2. Elsevier. 160 p.
- Stable Isotope Geochemistry. 1997. J. Hoefs, Springer-Verlag.
- Principles of Stable Isotope Distribution. 1999. R.E. Criss, Oxford University Press.
- Isotope Tracers in Catchment Hydrology. 1998 C. Kendall and J. McDonnell, Elsevier.
- Environmental Isotopes in Hydrogeology. 1997. I. Clark and P. Fritz. Lewis Publisher.
The Stable Isotope Hydrology and Ecology Laboratory is supported by three modern GV Instruments dual-inlet and continuous flow triple and multi-collector isotope-ratio mass spectrometers, and their associated automated sample preparation devices.
Three high temperature online elemental analyzers are used for routine flash combustion for 13C, 15N and 34S analyses of all sample matrices, as well as for flash pyrolysis for 2H and 18O analyses. The stable isotope analysis of waters are performed by a variety of means, including conventional dual-inlet CO2 and H2 equilibration, online gas equilibration methods, and Cr or C reduction, in order to offer a broad range of precision, price, and turnaround time. A gas chromatograph is linked to a mass spectrometer to offer molecular 13C and 2H analyses. State-of-the-art bench based extraction facilities include high-vacuum preparation lines for the preparation of MeCl for 37Cl isotope analyses. Micro-analytical balances, pulverizing, freeze drying, and other key sample preparation facilities are in the sample preparation laboratory.
Sample QA/QC is managed through the use of certified primary and internal stable isotope reference materials and the implementation of the USGS Stable Isotope Laboratory Information Management System (LIMS).
Working at the Isotope Ratio Mass Spectrometer.
Stable Isotope Methods Developed at NWRI
Koehler, G., L.I. Wassenaar and M.J. Hendry. 2000. An automated technique for measuring d D and d18 O values of porewater by direct CO2- and H2- equilibration. Analytical Chemistry 72(21): 5659-5664.
Lis, G.P., L.I. Wassenaar and M.J. Hendry. 2007. High precision laser spectroscopy D/H and 18O/16O measurements of microliter natural water samples. Analytical Chemistry 80: 287-293.
Venkiteswaran, J., L.I. Wassenaar and S. Schiff. 2007. Diel dynamics of dissolved oxygen isotopic ratios: primary production, respiration, and gas exchange in aquatic ecosystems. Oecologia 153(2): 385-398.
Wassenaar, L.I., M.J. Hendry, V.L. Chostner and GP Lis. 2008. High resolution pore water δ2H and δ18O measurements by H2O(liquid)-H2O(vapor) equilibration laser spectroscopy. Environmental Science and Technology (in press).
Wassenaar , L.I. and K.A. Hobson. 2000. Improved method for determining the stable-hydrogen isotopic composition ( d D) of complex organic materials of environmental interest. Environmental Science and Technology 34: 2354-2360.
Wassenaar, L.I. and K.A. Hobson. 2003. Comparative equilibration and online technique for determination of non-exchangeable hydrogen of keratins for animal migration studies. Isotopes in Environmental and Health Studies 39: 1-7.
Wassenaar, L.I. and K.A. Hobson. 2006. Stable hydrogen isotope heterogeneity in biological tissues: Isotope-Ratio Mass Spectrometry and migratory wildlife sampling strategies. Rapid Communications in Mass Spectrometry 20(16): 2505-2510.
Wassenaar, L.I. and G. Koehler. 2004. An on-line technique for the determination of the d37Cl of inorganic and total organic chloride in environmental samples. Anal. Chem. 76: 6384-6388.
Sample information must be provided using our Excel SIA Sample Submission Spreadsheet (email for a copy). This worksheet can be sent on a virus-free floppy disk or emailed, and a hard copy included with the samples. The SIA Sample Submission template must be fully completed and submitted before analyses will proceed. Sample turnaround times vary from a few weeks to several months depending on the workload and mass spectrometer configurations.
Sampling from dissolved oxygen isotopes in Lake Ontario.
Leonard Wassenaar received his Ph.D. in isotope geochemistry from the University of Waterloo in 1991. He is currently a senior research scientist with Environment Canada, and holds adjunct professorships in Earth Science at the University of Waterloo and the University of Saskatchewan.
Keith Hobson received his Ph.D. from the University of Saskatchewan in 1992 and specializes in applications of stable isotopes to avian, terrestrial and marine ecology. Keith is a senior research scientist in Environment Canada and an adjunct professor in Biology at the University of Saskatchewan.
Geoff Koehler received his Ph.D. in stable isotope geochemistry from the University of Saskatchewan in 1996 and specializes in isotope-ratio mass-spectrometry, methods development, instrument design and electronics. He manages the day-to-day operations of the stable isotope laboratory.
For further information about this laboratory at NWRI, please contact:
Dr. Leonard Wassenaar
National Water Research Institute
11 Innovation Blvd.
S7N 3H5 Canada
Phone: (306) 975-5747
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