Use of Environmental Isotopes to Evaluate Carbon and Nitrogen Cycling in Groundwater

The support of the UW-EIL has been crucial for the development of my research program, which applies environmental isotopes in hydrogeology and geochemistry. During the last few years I have focused my efforts on the behaviour of carbon and nitrogen compounds in groundwater. This research is linked to a larger program assessing sources and behaviour of organic and inorganic contaminants in groundwater, which is one the strongest research programs in the Department of Earth Sciences, UW. The isotope work has focused mainly on (a) sources and processes that affect nitrate in groundwater in agricultural settings and (b) sources and processes that affect chlorinated solvents and petroleum hydrocarbons in groundwater. The research on nitrogen has been expanded to evaluate the impact of landfills and manure lagoons in groundwater, following development of analytical techniques for determining ¹⁵N in ammonium and ¹³C and ²H in organic compounds. In addition, development of organic compound specific analysis of Cl isotopes in the UW-EIL has allowed for new opportunities.

My graduate students are being trained in this facility and have received assistance in the development or adaptation of the analytical techniques required for their research. In addition to supporting my own research projects, the UW-EIL allows my participation in collaborative projects within the UW and with national and international Universities. During the last three years, 7 UW graduate students, four international PhD students and five international scientists related to my research projects were and are being trained at UW-EIL. At least 2000 isotope analyses have being carried out at UW-EIL for my research projects during this period.

Selected publications

• Hunkeler, D., Aravena, R, Berry Spark, K., and Cox, E. 2005. Assessment of degradation pathways at a site with mixed chlorinated hydrocarbon contamination using stable isotope analysis. Environmental Science & Technology, 39: 5975 – 5981.
• Hunkeler, D., Chollet, N., Pittet, X., Aravena, R., Cherry, J.A., and Parker, B.L. 2004. Effect of source variability and transport processes on carbon isotope ratios of TCE and PCE in two sandy aquifers. Contaminant Hydrology, 74, 1-4: 265-282.
• Aravena, R., Harrison, S.M., Barker, J., Abercrombie, H., and Rudolph, D. 2003. Origin of methane in the Elk valley coalfield, Southeastern British Columbia, Canada. Chemical Geology, 195:219-227.
• Day, M., Aravena, R., Hunkeler, D., and Gulliver, T. 2002. Application of carbon isotopes to document biodegradation of tert-Butyl Alcohol under field conditions, AEHS 2002 Special Issue of Contaminated Soil, Sediment and Water, Oxygenated Fuels Issue, pp 88-92.
• Hunkeler, D., Aravena, R., and Cox, E. 2002. Carbon isotopes as a tool to evaluate the origin and fate of vinyl chloride: Laboratory experiments and modeling of isotope evolution. Environmental Science & Technology, 36: 3378-3384.