Carbon and nitrogen cycling in watersheds and wetlands

The role of greenhouse gases (GHGs) in affecting climate remains a global concern and a high research priority. In the past 15 years our research has focussed on using the isotopes of carbon (¹³C and ¹⁴C) to examine the source, transport and fate of the various forms of carbon in watersheds and wetlands.

Isotopic analysis of CO₂ and CH₄ are currently being used to develop new predictive models of the processes governing release of greenhouse gases following two large ecosystem scale flooding experiments conducted at the Experimental Lakes Area near Kenora, Ontario. Carbon isotopes yield information that is not obtainable from the study of carbon mass and flux alone.

Recently, we have explored the potential of δ¹⁸O-O₂ in five different aquatic environments; lakes (small lakes and Great Lakes), rivers, groundwaters, constructed wetlands and reservoirs. We demonstrated that this simple but powerful technique for science and management of aquatic systems was been even more fruitful than originally anticipated. Our research showed that δ¹⁸O-O₂ can be used to quantify in situ rates of P and R, gas exchange coefficients, whole ecosystem respiratory quotients (CO₂/O₂) and re-aeration rates in rivers, lakes and reservoirs. In wetlands and groundwater, δ¹⁸O-O₂ can quantify O₂ translocation by macrophytes and chemical transformations in aquifers. We built and tested a dynamic model for δ¹⁸O-O₂ and O₂ in water that includes P, R, and gas exchange (GE). The next step is to translate this demonstrated scientific potential into applications to benefit scientific advancement and environmental policy and management.

To this end, we have prepared a research proposal to concentrate on the Grand River watershed, a highly impacted system in Southern Ontario. The overarching goal of this proposal is to develop the δ¹⁸O-O₂ tool for science and science-based management of rivers Nitrous oxide (N₂O) is a potent greenhouse gas, having a global warming potential of approximately 300 times that of CO₂. Although N₂O has been increasing in the atmosphere, the sources are not well known. Rivers are supersaturated with N₂O, but emissions of N₂O from Canadian rivers have not been measured.

There are two main sources of N₂O in human-impacted rivers; application of N fertilizer in agriculture and N released from wastewater treatment plants (WWTPs). The processes of nitrification and denitrification can result in the creation of N₂O from NH₄+ and NO₃- depending on environmental conditions including O₂ concentration. Isotopic analysis will allow these two processes to be separated facilitating research into the processes controlling N₂O release and possible mitigation measures. Applications have been submitted to CFCAS and NSERC to assess the magnitude and importance of N₂O flux from Canadian rivers. These projects are possible due to UW-EIL’s recent acquisition of a trace gas analyzer and development of new techniques for the analysis of the isotopic composition of dissolved N₂O.

During the past five years I have supervised 7 PhD. and 12 MSc. students all with an isotopic component to their thesis research. In addition, 2 Post Doctoral Fellows, 7 undergraduates, 9 technicians, and 14 undergraduates (non-thesis) have been trained in preparing samples for ¹³C, ¹⁴C, ¹⁵N, ³⁴S and ¹⁸O analysis. The UW-EIL is crucial to our success. All our isotope measurements are completed in the EIL. Most of our samples in environmental research are not “routine”, and UW-EIL provides the expertise required for developing the new techniques we require. Ready access to well maintained world-class instrumentation and quick turn-around is crucial to timely technique development especially where graduate student projects are concerned.

Selected Publications

• Schiff, S., J. Spoelstra, R. Semkin, D. Jeffries. 2005. Drought induced pulses of SO4 from a Canadian Shield wetland: Use of δ34S and δ18O in SO42 to determine sources of S. Applied. Geochemistry. 20 691-700.
• Venkiteswaran, J. and S. Schiff. 2005. Methane oxidation: isotopic enrichment in boreal reservoirs. Applied Geochemistry. 20 4 683-690.
• Matthews CJD, Joyce EM, St.Louis VL, Schiff SL, Venkiteswaran JJ, Hall BD, Bodaly RA, Beaty KG. 2005. Carbon Dioxide and Methane Production in Small Reservoirs Flooding Upland Boreal Forest. Ecosystems 8: 267-285.

Dr. R. Aravena's testimonial

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.

Dr. M. Power's testimonial

Biological studies incorporating stable C, N, S and O isotopes

In my research stable isotopes (C, N, S and O) have become indispensable in answering questions related to nutritional pathways in terrestrial mammals, benthic-pelagic coupling in lakes, biomagnification of contaminants in aquatic ecosystems, niche partitioning and the determination of resource use overlap, study of trophic polymorphisms, the measurement of thermal habitat use and prediction of climate change impacts on northern fish populations and the study of other large scale ecosystem processes. In recent years (2003-05) the proportion of publications using isotope methods has risen to 58% from 19% in previous years (2000-02), such that in the last six years isotope methods figure directly in 38% of all publications. The trend is expected to continue as my students (n=8) now all use isotope mass spectrometry in thesis-related study, be it as a primary or supplemental analytical tool.

The UW-EIL features an array of specialized and technically advanced equipment that is of vital interest to this research, both because it provides novel instrumentation not widely available elsewhere and, importantly, because it has the capability to conduct high volume throughput analysis. As ecological use of stable isotopes has increased, it has become increasing important to increase the number of samples analysed.

Novel description of a relationship no longer suffices. Accurate description of sample and case variability is critically needed and can only be obtained from accurate, high volume analysis. The Uw-EIL has perfected the delivery of such analyses with an integrated team of specialists.

Advances in oxygen isotope measurement have facilitated the application of stable isotope analysis to archival fish otoliths for use in climate effect studies. For our research, it was the recognized capability of the UW-EIL that was crucial to being able to undertake climate-impact research and be awarded research grants to study climate change impacts on northern fishes. This analysis will require precise, high volume analysis that no other lab in Canada can currently provide. Herein lies the uniqueness of the Waterloo facility – its ability to provide apparently routine values on large numbers of samples in a timely manner. Only with such capability can broad scale macro-ecological phenomenon (e.g. climate change impacts) be clearly understood.

Similarly, a second case in point is the S-isotope capability that has allowed my students to undertake research collaborations with Fisheries and Oceans Canada to assess nearshore habitat use by keystone northern fish species in the Beaufort Sea. Without the continued development, measurement and analytical expertise in the UW-EIL, advanced training of graduate students in this laboratory would have to be significantly curtailed. Without the high quality services of the UW-EIL, this laboratory would not achieve the research success it does, including the Dempson & Power study reviewed in Nature (429:982).

Dr. B. Wolfe's testimonial

Present and past hydro-ecology of the Peace-Athabasca and Slave river deltas

Field- and laboratory-based research focuses on using elemental and stable isotope composition of lake sediments for reconstructing past hydrological and climatic change, evaluating the impact of human activities on watersheds, and documenting lake carbon and nitrogen cycling responses to past environmental change. Paleohydrological reconstructions are coupled with quantitative analysis of modern lake hydrology and their watersheds using water isotope tracers. Over the past several years, research has been carried out as part of team-based multidisciplinary national and international paleolimnological investigations in the circumpolar arctic and subarctic, subtropical Andes, temperate regions of North America, and in the Great Lakes of North America and East Africa.

Current research is centred on developing high-resolution, multi-centennial hydro-ecological histories in the Peace-Athabasca (PAD) and Slave River deltas (SRD) in northern Canada from multi-proxy analyses of lake sediment cores supported by comprehensive field-based studies of modern hydrology, limnology and aquatic ecology. The PAD and SRD have broad ecological and cultural significance and are ecosystems highly sensitive to prevailing climatic and hydrological conditions. Changing delta lake levels impact aquatic and terrestrial ecosystems, wildlife habitat, and First Nations communities who have historical connections with the PAD and SRD and their resources.

Results will address pressing concerns related to the potential environmental impact of river regulation, resource development and climate variability on the PAD and SRD. Knowledge of present and past hydro-ecological variability is vital for effective industry-, government-, and community-based environmental stewardship of the PAD and SRD in light of multiple stressors that may affect these internationally recognized northern ecosystems.

State-of-the-art equipment and expert personnel at the UW-EIL play a central and vital role in my NSERC Northern Research Chair program, which relies heavily on isotope analyses of several hundred water and sediment samples per year. Recent awarding of Canada Foundation for Innovation and Ontario Innovation Trust grants included funding to acquire a continuous-flow gas-source isotope ratio mass spectrometer to support my research activities, which represents a significant addition to the UW-EIL and clearly points to its continued recognition as a world-renowned research and training facility.

Selected publications

• Wolfe BB, RI Hall, WM Last, TWD Edwards, MC English, TL Karst-Riddoch, A Paterson and R Palmini. 2005. Reconstruction of multi-century flood histories from oxbow lake sediments, Peace-Athabasca Delta, Canada. Hydrological Processes (special issue on Hydrologic Processes of the Northern Rivers Ecosystem Initiative) (in press).
• Wolfe BB, TL Karst-Riddoch, RI Hall, TWD Edwards, MC English, R Palmini, S McGowan, PR Leavitt and SR Vardy. 2005. Classification of hydrologic regimes of northern floodplain basins (Peace-Athabasca Delta, Canada) from analysis of stable isotopes (of δ¹⁸18O, δH) and water chemistry. Hydrological Processes (in press).
• Wolfe BB, TL Karst-Riddoch, SR Vardy, MD Falcone, RI Hall and TWD Edwards. 2005. Impacts of climate and river flooding on the hydro-ecology of a floodplain basin, Peace-Athabasca Delta, Canada: A.D. 1700-present. Quaternary Research 64: 147-162.
• Edwards TWD, BB Wolfe, JJ Gibson and D Hammarlund. 2004. “Use of water isotope tracers in high-latitude hydrology and paleohydrology.” In Long-Term Environmental Change in Arctic and Antarctic Lakes, Developments in Paleoenvironmental Research, Volume 7 (R Pienitz, M Douglas and JP Smol, eds.). Springer, Dordrecht, pp. 187-207.

Dr. T. Edwards's testimonial

Water and Climate Studies Using Natural Isotope Tracers

The UW-EIL facility forms the cornerstone of my long-running program of water and climate studies using natural isotope tracers, the contributions that arise from this program and, most importantly, the training of highly qualified personnel involved in these efforts. Stated simply, I could not pursue this dynamic and viable research program without the ability to obtain high-quality isotopic analyses on water and other isotopic archives and the unparalleled opportunity for my students to gain hands-on experience in the creation of such data.

Highlights of the UW-EIL's contributions to my research over the past three years include analytical support provided for (1) the Canadian Network for Isotopes in Precipitation, which is the formal Canadian component of the Global Network for Isotopes in Precipitation program, jointly operated by the IAEA and WMO, in association with IGBP/PAGES. The CNIP program has now provided continuous monthly station time-series and gridded data products for contemporary precipitation isotope fields over Canada for a full seven years, plus coverage of the Canadian High Arctic over 14 years. In addition to uses in other water and climate studies, this unique (and growing) dataset is a fundamental resource in international efforts to evaluate and refine the water cycles of leading GCMs and RCMs, recently formalized under the international Stable Water Isotope Intercomparison Group initiative, involving both myself and Dr S.J. Birks (my former PhD student and long-time CNIP coordinator).

Over the past three years the EIL has also provided essential analytical service for (2) my participation in the multidisciplinary Mackenzie Basin Deltas research program, founded on Dr B. Wolfe's NSERC Northern Research Chair, and a large program of closely allied industrially-funded environmental and paleoenvironmental research in the Peace-Athabasca Delta, which rely heavily on the use of isotope tracers. A key feature of this research has been the opportunity for UW-EIL staff to collaborate with my students on the development and refinement of new analytical techniques, especially for analysis of water and nutrient isotope tracers (O, H, C, N) in organic matter.

Selected Publications

• Edwards TWD, Wolfe BB, Gibson JJ, Hammarlund D 2004 Ch.7: Use of water isotope tracers in high-latitude hydrology and paleohydrology In Long-term Environmental Change in Arctic and Antarctic Lakes. Developments in Paleoenvironmental Research. R Pienitz, MSV Douglas & JP Smol (eds). Kluwer, 121-140.
• Hall, R.I., Wolfe, B.B., Edwards, T.W.D., Karst-Riddoch, T.L., and Vardy, S. 2003. A Multi-Century Flood, Climatic, and Ecological History of the Peace-Athabasca Delta, Northern Alberta, Canada: Final Report. Submitted to BC Hydro, 28 February 2003, 250 pp.
• Wolfe, B.B., Edwards, T.W.D., Jiang, H.B., MacDonald, G.M., Gervais, B.R., and Snyder, J.A. 2003. Effect of varying oceanicity on early to mid-Holocene paleohydrology, Kola Peninsula, Russia: isotopic evidence from treeline lakes. The Holocene 13, 153-160.
• Gibson, J.J., and Edwards, T.W.D. 2002. Regional surface water balance and evaporation-transpiration partitioning from a stable isotope survey of lakes in northern Canada. Global Biogeochemical Cycles 16, 10.1029/2001GB001839.
• Birks, S.J., Gibson, J.J., Gourcy, L., Aggarwal, P.K., and Edwards, T.W.D. 2002. Maps and animations offer new opportunities for studying the global water cycle. EOS 83, 406 (plus electronic supplement).
• Motz, J., Shouakar-Stash, O., Drimmie, R.J., Edwards, T.W.D., Frape, S.K., and Annable, W.K. 2001. Hydrogen-isotope analysis of potentially-toxic organic materials employing manganese reduction and disposable nickel-pyrolysis tubes. Chemical Geology 181, 67-81.

Dr. S. Frape's testimonial

Stable Chlorine and Bromine Isotopes in Nature and “Fingerprinting” Contaminants

Chloride and bromide are key components of natural groundwater and rock systems, as well as being common environmental contaminants in road salt/deicers and organochlorine solvents. For over twenty-five years I have worked to develop a better understanding of halide (Cl, Br, F) systematics in the hydrosphere. As a result of this research, and because of increased research demand, UW-EIL set up a δ³⁷Cl preparation facility in the early 1990’s. We are now one of only ten laboratories in the world, and two in Canada, with the capability to analyze stable chlorine isotopes and the only facility to analyze this isotope on a regular basis. We are the second laboratory in the world to analyze stable bromine isotopes. The UW-EIL’s capability to analyze both of these isotopes in a wide variety of compounds and applications is truly unique and has become a rapidly expanding research tool for internal as well as external users.

Ongoing research in Canada and Finland is concerned with water-rock interaction studies related to the safe disposal of radioactive waste. Stable Cl and Br isotopes are used to differentiate geochemical signatures between different continental Shields, rock types and geographical areas. The importance of the UW-EIL’s ability to analyze δ³⁷Cl has been recognized by many of the research groups in Sweden, Finland, Switzerland and Canada that deal with the safe disposal of nuclear waste in crystalline rocks. Ongoing support from Scandinavian and Swiss waste disposal agencies has recently been successfully combined with Canadian support from Ontario Power Generation in an international collaboration. A key component to the study’s success is the UW-EIL’s capability to analyze Cl and Br stable isotopes and tritium.

Understanding of halide isotope geochemistry is continuing to grow with combination of Cl, C, H isotope fingerprinting. It is the first major attempt to fingerprint various subsets of organic compounds and mixtures involved in groundwater contamination. To date 3 ongoing PhD. (Shouakar-Stash, Stotler, Drimmie) theses and 6 completed PhD. theses (three are Professors: Blyth, ARC/Calgary; Harvey, Nebraska; Weaver, Melbourne) and 4 ongoing MSc. theses and 9 completed MSc. theses have been trained to use stable chlorine isotopes in the environment as one of their major research focuses. Past PhD students (Sherwood-Lollar, U of T; Hussain, industry; Cecil, USGS) have also benefited from the ability of UW-EIL to solve difficult isotopic problems.

Selected Publications

• Lehmann, B.E., Love, A. Purtschert, R., Collon, P., Loosli, H.H., Kutschera, W., Beryerle, U., Aeschbach-Hertig, W., Kipfer, R., Frape, S.K., Herczeg, A., Moran, J., Tolstikhin, I.N., Groning, M., 2003. A comparison of ⁸¹Kr-, ³⁶Cl- and ⁴He-groundwater dating in 4 wells in the Great Artesian Basin, Australia. Geochimica et Cosmochimica Acta. or Earth Sci. Planet. Letters, 211, 237-250.
• Shouakar-Stash, O., Frape, S.K. and Drimmie, R.J., 2005. Determination of bromine stable isotopes using continuous-flow isotope ratio mass spectrometry. Analytical Chemistry, 77(13): 4027-4033.
• Shouakar-Stash, O., Rostron, B. J. and Frape, S.K. 2003. Geochemistry and Stable Isotopic Signatures, Including Chlorine Isotopes of the Williston Basin, Canada. The Geological Society of America Annual Meeting, Seattle, USA, 235-10, 574.
• Shouakar-Stash, O., Frape, S.K. and Drimmie, R.J., 2003. Stable carbon, chlorine and hydrogen isotope measurement of selected chlorinated organic solvents. Jour. Contamin. Hydrology, 60:211-228.
• Alexeev, S. V., Alexeeva, L. P., Shouakar-Stash, O. and Frape, S. K. 2004. Geochemical and isotope features of brines of the Siberian platform. The 11th Water Rock Interaction Meeting. Saratoga Springs, NY, USA.
• Hesse, R., Frape, S.K., Egeberg, P.K. and Matsumoto, R., 2000. Stable isotopes studies (Cl, O, H) of interstitial waters from site 997, ODP Leg 164, Blake Ridge gas-hydrate field, west Atlantic Proc. Ocean Drilling Program, 164:129-137.
• Lyons, W.B., Frape, S.K. and Welch, K.A., 1999. History of McMurdo Dry Valley Lakes, Antarctica, from stable chlorine isotope data. Geology, 27:527-530.
• Beneteau, K.M., Aravena, R., and Frape, S.K., 1999. Isotopic characterization of chlorinated solvents – laboratory and field results. Organic Geochemistry, 30:739-753.
• Cecil, L.D., Frape, S.K., Drimmie, R.J., Flatt, H. and Tucker, B.J., 1998. Evaluation of archived water samples using chlorine isotopic data, Idaho National Engineering and Environmental Laboratory, Idaho, 1966-93. U.S. Geol. Surv. Water Res. Investigation Report 98-4008, 27p.