Ian Clark  
Research Interests
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Research Interests


 

Arctic PaleohydrologyPermafrost Hydrogeology129I in GroundwatersMine HydrogeologyNoble Gases in GroundwatersGroundwaters in Arid Regions

 

Ian Clark in the fieldMy research interests revolve around the use of environmental isotopes and geochemistry in groundwater and paleoclimate studies. Stable isotopes, measured at the natural abundance levels found in nature, are tracers of water, solutes and gases. Together with geochemical tools, we can look at the recharge origin of groundwaters, and the biogeochemical processes that occured in the subsurface. Applications of these methods range from water resources and groundwater contamination to paleoclimatology.

 

1) Arctic Paleohydrogeology

Work in the karst regions of the Yukon led to the discovery by Bernard Lauriol and myself of this remarkable material forming in fissures within limestone outcrops. Endostromatolites, so named for their micro-stromatilite structure and hidden growth within bedrock, are ubiquitous in permafrost carbonate regions. They form by bacterial activity involving the degradation of soil organics and production of methane, leaving an unusual isotopic signature. of I work with Bernard Lauriol in the Department of Geography. Our work to date has focussed on Endostromatolites: Hand specimen of a fissure surface with endostromatolite columns. Photo is about 10 cm wide. Columns are about 1 cm tall.

Endostromatolite

Endostromatolite is a previously undescribed biogenic calcrete that lines fissures in carbonate terrains throughout non-glaciated permafrost regions. This material is found in fissures to depths of up to 5 meters from modern bedrock surfaces, and has precipitated from groundwaters under closed system, anoxic conditions. We believe that the material documents periods of expanded talik and deepened permafrost due to increased summer warmth in the Arctic.

See: Clark, Lauriol, Marschner, Nicolas, Charet and Desrochers, 2004. Canadian Journal of Earth Sciences. PDF File

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2) Permafrost hydrogeology and Canadian Shield mine hydrology

The movement of groundwater in permafrost is of interest to understand the extent and permeability of permafrost, as well as the timing of recharge in permafrost regions.

We are now looking at groundwater recharge and circulation in permafrost, through the analysis of noble gas concentrations and other isotopic tools. The long term disposal of radioactive waste must consider the effects of climate change and renewed glaciation on the repository and nuclide transport.

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3) The movement of 129I in groundwaters

Iodine-129 is one of the nuclear reactor waste products of greatest concern. It is a fission product that is readily leached from spent fuel, and poses considerable radiological hazard due to its affinity for concentration in the thyroid gland. Its migration from a nuclear waste repository is of concern considering its relatively high mobility in natural groundwaters (the repository far-field). The Canadian Nuclear Safety Commission have funded this project in collaboration with Drs. Tom Kotzer (Canadian Light Source, University of Saskatoon) and Gwen Milton formerly with Atomic Energy of Canada Ltd. (AECL). Phase I focused on the high concentrations of 129I at the Chalk River Nuclear Laboratories site in Eastern Ontario. This was published by MSc student Nicholas Alvarado Quiroz in Radiochimica Acta (Alverado).  The project has had a second phase, looking at I-129 in the natural setting of the Sturgeon Falls, Ontario, site. Rob Renaud (now with AECL Chalk River) and his thesis is now published, also in Radiochimica Acta (Renaud).

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4) Mine Hydrogeology: Analogues for groundwater flow at a nuclear waste repository

We are now looking at groundwater recharge and circulation in permafrost, through the analysis of noble gas concentrations and other isotopic tools. The long term disposal of radioactive waste must consider the effects of climate change and renewed glaciation on the repository and nuclide transport. Recent publications on this include Douglas et al., Journal of Hydrology, 235:88-103, and Clark et al., Ground Water, 38: 735-742.

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5) Noble gases in groundwaters

Nick Battye (Co-supervised with Tom Kotzer) undertook his MSc project looking at noble gas concentrations in groundwaters from the Con Mine, Yellowknife. This work uses the concentrations of He, Ne, Ar, Kr and Xe to determine the temperature of recharge in shallow groundwaters, and the age of the brines found at greater depth. The former is based on the temperature-dependency of noble gas solubility, which provides a thermometer, set at the moment of recharge. In contrast, the deep brines have accumulated He and Ar over geological time periods, generated through alpha decay of U and Th (for 4He) and 40K decay (for 40Ar). In a second phase of the project, Shane Greene (MSc student) has developed a diffusion sampler (seen in picture above) to complement water samples for noble gases in mines.

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6) Groundwaters in Arid Regions

I continue research into the age and origin of groundwaters in arid regions, principally through collaboration with Dr. Hani Khoury and Dr. Elias Salameh at the University of Jordan in Amman. We have been studying groundwaters in the northern regions of Jordan, particularly in the Maqarin region, where groundwaters with pH up to 12.5 discharge from natural, metamorphic zones in marl where combustion in the past has created natural cement-kilns. This is part of an international Radioactive Waste Disposal Analogue program involving SKB (Sweden), NIREX (UK) and Nagra (Switzerland). We are learning about the behaviour of safety-relevant nuclides in cementitious environments through studies of the Maqarin (Jordan) high pH analogue site.

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