Hydrogeology, Chemical and Microbial Activity Measurement Through Deep Permafrost
Publication Year
2011
Type
Journal Article
Abstract
Little is known about hydrogeochemical conditions beneath thick permafrost, particularly in fractured crystalline rock, due to difficulty in accessing this environment. The purpose of this investigation was to develop methods to obtain physical, chemical, and microbial information about the subpermafrost environment from a surface-drilled borehole. Using a U-tube, gas and water samples were collected, along with temperature, pressure, and hydraulic conductivity measurements, 420 m below ground surface, within a 535 m long, angled borehole at High Lake, Nunavut, Canada, in an area with 460-m-thick permafrost. Piezometric head was well above the base of the permafrost, near land surface. Initial water samples were contaminated with drill fluid, with later samples <40% drill fluid. The salinity of the non-drill fluid component was <20,000 mg/L, had a Ca/Na ratio above 1, with δ18O values ∼5‰ lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH4 was present and the sample location was within methane hydrate stability field. Sampling lines froze before uncontaminated samples from the subpermafrost environment could be obtained, yet the available time to obtain water samples was extended compared to previous studies. Temperature measurements collected from a distributed temperature sensor indicated that this issue can be overcome easily in the future. The lack of methanogenic CH4 is consistent with the high sulfate concentrations observed in cores. The combined surface-drilled borehole/U-tube approach can provide a large amount of physical, chemical, and microbial data from the subpermafrost environment with few, controllable, sources of contamination. © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.
Keywords
Below ground surfaces,
Combined surface,
Conductivity measurements,
Distributed temperature sensor,
Fluid components,
Formation process,
Hydrogeochemical,
Isotopic composition,
Land surface,
Local surfaces,
Methane hydrates,
Microbial activities,
Pie- zometric Head,
Sample location,
Sampling lines,
Sulfate concentrations,
Water samples,
Crystalline rocks,
Drills,
Fluids,
Gas hydrates,
Groundwater,
Hydrogeology,
methane,
permafrost,
Temperature measurement,
Hydrochemistry,
water,
borehole,
crystalline rock,
hydraulic conductivity,
hydrogeochemistry,
Hydrogeology,
Isotopic composition,
methanogenesis,
microbial activity,
permafrost,
pollutant source,
salinity,
sampling,
temperature profile,
Arctic,
Article,
chemistry,
cold,
gas,
geology,
methodology,
microbiology,
Arctic Regions,
Cold Temperature,
Environmental Microbiology,
Gases,
geology,
water,
Canada,
Nunavut
Journal
Ground Water
Volume
49
Pages
348-364