Hydrogeology, Chemical and Microbial Activity Measurement Through Deep Permafrost

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 δ 18O values ~5‰ lower than the local surface water. The fluid isotopic composition was affected by the permafrost-formation process. Nonbacteriogenic CH 4 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 CH 4 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.

The interglacial–glacial cycle and geochemical evolution of Canadian and Fennoscandian Shield groundwaters

“…In crystalline rocks, groundwater transport is dominated by fracture flow and diffusion within the rock mass. Geochemical samples from within permafrost in crystalline rock indicate fluids are composed of a dilute, slightly oxidizing solution (Blowes and Logsdon, 1998;Stotler et al, 2009Stotler et al, , 2011. Because salinities increase with increasing depth, downward diffusion of freezing-affected waters would not be significant.…”

“…Several researchers have assumed that glacial meltwater was the only fluid with a depleted stable isotope value, and utilized this property to identify glacial meltwater recharge to groundwater in various locations (Perry et al, 1982;Siegel and Mandel, 1984;Clark et al, 2000; Ca-Na-Cl, Na-Ca-Cl 8-40 Ruskeeniemi et al (2002Ruskeeniemi et al ( , 2004, Frape et al (2004), Stotler et al (2009Stotler et al ( , 2010aStotler et al ( , 2011 and Onstott et al (2009) Fritz (1981, 1987), Fritz and Frape (1982), Frape et al (1984Frape et al ( , 2004, McNutt et al (1984), MacDonald (1986), Kaufmann et al (1987), Fritz et al (1987Fritz et al ( , 1994, Sherwood-Lollar et al (1988, 1993a, Bryant (1995), Douglas (1997), Bottomley et al (1999Bottomley et al ( , 2002Bottomley et al ( , 2005 Slave 30-610 Ca-SO 4 -Cl-HCO 3 , Ca-Mg-SO 4 -HCO 3 , Ca-Mg-SO 4 , Ca-Na-SO 4 , Ca-Mg-Na-SO 4 -HCO 3 , Ca-Mg-Na-SO 4 , Ca-Na-SO 4 -HCO 3 , Ca-Na-SO 4 -HCO 3 , Ca-Na-SO 4 -Cl, Na-Ca-SO 4 -Cl-HCO 3 , Ca-Na-Cl 0.7-80 Fritz (1981, 1987), Frape et al (1984), MacDonald (1986, SherwoodLollar et al (1988SherwoodLollar et al ( , 1993a, Fritz et al (1994) and Stotler et al (2010a) Manitoba, Canadian Shield Thompson Sporadic discontinuous…”

Trends and future challenges in sampling the deep terrestrial biosphere

“…In situ pore water chemistry can be estimated during drilling, via the use of devices that enable “probe-at-the-bit” measurements (Hall et al, 2008). Once a well has been developed, U -tube borehole fluid samplers can be used to remove the drilling fluid or monitor its dilution over time with ground water flow and then collect true formation fluids and gasses at near in situ conditions (Freifeld, 2009; Stotler et al, 2011). Further, geochemical conditions and microbial community structures for specific fractures can be determined through the use of packers that isolate those fractures within a borehole for sampling (Haveman et al, 1999; Shimizu et al, 2006; Purkamo et al, 2013).…”

Earth as a Microbial Habitat

“…These are a particularly attractive options for collecting spatially resolved water and microbial samples across subsurface chemical (e.g., redox) gradients (Takai et al, 2003) and for assessing community response to nutrient stimulation (Baldwin et al, 2008). U-tubes can also be effective for collecting subsurface gas and water samples for characterizing microbial communities and biogeochemical processes at depth (Stotler et al, 2011).…”

“…Such discussion is beyond the scope of this chapter but has been addressed in detail elsewhere (Kieft et al, 2007;Kieft, 2010). Upon recovery, materials can be maintained at in situ pressures using specialized devices, while formation fluids may be recovered using U-tube samplers (Stotler et al, 2011).…”