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http://hdl.handle.net/11375/22274
Title: | EARLY STAGE WATER CAP OXYGEN CONSUMPTION TRENDS WITHIN THE FIRST COMMERCIAL SCALE OIL SANDS PIT LAKE, BASE MINE LAKE. |
Authors: | Risacher, Florent Frédéric |
Advisor: | Warren, Lesley A |
Department: | Earth and Environmental Sciences |
Keywords: | Geochemistry;Oil sands;Pit Lake |
Publication Date: | 2017 |
Abstract: | Bitumen exploitation in Alberta’s oil sand region generates considerable amounts of waste including tailings and process-affected water that needs reclamation. Water capped tailings technology (WCTT) is currently being assessed as a potential wet reclamation strategy in the oil sand by the commission of Base Mine Lake (BML), the first commercial scale Pit Lake. Pit Lakes consist of ~40m of fluid fine tailings (FFT) deposited in old mine pit covered with a ~10m water cap. In order to be successful, pit lakes much achieve the ecological roles of a natural lake, which includes colonization of the water by macrofauna therefore necessitating the water cap to be oxic. Due to the reductive nature of the tailings, oxygen consuming constituents (OCC) such as methane, sulfide and ammonia are released from the FFT into the water cap potentially posing a threat to the success of the reclamation. Additional seasonal effects such as stratification and ice cover may further affect oxygen consumption by isolating parts of the water cap therefore allowing accumulation of OCC. Results shows that BML thermally stratifies during the summer and winter and that oxygen persist throughout the water cap despite reaching low level at the FFT-water interface (FWI) during summer. Consistent with the FFT acting as an OCC source, aqueous CH 4 and NH 4+ concentrations were highest closer to the FWI, decreasing upwards into the water cap. Using linear regression CH 4 was shown to be an important OCC during the summer of 2015 while NH 4+ and CH 4 were both important for the summer of 2016 highlighting the emergence of nitrification in BML. Detailed analysis of seasonal data revealed that accumulation of OCC below the hypolimnion depletes oxygen and favors methanotrophic activity. Results from both studies suggest that methanotrophs have a competitive advantage at low oxygen levels against nitrifiers. |
URI: | http://hdl.handle.net/11375/22274 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Florent_Frederic_Risacher_sept292017_MSCthesis.pdf | 4.99 MB | Adobe PDF | View/Open |
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