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A study of the chemical and physical properties of Syncrude's tailings pond, Mildred Lake, 1980 Open Access


Author or creator
MacKinnon, M.D.
Additional contributors
Environmental Research Report 1981-1
Tailings Pond
Tar Sands
Oil Sands
Type of item
Canada, Alberta, Fort McMurray
Selected chemical and physical properties of the tailings pond were examined in 1980. The distributions of specific variables with depth and season within the tailings pond were determined (temperature, pH, conductivity, suspended particulate matter, total solids, bitumen, major anions, major cations, organic carbon, nutrients, phenols, and trace metals). From the resulting information, a generalized picture of the present state of the tailings pond was obtained. In 1980, the tailings pond was a highly stratified waterbody with a low density, well mixed surface zone (0-6 m) overlying a high density deep water zone (>10 m) where mixing is slow. Between these two zones, lies a zone of rapidly changing values in which a thermocline (zone of rapid temperature change) and a pycnocline (zone of rapidly increasing density) are established. The exact depth at which these changes begin varies with season (shallowest in spring and early summer, deepening during summer and fall). In the surface zone (0-6 m), most concentrations were generally low and uniform, while in the deep zone (>10m), the concentrations of variables, particularly those associated with the particulate fraction (fines, bitumen), were high. In the deepest waters (>15m), a sludge zone of high fines (>4%) and high bitumen (>5000 mg L-1) concentration was evident. Throughout this tailings pond study, the concentrations of most dissolved variables (nutrients, trace metals, phenols, organic carbon) were generally higher than in surrounding waters. While the concentrations are high, I would not consider the levels to be high enough to be considered excessive, at present. The quality of the tailings pond waters during the 1980 study was acceptable for maintenance of maximum rate of recycle of water from the tailings pond for plant processes. The tailings pond is an environmental hazard both physically and chemically. The tailings waters are acutely toxic (LC50<4% for rainbow trout by 96 hour static bioassay). However, the quality of these waste waters in the tailings pond at this stage of its development has not deteriorated to a level where it cannot be reclaimed.
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Conditions of Use MacKinnon, M.D., 1981. A study of the chemical and physical properties of Syncrude's tailings pond, Mildred Lake, 1980. Syncrude Canada Ltd., Edmonton, Alberta. Environmental Research Report 1981-1. 126 pp. Permission for non-commercial use, publication or presentation of excerpts or figures is granted, provided appropriate attribution (as above) is cited. Commercial reproduction, in whole or in part, is not permitted without prior written consent. The use of these materials by the end user is done without any affiliation with or endorsement by Syncrude Canada Ltd. Reliance upon the end user's use of these materials is at the sole risk of the end user.
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