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TitleOrigin and geochemistry of saline spring waters in the Athabasca Oil Sands region, Alberta, Canada
AuthorGue, A; Mayer, B; Grasby, S EORCID logo
SourceApplied Geochemistry; Applied Geochemistry vol. 61, 2015 p. 132-145,
Alt SeriesEarth Sciences Sector, Contribution Series 20140367
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
Lat/Long WENS-112.0000 -110.0000 58.0000 57.0000
Subjectsenvironmental geology; fossil fuels; hydrogeology; groundwater geochemistry; groundwater pollution; groundwater resources; salt springs; hot springs geochemistry; thermal springs; carbonates; evaporites; oxygen isotopes; radiocarbon dating; tritium dates; sulphate; strontium; methane; Devonian
Illustrationslocation maps; graphs; sketch maps; tables; equations
ProgramGeoscience for future Energy Resources, Tailings Research
AbstractLarge-scale industrial development in the Athabasca oil sands region (AOSR) in northeastern Alberta (Canada) area has inspired efforts to distinguish between natural and anthropogenic effects on water quality of the Athabasca River and its tributaries. Naturally saline groundwaters of Na-Cl water type are known to discharge in some locations throughout the AOSR into river systems. In this study, the geochemistry of saline spring waters discharging from Devonian carbonate rocks into the Athabasca and Clearwater rivers was characterized using a comprehensive suite of analytical parameters including concentrations of major ions, trace elements, dissolved gases, and polycyclic aromatic hydrocarbons (PAHs). In addition, stable isotope analyses of H2O, SO4, dissolved inorganic carbon (DIC), Sr, and CH4 were used to trace the sources of spring waters and their dissolved solutes, and to identify subsurface processes affecting water chemistry. The spring waters had d18O values as low as -23.5¿, suggesting they are composed of up to 75% Laurentide glacial meltwater. This interpretation is supported by tritium and radiocarbon age-dating results, which revealed that the median age of the saline groundwaters ranged from 24,300 to 25,700 years before present. The high salinty of the spring waters (TDS 7,120 to 51,800 mg/L) was explained by dissolution of Devonian evaporite and carbonate deposits in the subsurface. Spring waters were affected by bacterial (dissimilatory) sulfate reduction, methanogenesis, and methane oxidation. Trace elements were present in spring waters at varying concentrations, with only one spring containing several predominant oil sands metals (As, Fe, Mo, Ni, Se, Zn) suggesting bitumen as a source. Five springs contained elements (Al, As, B, Fe, Se) at concentrations exceeding water quality guidelines for the protection of aquatic life. Seven PAHs were detected in spring waters (total PAH concentrations ranged from 7.3 to 273.6 ng/L), but most springs contained a maximum of two PAHs (phenanthrene and naphthalene), with more PAHs being detected in springs along the Athabasca River. This geochemical characterization of the saline groundwater discharging from the Devonian carbonates underlying oil sands deposits contributes to the knowledge of baseline groundwater chemistry in the AOSR which is of critical importance as the question of environmental effects of oil sands development in the AOSR continues to be explored.
Summary(Plain Language Summary, not published)
Natural inputs of saline groundwater into rivers in the Alberta Oil Sands Region (AOSR) have been poorly documented, but could contribute a portion of the dissolved load previously attributed to anthropogenic activity. This study provides comprehensive geochemical characterization of saline groundwater springs in the region. The source of salts was found to be the dissolution of carbonate and evaporite rocks found beneath oil sands deposits. In addition, small concentrations of trace metals and PAHs were found. Age dating revealed a median age of the saline groundwaters from 24,300 to 25,700 years before present, implying waters represent natural predevelopment conditions. This geochemical characterization of saline springs augments the knowledge of natural baseline conditions of groundwater contributions to the Athabasca River and its tributaries, and helps to fill a key knowledge gap in the AOSR. This was a joint activity of NRCan, Environment Canada and University of Calgary scientists.

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