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TitreInfluence of saline groundwater discharge on river water chemistry in the Athabasca oil sands region - a chloride stable isotope and mass balance approach
AuteurGue, A; Grasby, S E; Mayer, B
SourceApplied Geochemistry vol. 89, 2018 p. 75-85, https://doi.org/10.1016/j.apgeochem.2017.10.004
Année2018
Séries alt.Ressources naturelles Canada, Contribution externe 20170290
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.apgeochem.2017.10.004
Mediapapier; en ligne; numérique
Formatspdf
ProvinceAlberta
SNRC74E
Lat/Long OENS-112.0000 -110.0000 58.0000 56.5000
Sujetssables bitumineux; résurgence des eaux souterraines; eau souterraine; circulation des eaux souterraines; géochimie des eaux souterraines; pollution de l'eau souterraine; halite; carbonate; anhydrite; solides complètement dissous; géochimie de l'eau de source; sources; géochimie du chlore; etudes isotopiques; hydrocarbures aromatiques; hydrogéologie; Santé et sécurité; combustibles fossiles; Dévonien; Crétacé
Illustrationslocation maps; tables; graphs; histograms; plots
ProgrammeL'énergie géothermique, Les géosciences pour les nouvelles sources d'énergie
Résumé(disponible en anglais seulement)
A chloride mass and stable isotope (d37Cl) balance approach was employed to calculate the effect of saline groundwater discharge into the Athabasca and Clearwater rivers in the Athabasca Oil Sands Region (AOSR) in north-eastern Alberta, Canada. Saline groundwater affected by halite, carbonate, and anhydrite dissolution discharges Na-Cl type water with total dissolved solids (TDS) up to 51,700 mg/L from exposed Devonian and Cretaceous units in the river valleys in this area. In this study, nine springs of groundwater with median Cl concentration of 9800 mg/L were sampled and chloride stable isotope ratios were determined, with d37Cl values ranging from 0.2 to 1.0¿. In contrast, river waters had historical monthly median Cl concentrations between 5.9 and 49.5 mg/L and d37Cl values between -2.2 and -1.4¿. The discharge rate of saline groundwater was calculated to be 100 ± 20 L/s into the Clearwater River and 134 ± 68 L/s into the Athabasca River. The chemical composition and discharge rates of saline groundwater were used to estimate its contribution to the mass fluxes of major ions, metals, and PAHs in the Athabasca and Clearwater rivers. Overall, saline groundwater contributed less than 0.2% of river discharge, but 0.04 to 39% of major ion concentrations in the rivers, with highest contributions under winter low-flow conditions. In the Clearwater River, saline groundwater contributed 23-39% of average monthly Cl flux and 18-32% of average monthly Na flux. For the same major ion fluxes in the Athabasca River, saline groundwater contributed 12-18% and 6-12%, respectively. The influence of saline groundwater discharge on the mass flux of trace elements in the rivers was found to be negligible, contributing less than 1% of river fluxes of Cu, Ni, Pb, and Zn. Similarly, the influence on mass flux of PAHs in the rivers was found to be negligible (<0.03%) but quantifiable. These results provide important insights on the natural contributions of saline groundwater discharge to river chemistry in the AOSR, a necessary factor to consider when monitoring for anthropogenic effects of oil sands development on river water quality.
Résumé(Résumé en langage clair et simple, non publié)
La production de ressources de sables bitumineux dans le nord-est de l'Alberta a soulevé des préoccupations quant à l'impact potentiel sur la rivière Athabasca. Des études antérieures ont tenté d'évaluer cet impact en comparant simplement la chimie de l'eau en amont et en aval de la zone des sables bitumineux. Cette approche est compliquée cependant, car il y a un important déversement naturel d'eau salée dans la rivière à l'intérieur de la zone des sables bitumineux. Pour rendre compte de cette contribution naturelle au système fluvial, une nouvelle approche d'utilisation des isotopes stables au chlorure a été utilisée comme empreinte digitale pour suivre les contributions naturelles totales à la rivière dans la zone d'intérêt.
GEOSCAN ID306294