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TitreA geochemical characterization of southwestern Ontario's breathing well region
TéléchargerTéléchargement (publication entière)
AuteurFreckelton, C N; Hamilton, S M; Longstaffe, F J
SourceRegional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario open house; par Russell, H A J; Ford, D; Priebe, E H; Commission géologique du Canada, Dossier public 8212, 2017 p. 18, (Accès ouvert)
ÉditeurRessources naturelles Canada
RéunionOntario Geological Survey and Geological Survey of Canada groundwater geoscience open house; Guelph; CA; mars 1-2, 2017
Documentdossier public
Mediaen ligne; numérique
Référence reliéeCette publication est contenue dans Russell, H A J; Ford, D; Priebe, E H; (2017). Regional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario open house, Commission géologique du Canada, Dossier public 8212
SNRC30; 31C; 31D; 40; 41A; 41G; 41H/03; 41H/04; 41H/05; 41H/06; 41H/12; 41H/13
Lat/Long OENS -84.0000 -76.0000 46.0000 41.5000
SujetsDévonien moyen; eau souterraine; ressources en eau souterraine; aquifères; régimes des eaux souterraines; puits d'eau; géologie du substratum rocheux; lithologie; roches sédimentaires; carbonates; topographie karstique; évaporites; analyses du gaz naturel; échange de gaz; gaz carbonique; oxygène; géochimie des eaux souterraines; analyses géochimiques; analyses hydrauliques; sulfates; etudes isotopiques; soufre; fer; métaux en trace; zinc; plomb; cuivre; argent; strontium; célestine; Formation de Lucas ; Formation de Dundee ; hydrogéologie; géochimie; Phanérozoïque; Paléozoïque; Dévonien
ProgrammeGéoscience des eaux souterraines, Aquifer Assessment & support to mapping
Diffusé2017 02 22
Résumé(disponible en anglais seulement)
A physical and geochemical characterization has been completed for a 1400 km2 breathing well zone in a Middle Devonian, karstic carbonate aquifer system in southwestern Ontario. Breathing wells are unusual because they draw in or emit large volumes of air, in response to fluctuations in atmospheric pressure. This behavior causes gas exchange between the atmosphere and the subsurface and quite commonly the expelled gases are depleted in oxygen and enriched in carbon dioxide. To better understand this unique atmosphere-geosphere connection, geochemical, hydraulic, and barometric data were used to investigate the interconnectivity within the breathing well zone. Regionally, 102 sites were sampled for groundwater chemistry characterization, and 10 wells located within the breathing well zone were monitored monthly over one year. Spatial and time series analyses reveal that most wells affected by the breathing well phenomena are drilled through the Dundee Formation and finished in the underlying Lucas Formation. The results suggest that a significant amount of unsaturated void space exists within the Lucas Formation, and that hypoxic, high CO2 gases are generated by several processes and emitted during low atmospheric pressure periods. Locally, groundwater shows remarkable chemical and isotopic stability over the 1 year monitoring period, which suggests a very large degree of storage in the aquifer. Regional distributions of groundwater facies types are strongly influenced by local hydrogeological conditions and consist dominantly of Na-Ca-HCO3, Ca-Mg-HCO3, Ca-Sr-HCO3, and Ca-Mg-SO4-types. The groundwater composition includes detectable levels of dissolved oxygen and elevated concentrations of sulphate. Sulphur isotopic data indicate that the sulphate results from two endmember processes: evaporite dissolution and oxidation of metallic sulphides. Evidence for the latter process also includes elevated concentrations of iron and trace metals including Zn, Pb, Cu and Ag. Very high strontium up to 80 mg/L comes from the dissolution of celestite (or celestine; SrSO4) in the absence of gypsum. This provides insight on the solution-karstification process that appears to have formed the breathing well system and may provide a tool for mapping the system in areas to the north where void space is saturated and air exchange is prevented.