Location of Thesis Examination

Room 1027 B&GS

Degree

Master of Science

Program

Geology

Supervisor

Dr. Fred Longstaffe

Abstract

The geology and groundwater geochemistry are described for a 1400km2 breathing well zone within a Middle Devonian, karstic carbonate aquifer system in southwestern Ontario. Breathing wells are unusual because they draw in or emit large volumes of air, depending on fluctuations in atmospheric pressure which causes an exchange of gases between the atmosphere and the subsurface. To better understand this connection, geochemical, hydraulic, and barometric data were used to investigate interconnectivity within the breathing well zone. Spatial and temporal analyses reveal that a significant amount of unsaturated void space exists within the Lucas Formation, and that hypoxic and high CO2 gases are emitted during low atmospheric pressure periods. The groundwater chemistry displays elevated trace metals (e.g. Ag, Cu, Pb, Zn) and SO42- resulting from combined evaporite dissolution and sulphide oxidation. This study provides data useful in understanding the type of environment in which breathing wells are found, and the nature of the subsurface vadose zone gases and groundwater movement in these systems.

Keywords Breathing wells, karst, geochemistry, stable isotopes, hydrogeology, sulfide oxidation, evaporite dissolution, barometric logging

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