Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Geology

Supervisor

Dr. Brian Branfireun

Abstract

The Hudson Bay Lowlands (HBL) contains 26 Gt C sequestered in a 2 meter thick layer of peat which blankets a quarter of Ontario, Canada. The hydrological and chemical influence of the HBL peatlands to surface waters is recognized, but information on peatland runoff processes and the evolution of groundwater through this vast, carbon-rich landscape remain scant. This study focused on elucidating the groundwater flow patterns of a bog-fen-tributary complex in the central region of the HBL, and estimating exports of groundwater, dissolved organic carbon (DOC), total (THg), and methyl (MeHg) mercury during the 2011 ice-free season. Hydrometric data, combined with ions and stable water isotopes, reveal lateral flows in the uppermost meter of peat dominate the bulk transfer of groundwater in the bog (73-137 mm) and fen (55-131 mm). The direction and magnitude of the measured vertical gradients in the bog (-0.2 to 0.1) and fen (-0.1 to 0.2) are dictated by water table position and micro-to-mesoscale topography. The seasonal exports of DOC from the bog and fen are small, and comprise 5.4% (2.0±0.3 g C m-2 yr-1) and 1.4% (0.5±0.1 g C m-2 yr-1) of the Net Ecosystem Carbon Balance, respectively. Exports of THg and MeHg from the bog (132.9±45.4 and 3.4±2.8 ng m-2 yr-1) and fen (50.0±8.4 and 1.9±1.2 ng m-2 yr-1) are lower than reported in other boreal wetlands. The swamp and thicket riparian zone between the ribbed fen and tributary appears to influence the quality of water and augment solute concentrations of the water in small surface flows that flow directly into the nearby second-order stream.

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