Title

Numerical and multivariate statistical analysis of hydrogeology and geochemistry in large peatlands

Date of Award

1996

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor(s)

Donald Siegel

Keywords

Hydrology, Geochemistry, Environmental science, Albany River, Hudson Bay Lowland

Subject Categories

Hydrology

Abstract

Pore-water samples and hydraulic measurements were collected in the Albany River drainage basin of the Hudson Bay Lowland (HBL). Pore-water chemistry was evaluated using bivariate plots, cluster analysis, and principal component analysis to determine the importance of groundwater and to evaluate geochemical processes within the peat. Conceptual models of peatland hydrology were evaluated using numerical groundwater flow and mass transport simulations. These simulations were used to interpret the sparse hydraulic data sets collected in the HBL and collected by others in the Glacial Lake Agassiz peatlands. Data analysis of the peat pore-water chemistry indicates that: (1) the transport of dissolved constituents from the mineral soil into the peat column is a dominant control on peat pore-water chemistry, (2) bogs are characterized by elevated concentrations of dissolved organic carbon, CH$\sb4$, SiO$\sb2$ K$\sp+$ and larger mineral ion balance errors, whereas fens are characterized by their higher pH and alkalinity, (3) organic acids are important anions in bog pore waters, (4) marine sediments are releasing SO$\sb4\sp{2-}$, Cl$\sp-$, and Na$\sp+$ to the peat column at several locations in the study area, and (5) methane concentrations and SO$\sb4\sp{2-}$ concentrations are inversely related, suggesting that the presence of marine sediments may reduce methane production in portions of the HBL. Groundwater flow simulations indicate that the hydraulic conductivity of mineral soil underlying the peat influences the generation of vertical hydraulic gradients in the peat column and the development of local groundwater flow cells related to bog water-table mounds. Conceptual models used to explain differences in surface-water chemistry in different peat landforms assume that advective transport is the dominant process controlling pore-water chemistry. Numerical simulations indicate that dispersive mixing, driven by lateral flow, is capable of moving solutes in the mineral soil to surface water in peatlands. Dispersive mixing may influence carbon cycling in peatlands, moving labile substrate produced at the peat surface downward in the peat column. High methane pore-water concentration in the lower portion of the peat column may result from the conversion of this labile substrate to methane.

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