Dissolved organic carbon concentration, patterns and quality at a reclaimed and two natural wetlands, Fort McMurray, Alberta.

Abstract

The oil sands extraction process in Northern Alberta is very extensive, as it requires the removal of vegetation and overburden materials from the landscape surface. By law, mining companies are required to restore the land to its previous capability once operations have ceased. To achieve this, reclamation practices have been initiated; however, limited research has focused on upland-wetland systems in the oil sands region. In 2012, Syncrude Canada Ltd. (SCL) constructed a 52-hectare wetland, known as Sandhill Fen Watershed (SFW). SFW is a highly managed system that is composed of a water storage and outlet pond, underdrains, hummocks and perched and lowland fens. DOC is a major source of carbon and plays an important role in wetland biogeochemical and ecological functions. In disturbed landscapes, it is unclear as to how the quantity and quality of DOC compare with natural analogies. The objective of this thesis is to determine the spatial and temporal patterns of dissolved organic carbon (DOC) quality and quantity of SFW and compare these findings with those from two natural wetlands near Fort McMurray, AB. In 2014 and 2015, water samples were collected and analyzed for DOC concentration and optical properties. To assess DOC composition, four fluorescence indices were used: Fluorescence Index (FI), Freshness Index (β/α), Humification Index (HIX) and Specific Ultraviolet Absorbance at 254nm (SUVA254). Results indicate that there is significant difference between SFW and the natural fens for all fluorescence indices and DOC concentration. More specifically, DOC concentrations and composition at SFW are greater and more variable than at the natural wetlands - Pauciflora (PC) and Poplar fen (PP). Additionally, DOC concentrations at SFW appear to be primarily controlled by water table (WT), sodium (Na+) concentration and electrical conductivity (EC), whereas PC and PP are influenced by additional variables such as peat depth and vegetation. At SFW, fluorescence indices and a 3-component Parallel Factor Analysis (PARAFAC) model suggest that the carbon changes at a “transition zone” located at the boundary between the lowlands and margins from terrestrially-derived, old with high humification, aromaticity and molecular weight to microbially-derived, recently produced with low humification, aromaticity and molecular weight. Results from this research will help guide reclamation efforts through the characterization of carbon cycling processes and their relation to undisturbed systems.