An integrated analysis of sediment geochemistry and flood history of floodplain lakes in the Athabasca Region

Abstract

This research advances understanding of trace metal deposition in floodplain lakes within the context of the Athabasca oil sands. This thesis begins with an evaluation of geomorphometric changes and flood history in two floodplain lakes of the Athabasca region over the past century. Analyses of historical aerial photographs, weather data, and hydrometric data present a temporal perspective on changes occurring to the floodplain lake environment. These results show that, despite no corresponding climatic shifts or changes to flood frequency, there appears to have been an increase in the area of both Shipyard Lake and Isadore’s Lake, though their position with respect to the Athabasca River remains unchanged. Building on the exploration of floodplain lake geomorphometry, this thesis then presents an analysis of metals in three lakes in the Athabasca region as related to the early development and continuing expansion of the nearby oil sands mining operations. Physical and chemical characteristics of sediment cores, and the concentration of environmentally relevant metals, linked to the timing of development of oil sands mining operations by Pb-210 dating, present an evaluation of temporal changes in the sediment of lake NE20. Due to dynamic depositional environments in Isadore’s Lake and Shipyard Lake, no accurate age model could be constructed. Results show that, despite an initial increase in the normalized metal concentrations of As, Ni, and V in each of the lakes following the onset of oil sands mining operations, there appears to be no recent enrichment of trace metals corresponding to the continuing expansion of operations. Results also indicate that disturbances to sedimentation in floodplain lakes, most likely associated with flooding, are an important factor affecting changes in metal deposition. Overall, this research contributes to the following aspects of our understanding of trace metal content in lake sediments of the Athabasca Region by: i) elucidating trends in sediment quality within floodplain lakes adjacent to oil sands mining operations; ii) investigating methods of normalizing different fractions of metal concentration data to increase understanding of metal transportation and deposition; and iii) assessing the effect disturbances to sedimentation can have on the concentration of metals in lake environments.