Potential sulfate sources for the Paskapoo aquifer of Alberta

Abstract

The Paskapoo aquifer of Alberta is one of the most significant sources of groundwater for domestic and industrial use in the entire province. However, there are pronounced levels of sulfate in the southern part of the aquifer between Red Deer and Calgary, above the 500 mg/L drinking safety limit advised by Environment Canada. The focus of this study is to examine the potential origins of this sulfate from three primary sources: (1) self-sourced from the Paskapoo Formation, deposited ~60 million years ago; (2) overlying Cordilleran till; and (3) and overlying Laurentian till. Oxidation of sulphide minerals from Laurentide till is the primary source of sulfate based on findings from published research. The Cordilleran till has not been examined as a sulfate source to the same extent. This study used three methods to determine whether Cordilleran till had any potential to add sulfate to the Paskapoo aquifer. A geochemical test utilizing X-Ray Fluorescence (XRF) determined sulfur content in rock samples from several potential source formations of Cordilleran till. Next, we immersed two grain-sizes of sediment (10 grams) from each formation into distilled water (40 ml) and reacted the sample with barium chloride to determine if and how much sulfate each formation could generate. Finally, a GIS map was constructed using flow directions of the Cordilleran and Laurentide Ice sheets, and the outcrop distribution of bedrock formations. This was used to determine whether each formation had the potential to be integrated as till material and subsequently deposited over the Paskapoo. This study found that several of the tested formations from the Cordillera had sizeable levels of sulfate and were capable of producing sulfate when immersed in water. Although sulfur did have the potential to be integrated into Cordilleran till, the flow direction of the Laurentide glacier ultimately restricted placement of Cordilleran till over the Paskapoo aquifer and may have limited the western input of sulfate into the aquifer. However, regional groundwater flow could potentially transport the sulfate to other aquifers due to the regional dip of Tertiary and uppermost Cretaceous strata. This study presents a multidisciplinary approach involving GIS, geochemistry, geology, and hydrogeology to determine potential sources of groundwater contamination. *Indicates presenter