Arsenic Characterization of Surficial Deposits: Assessing Potential Source of Groundwater Contamination in Cold Lake Region of Alberta, Canada.

Groundwater arsenic (As) contamination is a global issue affecting millions of people around the world. Elevated levels of As (> 10 µg L-1) were found in domestic well waters in the Cold Lake region, Alberta. Groundwater contamination was attributed to As present in parent geological material. Therfore, the present study was carried out to characterize surficial deposits in Cold Lake region and investigate biogeochemical processes that control As availability and transport to groundwater. Alberta Geological Survey provided sediment (surficial deposit) samples from five different cores collected to a depth of ~200 m from Cold Lake Region. Total As concentration was measured by using ICP-MS to map the extent of As contamination. To evaluate As association with solid constituents, a modified chemical sequential extraction method was developed employed. Micro-XRF and XANES analyses were also performed on selected (high and low As) samples to identify As speciation and mineralogy. The results suggested that most of As was present in AsIII as FeAsS, and As2S3 minerals. Chemical analysis supported strong correlation between Fe-As and Sulfide-As. XRD and SEM analysis also confirmed the results of XANES analysis. Laboratory column experiments are being designed to predict As transport in surficial deposits under natural environment and at high temperature where oil sands mining operators inject very hot steam (~300o C) deep into the ground to extract bitumen that releases As from surficial deposits and enhances its transport to ground water. The results will have great implication in predicting and managing As contamination in Cold Lake region of Alberta.