Exposure to weathering reduces the water repellency of aggregated oil sand material from subsoils of the Athabasca region

This study assesses the water repellency (WR) of aggregated oil sand material (AOSM) from the Athabasca region, Canada, and evaluates the onion-skin weathering hypothesis, which postulates that with increasing depth into the soil profile or into individual AOSM samples, the exposure to and extent of weathering of AOSM decreases and petroleum hydrocarbon (PHC) content and WR increase. WR and PHC content were determined for outer and inner portions of AOSM from depths of 15–200 cm. Results show AOSM displays a wide range of WR, in terms of both contact angle (CA) (0° to 129°) and water drop penetration time (WDPT) (0 to > 3600 s). As salvage depth or depth into AOSM increases, PHC content and WR increase, confirming onion-skin weathering. These findings imply the benefit of discreet salvaging into separate layers, as opposed to composite salvaging of shallow and deep soils. Deep materials, which contain relatively high PHC contents, can be salvaged and replaced as deep layers to avoid the excessive drying and expression of WR which may occur in the near-surface. By controlling the location of AOSM within the soil profile, water storage in the rooting zone may be increased, allowing the establishment of relatively productive ecosystems.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author