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

Abstract

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.

Influence of contamination with diesel oil on water sorptivity and hydrophobicity of sandy loam soil

“…Contamination with crude oil compounds degrades the soil, deteriorating its physical, biological and chemical properties (Álvarez et al, 2016; Buzmakov et al, 2019; Gordon et al, 2018). Because of their low density, higher viscosity and lower emulsifying ability, PHs are easily absorbed on the surface of the ground, increasing the soil water repellency (SWR) (Neil & Si, 2018). This contributes to the reduction of soil wettability and free capillary flow, limiting the access of plants to rainwater (Kraemer et al, 2019; Li et al, 2019; Pawluśkiewicz et al, 2020; Wei et al, 2019).…”

Oil sands in glacial till as a driver of fast flow and instability in the former Laurentide Ice Sheet: Alberta, Canada

“…The oil sands are an unconventional heavy crude oil which is viscous at atmospheric temperature and pressure and is believed to behave as a non‐Newtonian shear fluid, meaning viscosity decreases with increasing shear (Bazyleva et al, 2010). The wettability structure of the Alberta Oil Sands (AOS) is also believed to be water‐wet, meaning that the sand grains are surrounded by a thin lens of water (nanometric in thickness) which separates the individual grains from the oil (Czarnecki et al, 2005; Neil & Si, 2018). This water‐wet property and relatively high porosity makes oil easily extractable from the oil sands deposits using hot water to agitate the oil and separate it from the surrounding sediment (Mossop, 1980).…”