Monitoring Wildlife Exposure and Recovery to Bitumen Release

Following a bitumen release in 2010, action was taken to minimize environmental impact, including the selective removal of the most highly impacted vegetation and the use of oil socks to minimize possible runoff.  An ecological risk assessment (ERA) was conducted based on reported concentrations of bitumen related contaminants in soil, vegetation and water.  The conclusion of the ERA was that the likelihood of long-term adverse health effects to ecological receptors in the area was negligible.  To provide evidence for this conclusion, a small mammal sampling plan targeting Southern red-back voles (Myodes gapperi) was carried out at two exposed sites and two relevant reference areas in 2014.emil

Voles were readily collected at all locations and no statistically significant differences in morpho-metric measurements (i.e., body mass, length, foot length, and adjusted liver weight) were found between animals collected from impact zones of varying levels of coverage.  Additionally, no trends corresponding with bitumen coverage were observed with respect to metal body burden in voles for metals that were previously identified in the source bitumen.

Hepatic ethoxyresorufin-O-deethylase (EROD) activity was statistically significantly elevated in voles collected from the high impact zones of sites compared to those collected from the reference areas, a finding that is indicative of continued exposure to contaminants. This increase in EROD however, was not correlated with any observable adverse population-wide biological outcomes.  Therefore the biological sampling program supported the conclusion of the initial ERA and supported the hypothesis of no significant long term population-wide ecological impact of the accidental bitumen releases.

The first phase of the work is published in Science of the Total Environment (Abstract). A second sampling program was completed in 2017.  Sample analysis is currently underway to determine the current status of the site as it relates to recovery pathway and corresponding EROD analysis of impact zone compared to reference sites.