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We examined the fate and behaviour of diluted bitumen (dilbit) as it weathered for 70 days in freshwater limnocorrals (10 m diameter × 1.5 m depth) installed in a boreal lake to simulate dilbit spills in a natural aquatic environment. We added seven different dilbit spill volumes, ranging from 1.5 to 180 L, resulting in oil-to-water ratios between 1:71,000 (v/v, %) and 1:500 (v/v, %). Volatile hydrocarbons in the dilbit slick decreased rapidly after the dilbit was spilled on the water's surface, and dilbit density and viscosity significantly increased (>1 g mL−1 and >5,000,000 mPa s, respectively). Dilbit sank to the bottom sediments in all treatments, and the time to sinking was positively correlated with spill volume. The lowest dilbit treatment began to sink on day 12, whereas the highest dilbit treatment sank on day 31. Dilbit submerged when its density surpassed the density of freshwater (>0.999 g mL−1), with wind, rain, and other factors contributing to dilbit sinking by promoting the break-up of the surface slick. This experiment improves our ability to predict dilbit's aquatic fate and behaviour, and its tendency to sink in a boreal lake. Our findings should be considered in future pipeline risk assessments to ensure the protection of these important aquatic systems.

Soil ingestion rates in the order of 400 mg d − 1 have been proposed and considered plausible for use in human health risk assessments (HHRA) of Aboriginal populations and justified by qualitative assessments of the traditional subsistence activities that could enhance soil ingestion. The purpose of this study was to assess and document the subsistence activities and food consumption practiced by a First Nation Community living in a wilderness community in Canada to allow for a comparison with the previous qualitative assessments of Aboriginal populations and a quantitative mass balance tracer element study of the community conducted concurrently. An ethno-cultural survey was conducted of the Xeni Gwet'in First Nations community living in the Nemiah Valley, approximately 230 km west of Williams Lake, British Columbia. The community diet was observed to consist mainly of fish and big game, and was supplemented by berries and roots. Outdoor cultural gatherings, hunting and food gathering trips and sporting events, with their attendant potential for enhanced soil exposure, were observed to be an important facet of community life. The survey concluded that a significant portion of the Xeni Gwet'in practise a lifestyle similar to the subsistence lifestyles of other indigenous communities, where soil exposure scenarios in the order of hundreds of mg d − 1 have been proposed.

The inadvertent ingestion of contaminated soil can be a major pathway for chemical exposure to humans. Few studies to date have quantified soil ingestion rates to develop exposure estimates for human health risk assessments (HHRA), and almost all of those were for children in suburban/urban environments. Here we employed a quantitative mass balance tracer approach on a rural population practicing outdoor activities to estimate inadvertent soil ingestion. This study followed 9 subjects over a 13 day period in Cold Lake, Alberta, near the largest in situ thermal heavy oil (bitumen) extraction operation in the world. The mean soil ingestion rate in this study using Al Ce, La, and Si tracers was 32 mg d − 1 , with a 90th percentile of 152 mg d − 1 and median soil ingestion rate of 18 mg d − 1 . These soil ingestion values are greater than the standard recommended soil ingestion rates for HHRA from Health Canada, and are similar to soil ingestion estimates found in the only other study on a rural population.