Simulating a Spill of Diluted Bitumen: Environmental Weathering and Submergence in a Model Freshwater System

• Published in: Environmental toxicology and chemistry 2019-12, Vol.38 (12), p.2621-2628
• Main Authors: Stoyanovich, Sawyer S., Yang, Zeyu, Hanson, Mark, Hollebone, Bruce P., Orihel, Diane M., Palace, Vince, Rodriguez‐Gil, Jose L., Faragher, Robert, Mirnaghi, Fatemah S., Shah, Keval, Blais, Jules M.
• Format: Article
• Language: English
• Subjects: Aquatic environment; Aromatic compounds; Bitumens; Canada; Chemical properties; Computer simulation; Condensates; Crude oil; Dilbit; Diluted bitumen; Dilution; Environmental assessment; Environmental conditions; Environmental effects; Environmental risk; Environmental studies; Fate and behavior; Freshwater environments; Gas condensates; Gas pipelines; Heavy petroleum; Hydrocarbons - chemistry; Hydrocarbons - isolation & purification; Lakes; Lakes - chemistry; Microcosm; Microcosms; Natural gas; Organic chemistry; Petroleum - analysis; Petroleum pipelines; Petroleum Pollution - analysis; Petroleum products; Pipelines; Risk assessment; Sediments; Sinking; Spills; Submergence; Viscosity; Volatile hydrocarbons; Water circulation; Water column; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - isolation & purification; Weather; Weathering
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.4600

The main petroleum product transported through pipelines in Canada is diluted bitumen (dilbit), a semiliquid form of heavy crude oil mixed with natural gas condensates to facilitate transport. The weathering, fate, behavior, and environmental effects of dilbit are crucial to consider when responding to a spill; however, few environmental studies on dilbit have been completed. We report on 11‐d‐long experimental spills of dilbit (Cold Lake Winter Blend) in outdoor microcosms meant to simulate a low‐energy aquatic system containing natural lake water and sediments treated with low (1:8000 oil:water) and high (1:800 oil:water) volumes of dilbit. In the first 24 h of the experiment, volatile hydrocarbons quickly evaporated from the dilbit, resulting in increased dilbit density and viscosity. These changes in dilbit's physical and chemical properties ultimately led to its submergence after 8 d. We also detected rapid accumulation of polycyclic aromatic compounds in the water column of the treated microcosms following the spills. The present study provides new information on the environmental fate and behavior of dilbit in a freshwater environment that will be critical to environmental risk assessments of proposed pipeline projects. In particular, the study demonstrates the propensity for dilbit to sink under ambient environmental conditions in freshwaters typical of many boreal lakes. Environ Toxicol Chem 2019;38:2621–2628. © 2019 SETAC