3 th Aug 2017
We are pleased to share details of a recent publication by one of our current Environmental Scientists, Zubair Hossain.
Zubair, who works as part of the DST Ottawa team, has recently published his co-authored article “Capillary Pressure-Saturation Relationships for Diluted Bitumen and Water in Gravel” in the Journal of Hydrology (Volume 551, August 2017, Pages 306-313).
The paper looks at the potential long-term impact of oil spills on fish habitat in Canadian rivers, and is based on research completed with his supervisor Dr. Kevin G. Mumford, as part of his Masters Thesis in Civil (Environmental) Engineering, at Queens University.
During his studies, he worked in a multidisciplinary research project that examined the effects of sediment contamination from diluted bitumen spills in gravel-bedded rivers. The objective was to understand the potential of spilled oil to become trapped in the river sediment pores and cause harm to fish and other organisms living and reproducing near the bed.
Another paper from his Master’s thesis work has been accepted for presentation at the Canadian Geotechnical Society’s annual conference, this year the GeoOttawa 2017. Zubair will be presenting his work for discussion under the Groundwater Contamination by Human Activities section.
Congratulations to Zubair for this great accomplishment and for his contribution to hydrogeological research in Canada.
Spills of diluted bitumen (dilbit) to rivers by rail or pipeline accidents can have serious long-term impacts on environment and ecology due to the submergence and trapping of oil within the river bed sediment. The extent of this problem is dictated by the amount of immobile oil available for mass transfer into the water flowing through the sediment pores. An understanding of multiphase (oil and water) flow in the sediment, including oil trapping by hysteretic drainage and imbibition, is important for the development of spill response and risk assessment strategies. Therefore, the objective of this study was to measure capillary pressure-saturation (Pc-Sw) relationships for dilbit and water, and air and water in gravel using a custom-made pressure cell. The Pc-Sw relationships obtained using standard procedures in coarse porous media are height-averaged and often require correction. By developing and comparing air-water and dilbit-water Pc-Sw curves, it was found that correction was less important in dilbit-water systems due to the smaller difference in density between the fluids. In both systems, small displacement pressures were needed for the entry of non-wetting fluid in gravel. Approximately 14% of the pore space was occupied by trapped dilbit after imbibition, which can serve as a source of long-term contamination. While air-water data can be scaled to reasonably predict dilbit-water behaviour, it cannot be used to determine the trapped amount.
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