Distributions of diluted bitumen and conventional crude oil in a range of water types

Abstract

Concern about the impacts that accidental discharge of under-investigated, heavy petroleum products may have on aquatic environments has prompted a comparative examination of the behaviours of diluted bitumen (DB) and light conventional crude (CC) oil in different water types. Distributions of oil among the water column and floating water-in-oil (w/o) emulsion are evaluated by a novel, reproducible procedure involving mixing oil with water, then separating, extracting, and quantifying the total absolute oil content of the water column via gravimetric and gas-chromatographic (high-temperature simulated distillation) analyses. The CC contents of water columns tend to be significantly greater than those of DB under comparable conditions, while the fraction of oil remaining afloat at the water's surface is greater for DB than for CC. The elucidated phase distribution patterns have important implications pertaining to the recoverability of these oils in the event of their release into aquatic environments, which serves to inform best practices for oil spill response. For both DB and CC, oil contents within water columns are the highest in waters of low salinity and high pH. Water contents of buoyant w/DB emulsions are significantly greater than those of w/CC emulsions after 60 min at rest, and are the highest in waters of low salinity and low pH. The effect of crude oil on the pH of water is also studied, and DB is found to have a greater effect than CC on water samples of varying initial pH.