Chemistry Weekly Seminar-Ian J. Vander Meulen, Senior Laboratory Technologist Environment and Climate Change Canada.

Title

Reflections on Emerging Gaps in Oilsands Tailings and Naphthenic Acids Research

Abstract

The Athabasca region of northern Alberta, Canada are home to an enormous quantity of unconventional petroleum (~1.7 T barrels-of-oil equivalent), which has now been extensively developed and mined. As a result of oil sands mining, considerable volumes of fluid tailings (~1.2B m³) now sit on the landscape. Oil sands tailings are a hyper-complex mixture of sand, clay, salts, metals, hydrocarbons, and water, but the acute toxicity of tailings has been consistently associated with naphthenic acids and related naphthenic acid fraction compounds (NAFCs). Despite sustained interest in these compounds, key gaps remain with respect these compounds’ occurrence and behaviour. For example, it will be necessary to expand sampling to provide more comprehensive characterization of background levels of NAFCs across the oil sands region. Such work should better define a baseline for contaminant concentrations that tailings treatment technologies might strive to meet. Further, it is necessary to put further work into understanding how NAFCs might occur in oil sands wetlands into the future, so as to chart a course for the longevity of reclaimed water bodies, especially in the face of a shifting climate. There is also a need to better understand the fundamental chemistry of naphthenates in solution. For example, new and past work examining the partitioning of NAFCs to and from soil has demonstrated that sorption trials are difficult to reproduce, and therefore it may be worthwhile to examine some of the more specific interactions that NAFCs are likely to have with simpler mixture components that make up soil (e.g., sands, clays, peat, detritus, etc.) to better model the overall process. Further, there is preliminary evidence to suggest that naphthenate anions can interact with metals in solution to change or stabilize their speciation, which is likely to have environmental availability and toxicity considerations for other contaminant classes.