Characterizing the toxicity of oil sands process-affected water

Abstract

Oil sands process-affected water (OSPW) is produced during extraction of bitumen in the surface-mining oil sands industry in Alberta, Canada. Due to observed acute and chronic toxicity of the dissolved organic fraction of OSPW, it is currently stored in tailings ponds to be remediated and eventually returned to the surrounding environment. To this end, endpit lakes are a proposed passive remediation strategy for OSPW related toxicity, of which BaseMine Lake (BML) is the first full scale commercial test. The purpose of this thesis was to identify and characterize toxic chemical classes in the dissolved organic fraction of OSPW collected from BML to aide the development of water quality objectives and release guidelines for the oil sands industry. Using a bioassay-effect directed analysis approach and ultrahigh resolution mass spectrometry, the dissolved organic fraction of OSPW was iteratively fractionated and biologically tested to identify acutely toxic chemical classes. This work was further built upon by the development of a predictive acute aquatic toxicity model for embryos of fathead minnow (Pimephales promelas) exposed to OSPW related chemicals to support the development of release guidelines in the oil sands. To investigate potential mechanisms of acute toxicity of dissolved organic chemicals in OSPW, an Escherichia coli whole genome reporter system was used and provided evidence to support narcosis as the critical mechanism of OSPW related acute toxicity. Furthermore, the fathead minnow short term 21-day reproductive bioassay was used to investigate the potential for OSPW related chemicals to disrupt reproduction. Results of this thesis support earlier works and confirmed a role for naphthenic acids in the acute toxicity of OSPW. However, novel acutely toxic chemical classes containing oxygen, sulphur or nitrogen were also identified. An acute aquatic toxicity model was developed which is sufficiently robust to predict toxicity of dissolved organic chemicals in OSPW within biological variation associated with toxicity tests and provides an alternative to in vivo test methods typically applied to complex environmental mixtures. In addition, hepatosomatic index was identified as an indicator of chronic exposure of male fathead minnow to OSPW. Overall, this work provides important toxicity and chemical information that will aide in the development of reclamation and monitoring programs in the oil sands region of Alberta, Canada.