Preliminary risk assessment of the wet landscape option for reclamation ofoil sands mine tailings: Bioassays with mature fine tailings pore water

Chemical and biological assays have been carried out on the "pore water" th at results from the settling of the tailings that accompany bitumen recover y from the Athabasca oil sands. Examination of the nonacidic extracts of po re water by gas chromatography-mass spectroscopy allowed the identification of numerous two- to three-ring polycyclic aromatic compounds (PACs), to a total concentration of 2.6 mug/L of pore water. The PACs were biodegraded b y microflora naturally present in the pore water. Acute toxicity was associ ated principally with the acidic fraction (naphthenic acids) of pore water extracts according to the Microtox assay; other work has shown that acute t oxicity dissipates fairly rapidly. Both individual PACs and concentrated po re water extracts showed minimal levels of binding to the rat Ah receptor a nd induced minimal ethoxyresorufin-O-deethylase activity in primary rat hep atocytes, showing an insignificant risk of inducing monooxygenase activity. Taken together with previous work showing negligible mutagenic activity of these extracts, we conclude that it should be possible to develop tailing slurries into biologically productive artificial lakes. (C) 2001 by John Wi ley & Sons, Inc.