Assessing accumulation and biliary excretion of naphthenic acids in yellow perch exposed to oil sands-affected waters

Abstract

Naphthenic acids are known to be the most prevalent group of organic compounds in oil sands tailings-associated waters. Yellow perch (Perca flavescens) were exposed for four months to oil sands-influenced waters in two experimental systems located on an oil sands lease 30km north of Fort McMurray Alberta: the Demonstration Pond, containing oil sands tailings capped with natural surface water, and the South Bison Pond, integrating lean oil sands. Yellow perch were also sampled from three lakes: Mildred Lake that receives water from the Athabasca River, Sucker Lake, at the edge of oil sands extraction activity, and Kimowin Lake, a distant reference site. Naphthenic acids were measured in perch muscle tissue using gas chromatography–mass spectrometry (GC–MS). Bile metabolites were measured by GC–MS techniques and by high performance liquid chromatography (HPLC) with fluorescence detection at phenanthrene wavelengths. A method was developed using liquid chromatography–high resolution mass spectrometry (LC–HRMS) to evaluate naphthenic acids in bile. Tissue analysis did not show a pattern of naphthenic acids accumulation in muscle tissue consistent with known concentrations in exposed waters. Bile fluorescence and LC–HRMS methods were capable of statistically distinguishing samples originating from oil sands-influenced waters versus reference lakes. Although the GC–MS and HPLC fluorescence methods were correlated, there were no significant correlations of these methods and the LC–HRMS method. In yellow perch, naphthenic acids from oil sands sources do not concentrate in tissue at a measurable amount and are excreted through a biliary route. LC–HRMS was shown to be a highly sensitive, selective and promising technique as an indicator of exposure of biota to oil sands-derived naphthenic acids.