A chemical and sensory study of odour compounds in the Athabasca River, Alberta, Canada

As of early 1993, the Athabasca River received effluent from one bleached kraft pulp mill (Mill A), three chemithermomechanical pulp and paper mills, one oil sands extraction and upgrading plant and a number of municipal effluents. In the latter half of 1993 a second bleached kraft pulp mill (Mill B) began operation midway along the river. An investigation was carried out to characterize the odours in the river water using both chemical and sensory methods, in a pre- and post-operational study of the second bleached kraft mill. Both surveys were carried out under ice during low flow conditions. Samples were analysed by gas chromatography-mass spectrometry after extraction using a closed-loop stripping apparatus (CLSA). In addition, sensory analysis by flavour profile panel and olfactory gas chromatography of the CLSA extracts were performed. In 1993 all analytical methods confirmed that compounds characteristic of bleached kraft mill effluent were detectable for more than 950 km downstream from Mill A and that this effluent was the major source of odour to the Athabasca River. Chemical and sensory results for 1994 samples (collected after Mill B began operation) indicated a decrease in the impact of Mill A compared with the 1993 survey. The Mill B effluent had distinctive odour but its impact on the river was difficult to detect due to dilution and background odour from the Mill A effluent.