UBC Theses and Dissertations
An evaluation of leeches as in situ biomonitors of chlorinated phenolic compounds discharged from bleached kraft pulp mills Prahacs, Steven Michael
Leeches were evaluated as biomonitors of chlorinated phenolic compounds discharged from bleached kraft pulp mills using integrated laboratory and field investigations. Semi-static laboratory bioassays of one week duration were carried out in order to determine how environmental factors such as contaminant concentration, water pH, water temperature and suspended sediments as well as biotic factors such as leech weight and species affect bioconcentration. In order to evaluate leeches under varying in situ conditions, three field monitoring trials during summer (July), fall (October) and winter (February) were conducted on the Fraser River, downstream of three bleached kraft pulp mills at Prince George B.C. There was a strong linear correlation (r² = 0.89 - 0.96) between water contaminant concentration (0.1 - 10 µg/L) and bioconcentration of chlorinated guaiacols, with slow depuration rates (t₁₋₂ > 28 days). Bioconcentration of chlorinated guaiacols was inversely related to pH (5.1 - 9.0), but was only weakly correlated with the concentration of the undissociated compound, indicating that the ionized compound also contributed to the bioavailable fraction. Bioconcentration increased between 4.4 and 11.8° C, but did not show a significant change from 11.8 to 20.0° C, indicating a bi-phasic model for the temperature - bioconcentration relationship. No clear relationship between suspended sediment concentration (0 0.15 g/L) and bioconcentration was observed, although the presence of 5% organic material in suspended sediments reduced bioavailability of the chlorinated phenolics. Water stirring in the suspended sediment bioassays increased bioconcentration relative to quiescent semi-static conditions. There was strong inverse relationship (r² = 0.90 - 0.94) between leech weight and bioconcentration with no clear trend between two different species of leech (Nephelopsis obscura and Percymoorensis marmorata). Field monitoring revealed chlorinated phenolics in pulp mill effluent (0.6 -17 μg/L) and water (0.002 - 0.073 μg/L) and suspended sediments (0.36 - 176 μg/kg) during the study periods. Leeches were effective biomonitors of tri- and tetrachlorinated guaiacols under diverse seasonal conditions, with bioconcentration factors ranging from 465 - 6000 and were accurate indicators of the relative proportions of these chlorinated contaminants in both pulp mill effluent and the Fraser River, 40 km downstream of pulp mill outfalls.
Item Citations and Data