Leeches as in situ biomonitors of chlorinated phenolic compounds. Part 1: Laboratory investigations

Leeches (Nephelopsis obscura Verrill) were evaluated as potential biomonitors of chlorinated phenolic compounds discharged from bleached pulp mills using semi-static laboratory bioassays of 1 week duration. The effect of factors such as contaminant concentration, water pH, water temperature and leech weight upon bioconcentration were examined. There was a strong linear correlation (r2 = 0.89–0.96) between water contaminant concentration (0.1–10 μg/l,) and bioconcentration of chloroguaiacols, with slow depuration rates (t/1/2 ≥ 28 days), indicating that both the quantities and proportions of contaminant may be estimated from bioconcentration data. Environmental conditions affected leech bioconcentration. Bioconcentration of chloroguaiacols was inversely related to pH (5.1–9.0), but was only weakly correlated with the concentration of 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 A strong inverse relationship (r2 = 0.09–0.94) between leech weight and bioconcentration indicated that routine biomonitoring using leeches would benefit from a uniform laboratory-reared leech stock.