LEECHES AS IN-SITU BIOMONITORS OF CHLORINATED PHENOLIC-COMPOUNDS .2. PULP-MILL INVESTIGATIONS

Leeches (Nephelopsis obscura Verrill) were evaluated as ill situ biomo nitors of chlorinated phenolic compounds in the Fraser River al Prince George, BC, downstream from three bleached kraft pulp mills practisin g chlorine dioxide (ClO2) substitution. Five biomonitoring periods, of 7 days duration, were selected to cover a full range of seasonal rive r conditions. Leeches bioconcentrated tri- and tetrachlorinated phenol ics (bioconcentration factors: 465-6000) in proportions similar to tho se present in both mill effluent and river water. Leeches showed 3,4,5 -trichloroguaiacol (3,4,5-TCG) to be the most consistent tracer of ble ached kraft mill discharge. Leeches provided direct evidence that incr easing ClO2 substitution reduces amounts of chlorinated phenolics accu mulated by aquatic organisms, with sharp decreases observed at ClO2 le vels greater than 90%. This study suggests that leeches could be appli ed as routine biomonitors for environmental impact monitoring. Copyrig ht (C) 1996 Elsevier Science Ltd