Abstract
The impact of effluent from a modern bleached kraft pulp mill was examined on the Spanish River, Ontario. The mill utilizes oxygen deligniflcation, chlorine dioxide substitution, and secondary treatment (aerated lagoon) resulting in the production of < 1.5 kg AOX/air dried metric tonne (ADMT) of pulp. However, the relatively low river flow results in an AOX concentration in the receiving waters of approximately 0.15 mg/L, similar to the level reported for other sites receiving both treated and untreated bleached kraft mill effluents. There was only a minimal reduction in the concentration of AOX and chlorophenolics in river water sampled over 51 km downstream of the outfall. In early August 1990, 14 to 30 live white sucker (Catostomus commersoni) were collected at each of two sites upstream and three sites downstream of the outfall (2, 28, 51 km). Each fish was examined for gross pathological changes, several condition indices, hematocrit, plasma electrolytes, plasma testosterone, and hepatic mixed function oxygenase enzyme activity (ethoxyresorufin-o-deethylase). Selected fish were also examined histologically for liver, gill, kidney, spleen, heart, muscle and gonad abnormalities. Liver somatic index was elevated in fish immediately below the outfall while elevation of EROD activity persisted 51 km downstream. There were no significant histopathological lesions observed observed and there were no consistent patterns observed in condition indices or plasma parameters.