Distribution of chlorophenolic compounds, from a pulp mill, in Lake Bonney, South Australia

Water and sediment samples from Lake Bonney (south-eastern South Australia) were collected at various distances from the effluent discharge point of a sulfite-based pulp mill and analysed for chlorophenolic compounds. The period of sample collection (July 1991 to January 1992) occurred during a time when bleaching process of the mill was being converted from using molecular chlorine to using hydrogen peroxide. In water samples, the major chlorophenolic compounds detected were 2,4,6-trichlorophenol, tetrachlorocatechol and chlorinated guaiacols. In sediment samples, the major chlorophenolic compounds detected were chlorinated guaiacols and chlorinated catechols. The concentrations of these compounds in lake water generally decreased over the sampling period, corresponding to the decrease in use of molecular chlorine. Concentrations in sediment decreased with increasing distance from the discharge point. The presence of chlorinated guaiacols in water and sediment at a site 17 km from the effluent discharge point indicated that these compounds degrade slowly in the lake. The presence of the chlorinated catechols in sediments at localities where these compounds were not detected in the water suggests that de-0-methylation of adsorbed chlorinated guaiacols occurs and/or that there is preferential adsorption of chlorinated catechols to sediment.