Environmental monitoring of bleached kraft pulp mill chlorophenolic compounds in a northern Canadian river system.

The environmental transport of pulp mill effluent compounds and the exposure of two fish species has been monitored by parallel analyses of effluent, water column and suspended sediment samples, and fish bile and muscle. Compounds analyzed included over 20 chlorophenolic compounds and 12 fatty and resin acids. The concentration of chlorophenols varied with seasonal river flows and mill process changes such as the substitution of chlorine dioxide (ClO2) for chlorine gas (Cl2) in the bleach plant. At 100% (ClO2) substitution, the effluent and the water column concentrations of most chlorophenolics approached the analytical detection limits of 0.1-1 parts per billion. Chlorophenolic and fatty/resin acid compounds were detected in the bile of both mountain whitefish (Prosopium williamsoni) and longnose sucker (Catostomus catostomus), but were rarely detected in fillets. Fish bile concentrations were observed in an apparent spatial gradient as far as 230 km downstream of the mill. A depuration experiment with fish held in uncontaminated water for eight days indicated a rapid decrease in chlorophenol levels. These observations corroborate previous investigations that chlorophenolic compounds are rapidly excreted and can be used as sensitive markers for recent exposure to mill effluents.