Chlorophenolic and isotopic tracers of pulp mill effluent in sedimenting particles collected from southern lake saimaa, Finland

Sediment traps were used to collect settling particles at two stations upstream of a pulp and paper mill and at four stations along the effluent gradient in Southern Lake Saimaa. The particle samples were collected monthly from May to October 1991. Trap materials were analyzed for concentration and stable isotopic composition of organic carbon and nitrogen. The May 1991 trap samples and water and surface sediment samples from the trap locations were also analyzed for chlorophenolics. The trapped particle flux in May was 6.4 g(dry wt.)/m2/day at the station closest to the pulp mill (3.3 km) and decreased to 2.6 g(dry wt.)/m2/day at the farthest station (16.1 km). The organic carbon content of the particles varied from 10.5% to 22.1% and was the highest at the station nearest to the mill. There was a strong point source signal in the nitrogen isotope composition of effluent material. The other sampling times revealed a similar pattern. The total concentration of chlorophenols, chloroguaiacols and chlorocatechols was 0.8, 17.1 and 16.3 μg/g (dry wt.) particles, respectively, at the nearest station and decreased downstream. The total extractable organic halogens in particles exhibited a similar concentration pattern to the identified chlorinated compounds. While about 60% of chloroguaiacols and about 90% of chlorocatechols are removed by sedimentation or degradation processes in the recipient area, most of the chlorophenols and adsorbable organic halogens are transported through the system.