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 effl uent gradient in Southern Lake Saimaa. The particle samples were colle cted monthly from May to October 1991. Trap materials were analyzed fo r concentration and stable isotopic composition of organic carbon and nitrogen. The May 1991 trap samples and water and surface sediment sam ples from the trap locations were also analyzed for chlorophenolics. T he trapped particle flux in May was 6.4 g(dry wt.)/m(2)/day at the sta tion closest to the pulp mill(3.3 km) and decreased to 2.6 g(dry wt.)/ m(2)/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 th e station nearest to the mill. There was a strong point source signal in the nitrogen isotope composition of effluent material. The other sa mpling times revealed a similar pattern. The total concentration of ch lorophenols, chloroguaiacols and chlorocatechols was 0.8, 17.1 and 16. 3 mu g/g (dry wt.) particles, respectively, at the nearest station and decreased downstream. The total extractable organic halogens in parti cles exhibited a similar concentration pattern to the identified chlor inated 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 organi c halogens are transported through the system.