Organohalogens of Natural and Industrial Origin in Large Recipients of Bleach-Plant Effluents

The long-term fate of chlorophenols and adsorbable organic halogens (AOX) was studied in two large recipients of bleach-plant effluents: Lake Vättern in Sweden and the Baltic Sea. The study showed that there is a long-distance transport (>100 km) of chloroguaiacols from bleach-plants to remote parts of receiving waters. However, there was no evidence of several-year-long accumulation of chloro-organics in the water-phase. A simple water-exchange model for Lake Vättern showed that the cumulated bleach-plant discharges from the past 35 years would have increased the AOX concentration in the lake by more than 100 µg Cl/l, if no AOX had been removed from the water by evaporation, sedimentation or degradation. However, the observed AOX concentration in Lake Vättern averaged only about 15 µg Cl/l, which was less than the average AOX concentration (32 µg Cl/l) in the “unpolluted” tributaries of the lake. Similar investigations in the Baltic Sea showed that non-point sources, including natural halogenation processes, accounted for a substantial fraction of the AOX in the open sea. The presence of 2,4,6-trichlorophenol in precipitation and “unpolluted” surface waters showed that non-point sources may also make a considerable contribution to the background levels of compounds normally regarded as indicators of bleach-plant effluents.