TOXIC EFFECTS OF POLLUTANTS ON THE MINERALIZATION OF CHLOROFORM IN RIVER SEDIMENTS

The influence of pollutants on the formation of (CO2)-C-14 from 3 mug/ liter labeled chloroform was studied in anaerobic Dutch river sediment s. All incubations were performed under anaerobic conditions. Addition of toxicants to sediment microcosms showed logistic dose-effect curve s. The concentration giving 10% inhibition of the chloroform mineraliz ation rate (IC10) was derived from these dose-effect curves. The IC10 values of added cadmium, chloropyrifos, benzene, mercury, or 1,2-dichl oroethane were 1300, 1300, 140, 90, and 0.07 mg/kg dry sediment, respe ctively. Mud samples taken at different dates from the same site indic ated a significantly different sensitivity to added pentachlorophenol and zinc. The IC10 of added pentachlorophenol was 150 mg/kg in one and 15 mg/kg in another sample. Chloroform-mineralizing bacteria are very sensitive to addition of zinc. The IC10 of added zinc was 700 mg/kg f or one sample and 11 mg/kg for another sample of the sediment which co ntained a background concentration of 800 mg Zn/kg. Therefore, a parti al inhibition of the mineralization of chloroform by the high concentr ations of zinc present in Dutch river sediments cannot be excluded. Th e high concentration of zinc might cause persistence of otherwise biod egradable pollutants in Dutch sediments. (C) 1994 Academic Press, Inc.