DECHLORINATION ACTIVITY (CROSS-ACCLIMATION) OF FRESH-WATER SEDIMENTS ADAPTED TO MONO-CHLOROPHENOLS AND DI-CHLOROPHENOLS

The reductive dechlorination of chlorophenols (CPs) in sediment slurri es (10% solids) adapted to dechlorinate mono- and di-CPs (DCP) was inv estigated to define the regiospecificity of the dechlorination reactio n. Unadapted sediment slurries amended with various ortho-substituted CPs exhibited lag periods ranging from 8 to 12 days before the onset o f dechlorination. In contrast, 2- and 3-CP as well as 2,3- and 2,4-DCP were dechlorinated without a lag period by sediments adapted to trans form 2-CP. Dechlorination of 4-CP was not observed after incubation fo r 35 days. Adaptation to 2-CP, therefore, enhanced the onset of dechlo rination of 3-CP and all ortho-substituted CPs tested. Dechlorination of 2-CP, 3-CP, 2,3-DCP, and 3,4-DCP was also effected without a lag pe riod by sediments adapted to transform 3-CP. Sediments adapted to dech lorinate individual DCPs (2,3-, 2,4-, and 3,4-DCP) exhibited dechlorin ation of 2-CP, 2,3-, 2,4-, and 3,4-DCP without a lag phase. The prefer ence for dechlorination by 2,3- and 2,4-DCP adapted sediments was at t he ortho chlorine. 3,4-DCP adapted sediments, which preferentially dec hlorinate at the para position of 3,4-DCP, exhibited rapid dechlorinat ion of the ortho and meta chlorines of all mono- and di-CPs tested. In terestingly, dechlorination at the para position was not detected when 4-CP was incubated with 3,4-DCP adapted sediment.