Biotransformation of dichloroaromatic compounds in nonadapted and adapted freshwater sediment slurries

Nonadapted freshwater sediment slurries and sediment slurries adapted to dechlorinate 2,3-dichloropyridine (2,3-Cl2Pyd), 2,3-dichloroaniline (2,3-Cl2Anl), 2,3-dichlorophenol (2,3-Cl2PhOH), 3,5-dichloropyridine (3,5-Cl2Pyd), 3,5-dichloroaniline (3,5-Cl2Anl) and 3,5-dichlorophenol (3,5-Cl2PhOH) were studied to determine the rate, range and extent of biotransformation of structurally related compounds under anaerobic conditions. 2,3-dichloroanisole (2,3-Cl2Ans) and 3,5-dichloroanisole (3,5-Cl2Ans) were initially demethylated, producing 2,3-Cl2PhOH and 3,5-Cl2PhOH as intermediate transformation products. All other dichloroaromatic compounds examined were initially dechlorinated. The rates of dechlorination of 2,3-Cl2PhOH, 2,3-Cl2Anl, and 2,3-Cl2Pyd were significantly lower (5-15 times) in nonadapted sediment slurries compared to sediment slurries adapted to 2,3-Cl2Anl or 2,3-Cl2Pyd. In 2,3-Cl2PhOH adapted sediment, the rate of dechlorination of 2,3-Cl2PhOH was 15 times greater than in nonadapted sediment; however, the rates of dechlorination of 2,3-Cl2Anl and 2,3-Cl2Pyd were similar for 2,3-Cl2PhOH-adapted and nonadapted sediment slurries. In adapted and nonadapted sediment slurries, 2,3-Cl2PhOH, 2,3-Cl2Anl, and 2,3-Cl2Pyd were preferentially dechlorinated at the ortho, meta, and meta positions, respectively. Additionally, 2,3-Cl2Pyd adapted sediment slurries dechlorinated 2,3-Cl2PhOH and 2,3-Cl2Pyd at both ortho and meta positions. Rates of dechlorination of 3,5-Cl2PhOH, 3,5-Cl2Anl, and 3,5-Cl2Pyd were lower (2-4 times) in nonadapted sediment slurries compared to sediment slurries adapted to 3,5-Cl2Anl or 3,5-Cl2Pyd. In 3,5-Cl2PhOH adapted sediment, the rate of dechlorination of 3,5-Cl2PhOH was approximately 10 times greater than in nonadapted sediment.(ABSTRACT TRUNCATED AT 250 WORDS)