Research Product

The reductive dechlorination of 2,4- and 3,4-dichlorophenol (DCP) was studied in slurries of marine and subsurface soils with dissolved organic carbon concentrations less than 1 ppm. Dechlorination was markedly greater in marine sediment slurries than in subsoil slurries, although similar products were observed in each case. From 25 to 98% of the 2,4- and 3,4-DCP (6.5 µm/L) added to most marine slurries was converted to 4- and 3-chlorophenol (CP), respectively, within 30 weeks. In contrast, 2,4-DCP was dechlorination to 4-CP (greater than 90%) in only one of 24 replicate subsoil slurries after 32 weeks of incubation. Dechlorination was observed within 2 weeks when yeast extract was added to subsoil slurries; yeast extract additions also stimulated dechlorination in marine sediments but to a lesser extent. The intermediate monochlorophenol products did not persist in marine slurries but did persist in the subsoil slurries. It was concluded that the total organic carbon at a site is not always a good predictor of the site's ability to support dechlorination activity.