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EFFECT OF CONTAMINANT AND ORGANIC MATTER BIOAVAILABILITY ON THE MICROBIAL DEHALOGENATION OF SEDIMENT-BOUND CHLOROBENZENES. (R825513C007)
Citation:
Prytula, M. AND S. G. Pavlostathis. EFFECT OF CONTAMINANT AND ORGANIC MATTER BIOAVAILABILITY ON THE MICROBIAL DEHALOGENATION OF SEDIMENT-BOUND CHLOROBENZENES. (R825513C007). WATER RESEARCH. American Chemical Society, Washington, DC, 30:2669-2680, (1996).
Description:
The extent of reductive dechlorination occurring in contaminated, estuarine sediments was investigated. Contaminant and organic matter bioavailability and their effect on the reductive dechlorination of sediment-bound chlorobenzenes was the main focus of the work presented here. Sediment and water samples were collected from a contaminated estuarine system with more than 40 yr of contamination history. Hexachlorobenzene and other chlorinated benzene congeners were the predominant chlorinated compounds encountered. Anaerobic batch assays revealed that the sediment natural organic matter is recalcitrant and unable to support active microbial growth. However, sediment nutrients (e.g. N, P) were available in sufficient quantities to support an accelerated microbial growth. Static microcosms were constructed with sediment and water from the study site. The sediment microbial consortia were able to reductively dechlorinate the sediment-bound polychlorinated benzene congeners, primarily to dichlorobenzene isomers. The first-order rate constant for hexachlorobenzene depletion (kobs) ranged from 2.2 × 10-3 to 2.9 × 10-3 d-1, the higher value being achieved in microcosms supplemented with dextrin. These rates were about two orders of magnitude lower than those observed with the same sediment-derived, mixed dechlorinating microbial consortium in liquid cultures supplemented with freshly added hexachlorobenzene. The extent of hexachlorobenzene removal over a long incubation time (more than 480 d) was only 43%, most of which occurred during the first 200 d of incubation. Both the recalcitrant nature of the sediment organic matter and the strong partitioning of the chlorinated compounds were responsible for the low rate and extent of contaminant transformation. When frequent additions of a degradable organic carbon source and ground sediment were used, an increased rate and extent of reductive dechlorination of the sediment-bound contaminants were observed (e.g. 95% hexachlorobenzene biotransformation within 205 d of incubation; kobs = 2.1 × 10-2 d-1).
Author Keywords: bioavailability; chlorobenzenes; estuary; reductive dechlorination; sediments