Reductive dehalogenation of chlorinated benzenes and toluenes under methanogenic conditions

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Applied and Environmental Microbiology; (United States)

OSTI ID:6716872

Ramanand, K; Balba, M T ^[1]; Duffy, J ^[2]

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1. TreaTek-CRA Company, Grand Island, NY (United States)
2. Occidental Chemical Corporation, Grand Island, NY (United States)

The anaerobic metabolism of chlorinated benzenes and toluenes was evaluated in soil slurry microcosms under methanogenic conditions. A mixture of hexachlorobenzene, pentachlorobenzene, and 1,2,4-trichlorobenzene (TCB) in soil slurries was biotransformed through sequential reductive dechlorination to chlorobenzene (CB). The metabolic pathway for hexachlorobenzene and pentachlorobenzene decay proceeded via 1,2,3,4-tetrachlorobenzene (TTCB) [yields] 1,2,3-TCB + 1,2,4-TCB [yields] 1,2-dichlorobenzene (DCB) + 1,4-DCB [yields] CB. In a mineral salts medium, the CB-adapted soil microorganisms dehalogenated individual 1,2,4,5-TTCB, 1,2,3,4-TTCB, 1,2,3-TCB, and 1,2,4-TCB but not 1,2,3,5-TTCB or 1,3,5-TCB. Similarly, a mixture of 2,3,6-trichlorotoluene (TCT), 2,5-dichlorotoluene (DCT), and 3,4-DCT was reductively dechlorinated in soil slurries to predominantly toluene and small amounts of 2-, 3-, and 4-chlorotoluene (CT). Toluene was further degraded. When tested individually in a mineral salts medium, the CT-adapted soil microorganisms dechlorinated several TCT and DCT isomers. Key metabolic routes for TCTs followed: 2,3,5-TCT [yields] 2,5-DCT [yields] 2-CT [yields] toluene; 2,4,5-TCT [yields] 2,5-DCT + 3,4-DCT [yields] 3-CT + 4-CT [yields] toluene. Among DCTs tested, 2,4-DCT and 3,4-DCT were dechlorinated via the removal of o- and m-chlorine, respectively, to 4-CT and subsequently to toluene via p-chlorine removal. Likewise, 2,5-DCT was dechlorinated via 2-CT to toluene. Evidently, microorganisms capable of removing o-, m-, and p-chlorines are present in the soil system, as reflected by the dechlorination of different isomers of CBs and CTs to CB and toluene, respectively. These findings help clarify the metabolic fate of chlorinated benzenes and toluenes in anaerobic environments.

• OSTI ID: 6716872
• Journal Information: Applied and Environmental Microbiology; (United States), Vol. 59:10; ISSN 0099-2240
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BACTERIA
BIOLOGICAL PATHWAYS
BENZENE
BIODEGRADATION
SOILS
ANAEROBIC CONDITIONS
TOLUENE
DECHLORINATION
DEHALOGENATION
ALKYLATED AROMATICS
AROMATICS
CHEMICAL REACTIONS
DECOMPOSITION
HYDROCARBONS
MICROORGANISMS
ORGANIC COMPOUNDS
540220* - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)