title: Biodegradation of 1,2,3- and 1,2,4-trichlorobenzene in soil and in liquid enrichment culture.
abstract: The biodegradation of radiochemically pure (99%) 1,2,3- and 1,2,4-trichlorobenzene (TCB) in soil was investigated. Experimental difficulties posed by the high volatility and slow biodegradation rate of the TCBs were partially overcome by using a specially designed incubation and trapping apparatus. Evolution of (14)CO(2) from active versus poisoned soil dosed with 50 mug of the individual TCBs per g gave conclusive proof that both isomers are biodegradable. At 20 degrees C, 1,2,4-TCB was mineralized at an approximate rate of 1 nmol/day per 20 g of soil sample, and 1,2,3-TCB was mineralized at one-half to one-third that rate. Mineral fertilizers or cosubstrates failed to increase TCB mineralization rates in soil. Anaerobic conditions had a negative effect on mineralization, and increased temperatures had a positive effect. With increasing 1,2,4-TCB concentrations, (14)CO(2) evolution exhibited saturation kinetics with an apparent K(m) of 55.5 nmol per g of soil. Recovery of total radioactivity was good from soil containing high organic matter concentrations. From low-organic-matter soil, some of the radioactivity was recovered only on combustion, and overall recovery was lower. In soil-inoculated liquid culture, the cosubstrates glucose and benzene caused a slight stimulation of 1,2,4-TCB mineralization. Cochromatography of known standards with the extracts of soil pretreated with [(14)C]TCBs indicated that 3,4,5-trichlorophenol, 2,6-dichlorophenol and, to a lesser degree, 2,3-dichlorophenol were present in soils incubated with 1,2,3-TCB. 2,4-, 2,5-, and 3,4-dichlorophenol were present in soils incubated with 1,2,4-TCB.
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001554:Benzene / Q000378:metabolism; D001673:Biodegradation, Environmental; D002245:Carbon Dioxide / Q000378:metabolism; D002722:Chlorobenzenes / Q000378:metabolism*; D002733:Chlorophenols / Q000378:metabolism; D003470:Culture Media; D005947:Glucose / Q000378:metabolism; D012988:Soil Microbiology; D012989:Soil Pollutants; D013237:Stereoisomerism
chemical_list: D002722:Chlorobenzenes; D002733:Chlorophenols; D003470:Culture Media; D012989:Soil Pollutants; D002245:Carbon Dioxide; D005947:Glucose; D001554:Benzene