4- Chlorobiphenyl PCB

Reported vapor pressures of 2-chlorobiphenyl (PCB-1) at various temperatures and the coefficients for the vapor pressure equations... 

FIGURE 7.1.1.1.1 Logarithm of vapor pressure and Henry s law constant versus reciprocal temperature for 2-chlorobiphenyl (PCB-1). 

Biological. A strain of Alcaligenes eutrophus degraded 35% of the congeners by dechlorination under anaerobic conditions (Bedard et ah, 1987). Indigenous microbes in the Center Hill Reservoir, TN oxidized 2-chlorobiphenyl (a congener present in trace quantities) into chlorobenzoic acid and chlorobenzoylformic acid. Biooxidation of the PCB mixture containing 54 wt % chlorine was not observed (Shiaris and Sayler, 1982). 

PCBs available for various uses. For this reason, 2-chlorobiphenyl and a mixture of Aroclor were studied. Samples (100 mL) of the mixtures were prepared with 265 (ig/mL of PCB and 25 pg/mL of Ti02. The pH of the samples was adjusted to 3, 7, and 10. The samples were irradiated under a UVA-340 light source for 120 min. The concentrations of the PCBs were determined using GC. The degradation rate of 2-chlorobiphenyl increased with decreasing pH values. After 1 hour of irradiation, more that 90% of the PCBs had been degraded at pH 3 and pH 7. The degradation rate constant, k, can be determined from the first-order reaction model ... 

FIGURE 7.1.1.3.2 Logarithm of vapor pressure versus reciprocal temperature for 4-chlorobiphenyl (PCB-3). 

Schulz-BuU, D.E., G. Petrick, R. Bruhn, and J.C. Duinker 1998. Chlorobiphenyls (PCB) and PAHs in water masses of the northern North Atlantic. Marine Chemistry 61(1-2) 101-114. 

For polychlorinated biphenyls (PCBs), rate constants were highly dependent on the number of chlorine atoms, and calculated atmospheric lifetimes varied from 2 d for 3-chlorobiphenyl to 34 d for 236-25 pentachlorobiphenyl (Anderson and Hites 1996). It was estimated that loss by hydroxy-lation in the atmosphere was a primary process for the removal of PCBs from the environment. It was later shown that the products were chlorinated benzoic acids produced by initial reaction with a hydroxyl radical at the 1-position followed by transannular dioxygenation at the 2- and 5-positions followed by ring fission (Brubaker and Hites 1998). Reactions of hydroxyl radicals with polychlorinated dibenzo[l,4]dioxins and dibenzofurans also play an important role for their removal from the atmosphere (Brubaker and Hites 1997). The gas phase and the particulate phase are in equilibrium, and the results show that gas-phase reactions with hydroxyl radicals are important for the... 

The following section discusses the priming of PCB-dechlorinating microorganisms with various compounds, such as (1) chlorobiphenyls, (2) bromobi-phenyls, and (3) benzoate ions. 

Photolytic. PCB-1260 in a 90% acetonitrile/water solution containing 0.2 to 0.3 M sodium borohydride and irradiated with UV light (X = 254 nm) reacted to yield dechlorinated biphenyls. After 2 h, about 75% of the congeners were destroyed. Without sodium borohydride, only 10% of the congeners had reacted. Products identified by GC include biphenyl, 2-, 3- and 4-chlorobiphenyl, six dichlorobiphenyls, three trichlorobiphenyls, l-phenyl-l,4-cyclohexadiene, and l-phenyl-3-cyclohexene (Epling et ah, 1988). 

Other work through the 1980s focused on the identification and characterization of various PCB degraders and included work on the biodegradation of mono-chlorobiphenyls in river water (Bailey et al., 1983), and the biodegradation of PCBs by mixed bacterial cultures grown on naphthalene and 2-methyl, 4-chloro-phenoxyacetic acid (Kilpi et al., 1988). The work of Parsons Sijm (1988) demonstrated the degradation of mono-, di- and tetrachlorobiphenyls in chemostat... 

Recently, the PCB-biodegradative capabilities of methanotrophs have been demonstrated (Adriaens, 1994). In this study, 2-CB was oxidized by a methanotrophic culture (CSC1) to a hydroxylated chlorobiphenyl intermediate identified as 2-hydroxy-3-chlorobiphenyl. This intermediate indicated that the metabolite was formed via a concerted oxidation involving an arene oxide which rearranges spontaneously via an NIH shift. No studies have shown, however, that methanotrophs can degrade more highly chlorinated PCBs, and their utility for bioremediation processes does not seem promising. 

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