Chlorobenzene/toluene degradation

Although the possibly incompatible pathways for the degradation of chlorobenzene and toluene has been noted, a strain of Ralstonia sp. from a site contaminated with chlorobenzene contained the genes for both chlorocatechol degradation and the dioxygenase system for the degradation of benzene/toluene (van der Meer et al. 1998). The evolution of this strain resulted in a natural lowering... 

In search of less expensive, less toxic, and lower viscosity eluants, a few authors have proposed diluting the active ingredient with a common SEC eluant such as toluene, dichloromethane, or chloroform. To lower the operating temperature and minimize polymer degradation, mixtures of m-cresol with chlorobenzene (50 50, v/v, 43°C), dichloromethane (50 50, room temperature), and chloroform have been used, with 0.25 wt% benzoic acid added to prevent adsorption. In the same vein, o-chlorophenol has been diluted with chloroform (25 75) and used at 20°C. The main disadvantage in this latter solvent was a small dnidc for the polymer, which rendered refractive index measurements difficult. In addition, careful purification of the phenol is required to obtain a detection signal. Dichloroacetic acid diluted to 20 vol% with dichloromethane has been proposed as the mobile phase. However, even at this concentration, PA tends to degrade at room temperature. 

Pyrolysis products of chlorinated polyethylene contain molecules similar to those found in polyethylene pyrolysates and, in addition, compounds similar to that obtained from vinyl chloride (significant amount of HCI). Chlorosulfonated polyethylene typically contains only about 1.5% sulfur, but sulfur-containing compounds such as SO2 can be detected among its pyrolysis products. The distribution of chlorine atoms in chlorinated polyethylene has been investigated using Py-GC [55, 56]. The polymer was considered equivalent with a terpoiymer poly[ethylene-co-(vinyl chloride)-co-(1,2-dichloroethylene)]. The level of specific degradation products such as aromatic molecules (benzene + toluene + styrene + naphthalene), chlorobenzene, and dichlorobenzenes correlates well with the carbon/chlorine ratio in the polymer. 

The importance of P. chrysosporium that is able to degrade simultaneously chlorobenzene and toluene (Yadav et al. 1995) is noted in Sections 4.8.1 and 8.1.2. 

Biotransformation of chlorobenzene by P. putida grown on toluene or benzene resulted in the formation of 3-chlorocatechol this inhibited further metabolism by catechol 2,3-dioxygenase, so that its presence resulted in the formation of catechols even from benzene and toluene (Gibson et al. 1968 Klecka and Gibson 1981 Bartels et al. 1984). The same situation has emerged in the degradation of 3-chlorobenzoate the inhibition that would result from... 

Reduced microbial activity and lower metabolic diversity are likely reasons for the reduced biodegradation of herbicides in subsoils and groundwater aquifers. Although the total microbial population in most aquifers range between 104 and 107 cells/g aquifer material (22). the proportion of these populations that can degrade xenobiotics appears to be low. In a pristine aquifer from Lulu, Oklahoma, degrader populations measured by 14C-MPN were less than 5 cells/g for chlorobenzene, napthalene, and toluene (4Q). 

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