2.3.4.6- tetrachlorobiphenyl dechlorination, temperature

Wu Q, DL Bedard, J Wiegel (1997a) Effect of incubation temperature on the route of microbial reductive dechlorination of 2,3,4,6-tetrachlorobiphenyl in polychlorinated biphenyl (PCB)-contaminated and PCB-free freshwater sediments. Appl Environ Microbiol 63 2836-2843. 

An anaerobic sediment sample was incnbated with 2,3,4,6-tetrachlorobiphenyl at various temperatures between 4 and 66°C (Wn et al. 1997). The main products were 2,4,6- and 2,3,6-trichlorobiphenyl and 2,6-dichlorobiphenyl the first of these was produced maximally and discontinnonsly at 12 and 34°C, the second maximally at 18°C, and the third was dominant from 25 to 30°C. Dechlorination was not observed above 37°C. 

Wu Q, Bedard DL, Wiegel J. 1997. Temperature determines the pattern of anaerobic microbial dechlorination of Aroclor 1260 primed by 2,3,4,6-tetrachlorobiphenyl in Woods Pond sediment. Appl Environ Microbiol 63( 12) 4818-4825. 

Studies of the anaerobic metabolism of 2,3,4,6-tetrachlorobiphenyl by freshwater sediments have demonstrated that temperature not only influences rate but may also influence metabolic pathways. The metabolism of this PCB congener was monitored for 1 year in sediments (exposed or not exposed to PCBs) under anaerobic conditions at temperatures ranging from 4 to 66°C. Dechlorination steps are summarized in Figure 9.11 with the black arrows indicating reactions observed in the nonexposed sediment. All reactions were observed with the exposed sediment. Little if any reaction was detected at 4°C and at the higher temperatures (37°C and above in the nonexposed sediment and 37-45°C with the exposed sediment). However, from 50-60°C almost 90% conversion to the 2,4,6-CB was observed. An example of the differences reported is provided in Figure 9.12. At 15 and 20°C, the first step was the loss of m-chlorine to produce the 2,4,6-CB. However, at 15°C the production of the 2,4-CB is favored along with the 4-CB in contrast... 

In another similar study for ME (Venkatachalam et al. 2008), palladium-based nanoparticles immobilized in polymeric matrices were applied to the reductive dechlorination of 3,3, 4,4 -tetrachlorobiphenyl (PCB77) at room temperature. Two different dechlorination platforms were evaluated using (1) Pd nanoparticles within conductive polypyrrole films or (2) immobilized Fe/Pd nanoparticles within PVDF MF membranes. The results indicated the removal of chlorine atoms from PCB77, which led to the formation of lower chlorinated intermediates and, ultimately, biphenyl. Toxicity associated with vascular dysfunction by PCB77 and biphenyl was compared using cultured endothelial cells. The data strongly suggest that the... 

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