PCB Biodegradation by a Dhc Culture Grown on Trichlorobenzenes and Tetrachlorobenzenes(ABSTRACT)

摘要

Polychlorinated biphenyls (PCBs) are an important group of environmental contaminants due to their persistence, toxicity, and tendency to bioaccumulate in the food chain. There are a total of 209 possible isomers of PCBs. Mixtures of PCBs used as insulator fluids are known as Aroclors and include; Aroclors 1260, 1254 and 1240. Aroclor 1260, with 8 to 9 chlorine atoms per two biphenyl rings, is biodegradable only under anaerobic conditions. Recently, Dehalococcoides (Dhc) has been shown to be involved in the reductive dechlorination of Aroclor 1260, although its role is not well understood. The rate of reductive dechlorination is slow (compared to that of chlorinated ethenes) and is highly dependent on factors such as Dhc strain (e.g., Dhc 195, CBDB1), cell density, type of inducer or alternative electron acceptor, and physiochemical factors such as the solubility of the PCB, and its absorption on strata such as soil or sediment. The challenge that makes biological treatment of PCBs different from that of other chlorinated compounds is low water solubility and low bioavailability. Aroclor 1260, for example, has an estimated water solubility of 14 ppb.