PRIMING MICROBIAL META-DECHLORINATION OF POLYCHLORINATED-BIPHENYLS THAT HAVE PERSISTED IN HOUSATONIC RIVER SEDIMENTS FOR DECADES

We recently demonstrated a strategy for stimulating or ''priming'' the indigenous microorganisms to dechlorinate weathered PCBs in sediments , but the dechlorination exhibited a very narrow para-dechlorination s pecificity. We tested the priming activity of various PCB congeners to discover those that would prime broader and more extensive PCB dechlo rination activity. 2,3,4,5,6-Pentachlorobiphenyl (23456-CB), 2346-CB, and 236-CB primed extensive and sustained meta-dechlorination (Process N) of the Aroclor 1260 residue in Housatonic River sediment. The dech lorination targeted most of the hexa-, hepta-, and octachlorobiphenyls and converted them to tetra- and pentachlorobiphenyls containing most ly ortho- and para-chlorines. Both 234-CB and 2345-CB also primed Proc ess N dechlorination, but the dechlorination ceased at 7 weeks and was much less extensive. 245-CB primed a narrow specificity para-dechlori nation (Process P). 2356-CB, 235-CB, and 23-CB did not prime PCB dechl orination. The results indicate that the 236-substitution pattern is i mportant for maximal priming of dechlorination Process N. A chlorine a t position 5 suppressed the priming activity, but the suppression was overcome by a chlorine at position 4. The discovery of non-PCB primers that are both effective and environmentally acceptable could lead to the development of practical methods for in situ PCB bioremediation.