AN ABSTRACT OF THE THESIS OF Darin James Trobaugh for the degree of Master of Science in Civil Engineering presented on July 1, 1998. Title: Reductive Dechlorination of Sediment-Sorbed Polychlorinated Biphenyls by Vitamin B12s. Abstract approved.:---

approved.:--Sandra L. Woods The reductive dechlorination of chlorobiphenyls in sediment by titanium(III) citrate-reduced vitamin Bus was studied in batch reactors. Long term ampoule studies demonstrated reductive dechlorination of sediment-sorbed 2,3,4,5,6-pentachlorobiphenyl (2,3,4,5,6-PeCB) to tetra-, tri-, di-, and monochlorobiphenyl products. Over 50% chlorine removal was observed over 160 days. The results of the ampoule experiment were compared to previous experiments with aqueous PCBs, and both systems appeared to follow the same pathway. Theoretical product distributions based on free energies of formation were compared to product distributions for the ampoule experiments, and both aqueous and sediment-sorbed PCB reductive dechlorination followed the thermodynamically favored pathway. Although chlorines were removed from all positions, reductive dechlorination was generally preferred at the ortho position. Redacted for Privacy Reductive Dechlorination of Sediment-Sorbed Polychlorinated Biphenyls by Vitamin B12s by Darin James Trobaugh A THESIS submitted to Oregon State University In partial fulfillment of the requirements for the degree of