DOWNCORE OCCURRENCE OF POLYCHLORINATED BIPHENYLS IN THE UTICA MARSH, CENTRAL NEW YORK STATE

Polychlorinated Biphenyls (PCB) were once used as heat-transferring fluids, in hydraulic and vacuum systems, as flame-retardants, and as insulating fluids in electrical transformers. The Utica Marsh is situated between the Mohawk River and the Barge Canal in Oneida County. PCB may be present in the marsh because Utica was formerly heavily industrialized, especially along the canal. Thus PCB may have entered the marsh through direct dumping, unintentional spills, or via flooding of the marsh by potentially contaminated canal water. We conducted downcore analyses to ascertain if PCB is present in the marsh, the timing of PCB introduction, and trends if any in its subsequent breakdown or mobilization.

Two cores (each ~40-cm) were collected using a Russian peat borer. PCB was extracted from Core 1 using standard EPA protocols for soxhlet extraction and analyzed by thin layer chromatography (TLC). An age model was determined from nearby Core 2 by performing 137Cs analysis using a 3-inch NaI well-detector equipped with a tube-base digital multichannel analyzer. Magnetic susceptibility was measured on both cores to correlate them and transfer the age model of Core 2 to Core 1. Sediment grain size of Core 1 was analyzed by laser diffraction.

A 137Cs peak at 11-cm indicates an average sedimentation rate of ~2.8mm/yr. TLC suggests PCB is present, but indications of PCB at the ~1912 horizon imply some downward leaching and thus the timing of introduction remains unclear. PCB is associated with fine sediment perhaps reflecting differential adsorption. If so, clay may play a role in spatial and temporal PCB redistribution. Alternatively, the association of PCB with fines may be an artifact of grain size analysis conducted on raw sediment containing abundant partially-decayed organics. Re-analysis following removal of organics is needed to clarify this. Additionally, planned analysis by GC-ECD/MS will facilitate verification and quantification of TLC results.