Forensic misidentification of aroclor sources in fractured bedrock due to "Chromatographic" polychlorinated biphenyl (PCB) congener separation

The effect of matrix diffusion subject to differential sorption on the potential for Aroclor source identification and quantification in a fractured bedrock environment is examined. Due to sorption, transport is seen to occur at greatly different rates for the various congeners, causing rapid changes in polychlorinated biphenyl (PCB) plume composition during migration. This article provides a rigorous method for optimally fitting PCB groundwater sample concentrations as a linear combination of known Aroclors. It then demonstrates, via transport simulations in fractured sandstone with realistic properties, that correctly determining the Aroclors comprising a PCB source through optimally "fingerprinting" groundwater samples obtained even a few meters downgradient is not generally possible.