A case study of a chemical spill: Polychlorinated biphenyls (PCBs): 1. History, distribution, and surface translocation

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Abstract
Between 6,800 and 21,000 1 of transformer oil containing polychlorinated biphenyls (Aroclor 1254) and chlorobenzenes were spilled when an underground pipe broke at a transformer manufacturing plant in Regina, Saskatchewan, Canada. Methods were developed to examine the surface and subsurface distribution of the contaminants. Contrary to initial expectations, large quantities of PCBs were found to have migrated both vertically and horizontally at the site. Polychlorinated biphenyls at concentrations of approximately 1000 mg/kg moved downward through granular fill and 9 m of fractured Regina clay. Contaminant migration along the interface of the clay and the upper unit of permeable granular fill probably accounts for the extensive lateral movement. It is argued that because of the low organic content of the geological units at the site (generally 0.9%) and the hydrophobicity of chlorinated organics like PCBs, contaminants at many locations exist in three phases: a dissolved aqueous phase, an adsorbed phase, and an oily liquid phase. Movement of the oily liquid seems to be the most likely explanation for the migration of large quantities of PCBs downward through fractures in the clay and laterally through the granular fill.