PCDDs/PCDFs contamination in soils at a former tannery site in Eastern Massachusetts was found to be widespread. PCDDs/PCDFs concentrations (the sum as (Cl4 – Cl8); tetra-octachloro totals) in the majority of the soil samples (17/32) far exceeded concentrations (10-1000 times) typically found in soils in industrial/urban settings worldwide (1-10 ppb). The distribution pattern of PCDDs/PCDFs in site soils in combination with highly elevated concentrations did not indicate significant influences from off-site sources (e.g. aerial distribution pattern). Widespread chromium contamination in soils often collocated with elevated concentrations of OCDD suggested that both contaminants could be attributed to a common industrial source: the former tannery operations. (total chromium concentrations in the soil samples ranged from 22.2 – 3,457 mg/kg).

Elevated PCDDs/PCDFs concentrations predominated by OCDD were most likely attributable to the historical use of pentachlorophenol (PCP) and/or products containing PCP. PCP was likely used as a fungicide/biocide in tannery processes that took place at the site. PCP origins were established through comparison of PCDDs/PCDFs profiles found in soils to those characteristic of PCP products as reported in the open literature (PCDDs/PCDFs profiles found in PCP products are predominated by hexa, hepta and octa congeners). Elevated OCDD concentrations present in site soils may not be solely attributable to historical use of PCP. OCDD, which is the most common PCDDs/PCDFs congener present as a contaminant (artifact of PCP production chemistry) in PCP may also be formed photochemically. The latter reaction takes place over time in surface soils with PCP serving as the precursor compound. The extent to which this reaction has contributed to OCDD levels found in soils has been estimated by comparison of profiles found in site soils to those characteristic of commercial PCP products.