Identification of Sulfonated and Hydroxy-Sulfonated Polychlorinated Biphenyl (PCB) Metabolites in Soil: New Classes of Intermediate Products of PCB Degradation?

Abstract

In this paper we describe the identification of two classes of contaminants: sulfonated-PCBs and hydroxy-sulfonated-PCBs. This is the first published report of the detection of these chemicals in soil. They were found, along with hydroxy-PCBs, in soil samples coming from a site historically contaminated by the industrial production of PCBs and in background soils. Sulfonated-PCB levels were approximately 0.4-0.8% of the native PCB levels in soils and about twice the levels of hydroxy-sulfonated-PCBs and hydroxy-PCBs. The identification of sulfonated-PCBs was confirmed by the chemical synthesis of reference standards, obtained through the sulfonation of an industrial mixture of PCBs. We then reviewed the literature to investigate for the potential agents responsible for the sulfonation. Furthermore, we predicted their physicochemical properties and indicate that, given the low pKa of sulfonated- and hydroxy-sulfonated-PCBs, they possess negligible volatility, supporting the case for in situ formation from PCBs. This study shows the need of understanding their origin, their role in the degradation path of PCBs, and their fate, as well as their (still unknown) toxicological and ecotoxicological properties.