POLYCHLORODIBENZOTHIOPHENES, THE SULFUR ANALOGS OF THE POLYCHLORODIBENZOFURANS IDENTIFIED IN INCINERATION SAMPLES

Polychlorodibenzothiophenes (PCDTs), the sulfur analogues of the polychlorodibenzofurans (PCDFs), were identified in fly ash from two municipal solid waste incinerators and from an electric-arc furnace of a carshredding facility. Gas chromatography/mass spectrometry (GC/MS) and MS/MS experiments were used to detect the new compounds in addition to the related polychlorodibenzodioxins (PCDDs) and PCDFs and to differentiate PCDTs from the nominally isobaric PCDDs. Among the PCDTs detected were tetra- and pentachloro isomers including the 2,3,7,8-tetrachlorodibenzothiophene. The concentrations of PCDTs in fly ash were up to 55 ng/g, at or 1 magnitude below the concentrations of the PCDDs and PCDFs in these samples. The sources and routes of formation of the new compounds are still unknown. Various pathways seem plausible, and as an example, we report on the formation of PCDTs from the thermal reaction of chloro aromatic compounds [polychlorobiphenyls (PCBs)] with elemental sulfur.