Analysis of individual polychlorinated naphthalene congeners and dioxin-like compounds in a dated sediment core from Lake Kitaura, Japan

Polychlorinated naphthalenes (PCNs) were used in a variety of industrial products including capacitor dielectrics; cutting oils; engine oil additives; die casting; ship insulation; wood, paper, and fabric preservatives; and wire insulation. The technical formulations of PCNs, polychlorinated biphenyls and other industrial thermal processes (e.g. incinerator, chloro-alkali plant) are considered to be additional sources of environmental contamination by this compound. PCNs are planar, similar to polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs); therefore, some PCN isomers elicit toxicy similar to that of PCDD/DFs. Vertical profiles of residues in dated sediment cores have been used as historical records of pollution. Our studies examined the vertical profiles of persistent organic contaminants, such as PCNs, PCBs and PCDDs/DFs, in a sediment core from Lake Kitaura. Heretofore, an analytical method of PCNs with insufficient performance was used. We developed a new method which conbined on accelerated solvent extractor, double column HPLC system with a porous graphitic carbon column (Hypercarb) and a pyrenyl-silica (PYE) column, preparative GC and HRGC-HRMS. The profile was characterized by lesser concentrations in deeper layers, followed by an exponential increase to a subsurface peak and a gradual decrease to the, surface. A maximum PCNs concentration of 733 pg/g, dry wt was found in a 14 similar to 15 cm section, which corresponded to the early 1980s. The composition of PCN isomers in environmental samples is characteristic of their sources. The profile of isomers typical to Halowax showed a similarity in which the maximum concentration occurred in the 14 similar to 15 cm section. In surface layers these isomers gradually decreased. The profile of combustion source isomers, was very interesting because these concentrations increase or don't decrease very remarkably from the 14 similar to 15 cm section to the surface. Although this suggests sources originating from incineration, there may also exist photodecomposition or biodegradation of HxCN and HpCN isomers resulting in the formation of lower chlorinated isomers, which are included in technical PCBs as impurities.