Historical trends of N-cyclohexyl-2-benzothiazolamine, 2-(4-morpholinyl)benzothiazole, and other anthropogenic contaminants in the urban reservoir sediment core

A new potential molecular marker, N-cyclohexyl-2-benzolhiazolamine (NCBA), was discovered in Various environmental matrices (i.e., road dusts, runoff- and river-water particles, river sediments, aerosols) taken in Tokyo, Japan. Concurrent determination of this compound together with 2-(4-morpholinyl)benzothiazole (24MoBT), previously proposed marker of road dust, demonstrated that both compounds are widely distributed in the urban environment (similar to ng/g to similar to mu g/g), derived from Vehicle tire tread, and transported in the environments in the same way. To assess utilities of NCBA and 24MoBT as molecular markers for vehicle-derived contaminants, these compounds were analyzed in a sediment core from the Chidorigafuchi Moat of Imperial Palace, situated in the center of Tokyo. Remarkable is that NCBA existed at higher concentrations than 24MoBT near the surface (0-6 cm depth) and bottom parts (16-24 cm depth) of the region where BTs were detected hut lower in the middle parts (6-16 cm depth). Dating of the core by using (137)Cs and tetrapropylene-based alkylbenzenes (TABs) revealed the two changeovers coincide well with changes in the production history of vulcanization accelerators containing the compounds. The dated downcore profile of Sigma BTs (sum of 24MoBT and NCBA) showed positive correlation with the traffic data in Tokyo Metropolitan Area. These results indicate the usefulness of NCBA and 24MoBT as time markers for recent sections of sediment cores and as molecular markers for reconstructing the history of traffic-induced contamination.