Investigation of airborne benzothiazoles in the North of Italy

Anthropogenic pressure on urban air quality is a concerning issue, and the transport sector plays a crucial role contributing with exhaust and non-exhaust emissions, such as Tyre and Road Wear Particles (TRWPs). TRWPs can accumulate on roadsides, be carried by stormwaters, and enter the atmosphere, together with their additives. Benzothiazoles (BTHs) are a family of compounds mostly employed as rubber additives in tire production, but they are also exploited in other applications. In urban environments, airborne BTHs are strongly linked to TRWPs, and they are potentially exploitable as traffic markers. Considering the limited information on airborne BTHs, and the unexplored potentiality as markers, a deepening on their occurrences, sources, and possible degradation phenomena was needed. PM10 aerosol samples were collected from thirteen cities in Northern Italy. BTH-SO3H was the most concentrated (up to 7 ng m−3), followed by BTH-MeS, BTH and BTH-OH. Cities close to airports showed a higher presence of BTHs, possibly indicating a new source for these compounds. BTH-SCNMeS, known to be easily degradable, was found in relative high concentrations (0.2 ± 0.1 ng m−3) only in Montebello Vicentino station, which is close to an industrial area with several leather manufacturing industry. In Aosta, at 580 m a.s.l., BTH-SH and BTH-NH2 were found higher than other stations, possibly indicating an additional apport from antifreeze liquids and stainless-steel industry. Accumulation and degradation phenomena, occurring on road and roadsides, might partially explain the higher concentrations of BTHs by-products.