Tracking the source: First evidence of Benzothiazoles in outdoor airport aerosol

The aviation sector is crucial to support worldwide connections, and it is esteemed to grow in the following years. Monitoring of aviation pollution has gained importance, but poor attention is brought to the chemical composition of non-exhaust emissions such as Tire Wear Particles (TWPs), produced after the abrasion of tires with the road pavement. TWPs can end up in water, soil, and air, resulting in a great source of microplastics. Not only, TWPs can transport and release rubber additives like Benzothiazoles (BTHs), a wide family of organic molecules used in rubber production. BTHs have been exploited as chemical markers to trace non-exhaust road traffic emissions, however, to the best of our knowledge no studies researched BTHs in airborne aircraft TWPs. This is a great gap in literature considering the great estimated amount of TWPs produced by aircrafts. BTHs were investigated for the first time in the outdoor PM10 of Milano Linate airport together with other chemical markers (major ions, carboxylic acids). The airport appears to be an important source of BTHs, especially BTH, BTH-NH2, BTH-MeS, and BTH-SO3H, and the aerosol composition appears like those of highly trafficked cities. A weekly trend was observed, and a strong link between BTH-NH2 and BTH-SO3H was noticed, suggesting a connection with the airport activities. A chemometric approach was also applied, and three major clusters were identified: one was attributed to the airplanes/airport vehicles' activity; one was linked to the airport de/anti-icing procedures; the last was related to a median-range transport and secondary atmospheric reactions.