Airborne particulate matter emissions from vehicle brakes in micro- and nano-scales: Morphology and chemistry by electron microscopy

Abstract Brake wear particles constitute a significant part of the non-exhaust related particulate matter (PM) associated to traffic. These particles derive from various components of the vehicles’ brake system and were recognized as an important pollution source only recently. In the present study, electron microscopy was applied to elucidate brake wear particle morphology and associated chemical composition. Sampling was carried out on a brake test bench. Particles were collected on 13 successive polycarbonate foil bags and a backup filter by means of a Dekati Low Pressure Impactor (DLPI), based on the equivalent aerodynamic particle diameter. The results revealed a broad size range from the micro-to the nano-scale, as measured on electron microscope images, including coarse (2.5–10 μm), fine (0.1–2.5 μm) and ultrafine ones (