Chemical and Mössbauer Spectroscopy Characterization associated to Oxidative Potential of particulate matter from Brake Wear Emissions
Résumé
The road transport is recognized to be an important contributor to the air pollution. Brake wear may contribute up 55% in mass of PM10 of total emission of non-exhaust particles. The presence of high content of heavy metal and their oxides (Kukutschova et al 2011) in brake dusts combined to a nanosized fraction predict of their cytotoxic effects and oxidative stresses (Gasser et al 2009). We report chemical characterization of brake wear using TEM/STEM-EDX single particle analysis, to identify chemical element size and morphology of particles, known to be key determinant in tissue interaction or cellular uptake (Buzea et al 2007). Particles were generated from a home-made bench test designed specifically to reproduce real-world driving conditions. Source of many health adverse effects, oxidative stress was assessed by measuring the oxidative intrinsic potential of particles using acellular depletion DTT, Ascorbic Acid and GSH assays. Findings show a significant ultrafine fraction <100nm. Embedding in a carbonaceous matrix, Fe, Cu are the both major metal elements present in more than 94% of ultrafine fraction. Additionnal elements Mg, S, Ca, Cr, Zn, Ti, Al and Ba are clustered within particles, reflecting a probable remodeling of primary chemical components. An original approach by Spectroscopy Mossbauer define
Iron-particles-content phases as mainly Fe0 (69%), and in lower proportion as Fe2+ (14%) and Fe3+ (17%). Compared to Diesel particles, brake wear exhibit high elevated oxidative potential starting with 14μg/ml of particles. Results provided pertinent information which can be used to study health effects via in vivo rodent exposure