3.1. UFPs Characterization

DEP and BB batches were provided by ENEA (Agenzia Nazionale per Le Nuove Tecnologie, L’Energia e Lo Sviluppo Economico Sostenibile) in the framework of the project “Biological effects and human health impacts of ultrafine particles sources” lead by Prof Camatini of the POLARIS research centre. Particle sampling procedures and their characterization are extensively reported elsewhere [56]. Briefly, DEP were sampled from five Teflon filters (Whatman pure Teflon filters, Maidstone, United Kingdom) obtained by a diesel Euro 4 light-duty vehicle without an anti-particulate filter fuelled by commercial diesel and run over a chassis dyno, while BB particles were collected from five Teflon filters (Whatman pure Teflon filters) obtained by a modern automatic 25 kW boiler propelled by a prime quality spruce pellet. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images of both diesel and biomass samples showed aggregates of round carbonaceous particles lower than 50 nm; in addition, biomass samples showed the presence of ash particles that completely dissolved in aqueous media [56]. PAHs and transition metals (Fe, Zn, Cr, Pb, V and Ni) concentration was higher in DEP compared to BB, which conversely resulted enriched in elements typical of wood combustion, such as Mn, K and S. Below we provide a table (Table 2) summarizing the results obtained by Longhin and colleagues [56].

Chemical compositions of UFPs from different anthropogenic sources, reported in Longhin et al., 2016. [56] Each value is expressed as mean concentrations (±SD).