Physicochemical and mutagenic analysis of particulate matter emissions from an automotive diesel engine fuelled with fossil and biofuel blends

In this paper, a complete characterization of diesel Particulate Matter (PM) in terms of mass, chemical composition, particles number, size distribution and mutagenic potential was carried out. As a test case, a Euro 5 1.3L passenger car diesel engine fueled with Ultra Low Sulphur Diesel (ULSD) and high-percentage blends (B30 − 30% vol.) of ULSD and biofuels (Rapeseed Methyl Ester, RME, and Hydrotreated Vegetables Oil, HVO) was considered. In addition, PM gravimetric analysis was compared with soot measurements carried out by means of standard laboratory equipment (e.g. smokemeters), showing a good correlation at medium and high load operating points. On the contrary, at low loads, as confirmed by thermo-gravimetric analysis, smokemeter measurements underestimated the Soluble Organic Fraction (SOF) fraction of PM, especially when for RME (B30). Then, a detailed investigation on Particles Number (PN) and size distribution was carried out, running the engine with the same fuel matrix. The results showed that adopting biofuel blends, both RME (B30) and HVO (B30), produces negligible differences in particles number distributions with respect to standard diesel. Finally, the analysis of the mutagenic potential of PM samples highlighted an increased genotoxicity for HVO (B30) and a decreased genotoxicity for RME (B30) with respect to ULSD.