Particulate emissions of the Euro 6 vehicles are very low both in laboratory and in real-driving conditions
Emissions from passenger cars are one of major sources that deteriorate urban air quality. The study conducted in collaboration of Tampere University, Finnish Meteorological Institute and Aristotle University of Thessaloniki, presents characterization of real-drive emissions from three Euro 6 emission level passenger cars (two gasoline and one diesel) in terms of fresh particles and secondary aerosol formation. The gasoline vehicles emissions were also characterized by chassis dynamometer studies.
The particle number emission factors for particles larger than 3 nm measured in laboratory were much higher than the regulatory value of 6x10-11 particles km-1. The higher emission factors measured result probably from the fact that the regulatory limit considers only non-volatile particles larger than 23 nm. In the research, all particles (also volatile) larger than 3 nm were measured. Clearly, the current regulatory value for particle emissions does not reflect the actual exposure-relevant emissions of the vehicles.
The number emissions of fresh particles larger than 7 nm for three Euro 6 vehicles measured in this study in real-drive use were low, generally below background noise. However, by extending the measured particle size range down to 3 nm, the real-drive particle emissions for the gasoline vehicles were significantly higher than the corresponding emissions measured in laboratory. The diesel vehicle emissions also in this size range were below background noise levels.
The higher real-drive emissions of the nanoparticles highlight the need to conduct real-world measurements in addition to laboratory tests to gain knowledge on exposure-relevant particle emissions.
In laboratory tests, secondary aerosol formation potential was observed to be the highest after a vehicle cold start when most of the secondary mass was organics. After the cold start, the relative contributions of ammonium, sulfate and nitrate increased. The real-drive secondary aerosol formation potential was below the detection limit. The laboratory-derived secondary organic aerosol (SOA) production factors can thus be expected to be representative of real driving SOA formation potential.
Three Euro 6 light-duty vehicles were tested: a gasoline vehicle equipped with port fuel injection (PFI), a gasoline vehicle equipped with direct injection (GDI), and a diesel vehicle. The gasoline vehicles were equipped with three-way catalysts (TWC) and the diesel vehicle with a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF) and a selective catalytic reduction device (SCR). The emissions of all three vehicles were measured in real-drive conditions by chasing, and the emissions of the two gasoline vehicles were additionally characterized by chassis dynamometer testing.
The research was supported by the Health relevant and energy efficient regulation of exhaust particle emissions (HERE) project [decision number 40330/13], funded by Business Finland (Tekes), AGCO Power Oy, Dinex Finland Oy, Dekati Oy, Neste Oyj, Pegasor Oy and Wärtsilä Finland Oy.
Further information:
Senior researcher Hilkka Timonen, Finnish Meteorological Institute, tel. +358 50 380 2864, hilkka.timonen@fmi.fi
Reference: Simonen, P., Kalliokoski, J., Karjalainen, P., Ronkko, T., Timonen, H., Saarikoski, S., Aurela, M., Bloss, M., Triantafyllopoulos, G., Kontses, A., Amanatidis, S., Dimaratos, A., Samaras, Z., Keskinen, J., Dal Maso, M., and Ntziachristos, L.: Characterization of laboratory and real driving emissions of individual Euro 6 light-duty vehicles - Fresh particles and secondary aerosol formation, Environmental pollution, 255, 113175, 10.1016/j.envpol.2019.113175, 2019.
https://www.sciencedirect.com/science/article/pii/S0269749119329586