Formation of secondary aerosol from emissions of a Euro 6d-compliant gasoline vehicle with particle filter

The most recent European regulation, the Euro 6d emission standard, require all gasoline direct injection (GDI) vehicles to use both a three-way catalyst (TWC) and a gasoline particle filter (GPF) as exhaust aftertreatment. These aftertreatment methods are aimed at reducing NOx and primary particle emissions. However, the formation of secondary organic aerosols (SOA) from the volatile organic compound (VOC) emissions of a Euro 6d compliant GDI vehicles, equipped with a GPF is yet not investigated. Therefore, to explore the SOA formation and effects of the GPF, the exhaust of a Euro 6d compliant GDI vehicle was characterized at 4 different steady state speeds, idling(0 km/h), 50, 80 and 100 km/h. The exhaust was oxidised in the Photochemical emissions aging flow tube reactor (PEAR) by reactions with OH radicals equivalent of 2.1 days of atmospheric day time oxidation. It was found that the GPF completely removes primary particles larger than 10 nm, at all investigated vehicle speeds. However, significant SOA was formed after oxidation, with the highest SOA formation potential pr kg fuel consumed at 50km/h. The main SOA precursors were determined to be Toulene, Xylene and Trimethyl-Benzene which were found to account for at least 50% of SOA formed at all driving speeds. Furthermore, high emissions of NH3 could be observed in the exhaust throughout all driving conditions which resulted in the subsequent formation of NH4NO3 after aging. The formation of NH4NO3 additionally facilitated the co-condensation of organic gas phase products after OH oxidation enhancing SOA mass even further.