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Atmospheric Chemistry and Physics Vol.15 Nr.22, 33253-33282 ; Changes in traffic systems and vehicle emission reduction technologies significantly affect traffic-related emissions in urban areas. In many densely populated areas the amount of traffic is increasing, keeping the emission level high or even increasing. To understand the health effects of traffic related emissions, both primary and secondary particles that are formed in the atmosphere from gaseous exhaust emissions need to be characterized. In this study we used a comprehensive set of measurements to characterize both primary and secondary particulate emissions of a modern gasoline passenger car. Our aerosol particle study covers the whole process chain in emission formation, from the engine to the atmosphere, and takes into account also differences in driving patterns. We observed that in mass terms, the amount of secondary particles was 13 times higher than the amount of primary particles. The formation, composition, number, and mass of secondary particles was significantly affected by driving patterns and engine conditions. The highest gaseous and particulate emissions were observed at the beginning of the test cycle when the performance of the engine and the catalyst was below optimal. The key parameter for secondary particle formation was the amount of gaseous hydrocarbons in primary emissions; however, also the primary particle population had an influence. Thus, in order to enhance human health and wellbeing in urban areas, our study strongly indicates that in future legislation, special attention should be directed into the reduction of gaseous hydrocarbons.

Concerns regarding noxious emissions from internal combustion engines have increased over the years. There is a strong need to understand the nature of sub-23 nm particles and to develop measurement techniques to evaluate the feasibility of new regulations for particle number emissions in the sub-23 nm region (down to at least 10 nm). This paper presents the results of three EU-funded projects (DownToTen, PEMs4Nano and SUREAL-23) which supported the understanding, measurement and regulation of particle emissions below 23 nm and have successfully developed sub-23 nm particle measurement devices, specifically laboratory systems and mobile devices for RDE tests. The new technology was validated in chassis dyno tests and on the real road. The results show that sub-23 nm particles are mainly generated at the engine start and during acceleration phases. The innovations show that the technology is mature and robust enough to serve as a basis for regulating sub-23 nm particles. ; The DownToTen project has received funding from the European Union's Horizon 2020 research and innovation programme under agreement No 724085. The PEMs4Nano project has received funding from the European Union's Horizon 2020 research and innovation programme under agreement No 724145. The SUREAL-23 project has received funding from the European Union's Horizon 2020 research and innovation programme under agreement No 724136.