Abstract
Abstract. Changes in 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 (direct) particulate emission and secondary particle formation (from gaseous precursors in the 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 Euro 5 level gasoline passenger car. Our aerosol particle study covers the whole process chain in emission formation, from the tailpipe to the atmosphere, and also takes into account 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.
Highlights
Vehicular emissions deteriorate the air quality locally (Wehner et al, 2002; Pirjola et al, 2012; Lähde et al, 2014) and contribute significantly to the air pollution levels in urban areas
Large particle number concentrations were observed during accelerations, especially during the first two accelerations when the engine had not yet reached steady temperature conditions, and they were associated with high engine loading and altering combustion conditions
Our aim was to create a basis for understanding the links between driving conditions, primary emissions of aerosols and their precursors and the formation of secondary particulate material
Summary
Vehicular emissions deteriorate the air quality locally (Wehner et al, 2002; Pirjola et al, 2012; Lähde et al, 2014) and contribute significantly to the air pollution levels in urban areas. In order to reduce the adverse health effects and exposure of people by pollutants, the emission regulation for vehicles with direct injection engines include limits for particulate mass (PM), and in Europe for some vehicle types, particle number (PN) (Dieselnet, 2016), of which the PN limit is considered to be stricter. Limits for gaseous compounds cover total hydrocarbon emissions, nitrogen oxides and carbon monoxide. Both particulate and gaseous emissions are strongly affected by technology development (e.g., catalysts and filters), driven by legislation activities. This technology development has, in general, other effects than required by emission legislation; for example, fuel sulfur content limitations affect the emissions of nanoparticles. It should be noted that, e.g., semi-volatile compounds (e.g., low-volatility organics, sulfuric compounds) are not directly regulated even though they are partially detected in the gravimetric PM determination as Published by Copernicus Publications on behalf of the European Geosciences Union
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