Atmospheric particles are a health risk and affect climate. Vehicular particle emissions are strictly regulated, but the particle mass that is formed when the vehicle exhaust oxidizes in the atmosphere is not taken into account in the emission limits. This is partly due to the lack of standardized methods to measure the secondary aerosol formation.
It is possible to estimate the secondary aerosol formation in the atmosphere by mimicking atmospheric conditions in laboratory measurements. In such experiments, the gaseous sample is exposed to atmospheric oxidants in an oxidation flow reactor, and the particle mass formed by the oxidation is measured. However, vehicle exhaust gas measurements have specific characteristics that need to be considered when using an oxidation reactor.
In his doctoral dissertation, MSc Pauli Simonen improved methods to determine the potential formation of secondary aerosol from combustion engines using an oxidation flow reactor. In his work, Simonen focused particularly on the characterization of the oxidation flow reactor, sample pre-treatment, the instrumentation used for particle mass measurement, and the data analysis related to the interpretation of the measurement results.
– Originally, oxidation flow reactors were not developed for emission measurements involving high concentrations of nitrogen oxides and hydrocarbons, as well as rapid changes in exhaust gas composition. For this reason, previous measurement and data analysis methods were not directly applicable to determining secondary aerosol formation from vehicles, Simonen says.
Using the measurement method developed in the dissertation, it is possible to study means to reduce vehicular secondary aerosol formation and thus improve the air quality. In his dissertation, Simonen found that the secondary aerosol formation could be reduced for example by increasing the ethanol content of gasoline or by increasing the exhaust after-treatment.
Pauli Simonen works in Aerosol Physics Laboratory at Tampere University.
Public defence on Friday 31 May
The doctoral dissertation of MSc (Tech) Pauli Simonen in the field of aerosol physics titled Development and Application of Oxidation Flow Reactors in Engine Exhaust Studies will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 12 o’clock on Friday 31 May 2024, at Hervanta campus, Sähkötalo auditorium S2 (Korkeakoulunkatu 3, Tampere).
The opponent will be Senior lecturer, Docent Axel Eriksson, Lund University. The Custos will be Professor Miikka Dal Maso from Tampere University.