Particle emissions from vehicles have been an important topic of discussion for decades and continue to be so. According to the World Health Organization, in 2019, 90 % of the global population lived in areas where clean air guidelines were exceeded mostly due to road transport. In Europe, the upcoming emission legislation (Euro 7) will continue to push vehicle manufacturers to ensure clean air for everyone.
Particles emitted by combustion engines deteriorate air quality, especially in urban areas where large populations are exposed to them. Studies suggest that nanoparticles (smaller than 50 nanometers in diameter) affect human health through mechanisms that differ from those of larger particles. The particle emissions of vehicles are a topic of scientific interest and are subject to increasingly stringent test protocols.
According to Sampsa Martikainen, the first step in finding a solution is understanding the problem. Fields of expertise related to particle emissions encompass epidemiology, toxicology, vehicle technology, and measurement methodology, among others.
“These fields are interconnected and present a plethora of fundamental problems that need to be addressed to advance our understanding and, ultimately, create solutions,” he says.
From a pragmatic perspective, choosing the most efficient and applicable ways to reduce a vehicle's particle emissions essentially requires the following:
1) Knowing how much particles the vehicle emits during typical use. "How much" refers to the number and mass of particles, as these two metrics are not necessarily well correlated.
2) Understanding what kind of particles a vehicle emits. "What kind" refers to relevant particle properties such as size and chemical composition.
3) Identifying the most important technical parameters that affect a vehicle's particle emissions, such as the type of fuel, lubricating oil, engine, and exhaust gas aftertreatment system.
New tools for analyzing nanoparticle properties
In the first part of his doctoral research, Martikainen characterized thoroughly the particle emissions of a farming tractor and a heavy-duty truck. Then he investigated the effects of different combinations of diesel, biodiesel, and lubricating oil. His dissertation also included an extensive description of the emitted particles, obtained with state-of-the-art methods and instruments, as well as the quantification of the effects of different fuels and oils on the emissions.
“I discovered that a significant reduction in particle emissions is possible simply by switching to a higher-quality fuel. Somewhat surprisingly, I found that changing the lubricating oil had an effect of comparable magnitude to changing the fuel. Furthermore, I observed evidence of synergistic effects between the fuel and lubricating oil. In practice, this suggests that for optimal particle emission reduction, a combination of fuel and oil should be chosen,” says Martikainen.
Particle properties such as size and chemical composition provide clues to both the origin of the particle and its effects on human health and the environment. However, the smaller the particles are, the harder it is to detect them and analyze their properties. In the second part of the dissertation, Martikainen focused on the development of nanoparticle measurement methodology, particularly in finding ways to analyze their chemical properties. As a result, he developed two new methods: the Aerosol Gas Exchange System (AGES) and the Soot Particle Agglomeration Inlet (SPAI).
“AGES is designed for the sampling of nanoparticles with minimal particle losses and for investigating their volatility, though it has various other applications as well. AGES offers several advantages over traditional methods for studying particle volatility. SPAI enables near-real-time measurement of nanoparticle chemical composition with a mass spectrometer (Soot Particle Aerosol Mass Spectrometer, SP-AMS), an instrument that typically loses information on small particles during use,” he explains.
Sampsa Martikainen is currently living in Graz, Austria, and working for AVL List GmbH, where his focus is on measuring particles emitted by vehicle brakes — a new upcoming inclusion in vehicle type approval in Europe.
Public defence on Friday 6 September
The doctoral dissertation of MSc Sampsa Martikainen in the field of aerosol physics titled Advances in Particle Emission Characterization of Heavy-duty Diesel Engines and Measurement of Exhaust Nanoparticles will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 12 o’clock on Friday 6.9.2024 at Hervanta campus, Tietotalo building, auditorium TB109 (Korkeakoulunkatu 1, Tampere).
The Opponent will be Docent Juha Kangasluoma from the University of Helsinki. The Custos will be Assistant Professor Panu Karjalainen from Tampere University.
The doctoral dissertation is available online.
The public defence can be followed via remote connection.