Ultra-fine particulate matter (PM), emitted primarily by automobile engines, is currently the topic of intensive research due to the link between PM levels, health effects and climate change. However, there is a critical lack of certification procedures for ultra-fine particles. The aim of the European H2020 PEMs4Nano project (www.pems4nano.eu) is to develop a portable emission monitoring system for particles with sizes below 23 nm, to be used in real driving conditions. The development of a precise and reliable measurement procedure requires extensive knowledge of PM characteristics (e.g. chemical composition) and their size-variation, before and after the removal of volatile components. This work presents a study on the influence of the catalytic stripper on size-selected particles emitted by a direct injection gasoline engine.

Mass spectroscopic studies of size-selected particulate matter in combination with advanced statistical procedures revealed that the smallest particles are the most affected by the catalytic stripper due to their higher surface organic fraction. This was also confirmed by on-line aerodynamic-mass-mobility measurements. The obtained detailed physico-chemical information is essential for developing a measurement procedure down to 10 nm within the PEMs4Nano project.