Assessment of toxicity of particulate matter in the sub-micrometric range by an Atmospheric Simulation Chamber

Atmospheric aerosols (or Particulate Matter, PM) play an important role in human health and global climate changes, being a central topic in atmospheric physics and chemistry. PM consists of solid and liquid particles suspended in the atmosphere, with high variability in size, composition, concentration, shape, life-time and sources. Among PM constituents, carbonaceous compounds cover a substantial fraction. My thesis focuses on soot particles that are carbonaceous particles generated as by-products of incomplete combustion of hydrocarbon fuels. Soot particles are responsible of negative impacts, both on climate and health. Therefore, it is necessary to investigate their properties and behaviour in the atmosphere in order to fully understand their adverse effects. Aerosols properties can be investigated by experiments performed in Atmospheric Simulation Chambers (ASCs), which are exploratory platforms that allow to study atmospheric processes under realistic but controlled conditions, for long enough time periods to reproduce realistic environments. My PhD took place in the Laboratory for Environmental Physics at the Physics Department of the University of Genoa, where the only Italian ASC, ChAMBRe, is installed. The employ of a soot generator is useful to perform experiments concerning soot particles. They are stable source that generate particles with controlled and known properties, similar to the real atmospheric ones. During my PhD, the Mini-Inverted Soot Generator (MISG) was used, fuelled with both ethylene and propane and varying the oxygen-fuel ratio. The main objective of this thesis was to develop an experimental setup and a procedure that allow to perform systematic studies on soot particles exposed and maintained in different conditions thus investigating their properties, effects and interactions with the other atmospheric pollutants. Combustion conditions and resulting flame shapes were classified; a deep characterization of MISG exhaust, in connection to ChAMBRe, was performed in terms of concentration of emitted particles and gases, particle size distribution, composition and optical properties. The characterization of the MISG exhausts is an important piece of information to design the subsequent experiments. Well-characterized soot particles could be used to investigate the effects that atmospheric parameters can have on soot particles, and to study the interactions between soot particles and other pollutants. During my PhD work, preliminary studies on the soot oxidative potential and toxicological effects as well on interactions between soot particles and bio-aerosols were performed.