Beyond single particle mass spectrometry: multidimensional characterisation of individual aerosol particles

The behaviour of small aerosol particles depends on a number of their physical and chemical properties, many of which are strongly coupled. The size, internal composition, density, shape, morphology, hygroscopicity, index of refraction, activity as cloud condensation nuclei and ice nuclei and other attributes of individual particles all play a role in determining particle properties and their impacts. The traditional particle characterisation approaches rely on separate parallel measurements that average over an ensemble of particles of different sizes and/or compositions and later attempt to draw correlations between them. As a result such studies overlook critical differences between particles and bulk and miss the fact that individual particles often exhibit major differences. Here, we review the recently developed methods to simultaneously measure in situ and in real time several of the attributes for individual particles using a single particle mass spectrometer (SPMS), SPLAT or its second generation SPLAT II. We also discuss novel approaches developed for classification, visualisation and mining of large datasets produced by the multidimensional single particle characterisation.