Technical note: Measurement of chemically-resolved volume equivalent diameter and effective density of particles by AAC-SPAMS

Abstract. Size and effective density (ρe) are important properties of aerosol particles and are related to their influences on human health and the global climate. The volume equivalent diameter (Dve) is an intrinsic property that is used to evaluate particle size. ρe, defined as the ratio of particle density to a dynamic shape factor (χ), is used to characterize the physical property of a particle as an alternative to particle density. However, it is still challenging to simultaneously characterize the Dve and ρe of particles. Here, we present a novel system that classifying particles with their aerodynamic diameter (Da) by aerodynamic aerosol classifiers (AAC) and determining their vacuum aerodynamic diameter (Dva) by single particle aerosol mass spectrometry (SPAMS) to achieve a measurement of Dve and ρe. The reliability of the AAC-SPAMS system for accurately obtaining Dve and ρe is verified based on the results that the deviation between the measured values and the theoretical values is less than 4 % for the size-resolved spherical polystyrene latex (PSL). The AAC-SPAMS system is applied to characterize the Dve and ρe of (NH4)2SO4 and NaNO3 particles, suggesting that these particles are aspherical and their ρe are independent of particle size. Finally, the AAC-SPAMS system is deployed in a field measurement, showing that it is a powerful technique to characterize the chemically-resolved Dve and ρe of particles in real time.