Hygroscopicity, CCN and volatility properties of submicron atmospheric aerosol in a boreal forest environment during the summer of 2010

摘要

A Volatility-Hygroscopicity Tandem Differential Mobility Analyzer (VH-TDMA)was applied to study the hygroscopicity and volatility properties ofsubmicron atmospheric aerosol particles in a boreal forest environment inHyytiälä, Finland during the summer of 2010. Aitken and accumulationmode internally mixed particles (50 nm, 75 nm and 110 nm in diameter) wereinvestigated. Hygroscopicity was found to increase with particle size. Therelative mass fraction of organics and SO is probably the majorcontributor to the fluctuation of the hygroscopicity for all particle sizes.The Cloud Condensation Nuclei Counter (CCNC)-derived hygroscopicityparameter κ was observed to be slightly higher thanκ calculated from VH-TDMA data under sub-saturated conditions, potential reasons for this behavior are discussed shortly. Also, thesize-resolved volatility properties of particles were investigated. Uponheating, more small particles evaporated compared to large particles. Therewas a significant amount of aerosol volume (non-volatile material) left, evenat heating temperatures of 280 °C. Using size resolvedvolatility-hygroscopicity analysis, we concluded that there was alwayshygroscopic material remaining in the particles at different heatingtemperatures, even at 280 °C. This indicates that theobserved non-volatile aerosol material did not consist solely of blackcarbon.