Influence of semi-volatile species on particle hygroscopic growth

摘要

The hygroscopic properties of aerosol particles are often related to theircontent of soluble material, on the basis of the Kohler theory. Recentstudies, however, seem to indicate that the role of aerosol particlesemi-volatile fraction properties has been underestimated. In this study, weuse a novel method based on a Tandem Differential Mobility Analyser (TDMA)system combining particle volatilization and humidification conditioning(VH-TDMA) to test the effect of the gentle volatilization of a small fractionof the atmospheric particles on the particle hygroscopic growth in severalenvironments (urban to remote). Results show that the particle hygroscopicproperties can either be enhanced or decreased after thermal conditioning ofthe particle at moderate temperatures (50 to 110°C). The hygroscopicgrowth factor changes induced by volatilization indicate that some volatilecompounds, although present at low concentrations, drastically influence thehygroscopic growth of particles in the way that can not be predicted by theKohler theory at equilibrium.