Effects of SO2 oxidation on ambient aerosol growth in water and ethanol vapours

[摘要] Hygroscopicity (i.e. water vapour affinity) of atmospheric aerosolparticles is one of the key factors in defining their impacts onclimate. Condensation of sulphuric acid onto less hygroscopicparticles is expected to increase their hygrocopicity and hence theircloud condensation nuclei formation potential. In this study,differences in the hygroscopic and ethanol uptake properties ofultrafine aerosol particles in the Arctic air masses with a differentexposure to anthropogenic sulfur pollution were examined. The maindiscovery was that Aitken mode particles having been exposed topolluted air were more hygroscopic and less soluble to ethanol thanafter transport in clean air. This aging process was attributed tosulphur dioxide oxidation and subsequent condensation during thetransport of these particle to our measurement site. Thehygroscopicity of nucleation mode aerosol particles, on the otherhand, was approximately the same in all the cases, being indicative ofa relatively similar chemical composition despite the differences inair mass transport routes.These particles had also been producedcloser to the observation site typically 3–8 h prior tosampling. Apparently, these particles did not have an opportunity toaccumulate sulphuric acid on their way to the site, but instead theirchemical composition (hygroscopicity and ethanol solubility) resembledthat of particles produced in the local or semi-regional ambientconditions.

[学科分类] 大气科学