Hygroscopic growth of sub-micrometer and one-micrometer aerosol particles measured during ACE-Asia

[摘要] Hygroscopic properties of aerosol particles in the sub-micrometer andone-micrometer size ranges were measured during the ACE-Asia study (AerosolCharacterization Experiment-Asia) in spring 2001. The measurements tookplace off the coasts of Japan, Korea, and China. All instrumentscontributing to this study were deployed in a container on the forward deckof the NOAA Research Vessel Ronald H. Brown. Air masses with primarilymarine influence and air masses from the Asian continent affected by bothanthropogenic sources and by the transport of desert dust aerosol wereencountered during the cruise.

Results showed very different hygroscopic behavior in the sub-micrometersize range compared to the one-micrometer size range. In general, for allcontinentally influenced air masses, the one-micrometer particle populationwas characterized by two different particle groups – a nearly hydrophobicfraction with growth factors around 1.0 representative of dust particles anda sea salt fraction with hygroscopic growth factors around 2.0. The numberfraction of dust particles was generally about 60% independent oflong-range air mass origin.

For sub-micrometer particles, a dominant, more hygroscopic particle fractionwith growth factors between 1.5 and 1.9 (depending on dry particle size)consistent with ammonium sulfate or non-neutralized sulfates as majorcomponent was always found. In marine air masses and for larger sizes withinthe sub-micrometer range (Dp=250 and 350 nm), a sea salt fraction with growthfactors between 2.0 and 2.1 was also observed. For all other air masses, themore hygroscopic particle fraction in the sub-micrometer size range wasmostly accompanied by a less hygroscopic particle fraction with growthfactors between 1.20 and 1.55 depending on both the continental sources andthe dry particle size. Number fractions of this particle group variedbetween 4 and 39% depending on dry particle size and air mass type.Nearly hydrophobic particles indicating dust particles in the sub-micrometersize regime were only found for particles with Dp=250 and 350 nm during atime period when the aerosol was influenced by transport from Asian desertregions.

[学科分类] 大气科学