Initial steps of aerosol growth

[摘要] The formation and growth of atmospheric aerosols depend on several steps,namely nucleation, initial steps of growth and subsequent – mainlycondensational – growth. This work focuses on the initial steps of growth,meaning the growth right after nucleation, where the interplay of curvatureeffects and thermodynamics has a significant role on the growth kinetics.More specifically, we investigate how ion clusters and aerosol particlesgrow from 1.5 nm to 20 nm (diameter) in atmospheric conditions usingexperimental data obtained by air ion and aerosol spectrometers. Themeasurements have been performed at a boreal forest site in Finland. Theobserved trend that the growth rate seems to increase as a function of sizecan be used to investigate possible growth mechanisms. Such a growth rate isconsistent with a recently suggested nano-Köhler mechanism, in which growthis activated at a certain size with respect to condensation of organicvapors. The results also imply that charge-enhanced growth associated withion-mediated nucleation plays only a minor role in the initial steps ofgrowth, since it would imply a clear decrease of the growth rate with size.Finally, further evidence was obtained on the earlier suggestion thatatmospheric nucleation and the subsequent growth of fresh nuclei are likelyto be uncoupled phenomena via different participating vapors.

[学科分类] 大气科学