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Article Dans Une Revue Atmospheric Chemistry and Physics Discussions Année : 2006

Hygroscopic properties of ultrafine aerosol particles in the boreal forest: diurnal variation, solubility and the influence of sulfuric acid

Résumé

Freshly formed atmospheric aerosol particles are neither large enough to efficiently scatter incoming solar radiation nor able to act as cloud condensation nuclei. As the particles grow larger, their hygroscopicity determines the limiting size after which they are important in both of the aforementioned processes. The condensing species resulting in growth alter the hygroscopicity of the particles. We have measured hygroscopic growth of aerosol particles present in a boreal forest, along with the very hygroscopic atmospheric trace gas sulfuric acid. The focus was on days with new particle formation by nucleation. The measured hygroscopic growth factors (GF) correlated positively with gaseous phase sulfuric acid concentrations. This correlation had a strong size dependency; the smaller the particle, the more condensing sulfuric acid is bound to alter the GF due to initially smaller mass. In addition, water uptake of nucleation mode particles was monitored during new particle formation events and followed during their growth to Aitken mode sizes. As the modal diameter increased, the solubility of the particles decreased. This indicated that initially more hygroscopic particles transformed into less hygroscopic or even hydrophobic particles. A similar behavior was seen also during days with no particle formation, with GF decreasing during the evenings and increasing during early morning. This can be tentatively explained by day- and nighttime differences in the hygroscopicity of condensable vapors.
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Dates et versions

hal-00302183 , version 1 (18-06-2008)

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  • HAL Id : hal-00302183 , version 1

Citer

M. Ehn, T. Petäjä, H. Aufmhoff, P. Aalto, K. Hämeri, et al.. Hygroscopic properties of ultrafine aerosol particles in the boreal forest: diurnal variation, solubility and the influence of sulfuric acid. Atmospheric Chemistry and Physics Discussions, 2006, 6 (5), pp.9937-9965. ⟨hal-00302183⟩

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