Solubility properties of surfactants in atmospheric aerosol and cloud/fog water samples

Abstract

[1] Organic films on deliquesced aerosols and cloud droplets lower the surface tension of water and may inhibit the exchange of water vapor and gases between the gas and the liquid phase, with important implications for aerosol and cloud microphysics and heterogeneous chemistry. This study provides an estimate of the solubility properties of surfactants in aerosol and fog/cloud water samples on the basis of the dilatational rheological properties of the surface films. The variations of surface tension induced by the fast expansion/compression of the films were measured by means of a drop shape tensiometer and were linked to the capacity of surfactants to exchange between the surface layer and bulk solution, and ultimately to their water-solubility. The results are in agreement with the properties of standards of soluble surfactants and can be interpreted by the theory of formation of hydrophilic adsorption layers. These findings suggest that the water-soluble organic compounds (WSOC) are the main contributors to the formation of films on cloud/fog droplets. It follows that the surface coverage of film-forming compounds is mainly controlled by the bulk concentration of WSOC, regardless of the available surface area. This also supports that the surface tension decreases observed under laboratory conditions actually occur in the atmosphere.

Hygroscopic growth and critical supersaturations for mixed aerosol particles of inorganic and organic compounds of atmospheric relevance

“…σ 0 represent the surface tension of pure water at the temperature of measurements. Previous work Decesari et al, 2003) have shown that this equation well describes the surface tension changes in atmospheric water, and it was shown that the surface coverage of WSOC surfactants is mainly controlled by the bulk concentration of WSOC. In the case of micrometer sized droplets and strongly surface active compounds, Eq.…”

“…However, the partitioning effects demonstrated for sodium dodecyl sulfate (SDS) might be less important in the case of atmospheric surfactants (Rood and Williams, 2001;Sorjamaa et al, 2004;Facchini et al, 2001). Therefore, in this work we used the surface tension data as suggested by Decesari et al (2003), i.e. as being independent of the available surface area.…”

Surface rheology of monolayers of phospholipids and cholesterol measured with axisymmetric drop shape analysis

“…The fact that η is determined with less precision was reported as well by Wüstneck et al [2] which found the confidential intervals (95% confidence level) of ε about 1-4%, whereas those for the η between 10 and 15%. Decesari et al [40] obtained an uncertainty on the ε determination of 10% for Π > 3 mN m −1 using the same instrument.…”

Water-soluble SOA from Alkene ozonolysis: composition and droplet activation kinetics inferences from analysis of CCN activity

“…Carbonaceous material (organic carbon, OC) can comprise up to 90% of aerosol mass (Andreae and Crutzen, 1997;Cachier et al, 1995;Yamasoe et al, 2000), 10-70% of which may be water-soluble (WSOC). Studies have shown that WSOC can influence aerosol hygroscopicity and surface tension (Decesari et al, 2003;Saxena and Hildemann, 1996;Shulman et al, 1996) and must be characterized to quantify the impact of these aerosols on cloud droplet formation. WSOC can be present in primary organic carbon but also formed during the oxidation of volatile organic carbon (VOC) to secondary organic aerosol (SOA) (Kanakidou et al, 2005;Robinson et al, 2007;Saxena and Hildemann, 1996).…”