Constraining the Effect of Surfactants on the Hygroscopic Growth of Model Sea Spray Aerosol Particles

Abstract

The cloud condensation nuclei activation of sea spray aerosol (SSA) is tightly linked to the hygroscopic properties of these particles and is defined by their physical and chemical properties. While hygroscopic sea salt in SSA strongly influences particle water uptake, the marine-derived components that make up the organic fraction of SSA constitute a complex mixture, and their effect on hygroscopic growth is unknown. To constrain the effect of organic compounds and specifically surface-active compounds that adsorb on particle interfaces, particle hygroscopic growth studies were performed on laboratory-generated model sea salt/sugar particles. For sea salt/glucose particles, ionic surfactants facilitated water uptake at low relative humidity (RH), increasing the particle growth factor (GF) by up to 7.61%, and caused a reduction in the deliquescence relative humidity (DRH), while nonionic surfactants had a minimal effect. Replacing glucose with polysaccharide laminarin in sea salt/sugar/surfactant particles caused a reduction in GF at low RHs and minimized the effect of ionic surfactants on the DRH. At RHs above the DRH, the addition of anionic or nonionic surfactants caused a decrease in GF for both sea salt/glucose and sea salt/laminarin particles. The addition of cationic surfactants, however, did not have a dampening effect on water uptake of sea salt/sugar particles and even showed a GF increase of up to 3.7% at 90% RH. An increase in the complexity of the sugar dampens the water uptake for particles containing nonionic surfactants but increases the water uptake for cationic surfactants. The cloud activation potential for 100 nm particles analyzed in this study is higher for ionic surfactants and decreases with an increase in surfactant molecular size when particle interfacial tension is considered. The surfactant effect on the hygroscopic growth and cloud activation potential of the particles containing sea salt/sugar is dependent on the surfactant ionicity and molecular size, the particle size and interfacial tension, and the interactions between inorganic salt and organic species under different RH conditions.

Morphology and hygroscopicity of nanoplastics in sea spray

“…6 also shows the comparison of the atomizer and AEGOR sea spray tank aerosols. Although the Collison atomizer has often been used to generate sea salt aerosol, 62,[66][67][68][69][70] in the marine boundary layer sea spray aerosol is generated by bubble bursting, which is more accurately simulated using a sea spray tank. 31,[71][72][73] For the same water salinity, the PSL-containing particles from the AEGOR tank were slightly smaller than those generated by the atomizer, and thus the expectation is that these dried particles will have smaller coatings.…”

Influence of Air Mass Source Regions on Signatures of Surface-Active Organic Molecules in Size Resolved Atmospheric Aerosol Particles

“…Surfactants are organic molecules that reduce the surface tension at the interface of a solution. , Surfactants have been measured in seawater − and in marine aerosol particles. , Other studies have observed surfactants in anthropogenic-influenced particles, , ambient urban particles, and biogenic terrestrial particles. , Surfactants can impact particle hygroscopic growth , and their potential to act as cloud condensation nuclei. − Recent work has used high-resolution mass spectrometry to identify fatty acids and other surfactants in aerosol particles. , These results can be combined with surface tension measurements to confirm the presence of surfactants …”

“… 47 , 48 Other studies have observed surfactants in anthropogenic-influenced particles, 49 , 50 ambient urban particles, 51 and biogenic terrestrial particles. 39 , 52 Surfactants can impact particle hygroscopic growth 53 , 54 and their potential to act as cloud condensation nuclei. 55 − 57 Recent work has used high-resolution mass spectrometry to identify fatty acids and other surfactants in aerosol particles.…”

Advances in Atmospheric Chemical and Physical Processes

“…Herein, Knight et al show the remarkable ability to monitor the evolution of the optical properties of a single particle as its composition changes. Other topics covered include a study of the impact of organic surfactants on the hygroscopicity of sea-salt/organic particles and a study showing that particle charge does not impact the photodegradation of oleic acid particles . Lastly, Edwards et al show that important human health-related properties of SOA, the presence of reactive organic species and environmentally persistent free radicals, vary with SOA precursor and the chemical regime in which the SOA is formed.…”