Low-Temperature Water Uptake of Individual Marine and Biologically Relevant Atmospheric Particles Using Micro-Raman Spectroscopy

Abstract

The interaction of water vapor and the water uptake behavior of atmospheric particles are often investigated as a function of relative humidity (0−100% RH) at ambient temperature. However, lower temperature studies are important to understand how atmospheric particles nucleate ice through various mechanisms including immersion freezing. Immersion freezing requires the formation of a condensed water droplet at lower temperatures prior to freezing. To better understand low-temperature water uptake behavior of marine and biologically relevant atmospheric particles, we have investigated water uptake of single atmospheric particles using a micro-Raman spectrometer coupled to an environmental cell for measurements at lower temperatures and as a function of relative humidity. These particles include sodium chloride, sucrose, Snomax, lipopolysaccharide, and laminarin. Particles range in size from 2 to 3 μm in diameter and can be monitored by using optical microscopy and Raman spectroscopy as a function of relative humidity at temperatures between 253 and 298 K. From the Raman spectra collected, we can determine a Raman growth factor defined as an increase in the intensity of the O−H stretch as a measure of the integrated water content of a particle compared to the dry particle. These data show that for lipopolysaccharide, laminarin, and Snomax, unlike simple saccharides such as sucrose and other soluble organics, as temperature decreases, water uptake begins at lower relative humidity and does not follow a solubility temperature dependence. This suggests that at lower temperatures the particles are adsorbing water on the surface rather than dissolving and absorbing water. Furthermore, repeated water uptake cycles cause a change in the morphology of some of these particles, which is shown to promote water uptake at lower relative humidity. These results give new insights into water uptake of these different marine and biologically relevant particles at low temperature at subsaturation relative humidity prior to droplet formation and immersion freezing.

Revealing the Impacts of Chemical Complexity on Submicrometer Sea Spray Aerosol Morphology

“…This finding supports the core–shell morphology to a limited extent; in addition to saturating the surface, organics, and specifically BCL, also accumulate in the center of the particle. Mael et al recently observed this phenomenon during water uptake experiments: neither complete phase separation nor full dissolution occurs in the case of some organics, leading to the formation of inclusions . Additionally, Huang et al observed that organic aerosols with an organic component containing an O:C ratio <0.8 exhibited phase coexistence .…”

“…Mael et al recently observed this phenomenon during water uptake experiments: neither complete phase separation nor full dissolution occurs in the case of some organics, leading to the formation of inclusions. 121 Additionally, Huang et al observed that organic aerosols with an organic component containing an O:C ratio <0.8 exhibited phase coexistence. 32 The O:C ratios of our SSA models align well with this observation (Table S3).…”

Emerging investigator series: surfactants, films, and coatings on atmospheric aerosol particles: a review

“…Advances in single particle techniques allow quantitative measurements of hygroscopic growth factors for individual aerosol particles. 240,241 Estillore et al 242 and Lee et al 243 used AFM to study water uptake on SSA particles with a core-shell morphology. They generated these particles in a wave ume with seawater collected off the coast of California, with an induced phytoplankton bloom.…”

Single-particle Raman spectroscopy for studying physical and chemical processes of atmospheric particles

“…Liang et al: Single-particle Raman spectroscopy ics, and their mixtures (Chu et al, 2015;Laskina et al, 2015;W. Wang et al, 2021;Tobon et al, 2021;Ashraf et al, 2021), as well as mineral dust (Liu et al, 2008), secondary organic aerosols (Wu et al, 2020), and atmospherically relevant biological macromolecules (Mael et al, 2021), using single-particle Raman spectroscopy. It should be noted that evaporation of some components and precipitation of some salts could occur during the RH cycling in hygroscopicity measurements (Li et al, 2017(Li et al, , 2021Cai and Zhao, 2018;Ma et al, 2019a, b;Wu et al, 2020).…”