Abstract View
Water Uptake of Alginic Acid Sodium Salt as a Proxy for Marine Hydrogels and Its Mixtures with Different Inorganic Salts
BEHNAZ ASADZADEH, Hichem Bouzidi, Jakub Ondráček, Jaroslav Schwarz, Vladimír Ždímal, ICPF of CAS, Prague, Czech Republic
Abstract Number: 226
Working Group: Aerosols, Clouds and Climate
Abstract
Sea spray aerosol (SSA) represents the largest source of natural primary aerosol with climate relevance in cloud formation. Marine hydrogel has been postulated to represent large fraction of sea spray aerosols due to their unique physicochemical and hydrological properties. Alginate is the most abundant marine biopolymer and, next to cellulose, the most abundant biopolymer in the world. Alginates (ALG) are a group of naturally occurring anionic polysaccharides derived from brown algae cell walls, and several bacteria strains. In this study we used alginic acid sodium salt (HAG) as a proxy for marine hydrogels. Hygroscopic measurements were performed for pure (HAG) aerosol particles and their mixtures with sodium chloride NaCl, ammonium sulfate (NH4)2SO4, and sodium sulfate Na2SO4 at different dry mass ratios with a hygroscopicity tandem differential mobility analyzer (H-TDMA). The Zdanovskii–Stokes–Robinson (ZSR) mixing rule is used to estimate the hygroscopic growth of internally mixtures. Pure (HAG) aerosol particles and their mixtures with (NH4)2SO4 and Na2SO4 show the obvious diameter reduction at medium RH. For all mixtures, the ZSR-calculated GFs are in relatively good agreement with the measured hygroscopic growth at high RH. Furthermore, the aerosol hygroscopicity parameter κHTDMA is derived from hygroscopic growth factor measurements at water activity (aw) = 0.9. The obtained κHTDMA of different mixtures indicates that the mixed HAG/NaCl particles have high κHTDMA at high NaCl mass fractions and can be considered as highly CCN-active compounds.