Laboratory studies of the cloud droplet activation properties and corresponding chemistry of saline playa dust

Gaston, CJ, Pratt KA, Suski KJ, May NW, Gill TE, Prather KA.  2017.  Laboratory studies of the cloud droplet activation properties and corresponding chemistry of saline playa dust. Environmental Science & Technology. 51:1348-1356.

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aerosol-particles, california, ccn activation, condensation nuclei activity, mass-spectrometer, mineral dust, nitric-acid, owens dry lake, precipitation, water-uptake


Playas emit large quantities of dust that can facilitate the activation of cloud droplets. Despite the potential importance of playa dusts for cloud formation, most climate models assume that all dust is nonhygroscopic; however, measurements are needed to clarify the role of dusts in aerosol-cloud interactions. Here, we report measurements of CCN activation from playa dusts and parameterize these results in terms of both kappa-Kohler theory and adsorption activation theory for inclusion in atmospheric models. kappa ranged from 0.002 +/- 0.001 to 0.818 +/- 0.094, whereas Frankel-Halsey-Hill (FHH) adsorption parameters of A(FHH) = 2.20 +/- 0.60 and B-FHH = 1.24 +/- 0.14 described the water uptake properties of the dusts. Measurements made using aerosol time-of flight mass spectrometry (ATOFMS) revealed the presence of halite, sodium sulfates, and sodium carbonates that were strongly correlated with kappa underscoring the role that mineralogy, including salts, plays in water uptake by dust. Predictions of kappa made using bulk chemical techniques generally showed good agreement with measured values. However, several samples were poorly predicted suggesting that chemical heterogeneities as a function of size or chemically distinct particle surfaces can determine the hygroscopicity of playa dusts. Our results further demonstrate the importance of dust in aerosol-cloud interactions.