Hygroscopicity and Ice Nucleation Properties of Dust/Salt Mixture Originated from the Source of East Asian Dust Storm

<p>Dust storms are common meteorological disasters which occur frequently in the late spring and early summer in arid and semi-arid areas. Deserts in North Africa, Middle East Asia, Western Australia and Western North America are the most important dust-prone areas in the world. Along with the dust storm, salt components originated from inland saline lake and playas are often mixed with dust and transported to long distances. Dust/salt mixtures from the source of East Asian Dust Storm have great impacts on atmospheric chemistry processes and climate system due to their high hygroscopicity and efficient ice nucleation ability.</p><p>&#160;</p><p>In this study, dust/salt mixture samples are collected from important sources of East Asian Dust Storm, i.e., Badain Jaran Desert, Tengger Desert and Ulan Buh Desert in northwestern China. Ion chromatography (IC) measurements were performed to determine the concentrations of cations (Na⁺, K⁺, Mg²⁺, Ca²⁺, and NH₄⁺) and anions (Cl^&#8722;, SO₄^2&#8722;, NO₃^&#8722;, NO₂^&#8722;, and F^&#8722;). Synchrotron-based scanning transmission X-ray microscopy (STXM) was carried out to show the morphology and chemical mapping of typical dust/salt particles. Hygroscopic properties of the samples are measured by a vapor sorption analyzer, and a thermodynamic model is used to predict the deliquescence relative humidity (DRH) based on chemical composition of the samples. To further understand the linkages between the physiochemical properties and the origins/types of the samples, we performed positive matrix factorization (PMF) receptor model to analyze the results of the IC and the DRH results. In addition, the ice nucleation abilities were conducted with the portable ice nucleation chamber II (PINCii), where both homogeneous freezing and deposition nucleation were observed on the dust/particle aerosol particles/droplets.</p>