Direct observation of completely processed calcium carbonate dust particles

Abstract

This study presents, for the first time, field evidence of complete, irreversible processing of solid calcium carbonate (calcite)-containing particles and quantitative formation of liquid calcium nitrate particles apparently as a result of heterogeneous reaction of calcium carbonate-containing mineral dust particles with gaseous nitric acid. Formation of nitrates from individual calcite and sea salt particles was followed as a function of time in aerosol samples collected at Shoresh, Israel. Morphology and compositional changes of individual particles were observed using conventional scanning electron microscopy with energy dispersive analysis of X-rays (SEM/EDX) and computer controlled SEM/EDX. Environmental scanning electron microscopy (ESEM) was utilized to determine and demonstrate the hygroscopic behavior of calcium nitrate particles found in some of the samples. Calcium nitrate particles are exceptionally hygroscopic and deliquesce even at very low relative humidity (RH) of 9-11% which is lower than typical atmospheric environments. Transformation of non-hygroscopic dry mineral dust particles into hygroscopic wet aerosol may have substantial impacts on light scattering properties, the ability to modify clouds and heterogeneous chemistry.

Interactions of Water with Mineral Dust Aerosol: Water Adsorption, Hygroscopicity, Cloud Condensation, and Ice Nucleation

“…273 As shown in Figure 5, surface adsorbed water has two distinctive 407 IR absorption peaks in the region extending from 1500 to 4000 cm -1 , one near 3400 cm -1 Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). Two years later the atmospheric 433 significance of this finding was supported by a field study, 245 which showed that dust particles 434 collected in Israel have been substantially processed in the atmosphere and could exist in aqueous 435 state even at very low RH (9-11%). Transmission Electron Microscopy can also be used to monitor 436 the morphology change of mineral dust particles.…”

“…Kanazawa, Japan Some Ca-rich particles contain substantial amount of chloride, and they existed in an amorphous state and were nearly spherical even under high vacuum. Laskin et al 245 collected mineral dust particles at Shoresh, Israel, and analyzed the morphology 1845 and composition of individual dust particles using scanning electron microscopy with energy 1846 dispersive analysis of X-ray (SEM-EDX). For the first time, they 245 provided field evidence that 1847 due to heterogeneous reactions with HNO3, solid nonspherical calcium carbonate particles were 1848 converted to spherical liquid droplets which contain Ca(NO3)2.…”

“…For example, atmospheric mineral dust is often associate with surface coatings due to 310 heterogeneous reactions with reactive trace gases, 158,161,202,245 but laboratory studies most often 311 consider unprocessed particles which may be only representative of mineral dust particles freshly 312 emitted into the troposphere. 313 314 Recent studies have shown that mineral dust particles generated by these two methods can have 328 distinctive hygroscopicity and CCN activities, 49,217,262,263 with wet-generated aerosol particles 329 having higher hygroscopicity and CCN activities.…”

Morphological and chemical modification of mineral dust: Observational insight into the heterogeneous uptake of acidic gases

“…[19] More recently, Laskin et al [2005b] found significant number of large droplets in-situ on the mountain site (Shoresh) in Israel. They also concluded that such droplets form when Ca-carbonate particles react with HNO 3 in the atmosphere.…”

Generation of Internally Mixed Insoluble and Soluble Aerosol Particles to Investigate the Impact of Atmospheric Aging and Heterogeneous Processing on the CCN Activity of Mineral Dust Aerosol

“…914 915 The carbonate component of mineral dust (calcite, CaCO 3 , and dolomite, CaMg(CO 3 ) 2 ) has been shown to be particularly reactive with trace atmospheric gases such as HNO 3 and N 2 O 5 (Krueger et al 2003;Mogili et al 2006). Single particle analysis measurements have shown that carbonates can be completely converted to nitrates in the atmosphere (Laskin et al 2005;Matsuki et al 2005). Consequently, it is expected that in the atmosphere freshly emitted, partially processed, and fully reacted CaCO 3 will be present.…”