Immersion mode heterogeneous ice nucleation by an illite rich powder representative of atmospheric mineral dust

Abstract. In many clouds, the formation of ice requires the presence of particles capable of nucleating ice. Icenucleating particles (INPs) are rare in comparison to cloud condensation nuclei. However, the fact that only a small fraction of aerosol particles can nucleate ice means that detection and quantification of INPs is challenging. This is particularly true at temperatures above about − 20 • C since the population of particles capable of serving as INPs decreases dramatically with increasing temperature. In this paper, we describe an experimental technique in which droplets of microlitre volume containing ice-nucleating material are cooled down at a controlled rate and their freezing temperatures recorded. The advantage of using large droplet volumes is that the surface area per droplet is vastly larger than in experiments focused on single aerosol particles or cloud-sized droplets. This increases the probability of observing the effect of less common, but important, high-temperature INPs and therefore allows the quantification of their ice nucleation efficiency. The potential artefacts which could influence data from this experiment, and other similar experiments, are mitigated and discussed. Experimentally determined heterogeneous ice nucleation efficiencies for K-feldspar (microcline), kaolinite, chlorite, NX-illite, Snomax ® and silver iodide are presented.

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“…Vali, 1971) and time-dependent models of varying complexity (e.g. Marcolli et al, 2007;Herbert et al, 2014;Broadley et al, 2012).…”

Section: T F Whale Et Al: Quantifying Heterogeneous Ice Nucleationmentioning

confidence: 99%

A technique for quantifying heterogeneous ice nucleation in microlitre supercooled water droplets

et al. 2015

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“…It features typical properties of desert dust common in the Southwestern USA. Broadley et al (2011) performed a X-ray diffraction analysis of ATD ("nominal 0-3 micron ATD", Powder Technology Inc., Burnsville, MN, USA) and showed that the bulk ATD material mainly consists of silicate minerals (5.6 % carbonate, 33.2 wt% feldspar, 7.5 wt% illite, 10.2 wt% illite-smectite mixed layer, 2 wt% kaolinite, 17.1 wt% quartz and 24.4 wt% other clay minerals). These minerals also include compounds like iron, calcium, magnesium, etc.…”

Section: Particle Generation and General Setupmentioning

confidence: 99%

Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles

et al. 2011

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Abstract. During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influence of various surface modifications on the ice nucleating ability of Arizona Test Dust (ATD) particles in the immersion freezing mode. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 • C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a single particle. Temperature dependent frozen fractions of these droplets were determined in a temperature range between −40 • C ≤T ≤−28 • C. The pure ATD particles nucleated ice over a broad temperature range with their freezing behavior being separated into two freezing branches characterized through different slopes in the frozen fraction vs. temperature curves. Coating the ATD particles with sulfuric acid resulted in the particles' IN potential significantly decreasing in the first freezing branch (T >−35 • C) and a slight increase in the second branch (T ≤−35 • C). The addition of water vapor after the sulfuric acid coating caused the disappearance Correspondence to: D. Niedermeier (niederm@tropos.de) of the first freezing branch and a strong reduction of the IN ability in the second freezing branch. The presence of ammonia gas during water vapor exposure had a negligible effect on the particles' IN ability compared to the effect of water vapor. Heating in the thermodenuder led to a decreased IN ability of the sulfuric acid coated particles for both branches but the additional heat did not or only slightly change the IN ability of the pure ATD and the water vapor exposed sulfuric acid coated particles. In other words, the combination of both sulfuric acid and water vapor being present is a main cause for the ice active surface features of the ATD particles being destroyed. A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates. The strongly enhanced reaction between sulfuric acid and dust in the presence of water vapor and the resulting significant reductions in IN potential are of importance for atmospheric ice cloud formation. Our findings suggest that the IN concentration can decrease by up to one order of magnitude for the conditions investigated.

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“…Mineral dusts (particularly clay minerals) have been shown to be effective ice nucleating particles (INPs) [21][22][23][24][25][26], but determining precisely how composition and mineralogy affect ice nucleation activity (INA) is still up for debate. One study [27] investigated nine abundant minerals (quartz, albite, microcline, calcite, gypsum, montmorillonite, hematite, illite, and kaolinite) commonly found in mineral dust [28] and concluded that kaolinite, illite, and hematite were the most efficient INPs in the depositional mode.…”

Section: Introductionmentioning

confidence: 99%

Compositional and Mineralogical Effects on Ice Nucleation Activity of Volcanic Ash

et al. 2018

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Volcanic ash produced during explosive eruptions may serve as ice nuclei in the atmosphere, contributing to the occurrence of volcanic lightning due to tribocharging from ice-ice or ice-ash collisions. Here, different ash samples were tested using deposition-mode and immersion-mode ice nucleation experiments. Results show that bulk composition and mineral abundance have no measurable effect on depositional freezing at the temperatures tested, as all samples have similar ice saturation ratios. In the immersion mode, there is a strong positive correlation between K 2 O content and ice nucleation site density at −25 • C and a strong negative correlation between MnO and TiO 2 content at temperatures from −35 to −30 • C. The most efficient sample in the immersion mode has the highest surface area, smallest average grain size, highest K 2 O content, and lowest MnO content. These results indicate that although ash abundance-which creates more available surface area for nucleation-has a significant effect on immersion-mode freezing, composition may also contribute. Consequently, highly explosive eruptions of compositionally evolved magmas create the necessary parameters to promote ice nucleation on grain surfaces, which permits tribocharging due to ice-ice or ice-ash collisions, and contribute to the frequent occurrence of volcanic lightning within the eruptive column and plume during these events.

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Immersion mode heterogeneous ice nucleation by an illite rich powder representative of atmospheric mineral dust

Cited by 45 publications

References 44 publications

A technique for quantifying heterogeneous ice nucleation in microlitre supercooled water droplets

A technique for quantifying heterogeneous ice nucleation in microlitre supercooled water droplets

Experimental study of the role of physicochemical surface processing on the IN ability of mineral dust particles

Compositional and Mineralogical Effects on Ice Nucleation Activity of Volcanic Ash

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