Volcanic ash ice nucleation activity is variably reduced by aging in water and sulfuric acid: the effects of leaching, dissolution, and precipitation

Fahy, William D.; Maters, Elena; Giese-Miranda, Rona; Adams, Michael P.; Jahn, Leif G.; Sullivan, R. C.; Murray, Benjamin J.

doi:10.1039/d1ea00071c

Cited by 6 publications

(10 citation statements)

References 121 publications

(262 reference statements)

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“…1. The Fuego ground PM37 sample (FUE) from Jahn et al (2019) was tested for ice nucleation activity before and after being exposed to water in a 1 wt % suspension and allowed to dry under a constant 1 Lpm flow of pre-dried lab air similarly to Fahy et al (2022b). In both cases, a 0.1 wt % suspension of unaged or aged ash was created in water (HPLC grade, Sigma) filtered through a 0.02 micrometer pore size Anatop syringe filter.…”

Section: Sample Data and Preprocessingmentioning

confidence: 99%

“…An alternative method of parametric bootstrapping for confidence intervals of IN spectra models individual droplets freezing as a Poisson point process (again the same assumption used in deriving ice active site density spectra) as shown in Vali (2019) and applied in Jahl et al (2021) and Fahy et al (2022b). In this approach, the number of droplets that freeze in each temperature interval (or equivalently, the rate of droplet freezing) is used as the mean value of a discrete Poisson distribution.…”

Section: Parametric Bootstrapping and Its Shortcomingsmentioning

confidence: 99%

“…The calculations based on the Poisson distribution (Vali, 2019;Fahy et al, 2022b;Jahl et al, 2021) have very different assumptions. Stochasticity and IN site variability are accounted for in the process of simulation from the measured IN spectrum, however this method requires coarse binning, as ideally multiple freezing events will occur within each bin.…”

Section: Parametric Bootstrapping and Its Shortcomingsmentioning

confidence: 99%

“…Figure 6a and b show the ratio and difference between the IN spectra of water aged volcanic ash and unaged volcanic ash with confidence intervals. Suspension of minerals and volcanic ash in water can cause alteration of the ice-active surface sites due to a variety of geochemical processes as shown in recent literature (Harrison et al, 2019;Jahn et al, 2019;Kumar et al, 2019;Maters et al, 2020;Perkins et al, 2020;Fahy et al, 2022b). Based on the confidence bands of either metric, it can easily be seen that below approximately −12 • C, there is a statistically significant difference between the IN activity of the aged ash and unaged ash with p < 0.05, confirming that in this experiment there is an alteration of the IN activity of volcanic ash due to suspension in water.…”

Section: Calculating Confidence Bands For Difference Spectramentioning

confidence: 99%

“…In other cases, authors have used a model of ice nucleation to simulate their experiments and use that simulated distribution to estimate the uncertainty present in their experiment. In simpler models, droplet freezing is modeled as a Poisson point process (Vali, 2019;Jahl et al, 2021;Fahy et al, 2022b). In more sophisticated models, random variables such as the number of sites, mass of material, and temperature variations are parameterized to run completely new simulated experiments (Wright and Petters, 2013;Harrison et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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A universally applicable method of calculating confidence bands for ice nucleation spectra derived from droplet freezing experiments

2022

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Abstract. A suite of generally applicable statistical methods based on empirical bootstrapping is presented for calculating uncertainty and testing the significance of quantitative differences in temperature and/or ice active site densities between ice nucleation temperature spectra derived from droplet freezing experiments. Such experiments are widely used to determine the heterogeneous ice nucleation properties and ice nucleation particle concentration spectra of different particle samples, as well as in studies of homogeneous freezing. Our methods avoid most of the assumptions and approximations inherent to existing approaches, and when sufficiently large sample sizes are used (approximately >150 droplets and >=1000 bootstrap samples in our system), can capture the full range of random variability and error in ice nucleation spectra. Applications include calculation of accurate confidence intervals and confidence bands, quantitative statistical testing of differences between observed freezing spectra, accurate subtraction of the background filtered water freezing signal, and calculation of a range of statistical parameters using data from a single droplet array freezing experiment if necessary. By providing additional statistical tools to the community, this work will improve the quality and accuracy of statistical tests and representations of uncertainty in future ice nucleation research, and will allow quantitative comparisons of the ice nucleation ability of different particles and surfaces.

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Section: Sample Data and Preprocessingmentioning

confidence: 99%

Section: Parametric Bootstrapping and Its Shortcomingsmentioning

confidence: 99%

Section: Parametric Bootstrapping and Its Shortcomingsmentioning

confidence: 99%

Section: Calculating Confidence Bands For Difference Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A universally applicable method of calculating confidence bands for ice nucleation spectra derived from droplet freezing experiments

2022

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The ice-nucleating activity of African mineral dust in the Caribbean boundary layer

et al. 2022

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Abstract. African mineral dust is transported many thousands of kilometres from its source regions, and, because of its ability to nucleate ice, it plays a major role in cloud glaciation around the globe. The ice-nucleating activity of desert dust is influenced by its mineralogy, which varies substantially between source regions and across particle sizes. However, in models it is often assumed that the activity (expressed as active sites per unit surface area as a function of temperature) of atmospheric mineral dust is the same everywhere on the globe. Here, we find that the ice-nucleating activity of African desert dust sampled in the summertime marine boundary layer of Barbados (July and August 2017) is substantially lower than parameterizations based on soil from specific locations in the Sahara or dust sedimented from dust storms. We conclude that the activity of dust in Barbados' boundary layer is primarily defined by the low K-feldspar content of the dust, which is around 1 %. We propose that the dust we sampled in the Caribbean was from a region in western Africa (in and around the Sahel in Mauritania and Mali), which has a much lower feldspar content than other African sources across the Sahara and Sahel.

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The importance of acid-processed meteoric smoke relative to meteoric fragments for crystal nucleation in polar stratospheric clouds

et al. 2023

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Abstract. The crystal formation of nitric acid trihydrate (NAT) in the absence of water ice is important for a subset of polar stratospheric clouds (PSCs) and thereby ozone depletion. It has been suggested that either fragmented meteoroids or meteoric smoke particles (MSPs), or possibly both, are important as heterogeneous nuclei of these crystals. Previous work has focused on the nucleating ability of meteoric material in nitric acid in the absence of sulfuric acid. However, it is known that when immersed in stratospheric sulfuric acid droplets, metal-containing meteoric material particles partially dissolve and components can reprecipitate as silica and alumina that have different morphologies to the original meteoric material. Hence, in this study, we experimentally and theoretically explore the relative role that sulfuric acid-processed MSPs and meteoric fragments may play in NAT nucleation in PSCs. We compared meteoric fragments that had recently been prepared (by milling a meteorite sample) to a sample annealed under conditions designed to simulate heating during entry into the Earth's atmosphere. Whilst the addition of sulfuric acid decreased the nucleating ability of the recently milled meteoric material relative to nucleation in binary nitric acid-water solutions (at similar NAT saturation ratio), the annealed meteoric fragments nucleated NAT with a similar effectiveness in both solutions. However, combining our results with measured fluxes of meteoric material to the Earth, sedimentation modelling and recent experiments on fragmentation of incoming meteoroids suggests that it is unlikely for there to be sufficient fragments to contribute to the nucleation of crystalline NAT particles. We then considered silica formed from sulfuric acid-processed MSPs. Our previous work showed that nanoparticulate silica (radius ∼6 nm) is a relatively poor promoter of nucleation compared with micron-scaled silica particles, which were more effective. Both materials have similar chemical and structural (crystallographically amorphous) properties, indicating that size is critical. Here, we account for surface curvature of primary grains using the Classical Nucleation Theory (CNT) to explore this size dependence. This model is able to explain the discrepancy in nucleation effectiveness of fumed silica and fused quartz by treating their nucleating activity (contact angle) as equal but with differing particle size (or surface curvature), assuming interfacial energies that are physically reasonable. Here, we use this CNT model to present evidence that nucleation of NAT on acid-processed MSPs, where the primary grain size is tens of nanometres, is also effective enough to contribute to NAT crystals in early season PSCs where there is an absence of ice. This study demonstrates that the modelling of crystal nucleation in PSCs and resulting ozone depletion relies on an accurate understanding of the transport and chemical processing of MSPs. This will affect estimated sensitivity of stratospheric chemistry to rare events such as large volcanic eruptions and long-term forecasting of ozone recovery in a changing climate.

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Volcanic ash ice nucleation activity is variably reduced by aging in water and sulfuric acid: the effects of leaching, dissolution, and precipitation

Abstract: Volcanic ash nucleates ice when immersed in supercooled water droplets, giving it the potential to influence weather and climate from local to global scales. This ice nucleation activity (INA) is...

Cited by 6 publications

References 121 publications

A universally applicable method of calculating confidence bands for ice nucleation spectra derived from droplet freezing experiments

A universally applicable method of calculating confidence bands for ice nucleation spectra derived from droplet freezing experiments

The ice-nucleating activity of African mineral dust in the Caribbean boundary layer

The importance of acid-processed meteoric smoke relative to meteoric fragments for crystal nucleation in polar stratospheric clouds

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