the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Nov 2024
Physical-chemical properties of particles in hailstones from Central Argentina
Abstract. This study presents a novel analysis of two hailstones collected in central Argentina to provide insights into the size distribution, composition, and potential sources of non-soluble particles within hailstones. Using this new method, non-soluble particles are trapped beneath a thin layer of polyvinyl resin and analyzed with Confocal Laser and Scanning Electron Microscopy combined with Energy-Dispersive Spectroscopy, preserving their in-situ location and physical characteristics. The study characterized these particles' distribution, shape, and size and identified their elemental composition, which is used to interpret possible source regions. Particles ranged in diameter from 1.2 to 256.0 microns, with the largest found in hailstone embryos. Agglomerated mineral and organic particles dominated the elemental composition, followed by organics and quartz, and were present throughout the hailstones. Agglomerated salt particles detected in one sample were traced to a nearby salt lake, while copper chloride and zinc chloride particles found in the second sample were potentially associated with agrochemicals commonly used for pest control and fertilizer, including in Argentina. Various local and regional land-use types, including shrublands, mixed vegetation, croplands, and urban areas, were linked to specific types of particles. This study, therefore, highlights the regional influence of various land use types on hail formation and growth, pointing to the potential impacts of natural and anthropogenic factors on hailstone composition.
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RC1: 'Comment on egusphere-2024-3215', Anonymous Referee #1, 02 Dec 2024
Overview:
In this manuscript the authors describe the particles associated with 2 hail particles using confocal microscopy for imaging and SEM for imaging along with EDS in the SEM for elemental analysis. The technique used to collect and preserve the particles specially was thought out but has some significant issues when trying to quantify the results with a thick layer of polymer and then coated with gold. Drawing a lot of the conclusions from small number of particles is difficult. Cut multiple layers to get more statistics on the exterior particles. There is a lot of potentially interesting data, but needs to be analyzed better/concisely. The major conclusion seems to be that the embryo is not different than the outer shell particles? Also the particles in each are similar? This needs to be shown better by the results that are to spread out. Analysis is concerning about the points the paper tries to make from very few number of particles. The EDS assumptions as described below have some issues that would cause erroneous results. Overall I think there is definitely some interesting data here that needs further analysis and writeup to be more convincing. I would suggest to possibly reconsider this paper with very major changes and revisions.
General Comments:
The term ‘non-soluble’ is used throughout. This would be true when they talk about melted samples that are analyze whereas here the ice is sublimed and that would leave soluble particles as well as insoluble particles.
Better comparison of core vs. shell. This gets lost with some of the singling out of smaller regions (e.g. Figure 6 could be embryo vs. outer shell to get better statistics) otherwise just noise that you cannot make conclusions from.
Need to include SEM imagery of particle. Talked about aggregated particles a bit with no supporting images. You should be able to get better size information than with confocal.
There needs to be the EDS shown in reference to particles. This could be some nice supplementary information. Additionally please show example EDS spectra for each particle type.
EDS issues are mentioned, but subsequently ignored especially in relationship to carbon and oxygen going through 10-20nm of Au and 1micron plus of formvar. See simple Montecarlo simulation at 15 kV below for EDS and imaging issues with some conclusions using this approach. 10 nm Au, 1um Formvar, 10 micron sample (used CaCO3), substrate
Specific Comments:
41: melting only looks at non-soluble particles, it removes soluble particles
89: How collected and transported?
95: how close to the center? How did you know it was the embryo and directly grown from that point?
104-108: Figures 2 and 3 are very confusing with different ways of designating the core/shell and how the sample is analyze. It would be helpful to keep these consistent (with the S# I was trying to find the supplemental information) and also show how they are related to each other distance wise since it is unclear in the figure. It would be great to stitch the entire confocal images together of the entire sample and maybe put that in supplemental information and pull images from that for the main document.
131: Single point EDS is not sufficient to get particles information about micron size particles, it would be better to average over most of the particle area to get an overall particle idea if they are agglomorates.
136: “unique feature… particles with location” This needs to be more pronounced in the paper. You have some size information and it would be good to talk about size and composition versus distance from the embryo on the paper
146: Deconvolution will not be good especially for carbon and provide very unreliable results since you don’t know exact thickness of formvar, Au, or particle. Plus heterogeneity will cause issues. Carbon coating would be better than Au to have less overlap of peaks and absorption of signal.
153-157: Extraneous, you are doing the analysis not the instrument and need to ID them and understand not say what the problems are of possibilities.
158: ‘activation’ should be ‘interaction’
160: ‘we did not place high confidence’ – just say what you did.
207: 1.9 um – is this area equivalent diameter? You did EDS on these particles, can you measure more accurately? It is concerning with a thickness of 1micron+ of formvar getting much BSE signal out of the sample (see a Montecarlo simulation).
211: Hard to make argument of size since the embryo particles are only analyzing 22 particles and the particles in the shell are mostly similarly sized. Larger ones could have just been cut down or missed easily
215/Figure 5: 15 different classifications for only small number of particles makes this not significantly relevant. Cut down on the number of classifications since there are multiples with 0%
219: range from 2-75 microns. This is a few particles, the range is basically meaningless since you are basically saying it is the few particle analyzed.
220: ‘Agglomorated salts’ these are soluble particles. Make sure to change around the solubility
223: BSE imagery did not show cubic crystal – please show some SEM images of these? This could be from a brine solution that sublimed and did not form a nice single cubic particle.
228: Cl could be problematic since you see a lot of NaCl above that is not crystalline single particles.
245: ‘no detectable carbon’ there is a 1um layer of formvar. No way you can say there is no carbon present.
293: 35+/-34 microns is not anything useful. Maybe range is, but hard to make conclusions like this with such a small data set.
346: ‘size, composition, and distribution’ it would be great to actually compare all of these. They are spread out and composition vs. size is not shown.
354: ‘carbon (76%) and oxygen (22%)’ – there is a 100 micron layer of C/O on top of this. It is impossible to try and quantify the C:O ratios of this with how the procedure was performed.
357-58: ‘particle agglomeration played a significant role’ – please show imagery of particles. You mention lots of morphology throughout the paper, but there are no SEM images of the particles to show any of these conclusions.
375: the Cu/Cl can just be agglomorates, hard to tell without higher resolution data.
Citation: https://doi.org/10.5194/egusphere-2024-3215-RC1 -
RC2: 'Comment on egusphere-2024-3215', Anonymous Referee #2, 13 Jan 2025
This paper by Bernal et al., provides a comprehensive analysis of non-soluble particles trapped within hailstones collected in Central Argentina, offering novel insights into their physical and chemical properties, sources, and implications for hail formation processes. By employing innovative methodologies such as Confocal Laser and Scanning Electron Microscopy combined with Energy-Dispersive Spectroscopy, the authors effectively preserved and analyzed the in-situ characteristics of particles, marking a significant advancement over traditional methods. The study is well-grounded in its regional focus, exploring the link between local land-use types and particle sources, while also addressing broader implications for understanding hail formation under varying storm modes. The manuscript is technically robust, methodologically detailed, and contributes valuable findings to the fields of atmospheric science and aerosol research. However, to maximize the study’s impact, the manuscript would benefit from a more concise presentation of results, a clearer articulation of its global relevance, and streamlined technical details to enhance accessibility for a broader audience. Overall, the study makes a substantial contribution to the understanding of hail microphysics and its environmental drivers, warranting publication with minor revisions.
Here are my suggestions for improvement:
Suggestions for Improvement:
1. Highlight the broader significance of understanding hail microphysics in the context of extreme weather forecasting, climate modeling, and hydrological cycles. This will help position the study as not just regionally significant but also globally relevant.
2. Ensure consistent usage of terminology, particularly between "non-soluble particles" and "insoluble particles," to avoid confusion.
3. Provide a rationale for the selection of key parameters, such as the particle size threshold (e.g., 1 µm) and the use of specific coating materials (gold and gold-palladium). This would help readers understand how these choices were optimized for the study.
4. Include scale bars on Figures 2 and 3 to provide accurate spatial context for the microscopy images. Ensure the scale bars are consistent with the magnifications used and are clearly visible.
5. Present the data in Figures 4 and 8 using dN/dlogDp plots to normalize and log-scale particle size data. This will provide a clearer and more accurate representation of modal size ranges and size distributions.
6. Increase the size of Figure 7a to make the axes and findings more legible. Additionally, enlarge the font size in Figure 7c to improve readability.
7. Include a brief discussion of the study’s limitations, such as particle size detection thresholds and uncertainties in EDS composition analysis. Suggest directions for future research, such as using complementary techniques to confirm findings or expanding the geographical scope of the study.Citation: https://doi.org/10.5194/egusphere-2024-3215-RC2
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