the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Jan 2024
Revolutionizing Hailstone Analysis: Exploring Non-Soluble Particles through Innovative Confocal Laser and Scanning Electron Microscopy Techniques
Abstract. This paper introduces an innovative microscopy analysis methodology to preserve in situ non-soluble particles within hailstones using a protective porous plastic coating, overcoming previous limitations related to melting the hailstone sample. The method is composed of two techniques: trapping non-soluble particles beneath a plastic coat by using the adapted sublimation technique and then analyzing the particles individually with both Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy with Energy-Dispersive Spectroscopy (SEM-EDS). CLSM provides insights into physical attributes like particle size and surface topography, enhancing understanding of ice nucleation. SEM-EDS complements CLSM by offering detailed information on individual particle elemental chemistry, enabling classification based on composition. Strategies to reduce background noise from glass substrates during EDS spectral analysis are proposed. By combining powerful, high resolution microscopy techniques, this methodology provides valuable data on hailstone composition and properties. This information can give insights into hail developmental processes by enhancing our understanding of the role of atmospheric particles.
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RC1: 'Comment on egusphere-2023-2971', Anonymous Referee #1, 02 Feb 2024
General comments: This manuscript by Bernal Ayala et al. has developed a method to analyze hailstone using CLSM and SEM. It would be interesting to understand the particles mixed with hailstones to interpret their formation processes. They described their method in detail, but I have comments to clarify the study.
Major comments:
1. Although they focus on insoluble particles, as indicated in the title, I believe the authors measured sea salt, soluble particles. The composition shown in Figure 7 shows a strong presence of Na and Cl. The result may indicate that they measured crystallized particles that were once soluble in the hailstones or their precursors. I believe that the result is still good, but some discussion needs to be clarified including the title.
2. I think Figure 9 is the most important result in this study, but they simply classify the particles into three categories: C-, Cl-, and Si-based. I suggest they discuss their particle categories more. I assume they are carbonaceous, sea salt, and dust particles. With particle shape analysis and more detailed compositional analyses, it would be possible to identify them. At least for simple classifications such as those in Fig. 9, there is no need to discuss SEM-EDS conditions, but a rough qualitative measurement can classify them.
3. In the later discussion, there is very limited discussion of the results from the CLSM. I suggest more discussion using the results.
4. Although the authors have many discussions about the influence of glass plates, I suggest using a metal plate or a substrate consisting of single elements (e.g., Cu, Al, and C). A glass plate contains so many elements that it interferes with the particle composition. By using other substrates, you will reduce such interferences.
5. Did formvar coatings also contribute to the C signal? If so, C-based particles may need to be reconsidered.
6. In the conclusion section, I do not think it is good to introduce other techniques such as Raman spectroscopy and STXM. They could be placed in the recommendation or other sections.
7. Could biological particles be identified by SEM using their specific morphology and composition, such as a tracer of P, S, and Cl?Specific comments:
1. Line 80: "Energy dispersive spectroscopy" should read "Energy dispersive X-ray spectroscopy".
2. Line 83: SEM works by scanning a focused beam of electrons.
3. Line 108: I think a sublimation point depends on both humidity and temperature, whereas a melting point depends only on temperature.
4. Line 170: I was not sure if sublimation in dry air can occur with silica gel. Although it can be determined by a detailed calculation, I think silica gel may not achieve the low humidity needed for sublimation. I am not sure about the current conditions, but it is better to check.
5. Line 197-200: Although a high vacuum SEM has a better SEM image than a low vacuum SEM, a low vacuum SEM has sufficient EDS capability for the purpose used in this study.
6. Line 204: Is "sigma" OK?
7. Line 208-209: A high voltage does not always improve the spatial resolution of SEM images due to its expansion in the materials. Please check again.
8. Line 214: I believe that a working distance does not affect the beam diameter. Please check it.
9. Line 225: A 15 kV can measure higher than Fe. Please check it.
10. Line 237: There is no Figure 7D.
11. Line 239: I agree. Please see my major comment 7.
12. Line 258-260: If the particles have been classified according to these criteria, there is no need to use the cluster analysis (line 253-257).
13. Line 275: Is it true that CCSEM can load samples automatically?
14. Line 276-277. I do not believe that CCSEM can measure thousands of particle compositions in less than an hour. EDS needs an acquisition time of at least several seconds.
15. Line 280: There is no section 2.4.2.
16. Line 285-288. I do not think changing the acceleration voltage is effective. First, when using low voltage first, you will not see heavy elements. Second, it is very time-consuming, as suggested in line 278.
17. Figure 7. There is a missing peak identification around 2.1 keV. Why is this?
18. Figure 9. I cannot see the right images. Are they from Figure 6?Citation: https://doi.org/10.5194/egusphere-2023-2971-RC1 - AC1: 'Reply on RC1', Anthony Crespo Bernal Ayala, 21 Feb 2024
- AC2: 'Reply on RC1', Anthony Crespo Bernal Ayala, 21 Feb 2024
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RC2: 'Comment on egusphere-2023-2971', Anonymous Referee #2, 28 Mar 2024
The manuscript, "Revolutionizing Hailstone Analysis: Exploring Non-Soluble Particles through Innovative Confocal Laser and Scanning Electron Microscopy Techniques," is an account of investigating hailstones by applying multiple analytical techniques and employing a special FORMVAR coating procedure to preserve the spatial distribution of particles captured within hailstone thin sections. While the manuscript makes several interesting points it suffers from some significant shortcomings. The most concerning of these in my opinion is that the manuscript really focuses on findings from what appears to be one thin section of one hailstone. It is very unclear how representative the results are and moreover, if the focus is more to present the methodology, they to not inspire belief that these types of experiments would be easy and straightforward to reproduce in a manner that would lead to statistically significant data.
Several areas for improvement are:
1. The hailstone preparation and sublimation method could benefit from a better descriptive illustration/figure. The utilization of FORMVAR seems to be a legacy technique that it is not common so that readers might have intuition about how it works.
2. Links between particles and nucleating particles are quite tenuous. There are many particles in the analyzed sample and it appears impossible to deconvolute what was there when the ice began to form, versus what was accumulated during transport in the cloud etc.
3. Figure 9 appears to be the most interesting result, but is difficult to interpret and the photographs that are included are extremely small.
4. Given the lack of duplicates etc. (see comment above) it is very hard to assess the utility of all of the effort that went into this analysis. If one were to take a second thin section of the same stone and repeat the analysis, would we get wildly different results, or similar? What do we learn in either case? What about with another stone from the same storm? Is it even practical to do this work on many stones?
5. The CLSM work that lays the foundation for SEM analysis appears to resolve particles down to 1 micron. This is still quite a large size, and many particles will be much smaller than this. Even ice nucleation parameterizations are largely based on particles with sizes greater than 0.5 microns. Many such particles missed here.
My overall reaction to the submitted manuscript is that in its current form the work falls short of a new atmospheric measurement technique, or some protocol that could be widely adopted. Rather it is a report on the application of several analytical methods to a single hailstone (or single thin section from a single hailstone) from a unique event. The authors mix cases and do at times refer to the plural "hailstones". If they have more data, I would encourage them to complement the manuscript to find more general conclusions. Without this I do not see the extension to the interests of a general readership. That said, I do complement the authors on the incorporation of citizen science.
Citation: https://doi.org/10.5194/egusphere-2023-2971-RC2
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