the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 May 2025
Developing A Custom-Built Metal Cloud Chamber: Analysis of Aerosol Coagulation at Low Humidities
Abstract. We are developing an intermediate size (906 L) cloud chamber, and this paper reports on the design and initial characterization of dry aerosol experiments. Specifically, we are determining wall-loss and coagulation correction factors using the observed size distribution measurements for surrogates of common aerosol classes: sodium chloride, sucrose, and soot. Results show that, on average, sodium chloride, sucrose, and soot wall-loss rates converge to similar values on relatively short time scales (<1 hour). The fitted coagulation correction factor, Wc-1, for soot particles (1.23 ± 0.312), indicates they adhere to each other more than sodium chloride (0.969 ± 0.524) and sucrose (1.16 ± 1.38). This study lays the foundation for future experiments at elevated humidity and supersaturation conditions to characterize the influence of particle shape on coagulation and cloud parameters.
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Status: open (until 11 Jul 2025)
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RC1: 'Comment on egusphere-2025-1503', Anonymous Referee #1, 08 Jun 2025
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Franco et al. designed and developed a cloud chamber at LANL and characterized the wall loss and coagulation correction factors of sodium chloride, sucrose, and soot. Their results show similar wall loss across all particle types, while the coagulation correction factor of soot is higher than others. This manuscript is overall well written and provides many useful information for chamber design, making it good fit for AMT journal. However, before the publication, I would like the authors to address the following issues.
1. For soot experiments, the authors generated them from biomass combustion, which produces complex emissions of both gas and particles. How do the authors ensure that only soot particles were injected into the LANL chamber? For example, biomass combustion emits abundant SOA, how might these SOA contribute to or interfere with soot growth in the chamber? Additionally, VOCs and SVOCs can also play a role in particle growth, thus change particle size. How do authors account for the influence of these gas species on the observed soot behavior in the authors’ soot experiments?
2. The manuscript presents particle number size distributions, but volume distributions are not discussed. Could the authors provide and discuss volume distribution? For example, have the dilution and wall loss corrections been validated using measured volume distributions, by quantifying the volume fraction of particles lost due to these processes?
3. Since no size selection was applied before aerosol injected into the chamber, how do the authors expect larger particles (e.g. PM>1) to influence coagulation and wall loss behavior of submicron particles? Also, would it be possible for the authors to size-select particles to a specific mode prior to chamber injections to compare the size mode at the chamber outlet? Such an approach could help elucidate the role of coagulation in shifting size distributions.
Citation: https://doi.org/10.5194/egusphere-2025-1503-RC1
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