the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Feb 2026
Critical Role of Dust Induced Electrostatic Coagulation in the Evolution of Aerosol Size Distributions in the Atmosphere
Abstract. Coagulation modifies the particle size distributions (PSD) of atmospheric aerosols, affecting their optical properties, cloud droplet activation, and gravitational deposition. While Coulomb forces may impact coagulation processes between charged aerosols, such as dust, most coagulation models neglect the effects of aerosol charge. Here, we address the lack of single-particle charge measurements for dust aerosols by developing a method to retrieve their joint size-charge distributions. By incorporating aerosol charge into the coagulation kernel, simulations in a dust-only scenario at typical environmental concentrations show that, on hourly timescales, electrostatic force leads to a reduction of up to ~64 % in number concentration relative to Brownian coagulation. Moreover, electrostatic coagulation between dust and ambient sub-500 nm aerosols modifies the latter's PSD by ~10 % compared with Brownian coagulation. These results strongly suggest that electrostatic coagulation should be considered in air quality models.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1248 KB) - Metadata XML
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Supplement
(1794 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2026-486', Anonymous Referee #1, 23 Feb 2026
- AC2: 'Response to Reviewer 1's comments', Xiaofei Wang, 03 May 2026
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RC2: 'Comment on egusphere-2026-486', Anonymous Referee #2, 28 Feb 2026
This manuscript highlights the important role of electrostatic interactions in aerosol coagulation and their impact on the resulting PSD evolution. The study uses DMA–APS measurements to obtain joint size–charge distributions of aerosols, enabling characterization of single-particle charge properties. Based on this information, the authors combine coagulation modeling with numerical simulations, demonstrating a significant role of highly charged aerosols in the coagulation process. These results help improve understanding of atmospheric aerosol microphysical processes. Overall, the experimental design and modeling framework are generally reasonable; however, several key methodological aspects—such as size conversion, charge data processing, and model parameter assumptions—require further clarification to improve the transparency and reproducibility of the study. In addition, the applicability of some results should be more clearly defined.
- The manuscript assumes a dynamic shape factor of χ=1 in the conversion from aerodynamic diameter to electrical mobility diameter. Since mineral dust aerosols are typically irregular in shape, this assumption may introduce a systematic shift in the mapped diameter and therefore alter aerosolbin assignment in the joint size–charge distribution. Given that the reported electrostatic enhancement depends on this joint distribution, please clarify how adopting representative χ values for mineral dust (χ>1) would shift the size range associated with highly charged aerosols, and whether such shifts could affect the qualitative conclusions regarding PSD evolution. Clarifying this point would help readers assess the sensitivity of the results to aerosol morphology assumptions.
- The manuscript uses linear interpolation along the charge axis to fill missing charge-bin concentrations. Since the high-charge tail is inherently sparsely populated, this region is typically sensitive to data-processing methods. When linear interpolation is applied, high-charge bins that would otherwise be zero or undetectable may be assigned non-zero concentrations, thereby artificially smoothing and elevating the tail of the distribution. Given that the reported electrostatic enhancement depends on the fraction and distribution of highly charged aerosols, this treatment may affect the fraction of highly charged aerosols and consequently influence the related analysis results. The authors are therefore encouraged to clarify the robustness of this interpolation step for subsequent analysis results.
- In the mixed-system simulations, the inclusion of electrostatic interactions leads to an approximately 10% difference in the peak ambient sub-500 nm aerosol number concentration compared with simulations without electrostatic effects. The authors are encouraged to clarify in the Results and Discussion section of the manuscript the significance of this difference for the evaluation of environmental impacts such as radiative forcing and CCN number concentration, and whether it should be highlighted in the discussion of the results or regarded as only a secondary effect within the model. Providing such clarification would help readers better understand the implications of this difference for atmospheric applications.
- The study adopts a closed-box framework, in which no new aerosol input is considered. Under this assumption, aerosolcharges gradually neutralize and decay through coagulation. However, during real atmospheric transport, dust plumes may continuously introduce newly emitted or mixed-in aerosols that can retain relatively high initial charge. Given that the reported electrostatic enhancement depends on the presence of highly charged aerosols, the authors are encouraged to clarify whether such continuous input of highly charged aerosols could delay charge decay and sustain stronger electrostatic coagulation, thereby affecting the reported PSD evolution.
- In Fig. 3, the caption refers to aerodynamic diameter, whereas the main text indicates that aerosol sizes were converted to mobility diameter. To avoid potential confusion, the authors are encouraged to clarify in the caption which diameter is shown on the x-axis and to ensure consistent terminology between the text and the figure.
Citation: https://doi.org/10.5194/egusphere-2026-486-RC2 - AC3: 'Response to Reviewer 2's comments', Xiaofei Wang, 03 May 2026
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AC1: 'Comment on egusphere-2026-486', Xiaofei Wang, 03 May 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-486/egusphere-2026-486-AC1-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2026-486', Anonymous Referee #1, 23 Feb 2026
This paper aims to address a critical gap in atmospheric aerosol modeling by investigating how electrostatic forces influence coagulation processes of dust particles. The authors applied DMA-APS to retrieve joint size-charge distributions of dust aerosols, which can potentially overcome the lack of single-particle charge measurements. By incorporating aerosol charge into the coagulation kernel, their simulations reveal significant electrostatic effects on particle size distribution. Although the topic of paper is interesting, I have doubts on the methodology used in this work, which need to be cleared before a second round of review.
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- The first critical point is the inherent limitations of the DMA-APS setup. The DMA can only select a finite range of particle mobilities, which makes it impossible to select particles with large sizes and only a few charges, as they their mobility is below the selection limit of the DMA. Therefore, the charge measurements are biased towards higher charge state. Such bias challenges the validity of the measurements and must be addressed in the revision.
- For quantitative assessment of the previous point, please add particle size to Table S2 assuming the particle only carries 1 charge. Also, please add the information of DMA sheath flow rate.
- The second critical point is that dust particles produced by the dust aerosol generators are representative only of the freshly produced dust particles. After some time in the atmospheres, I would expect their charge state are significantly reduced (as shown in the simulations). Please make this point very clear in the manuscript.
- Is mass conservation checked for the simulation model? It seems that the product particle is put into a single bin rather than distributed between neighboring bins, which is common practice in aerosol simulations with the sectional method (the distribution method is well documented in the literature).
- Please elaborate on the method to compile figure 3 from DMA-APS measurements. My understanding is that each DMA-APS measurement at a fixed DMA voltage provide an oblique line in the mobility diameter-charge space, how are the raw data inverted to give dN/dlogdp?
Citation: https://doi.org/10.5194/egusphere-2026-486-RC1 - AC2: 'Response to Reviewer 1's comments', Xiaofei Wang, 03 May 2026
-
RC2: 'Comment on egusphere-2026-486', Anonymous Referee #2, 28 Feb 2026
This manuscript highlights the important role of electrostatic interactions in aerosol coagulation and their impact on the resulting PSD evolution. The study uses DMA–APS measurements to obtain joint size–charge distributions of aerosols, enabling characterization of single-particle charge properties. Based on this information, the authors combine coagulation modeling with numerical simulations, demonstrating a significant role of highly charged aerosols in the coagulation process. These results help improve understanding of atmospheric aerosol microphysical processes. Overall, the experimental design and modeling framework are generally reasonable; however, several key methodological aspects—such as size conversion, charge data processing, and model parameter assumptions—require further clarification to improve the transparency and reproducibility of the study. In addition, the applicability of some results should be more clearly defined.
- The manuscript assumes a dynamic shape factor of χ=1 in the conversion from aerodynamic diameter to electrical mobility diameter. Since mineral dust aerosols are typically irregular in shape, this assumption may introduce a systematic shift in the mapped diameter and therefore alter aerosolbin assignment in the joint size–charge distribution. Given that the reported electrostatic enhancement depends on this joint distribution, please clarify how adopting representative χ values for mineral dust (χ>1) would shift the size range associated with highly charged aerosols, and whether such shifts could affect the qualitative conclusions regarding PSD evolution. Clarifying this point would help readers assess the sensitivity of the results to aerosol morphology assumptions.
- The manuscript uses linear interpolation along the charge axis to fill missing charge-bin concentrations. Since the high-charge tail is inherently sparsely populated, this region is typically sensitive to data-processing methods. When linear interpolation is applied, high-charge bins that would otherwise be zero or undetectable may be assigned non-zero concentrations, thereby artificially smoothing and elevating the tail of the distribution. Given that the reported electrostatic enhancement depends on the fraction and distribution of highly charged aerosols, this treatment may affect the fraction of highly charged aerosols and consequently influence the related analysis results. The authors are therefore encouraged to clarify the robustness of this interpolation step for subsequent analysis results.
- In the mixed-system simulations, the inclusion of electrostatic interactions leads to an approximately 10% difference in the peak ambient sub-500 nm aerosol number concentration compared with simulations without electrostatic effects. The authors are encouraged to clarify in the Results and Discussion section of the manuscript the significance of this difference for the evaluation of environmental impacts such as radiative forcing and CCN number concentration, and whether it should be highlighted in the discussion of the results or regarded as only a secondary effect within the model. Providing such clarification would help readers better understand the implications of this difference for atmospheric applications.
- The study adopts a closed-box framework, in which no new aerosol input is considered. Under this assumption, aerosolcharges gradually neutralize and decay through coagulation. However, during real atmospheric transport, dust plumes may continuously introduce newly emitted or mixed-in aerosols that can retain relatively high initial charge. Given that the reported electrostatic enhancement depends on the presence of highly charged aerosols, the authors are encouraged to clarify whether such continuous input of highly charged aerosols could delay charge decay and sustain stronger electrostatic coagulation, thereby affecting the reported PSD evolution.
- In Fig. 3, the caption refers to aerodynamic diameter, whereas the main text indicates that aerosol sizes were converted to mobility diameter. To avoid potential confusion, the authors are encouraged to clarify in the caption which diameter is shown on the x-axis and to ensure consistent terminology between the text and the figure.
Citation: https://doi.org/10.5194/egusphere-2026-486-RC2 - AC3: 'Response to Reviewer 2's comments', Xiaofei Wang, 03 May 2026
-
AC1: 'Comment on egusphere-2026-486', Xiaofei Wang, 03 May 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-486/egusphere-2026-486-AC1-supplement.pdf
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Luoqiu Quan
Ruoyu Zhang
Gui Dai
Xinghua Jiang
Xiangyang Wang
Xiewen Ma
Xinyu Liu
Qianqian Gao
Xiaohui Lu
Xiaofei Wang
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1248 KB) - Metadata XML
-
Supplement
(1794 KB) - BibTeX
- EndNote
- Final revised paper
This paper aims to address a critical gap in atmospheric aerosol modeling by investigating how electrostatic forces influence coagulation processes of dust particles. The authors applied DMA-APS to retrieve joint size-charge distributions of dust aerosols, which can potentially overcome the lack of single-particle charge measurements. By incorporating aerosol charge into the coagulation kernel, their simulations reveal significant electrostatic effects on particle size distribution. Although the topic of paper is interesting, I have doubts on the methodology used in this work, which need to be cleared before a second round of review.
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