Aerosol Fe solubility is a key parameter for impacts of aerosol Fe on marine biogeochemistry, is still not well constrained. Several sources and processes may contribute to dissolved aerosol Fe, but quantitative explanations are still difficult. Sakata et al. explored the possibility to use the ratio of dissolved Al to dissolved Fe to understand factors which control aerosol Fe solubility in fine and coarse particles, and then discussed sources of dissolved aerosol Fe. This idea is novel, and the results are very interesting. This manuscript can still be substantially improved to increase its readability, clarity and impacts. I also posted a community comment 28 March, and the authors may also need to take it into account.

Overall, I urge the authors to check this manuscript carefully and thoroughly, as there are a lot of language issues. Professional editing is also recommended. In the community comment I posted on 28 March, I provided a few examples.

Line 267-268: Although these numbers can be found in the SI, could the author provide average EF values of Fe in TSP for different seasons?

Line 305-306: This sentence “The d-Fe and d-Al of fine aerosol particles were 72.0 ± 8.87 % and 53.1 ± 9.90 %, respectively” may need revision.

Line 311-318: Our previous work (Zhang et al., 2022; Zhang et al., 2023) also found and try to explain enrichment of dissolved Fe in fine particles, when compared to total Fe.

Section 3.4.2: Our previous studies (Zhang et al., 2022; Zhang et al., 2023) also suggested that chemical aging played a more important role in regulating Fe solubility in coarse particles than fine particles.

It may increase the readability to group Sections 3.5-3.7 into a new section. The current Section 3 is very long, and contents in Sections 3.5-3.7 are different from Section 3.1-3.4? 

In addition, I feel the current manuscript is very long, and the quality of some figures is not good (they contain many panels and are very busy). Sections 3.5-3.7 contain key information in this manuscript, but are not easy to follow. Perhaps the authors could improve them during the revision, but I cannot provide specific suggestions.

References:

Zhang, H. H., Li, R., Dong, S. W., Wang, F., Zhu, Y. J., Meng, H., Huang, C. P., Ren, Y., Wang, X. F., Hu, X. D., Li, T. T., Peng, C., Zhang, G. H., Xue, L. K., Wang, X. M., and Tang, M. J.: Abundance and Fractional Solubility of Aerosol Iron During Winter at a Coastal City in Northern China: Similarities and Contrasts Between Fine and Coarse Particles, J. Geophys. Res.-Atmos, 127, e2021JD036070, 2022.

Zhang, H. H., Li, R., Huang, C. P., Li, X. F., Dong, S. W., Wang, F., Li, T. T., Chen, Y. Z., Zhang, G. H., Ren, Y., Chen, Q. C., Huang, R. J., Chen, S. Y., Xue, T., Wang, X. M., and Tang, M. J.: Seasonal variation of aerosol iron solubility in coarse and fine particles at an inland city in northwestern China, Atmo. Chem. Phys., 23, 3543-3559, 2023.

Comments

This paper by Sakata et al. presented a detailed analysis of annual observations of Fesol% in size-fractionated (seven fractions) aerosol particles at Higashi-Hiroshima, Japan. The [d-Fe]/[d-Al] ratios were proposed to identify the source of d-Fe in aerosol particles and to understand the seasonal variability of the fraction of mineral dust and anthropogenic Fe in d-Fe in aerosols. They compared the differences of total Fe and dissolved Fe and [d-Fe]/[d-Al] between in coarse aerosol particles and fine aerosol particles. What’s the most important, they provided a simple but useful marker ([d-Fe]/[d-Al] ratio) to estimate the emission sources of d-Fe in marine aerosol particles. Overall, this paper is well written and logical, and the scientific questions discussed clearly, which meets the scope of ACP. I recommend this manuscript to be published after the following comments are addressed.

Major concerns:

1. Line 15-17: The first two sentences in the Abstract seem to be repetitive and appear to be a mess. Please simplify the expression to make it clearer.
2. Line 103-106: “Our previous study identified that fine aerosol particles collected at the sampling site contained anthropogenic Fe with a negative δ⁵⁶Fe. Therefore, the sampling site is useful for evaluating the availability of the [d-Fe]/[d-Al] ratio as an indicator of the fractions of mineral dust and anthropogenic Fe in d-Fe in aerosol particles.” Here the author stated that sampling location is of significance, however, in my opinion, there is no causal relationship between the preceding and following of this sentence. Why are sampling locations useful? Is it the unique research data provided?
3. Line 160: In the section of “Estimation of aerosol pH”, as far as I know, the input data of E-AIM model requires high relative humidity, generally over 60%, so the authors need to specify whether the data used meet the input requirements of the model.
4. Normally, an enrichment factor greater than 10.0 for an element is generally considered to be an enrichment, possibly from anthropogenic source, however, it can be seen from Figure 3c that the EFs of Fe is less than 10.0 for all particle size, making it difficult to say that Fe was enriched. How do the authors interpret this?
5. Line 387: The statement of “The [d-Fe]/[d-Al] ratio is also decreased with increasing pH” is repeated.
6. Too many figures, the authors can use correlation matrix to illustrate the relationship between Fe and other elements by merging Figure 4 and Figure 5.

Some other minor issues:

1. Line 274: Please change “1.99 ± 0.892” to “1.99 ± 0.89”. Many similar issues in the manuscript.
2. Line 311 missing recent reference npj Climate and Atmospheric Science 5(1), 53.
3. Line 368: Remove “that” in the statement of “One of the reasons is that that……”
4. Line 381 and 386: The number of decimal places should be consistent throughout the manuscript.
5. Line 690: The descriptions off (g), (h) and (i) are not consistent with Figure 2 (g) and (h).
6. Line 705: Figure 3c is the enrichment factor of Fe, not the Fe_sol% in each size fraction.