the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Measurement report: Stoichiometry of dissolved iron and aluminum as an indicator of the factors controlling the fractional solubility of aerosol iron: Results of the annual observations of size-fractionated aerosol particles in Japan
Aya Sakaguchi
Yoshiaki Yamakawa
Chihiro Miyamoto
Minako Kurisu
Yoshio Takahashi
Abstract. Atmospheric deposition of iron (Fe) in aerosol particles is enhanced primary production on the ocean surface, resulting in promoting the uptake of carbon dioxide into the surface seawater. Atmospheric deposition of iron (Fe) promotes primary production in the surface ocean, resulting in enhanced uptake of carbon dioxide into surface seawater. Since microorganisms in seawater utilize dissolved Fe (d-Fe) as a nutrient, the bioavailability of Fe in aerosol particles depends on its solubility. However, factors controlling fractional Fe solubility (Fesol%) in aerosol particles have not been fully understood. This study performed annual observations of Fesol% in size-fractionated (seven fractions) aerosol particles at Higashi-Hiroshima, Japan. In particular, the feasibility of the molar concentration ratio of d-Fe relative to dissolved Al ([d-Fe]/[d-Al]) as an indicator of the sources of d-Fe in aerosol particles because this ratio is likely dependent on the emission sources of Fe (e.g., mineral dust, fly ash, and anthropogenic Fe oxides) and their dissolution processes (proton-promoted and ligand-promoted dissolutions). Approximately 70 % of total Fe and dissolved Fe was present in coarse and fine aerosol particles, respectively, and the average Fesol% in fine aerosol particles (11.4 ± 6.97 %) was higher than that of coarse aerosol particles (2.19 ± 2.27 %). In addition, the average ratio of [d-Fe]/[d-Al] in coarse aerosol particles (0.408 ± 0.168) was lower than that in fine aerosol particles (1.15 ± 0.803). The range of [d-Fe]/[d-Al] ratios in the coarse aerosol particles (0.121–0.927) was similar to that obtained by proton-promoted dissolutions of mineral dust (0.1–1.0), indicating that d-Fe in coarse aerosol particles were derived from mineral dust. The [d-Fe]/[d-Al] ratios of aerosol particles ranged from 0.386 to 4.67, and [d-Fe]/[d-Al] ratios greater than 1.5 cannot be explained by proton-promoted dissolution and ligand-promoted dissolution (1.0 < [d-Fe]/[d-Al] < 1.5). The [d-Fe]/[d-Al] ratio correlated with the enrichment factor of Fe in fine aerosol particles (r: 0.505), indicating that anthropogenic Fe with a high [d-Fe]/[d-Al] ratio was the source of d-Fe in fine aerosol particles. The high [d-Fe]/[d-Al] ratio was attributed to Fe-oxides emitted from high-temperature combustions (high-temp-FeOx). Finally, the fraction of high-temp-FeOx to d-Fe in total suspended particulate (TSP) was calculated based on the [d-Fe]/[d-Al] ratio of aerosols and their emission source samples. As a result, the fraction of high-temp-FeOx to d-Fe in TSP varied from 1.48 to 80.7 %. The high fraction was found in summer when air masses originated from industrial regions in Japan. By contrast, approximately 10 % of d-Fe in the TSP samples collected in spring and during Asian dust events was derived from high-temp-FeOx, when air masses were frequently transported from East Asia to the Pacific Ocean. Thus, mineral dust is the dominant source of d-Fe in Asian outflow to the Pacific Ocean.
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Kohei Sakata et al.
Status: final response (author comments only)
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CC1: 'Comment on acp-2023-20', Mingjin Tang, 28 Mar 2023
Sakata et al. explored the possibility to use the ratio of dissolved Al to dissolved Fe to understand factors which control aerosol Fe solubility. I went through this manuscript quickly, and found it very interesting.
Line 15-17: The second sentence in the abstract largely repeats the first sentence. In addition, there are some typos elsewhere in this manuscript (for example, line 305-306; line 29: should there be "for fine particles" after "from 0.386 to 4.67"?). The authors may want to check the language thoroughly.
Line 155-159: It would be nice to provide values used for [X]/[Na+] for seawater and references.
Recently we published two papers (Zhang et al., 2022; Zhang et al., 2023), which discussed sources of dissolved Fe and Fe solubility for fine and coarse particles and are highly relevant to the work presented by Sakata et al. Our two papers reported many similar results as Sakata et al., including what Sakat et al. presented in Sections 3.3-3.4. There are also some differences between our work and the work by Sakata et al. (2023). Therefore, I would like to bring the authors' attention to our recent work (Zhang et al., 2022; Zhang et al., 2023).
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.
Citation: https://doi.org/10.5194/acp-2023-20-CC1 -
AC1: 'Reply on CC1', Kohei Sakata, 04 Jun 2023
Dear Dr.Mingjin Tang
Thank you very much for taking the time to review our paper. We have revised our manuscript according to your comments. We replied to your CC comments with RC1 comments. Therefore, please refer to the file attached to RC1's reply for detailed replies to the CC comments.
Sincerely yours,
Kohei Sakata behalf of the authors.
Citation: https://doi.org/10.5194/acp-2023-20-AC1
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AC1: 'Reply on CC1', Kohei Sakata, 04 Jun 2023
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RC1: 'Comment on acp-2023-20', Mingjin Tang, 05 Apr 2023
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.
Citation: https://doi.org/10.5194/acp-2023-20-RC1 -
AC2: 'Reply on RC1', Kohei Sakata, 04 Jun 2023
Dear Dr. Mingjin Tang
We sincerely thank the reviewer for the time and effort put into this review. We apologize for the inconvenience for your peer-preview processes due to our poor English. English editing was conducted by a native English speaker prior to submission.
We have carefully revised the manuscript with full consideration of the comments and suggestions provided. We also reply to your comments posted as community comments in this sheet. Please find the point-to-point replies listed in the attached file.
Sincerely yours,
Kohei Sakata behalf of the authors.
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AC2: 'Reply on RC1', Kohei Sakata, 04 Jun 2023
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RC2: 'Comment on acp-2023-20', Anonymous Referee #2, 26 Apr 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:
- 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.
- 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?
- 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.
- 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?
- Line 387: The statement of “The [d-Fe]/[d-Al] ratio is also decreased with increasing pH” is repeated.
- 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:
- Line 274: Please change “1.99 ± 0.892” to “1.99 ± 0.89”. Many similar issues in the manuscript.
- Line 311 missing recent reference npj Climate and Atmospheric Science 5(1), 53.
- Line 368: Remove “that” in the statement of “One of the reasons is that that……”
- Line 381 and 386: The number of decimal places should be consistent throughout the manuscript.
- Line 690: The descriptions off (g), (h) and (i) are not consistent with Figure 2 (g) and (h).
- Line 705: Figure 3c is the enrichment factor of Fe, not the Fesol% in each size fraction.
Citation: https://doi.org/10.5194/acp-2023-20-RC2 -
AC3: 'Reply on RC2', Kohei Sakata, 04 Jun 2023
Dear Reviewer
We sincerely thank the reviewer for their time and effort on this review. We have carefully revised the manuscript with full consideration of the comments and suggestions provided.
Please find the point-to-point replies in the attached file.
Sincerely yours,
Kohei Sakata behalf of the authors.
Kohei Sakata et al.
Data sets
Concentration data of major ions, metals and dissolved metals in size-fractionated (seven-fractions) aerosol particels collected in Higashi-Hiroshima, JapanConcentration data of major ions, metals and dissolved metals in size-fractionated (seven-fractions) aerosol particels collected in Higashi-Hiroshima, Japan Kohei Sakata, Aya Sakaguchi, Yoshiaki Yamakawa, Chihiro Miyamoto, Minako Kurisu, and Yoshio Takahashi https://doi.org/10.34355/CRiED.U.Tsukuba.00156
Kohei Sakata et al.
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