the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 Jul 2025
Measurement of soluble aerosol trace elements: inter-laboratory comparison of eight leaching protocols
Abstract. A range of leaching protocols have been used to measure the soluble fraction of aerosol trace elements worldwide, and therefore these measurements may not be directly comparable. This work presents the first large-scale international laboratory intercomparison study for aerosol trace element leaching protocols. Eight widely-used protocols are compared using 33 samples that were subdivided and distributed to all participants. Protocols used ultrapure water, ammonium acetate, or acetic acid (the so-called “Berger leach”) as leaching solutions, although none of the protocols were identical to any other. The ultrapure water leach resulted in significantly lower soluble fractions, when compared to the ammonium acetate leach or the Berger leach. For Al, Cu, Fe and Mn, the ammonium acetate leach resulted in significantly lower soluble fractions than those obtained with the Berger leach, suggesting that categorizing these two methods together as “strong leach” in global databases is potentially misleading. Among the ultrapure water leaching methods, major differences seemed related to specific protocol features rather than the use of a batch or a flow-through technique. Differences in trace element solubilization among leach solutions were apparent for aerosols with different sources or transport histories, and further studies of this type are recommended on aerosols from other regions. We encourage the development of “best practices” guidance on analytical protocols, data treatment and data validation in order to reduce the variability in soluble aerosol trace element data reported. These developments will improve understanding of the impact of atmospheric deposition on ocean ecosystems and climate.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Measurement Techniques. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.-
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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.
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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.
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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-3274', Anonymous Referee #1, 21 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-RC1-supplement.pdfCitation: https://doi.org/
10.5194/egusphere-2025-3274-RC1 -
AC1: 'Reply on RC1', Mingjin Tang, 19 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-AC1-supplement.pdf
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AC1: 'Reply on RC1', Mingjin Tang, 19 Sep 2025
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RC2: 'Comment on egusphere-2025-3274', Anonymous Referee #2, 04 Aug 2025
The impact of iron (Fe) on marine ecology and climate has been a major research focus since the “Iron Hypothesis” was proposed in the 1980s, and substantial data have been accumulated to date. However, analytical methods for dissolved Fe vary significantly across laboratories, research objectives, and projects, creating challenges in synthesizing these datasets. A critical first step is to conduct systematic intercomparisons of results obtained from different methods or laboratories. This study is a significant step toward harmonizing aerosol trace element solubility. Overall, the topic is of very suitable for ATM, and this is a well-written manuscript that presents a logically structured argument supported by rigorous experimental data. A minor revision is suggested before it can be published.
The manuscript would benefit from the following revisions for improved clarity and completeness:
1） Table 1 should comprehensively list all 26 samples analyzed by each institute, with clear definitions provided for abbreviations like C1-C7 in either the caption or a footnote.
2） The presentation of methodological information could be enhanced by:
a) Consolidating all sample details (methods and sample numbers per institute) into Table 1;
b) Creating a separate Table 2 summarizing all leaching methods with corresponding sample counts
3) While the authors have noted the limitation regarding standard solutions, the discussion should further emphasize how using identical standard solutions across laboratories would reduce calibration variability and improve intercomparability.
4）Figure 1 could be strengthened by including additional trajectory data (e.g., altitude or pressure) where available. An analysis of Fe solubility across different airmasses source samples (including the data comparison in Figure 7) is not essential unless these source differences directly affect methodological variations.
5）Table 5 requires clarification of undefined terms like “UEA-a” and “UEA-” through either table footnotes or explanatory text.
6）To improve accessibility, schematic diagrams illustrating all leaching procedures could be included in the Supplementary Information. Readers can quickly grasp all key information from this paper alone, improving both readability and audience engagement.
7）Appropriate references should be added to support the discussion at Line 512.
Citation: https://doi.org/10.5194/egusphere-2025-3274-RC2 -
AC2: 'Reply on RC2', Mingjin Tang, 19 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-AC2-supplement.pdf
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AC2: 'Reply on RC2', Mingjin Tang, 19 Sep 2025
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RC3: 'Comment on egusphere-2025-3274', Anonymous Referee #3, 11 Aug 2025
This manuscript presents a comparison of trace elements measurements in aerosols using eight different leaching methods from different institutes. It is important to have good practical protocols to determine the contents or solubility of elements. The manuscript found significant variations among the leaching methods in determining the elemental contents in aerosols at this specific sampling location. There are two comments that I wish the author can address in the revision. (1) In the Figures 3,4,5, It would be helpful to convert the mass to concentration in the atmosphere, which may be easy for comparison with other studies. The samples marked with YS show higher variations in elemental masses and some of them have much higher values. Please comment on the potential reasons for this. (2) It would be interesting to see the overall variations among these leaching methods for each element in each sample. For example, showing the ratio (to the median or means of all eight methods) for each leaching method (and elements). Such information could give us a general idea of the magnitude of variations that one may expect. Please include a summary or section of this information.
Citation: https://doi.org/10.5194/egusphere-2025-3274-RC3 -
AC3: 'Reply on RC3', Mingjin Tang, 19 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-AC3-supplement.pdf
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AC3: 'Reply on RC3', Mingjin Tang, 19 Sep 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-3274', Anonymous Referee #1, 21 Jul 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-RC1-supplement.pdf
-
AC1: 'Reply on RC1', Mingjin Tang, 19 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Mingjin Tang, 19 Sep 2025
-
RC2: 'Comment on egusphere-2025-3274', Anonymous Referee #2, 04 Aug 2025
The impact of iron (Fe) on marine ecology and climate has been a major research focus since the “Iron Hypothesis” was proposed in the 1980s, and substantial data have been accumulated to date. However, analytical methods for dissolved Fe vary significantly across laboratories, research objectives, and projects, creating challenges in synthesizing these datasets. A critical first step is to conduct systematic intercomparisons of results obtained from different methods or laboratories. This study is a significant step toward harmonizing aerosol trace element solubility. Overall, the topic is of very suitable for ATM, and this is a well-written manuscript that presents a logically structured argument supported by rigorous experimental data. A minor revision is suggested before it can be published.
The manuscript would benefit from the following revisions for improved clarity and completeness:
1） Table 1 should comprehensively list all 26 samples analyzed by each institute, with clear definitions provided for abbreviations like C1-C7 in either the caption or a footnote.
2） The presentation of methodological information could be enhanced by:
a) Consolidating all sample details (methods and sample numbers per institute) into Table 1;
b) Creating a separate Table 2 summarizing all leaching methods with corresponding sample counts
3) While the authors have noted the limitation regarding standard solutions, the discussion should further emphasize how using identical standard solutions across laboratories would reduce calibration variability and improve intercomparability.
4）Figure 1 could be strengthened by including additional trajectory data (e.g., altitude or pressure) where available. An analysis of Fe solubility across different airmasses source samples (including the data comparison in Figure 7) is not essential unless these source differences directly affect methodological variations.
5）Table 5 requires clarification of undefined terms like “UEA-a” and “UEA-” through either table footnotes or explanatory text.
6）To improve accessibility, schematic diagrams illustrating all leaching procedures could be included in the Supplementary Information. Readers can quickly grasp all key information from this paper alone, improving both readability and audience engagement.
7）Appropriate references should be added to support the discussion at Line 512.
Citation: https://doi.org/10.5194/egusphere-2025-3274-RC2 -
AC2: 'Reply on RC2', Mingjin Tang, 19 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Mingjin Tang, 19 Sep 2025
-
RC3: 'Comment on egusphere-2025-3274', Anonymous Referee #3, 11 Aug 2025
This manuscript presents a comparison of trace elements measurements in aerosols using eight different leaching methods from different institutes. It is important to have good practical protocols to determine the contents or solubility of elements. The manuscript found significant variations among the leaching methods in determining the elemental contents in aerosols at this specific sampling location. There are two comments that I wish the author can address in the revision. (1) In the Figures 3,4,5, It would be helpful to convert the mass to concentration in the atmosphere, which may be easy for comparison with other studies. The samples marked with YS show higher variations in elemental masses and some of them have much higher values. Please comment on the potential reasons for this. (2) It would be interesting to see the overall variations among these leaching methods for each element in each sample. For example, showing the ratio (to the median or means of all eight methods) for each leaching method (and elements). Such information could give us a general idea of the magnitude of variations that one may expect. Please include a summary or section of this information.
Citation: https://doi.org/10.5194/egusphere-2025-3274-RC3 -
AC3: 'Reply on RC3', Mingjin Tang, 19 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3274/egusphere-2025-3274-AC3-supplement.pdf
-
AC3: 'Reply on RC3', Mingjin Tang, 19 Sep 2025
Peer review completion
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Ashley T. Townsend
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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.
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(1471 KB) - BibTeX
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