the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 Jun 2023
Influences of sources and weather dynamics on atmospheric deposition of Se species and other trace elements
Abstract. Atmospheric deposition is an important source of the essential trace element selenium (Se) to terrestrial ecosystems and food chains. The fate of Se supplied to surface environments by atmospheric deposition strongly depends on total Se concentrations as well as its chemical form (speciation). However, the factors determining total Se and its speciation in atmospheric deposition remain poorly understood. Here, we applied different chemical measurements to aerosol samples taken at a weekly resolution over 5 years (2015–2019), as well as precipitation and cloud water samples taken during a field campaign of two months in 2019 at Pic du Midi Observatory (French Pyrenees; 2877 m a.s.l.) and combined these observations with sophisticated modelling approaches. The high-altitude site enables the investigation of local and long-range elemental transport from both marine and continental sources and the role of different weather systems in elemental deposition. Total concentrations of trace elements were measured in aerosol extracts and wet deposition, and Se speciation was obtained with an optimized chromatographic method coupled to inductively coupled plasma tandem mass spectrometry (LC-ICP-MS/MS). These analyses were combined with molecular organic compound analysis by pyrolysis-gas chromatography mass spectrometry (Py-GC-MS). For modelling the source contributions to Se, we used a combination of i) a Eulerian approach with the atmospheric aerosol-chemistry-climate model SOCOL-AERv2, and ii) a Lagrangian approach with air parcel backward trajectories and a moisture source diagnostics. While weekly Se measurements in the 2015–2020 aerosol time series agreed very well (r~0.8) with SOCOL-AERv2 model results, the higher Se concentrations (>0.05 ng·m-3) observed in summer were underestimated by the model. We could explain these higher concentrations in summer by convection related to thunderstorms that led to high aerosol loadings and which are not resolved explicitly in the model. In addition, convective events, associated with continental moisture sources, also explained the highest concentrations of Se and most other trace elements in wet deposition, due to efficient below cloud scavenging, indicating the importance of local cloud dynamics on the supply of Se and other, essential and non-essential, trace elements to surface environments. While data for water isotopes in precipitation indicated an uncoupling of hydrological and trace element cycling related to below cloud scavenging, cloud water isotopes and trace elements showed high correlations indicating that the water and trace element cycles are strongly coupled from the source to the formation of clouds with a possible decoupling occurring during precipitation. Furthermore, cloud water showed more regional trace element and moisture sources than precipitation samples. With this comprehensive set of observations and model diagnostics we could explain inorganic Se speciation in unprecedented detail by linking moisture sources and organic chemical compounds in aerosols to speciation data of Se and S, indicating local vs long-range transport and anthropogenic vs natural Se sources. We report for the first-time organic Se in precipitation (and aerosols), for which we could elucidate a marine biogenic source. Our study thus provides new insights into the factors explaining atmospheric deposition of Se and other trace elements and highlights the importance of weather system dynamics in addition to source contributions for the atmospheric supply of trace elements to surface environments.
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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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Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-1135', Anonymous Referee #1, 05 Jul 2023
Referee comment - EGUsphere, egusphere-2023-1135
Influences of sources and weather dynamics on atmospheric deposition of Se species and other trace elements
Esther S. Breuninger, Julie Tolu, Iris Thurnherr, Franziska Aemisegger, Aryeh Feinberg, Sylvain Bouchet, Jeroen E. Sonke, Véronique Pont, Heini Wernli, Lenny H. E. Winkel
General comments The relevant topic concerning sources and speciation of selenium in atmospheric deposition is addressed in this manuscript where a considerable amount of data is reported. Data were obtained by combining modelling and complementary analytical approaches that were applied to a set of precipitation/cloud water samples (respectively 18 and 12 events in a period of 2 months, that were sampled in sub-events) and a significant series of aerosol samples collected with weekly resolution during five years. The complexity of the topic is illustrated by the multiplicity of atmospheric processes identified to be involved in the cycling of elements, which is mainly discussed quantitatively and qualitatively for selenium but also applies to other elements. My opinion is that research reported in this manuscript, with impressive number of data, is well conducted and significant. However, and in spite of the size/length of the document, some important information is missing and some conclusions should be tempered (see below specific comments).
Specific comments
- Sample processing (lines 172-173, lines 182-184, line 192) and Chemical analysis (lines 215-218): from the methods description given, I understand that the conditions of sample treatments (extraction of water-soluble fraction of aerosol samples and pre-concentration of these fractions and of precipitation/cloud water samples) was the same before speciation analyses of Se and S species. However, details of method development given in Supplement S2 (in particular species stability during extraction and pre-concentration) only target on Se species and no information about the stability of S species is provided. This may be due to the fact that such extraction and/or pre-concentration methods were previously validated for S species? In that case corresponding reference(s) should be added. Otherwise, the whole discussion around identified S species may be somewhat more complicated.
- Lines 236-245: the quantification method used for Se and S species must be specified in this section.
- Line 351: as the indication of the range of values is given in previous sentence, the median value would be more meaningful here.
- Lines 519-533 and corresponding supplements: the comparison of example Se chromatograms illustrating the presence of a third Se-containing peak (fig S18a) to the standards one (supplement S3) seems to indicate a shift in retention times, although retention time units being different. It is not obvious to distinguish if the retention time of Org Se is different from the one of selenocystine standard? To facilitate readability, it would be helpful if chromatograms are plotted with same units (select min or s, and counts or counts per second for all layouts). The complementary use of cation exchange chromatography to try to understand the nature of Org Se peak is interesting. However, from Fig S19, the result of DMSeP addition is not quite clear as 2 peaks are increasing and one is decreasing. Then Se species recoveries are given (lines 524-525) but as indicated in previous comment, species quantification method was not indicated, which is important to know in particular in the case of Org Se peak, for which no commercial standard is available, to clarify recoveries and concentrations values (lines 530-533).
- Lines 539-541 and corresponding supplement: examples of S chromatograms of fig S18b indicate poor chromatographic separation of HMS (hydroxymethanesulfonate) and MSA (methanesulfonic acid) peaks for which resolution does not allow accurate compounds quantification thus calling into question the following discussion and correlations using proportions or concentrations of these S compounds.
- Lines 551-552: SeIV proportion in aerosol water extracts appears to be significantly lower in summer than in autumn samples, does this difference remain if proportion is calculated as % of total Se in aerosol instead of its water-soluble extract?
- Lines 558-562: as indicated in previous comments, without information about S species stability during extraction (and if so, preconcentration) and given the poor resolution between HMS and MSA peaks, the discussion involving HMS is very hypothetical.
- Lines 571-572: precipitation/cloud waters were collected in the period from end of August to October, comparison with aerosol water extracts of the same period (September to October) only indicates a difference between aerosol extracts and cloud waters, while SeIV proportion in precipitation waters was not significantly different neither from cloud waters nor aerosol extracts (from letters indicated in fig 5).
- Lines 622-624: same comment for discussion around MSA as previously indicated for discussion involving HMS.
- Line 662: Org Se was detected and not identified, the presence of single species in this chromatographic peak eluting at or close to the void volume of the column was not proven here.
- Supplement S2: the verification of Se species stability during extraction of water-soluble fraction of aerosols and pre-concentration step is well conducted using available commercial standards for validation of used methods. I have however a couple of points:
Line 59: partial transformation of SeMet is indicated to explain its lower recovery following extraction of water-soluble fraction of aerosols. It would be interesting to learn more (chromatographic detection of other Se-containing compound(s) and if so, which retention time(s)? ).
Lines 87-88: lyophilisation to dryness led to losses of organic Se species for which the authors indicated a possible "transformation to other organic Se species that are not retained by anion exchange". This is a very important point as compounds not retained by anion exchange should elute at or close to the void volume of the column, as it is the case for the unknown organic Se compound/pool later detected in samples.
Lines 97-104: the second set of tests compared different containers using lyophilisation to a residual volume < 1,5 mL. In this part, it is not clear in which aqueous medium (or media) the test was done? In the same way, tested media (lines 74-78) were ultrapure water, ammonium citrate solution and rainwater, but water-soluble fraction of aerosols does not seem to have been considered, is that right?
- Supplement S10: add in the table caption, the number of samples considered for calculated correlations. It is important information as although statistically significant with p-values < 0.01 or <0.05, the strength of correlations is weak to moderate.
Technical corrections
- Abstract line 19: check for duration of aerosol sampling 2015-2019 or 2015-2020?
- Line 167: "53.6 ± 2.8" round to the number of significant figures
- Line 205: revise "equipped with and SPS4…"
- Line 321: revise "in order to minimized…"
- Lines 352-354, 530-532 and 536-538: round to the number of significant figures
- Fig 5: aerosol time series is 2015-2019 in the figure, 2015-2020 in figure caption
- Supplement S3 line 127: revise "an anion exchanges…"
- Table S3: round to the number of significant figures (recoveries column)
Citation: https://doi.org/10.5194/egusphere-2023-1135-RC1 - AC1: 'Reply on RC1', Esther Breuninger, 30 Nov 2023
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CC1: 'Comment on Breuninger et al.', Nadine Borduas-Dedekind, 19 Aug 2023
My research group at UBC reviewed this manuscript as a group exercise during a recent group meeting, and I've decided to share the feedback here. We hope it supports the research.
Praise for the work:
This paper represents a large undertaking by the team of authors of method development, monitoring data, reporting of unique Se concentration datasets, hypothesis-generating analysis related to the role of thunderstorm clouds AND climate modeling. It’s a super paper. The reported data is of the highest quality, the methods are accurate, and the details included in this paper are remarkable. This manuscript also includes a highly detailed SI.
Creation of their aerosol sample (n=134) at weekly resolution over 5 years is impressive.
The figures in this paper are remarkable! Some of the best made figures we’ve seen. The TOC figure is clean, clear, precise, and really compelling. Figure 1 is so clean and clear and yet has a ton of information portrayed. The use of symbols is particularly clever. Figure 6b also allows an unusually large amount of information to be presented clearly.
The results presented in Figure 4 are particularly compelling. The enhancement due to thunderstorms is clear (and unexpected to us).
(section 3.2.1) The measurement of the “third peak” as organo-selenium compound was particularly exciting for our group (since we are working on atmospheric methylated selenium compounds and their atmospheric fate). And the authors present convincing evidence of the presence of reduced Se species.
Comments and thoughts for the authors to consider:
We felt there were two stories in this paper: Se concentrations over 5 years (Fig 2), and trace elements in atmospheric deposition/role of thunderstorms (Fig 3). It makes for a super paper; but it wasn’t clear to us, the readers, why these stories needed to be present in one super paper. If the authors could connect the two storylines better, it would be beneficial for the future reader.
References to further support lines 60-62 discussing oxidation of volatile selenium should include (Atkinson et al., 1990) and could also include our very recently accepted work: https://doi.org/10.1021/acs.est.3c01586 (in press, Heine & Borduas-D., ES&T, 2023). We observed selenic acid and dimethyl selenoxide as products. Same references are also relevant for discussion in lines 646-649.
The discussion about variability of Se over the 5 years dataset in section 3.1.1. is likely location-dependent. We saw in (Lao et al., 2023) that the seasonal trends were drastically different and could be categorized in 6 distinct profiles related to geographical location in the US. Did the authors consider normalized their Se data with PM total mass? That analysis would help identify times of Se depletion or enhancement events (Lao et al., 2023). We were therefore curious about the “similar patterns” referred to on lines 356-358. Could the authors show these similarities in their SI for example?
Lines 400-405 We thought it would be worth tabulating this information from the literature. It would be a great resource to point to and build upon for the authors, but also for the community.
(section 3.2.2) lines 551-552 and subsequent paragraph: do the authors have an idea why there was no clear seasonal difference for Se(VI)? We thought that correlations with aromatics and aliphatics which likely oxidize quickly was surprising. What role of aerosol partitioning, aerosol viscosity could play here?
- Se can also undergo fast redox, and could Se(IV) and Se(VI) undergo redox chemistry in the atmosphere? See for example: (Reich and Hondal, 2016)
Figure 6a: could the relationship be due to chemical transformations or/and to partitioning?
Technical feedback:
Line 204: “Se” is missing in the list just before Br.
References:
Atkinson, R., Aschmann, S. M., Hasegawa, D., Thompson-Eagle, E. T., and Frankenberger, W. T.: Kinetics of the atmospherically important reactions of dimethyl selenide, Environ. Sci. Technol., 24, 1326–1332, https://doi.org/10.1021/es00079a005, 1990.
Heine, P. A., Borduas-Dedekind, N.: The ozonolysis of methylated selenium compounds in the atmosphere: isotopes, kinetics, products and mechanism. Environ. Sci. Technol., https://doi.org/10.1021/acs.est.3c01586, 2023.
Lao, I. R., Feinberg, A., and Borduas-Dedekind, N.: Regional Sources and Sinks of Atmospheric Particulate Selenium in the United States Based on Seasonality Profiles, Environ. Sci. Technol., 57, 7401–7409, https://doi.org/10.1021/acs.est.2c08243, 2023.
Reich, H. J. and Hondal, R. J.: Why Nature Chose Selenium, ACS Chem. Biol., 11, 821–841, https://doi.org/10.1021/acschembio.6b00031, 2016.
Citation: https://doi.org/10.5194/egusphere-2023-1135-CC1 - AC2: 'Reply on CC1', Esther Breuninger, 30 Nov 2023
-
RC2: 'Comment on egusphere-2023-1135', Anonymous Referee #2, 20 Oct 2023
Referee comments on the article: egusphere-2023-1135:
Influences of sources and weather dynamics on atmospheric deposition of Se species and other trace elements
By Esther S. Breuninger, Julie Tolu, Iris Thurnherr, Franziska Aemisegger, Aryeh Feinberg, Sylvain Bouchet, Jeroen E. Sonke, Véronique Pont, Heini Wernli, and Lenny H. E. Winkel
General comment
In the paper, the authors present a comprehensive study of the main factors describing the atmospheric deposition of Se. For this purpose, the authors present experimental measurements that are correlated with model results. It is important to highlight the large number of samples collected for the analysis (weekly samples during 5 years), as well as the precipitation samples obtained. Another interesting aspect of this work is the analysis performed at the high-altitude atmospheric observatory (Pic du Midi (French Pyrenees; 2877 m a.s.l.), which allows the analysis of the synoptic transport of Se. I consider that this article can be accepted in its present form because it is well-written and presents very interesting results.
Here are some minor details and suggestions.
Specific comments
- I recommend the authors write a shorter abstract. Please, introduce a more summarized writing where you highlight the main findings of the article. I think this paper presents a very complete analysis, but if the authors abbreviate this section, it makes it more appealing to the reader.
- Line 37 The authors state that trace elements and isotopes in water are decoupled from clouds during precipitation. Can the authors indicate the specific result where this effect is observed?
- This is a very long article, as it presents different subsections. I recommend introducing a table of contents at the beginning of the manuscript.
- Methods section: the reviewer strongly recommends the authors extend the description of the study region, specifically to detail the Pic du Midi Observatory monitoring station site. It would be interesting to know the height of the mixing layer in the region. Since this study deals with a synoptic transport of Se, it would be interesting to know if the authors discarded the local influence (convective transport in the mixed layer).
- From your results: ¿it is possible to assess if Se concentrations decline with precipitation amount?
- What about the solubility of Se species: your study, only measures dilute Se species?
- In the conclusions, you state that: "for the first time we were able to identify an organic Se species as a biomarker of marine biogenic sources".
Could you describe the specific result that allows you to conclude this?
- Line 365: Se can be released to the atmosphere from a variety of sources (e.g., natural sources such as soil, water, and vegetation, as well as anthropogenic sources). Are the terrestrial contributions of Se at Pic du Midi only due to synoptic transport or to local sources?
- AC3: 'Reply on RC2', Esther Breuninger, 30 Nov 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-1135', Anonymous Referee #1, 05 Jul 2023
Referee comment - EGUsphere, egusphere-2023-1135
Influences of sources and weather dynamics on atmospheric deposition of Se species and other trace elements
Esther S. Breuninger, Julie Tolu, Iris Thurnherr, Franziska Aemisegger, Aryeh Feinberg, Sylvain Bouchet, Jeroen E. Sonke, Véronique Pont, Heini Wernli, Lenny H. E. Winkel
General comments The relevant topic concerning sources and speciation of selenium in atmospheric deposition is addressed in this manuscript where a considerable amount of data is reported. Data were obtained by combining modelling and complementary analytical approaches that were applied to a set of precipitation/cloud water samples (respectively 18 and 12 events in a period of 2 months, that were sampled in sub-events) and a significant series of aerosol samples collected with weekly resolution during five years. The complexity of the topic is illustrated by the multiplicity of atmospheric processes identified to be involved in the cycling of elements, which is mainly discussed quantitatively and qualitatively for selenium but also applies to other elements. My opinion is that research reported in this manuscript, with impressive number of data, is well conducted and significant. However, and in spite of the size/length of the document, some important information is missing and some conclusions should be tempered (see below specific comments).
Specific comments
- Sample processing (lines 172-173, lines 182-184, line 192) and Chemical analysis (lines 215-218): from the methods description given, I understand that the conditions of sample treatments (extraction of water-soluble fraction of aerosol samples and pre-concentration of these fractions and of precipitation/cloud water samples) was the same before speciation analyses of Se and S species. However, details of method development given in Supplement S2 (in particular species stability during extraction and pre-concentration) only target on Se species and no information about the stability of S species is provided. This may be due to the fact that such extraction and/or pre-concentration methods were previously validated for S species? In that case corresponding reference(s) should be added. Otherwise, the whole discussion around identified S species may be somewhat more complicated.
- Lines 236-245: the quantification method used for Se and S species must be specified in this section.
- Line 351: as the indication of the range of values is given in previous sentence, the median value would be more meaningful here.
- Lines 519-533 and corresponding supplements: the comparison of example Se chromatograms illustrating the presence of a third Se-containing peak (fig S18a) to the standards one (supplement S3) seems to indicate a shift in retention times, although retention time units being different. It is not obvious to distinguish if the retention time of Org Se is different from the one of selenocystine standard? To facilitate readability, it would be helpful if chromatograms are plotted with same units (select min or s, and counts or counts per second for all layouts). The complementary use of cation exchange chromatography to try to understand the nature of Org Se peak is interesting. However, from Fig S19, the result of DMSeP addition is not quite clear as 2 peaks are increasing and one is decreasing. Then Se species recoveries are given (lines 524-525) but as indicated in previous comment, species quantification method was not indicated, which is important to know in particular in the case of Org Se peak, for which no commercial standard is available, to clarify recoveries and concentrations values (lines 530-533).
- Lines 539-541 and corresponding supplement: examples of S chromatograms of fig S18b indicate poor chromatographic separation of HMS (hydroxymethanesulfonate) and MSA (methanesulfonic acid) peaks for which resolution does not allow accurate compounds quantification thus calling into question the following discussion and correlations using proportions or concentrations of these S compounds.
- Lines 551-552: SeIV proportion in aerosol water extracts appears to be significantly lower in summer than in autumn samples, does this difference remain if proportion is calculated as % of total Se in aerosol instead of its water-soluble extract?
- Lines 558-562: as indicated in previous comments, without information about S species stability during extraction (and if so, preconcentration) and given the poor resolution between HMS and MSA peaks, the discussion involving HMS is very hypothetical.
- Lines 571-572: precipitation/cloud waters were collected in the period from end of August to October, comparison with aerosol water extracts of the same period (September to October) only indicates a difference between aerosol extracts and cloud waters, while SeIV proportion in precipitation waters was not significantly different neither from cloud waters nor aerosol extracts (from letters indicated in fig 5).
- Lines 622-624: same comment for discussion around MSA as previously indicated for discussion involving HMS.
- Line 662: Org Se was detected and not identified, the presence of single species in this chromatographic peak eluting at or close to the void volume of the column was not proven here.
- Supplement S2: the verification of Se species stability during extraction of water-soluble fraction of aerosols and pre-concentration step is well conducted using available commercial standards for validation of used methods. I have however a couple of points:
Line 59: partial transformation of SeMet is indicated to explain its lower recovery following extraction of water-soluble fraction of aerosols. It would be interesting to learn more (chromatographic detection of other Se-containing compound(s) and if so, which retention time(s)? ).
Lines 87-88: lyophilisation to dryness led to losses of organic Se species for which the authors indicated a possible "transformation to other organic Se species that are not retained by anion exchange". This is a very important point as compounds not retained by anion exchange should elute at or close to the void volume of the column, as it is the case for the unknown organic Se compound/pool later detected in samples.
Lines 97-104: the second set of tests compared different containers using lyophilisation to a residual volume < 1,5 mL. In this part, it is not clear in which aqueous medium (or media) the test was done? In the same way, tested media (lines 74-78) were ultrapure water, ammonium citrate solution and rainwater, but water-soluble fraction of aerosols does not seem to have been considered, is that right?
- Supplement S10: add in the table caption, the number of samples considered for calculated correlations. It is important information as although statistically significant with p-values < 0.01 or <0.05, the strength of correlations is weak to moderate.
Technical corrections
- Abstract line 19: check for duration of aerosol sampling 2015-2019 or 2015-2020?
- Line 167: "53.6 ± 2.8" round to the number of significant figures
- Line 205: revise "equipped with and SPS4…"
- Line 321: revise "in order to minimized…"
- Lines 352-354, 530-532 and 536-538: round to the number of significant figures
- Fig 5: aerosol time series is 2015-2019 in the figure, 2015-2020 in figure caption
- Supplement S3 line 127: revise "an anion exchanges…"
- Table S3: round to the number of significant figures (recoveries column)
Citation: https://doi.org/10.5194/egusphere-2023-1135-RC1 - AC1: 'Reply on RC1', Esther Breuninger, 30 Nov 2023
-
CC1: 'Comment on Breuninger et al.', Nadine Borduas-Dedekind, 19 Aug 2023
My research group at UBC reviewed this manuscript as a group exercise during a recent group meeting, and I've decided to share the feedback here. We hope it supports the research.
Praise for the work:
This paper represents a large undertaking by the team of authors of method development, monitoring data, reporting of unique Se concentration datasets, hypothesis-generating analysis related to the role of thunderstorm clouds AND climate modeling. It’s a super paper. The reported data is of the highest quality, the methods are accurate, and the details included in this paper are remarkable. This manuscript also includes a highly detailed SI.
Creation of their aerosol sample (n=134) at weekly resolution over 5 years is impressive.
The figures in this paper are remarkable! Some of the best made figures we’ve seen. The TOC figure is clean, clear, precise, and really compelling. Figure 1 is so clean and clear and yet has a ton of information portrayed. The use of symbols is particularly clever. Figure 6b also allows an unusually large amount of information to be presented clearly.
The results presented in Figure 4 are particularly compelling. The enhancement due to thunderstorms is clear (and unexpected to us).
(section 3.2.1) The measurement of the “third peak” as organo-selenium compound was particularly exciting for our group (since we are working on atmospheric methylated selenium compounds and their atmospheric fate). And the authors present convincing evidence of the presence of reduced Se species.
Comments and thoughts for the authors to consider:
We felt there were two stories in this paper: Se concentrations over 5 years (Fig 2), and trace elements in atmospheric deposition/role of thunderstorms (Fig 3). It makes for a super paper; but it wasn’t clear to us, the readers, why these stories needed to be present in one super paper. If the authors could connect the two storylines better, it would be beneficial for the future reader.
References to further support lines 60-62 discussing oxidation of volatile selenium should include (Atkinson et al., 1990) and could also include our very recently accepted work: https://doi.org/10.1021/acs.est.3c01586 (in press, Heine & Borduas-D., ES&T, 2023). We observed selenic acid and dimethyl selenoxide as products. Same references are also relevant for discussion in lines 646-649.
The discussion about variability of Se over the 5 years dataset in section 3.1.1. is likely location-dependent. We saw in (Lao et al., 2023) that the seasonal trends were drastically different and could be categorized in 6 distinct profiles related to geographical location in the US. Did the authors consider normalized their Se data with PM total mass? That analysis would help identify times of Se depletion or enhancement events (Lao et al., 2023). We were therefore curious about the “similar patterns” referred to on lines 356-358. Could the authors show these similarities in their SI for example?
Lines 400-405 We thought it would be worth tabulating this information from the literature. It would be a great resource to point to and build upon for the authors, but also for the community.
(section 3.2.2) lines 551-552 and subsequent paragraph: do the authors have an idea why there was no clear seasonal difference for Se(VI)? We thought that correlations with aromatics and aliphatics which likely oxidize quickly was surprising. What role of aerosol partitioning, aerosol viscosity could play here?
- Se can also undergo fast redox, and could Se(IV) and Se(VI) undergo redox chemistry in the atmosphere? See for example: (Reich and Hondal, 2016)
Figure 6a: could the relationship be due to chemical transformations or/and to partitioning?
Technical feedback:
Line 204: “Se” is missing in the list just before Br.
References:
Atkinson, R., Aschmann, S. M., Hasegawa, D., Thompson-Eagle, E. T., and Frankenberger, W. T.: Kinetics of the atmospherically important reactions of dimethyl selenide, Environ. Sci. Technol., 24, 1326–1332, https://doi.org/10.1021/es00079a005, 1990.
Heine, P. A., Borduas-Dedekind, N.: The ozonolysis of methylated selenium compounds in the atmosphere: isotopes, kinetics, products and mechanism. Environ. Sci. Technol., https://doi.org/10.1021/acs.est.3c01586, 2023.
Lao, I. R., Feinberg, A., and Borduas-Dedekind, N.: Regional Sources and Sinks of Atmospheric Particulate Selenium in the United States Based on Seasonality Profiles, Environ. Sci. Technol., 57, 7401–7409, https://doi.org/10.1021/acs.est.2c08243, 2023.
Reich, H. J. and Hondal, R. J.: Why Nature Chose Selenium, ACS Chem. Biol., 11, 821–841, https://doi.org/10.1021/acschembio.6b00031, 2016.
Citation: https://doi.org/10.5194/egusphere-2023-1135-CC1 - AC2: 'Reply on CC1', Esther Breuninger, 30 Nov 2023
-
RC2: 'Comment on egusphere-2023-1135', Anonymous Referee #2, 20 Oct 2023
Referee comments on the article: egusphere-2023-1135:
Influences of sources and weather dynamics on atmospheric deposition of Se species and other trace elements
By Esther S. Breuninger, Julie Tolu, Iris Thurnherr, Franziska Aemisegger, Aryeh Feinberg, Sylvain Bouchet, Jeroen E. Sonke, Véronique Pont, Heini Wernli, and Lenny H. E. Winkel
General comment
In the paper, the authors present a comprehensive study of the main factors describing the atmospheric deposition of Se. For this purpose, the authors present experimental measurements that are correlated with model results. It is important to highlight the large number of samples collected for the analysis (weekly samples during 5 years), as well as the precipitation samples obtained. Another interesting aspect of this work is the analysis performed at the high-altitude atmospheric observatory (Pic du Midi (French Pyrenees; 2877 m a.s.l.), which allows the analysis of the synoptic transport of Se. I consider that this article can be accepted in its present form because it is well-written and presents very interesting results.
Here are some minor details and suggestions.
Specific comments
- I recommend the authors write a shorter abstract. Please, introduce a more summarized writing where you highlight the main findings of the article. I think this paper presents a very complete analysis, but if the authors abbreviate this section, it makes it more appealing to the reader.
- Line 37 The authors state that trace elements and isotopes in water are decoupled from clouds during precipitation. Can the authors indicate the specific result where this effect is observed?
- This is a very long article, as it presents different subsections. I recommend introducing a table of contents at the beginning of the manuscript.
- Methods section: the reviewer strongly recommends the authors extend the description of the study region, specifically to detail the Pic du Midi Observatory monitoring station site. It would be interesting to know the height of the mixing layer in the region. Since this study deals with a synoptic transport of Se, it would be interesting to know if the authors discarded the local influence (convective transport in the mixed layer).
- From your results: ¿it is possible to assess if Se concentrations decline with precipitation amount?
- What about the solubility of Se species: your study, only measures dilute Se species?
- In the conclusions, you state that: "for the first time we were able to identify an organic Se species as a biomarker of marine biogenic sources".
Could you describe the specific result that allows you to conclude this?
- Line 365: Se can be released to the atmosphere from a variety of sources (e.g., natural sources such as soil, water, and vegetation, as well as anthropogenic sources). Are the terrestrial contributions of Se at Pic du Midi only due to synoptic transport or to local sources?
- AC3: 'Reply on RC2', Esther Breuninger, 30 Nov 2023
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Esther S. Breuninger
Julie Tolu
Iris Thurnherr
Franziska Aemisegger
Aryeh Feinberg
Sylvain Bouchet
Jeroen E. Sonke
Véronique Pont
Heini Wernli
Lenny H. E. Winkel
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1756 KB) - Metadata XML
-
Supplement
(1917 KB) - BibTeX
- EndNote
- Final revised paper