Influence of Spring Dust Storm on Atmospheric Particulate-Bound Mercury in a Typical Inland City of Northern China: Characteristics, Sources, and Risk Assessment

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

This is an interesting and useful work, which will be able to be published in Sustainability, after a significant number of corrections are performed. The manuscript presents some methodological weaknesses, which prevent publication at this stage and require revision. I will refer to these aspects here. Please consider the following comments as a constructive contribution for improving your manuscript.

Note: I also attach the manuscript file with these comments inserted in the respective lines, for easier reference. Furthermore, the attachment also identifies many English language corrections that are needed. 

 

Comments and proposed corrections:

-lines 109-113: The experimental details have been presented in Text S5, but in "2.3. Chemical analysis", at least the chemical analysis techniques must be referred;

 

-line 115: An impersonal style should be used in the manuscript ("...the back trajectory clustering technique was used...");

 

-line 117: The meaning of the two acronyms must be stated in full;

 

-lines 115-123: The experimental details have been presented in Text S6, but at least the used softwares (namely EPA PMF 5.0), the founding references for each model (e.g. "Paatero, 1999", for PMF) and the main parameters, must be referred in n "2.4. Source analysis";

 

-lines 138-139: This sentence should be rephrased (because an element can not be referred both as "carcinogen" and "non-carcinogen")...

 

-line 140: "Text S7" (and not "Text S8");

 

-line 151: Reference 32 (and the presented value) should be included in Table S5 for comparison

 

-lines 153-157: The mean value in each mentioned location should be referred in the text (in parentheses). Note: The fact that the same references in the text and in Table S5 have different numbers creates potential confusion.

 

-lines 153-154: It is stated "The PBM concentration in Xi'an is much higher than Lhasa". Is this true? The Lhasa value presented in Table S5 is 80 pg/m3, and the Xi'an mean concentration is 83.57;

 

-line 157: It is stated: The average PBM concentration in Xi'an "is also 8-9 fold lower than the PBM levels measured in Kathmandu (39)". This does not seem to be true based on the value presented in Table S5 (1855.4 pg/m3).

 

-line 170: PBM and PM2.5 concentrations are positively correlated, but the correlation in weak (r2=0.27), and this should be mentioned. 

 

-line 173-174: The argument makes no clear sense. It should be clarified or removed.

 

-line 193: From the observation of Figure 1, the value 50.88 does not seem correct.

 

-line 199: "The heating period in Xi'an ended on March 15..."

Is there such a set date for the terminus of the heating in Xi'an?

 

-line 203: The meaning of the yellow zone in the Figure should be explained in the caption.

 

-Figure 1: Negative PBM concentrations do not make sense, and so the axis should be altered.

 

-Table 1: I can not reproduce the values PBM/PM2.5 based on the other columns.

 

-line 206: Refer the yy axis first, as in the other graphs: "PBM/PM2.5 ratio and PM2.5 mass concentration"

 

-line 221-222: Please rephrase.

 

-line 238-241: The presented values, expressed in kg.y-1, are not "deposition flux"...

Furthermore, it does not make much sense to present minimum and maximum deposition "per year"; what should be present is the (average) amount of deposition in that year, considering both the dust and non-dust periods. For that, the "whole year" deposition flux should be presented in Table S8.

 

-line 248: Table S9 should be referred here.

 

-line 253-255: It is stated: ..."SO42-... mainly come from the desert surface soil, instead of the secondary generation through the photochemical oxidation of SO2." I do not think this is true. SO42- is mainly secondary.

 

-line 266-267: It is stated: "Water-soluble ions in PM2.5 can be regarded as an influencing factor and tracer, representing a potential source of Hg and other toxic air pollutants [52]. The sentence is not accurate (the water-soluble ions can be tracers of emission sources, they are not "influencing factors", and they in themselves, do not "represent a potential source of Hg"). Please rephrase.

 

-line 270-271: Please rephrase and add that all the correlations are weak (r2=0.12-0.36), except for the case of Cl-, which is moderate (r2=0.54).

 

-line 271: There is no correlation for NH4+ and NO3- (r2=0.01)... (please remove).

 

-line 272: The correlation for Ca2+ (r2=0.12) is too low to draw such a conclusion...

 

-line 280-281: The sentence is not true (there is no correlation between PBM and NO3-, r2=0.01). Please remove.

 

-line 280-286: Please remove (for the reasons specified in the attach)

 

-Section 3.2. and Figure 3: Many elements have also been determined (namely, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Cd, Ba and Pb), according to Figure S6. Did you study the bivariate correlation between these elements and PBM (and between elements)? It would bring important information on the sources.

 

-line 300: It is stated: "38.26% and 25.38%, respectively". The order of the values is reversed.

 

-line 322: The software used should be referred in the Figure caption.

 

-line 338-339: It is stated:"As performed in Figure 5b, the environmental parameters of WCWT are similar to those of WPSCF." Which "environmental parameters"? It should be "PBM concentrations". Please rephrase: "As depicted in Figure 5, the results of WCWT and WPSCF for PBM concentration show similarities."

 

-line 348 (caption): Which environmental parameters? It should be "PBM concentrations."

 

-line 352-353: The sentence makes no sense (The elements Ca, Na etc are not "sources of dust"). Please remove.

 

-Section 3.3.2.: Please specify the technique used for the determination of the element concentrations.

 

-line 354-355: It is not "In addition to Zn and Cd...", but "With the exception of Zn and Cd...".

 

-line 358: Have you performed statistical test, to verify if the difference was significant between periods? If not, the word "significantly" should be removed.

 

-line 360-361: "China National Environmental Monitoring Centre, 360

CNEMC, 1990". This reference is missing (please add).

 

-line 377-378: Ref. 66 is out of place.

 

-line 380: Refer the Figure.

 

-Section "3.3.3. Source Apportionment for PBM by PMF": The Authors have run the PMF model with just 1 month sampling... This is not possible, since PMF requires a much higher number of samples (around 100 samples), for this number of variables/elements). The manuscript can not be accepted with this PMF analysis, since it is certainly flawed and must therefore be removed from the paper. 

Other aspects on the PMF section:

-For a properly performed PMF analysis, modeling Quality parameters should be presented (and are missing).

-It should have been specified, in lines 385-386, that the PBM concentration was also considered in the PMF model, and what type of variable it was considered.

-Furthermore, it is not clear if the Authors have determined the source contributions for PM2.5 or for PMB (it is not the same thing...). 

-K and K+ should not have been included simultaneously in the PMF analysis (colinearity). 

-Other elements (Co, Cu, Ga, Se, Rb, Ba) have also been determined (according to Figure S6). It should have been explained why these elements were not included (or were excluded) from the PMF analysis.

-line 398-402: As I said, the PMF approach must be removed (due to the very small number of samples), but if the results were valid, I do not think Factor 3 would represent traffic emissions, but "Secondary aerosol" instead (as it is characterized by NH4+, NO3- and SO42-).

 

-line 414-415: The sentence does not make sense (please remove).

 

-Table 2: It must be specified that in the pre-dust and post-dust periods, mean values are presented.

 

SUPPLEMENTARY MATERIAL

In the Supplementary Material, several aspects have been corrected by the Reviewer (identified by track changes), but several other aspects must be corrected, namely:

Text S3:

-The expression (2) is not correct (it should be x6 and not x1/6).

-Please insert a reference for the expression (3).

-line below expression (3): Attention because these units of dry deposition flux are not correct! (it should be μg m−2 time-1).

-last line of Text S3: Reference 1 is not correct, since it does not refer the empirical value of dry deposition rate.

 

Text S4:

-1st line of Text S4: Please refer how the detection limit was determined (or cite a reference).

 

Text S5:

-Expression (4): “sample”, not “simple”.

 

Text S6:

-Attention: the expression (12) is not correct (“fkj” instead of “fik").

-A reference should be inserted for expression (12).

 

Text S7:

-Expression (13) and line below the expression: "sample", not "simple".

-A reference should be inserted for expression (14).

-Expression (14): "sample", not "simple".

-A reference should be inserted for expressions (15-17) and (18-25).

-The units of IUR are wrong (it should be (microg.m-3)-1, vd e.g. https://doi.org/10.1016/j.scitotenv.2021.148748), because CRinh is dimensionless.

-The reference of IRIS should be inserted.

-The reference for the classification of CR should be inserted.

 

Text S8:

-A reference should be inserted for expression (26).

 

Figures in Suppl. Material:

Figure S4: -A reference should be inserted for expressions (15-17) and (18-25).

Figure S6: Please specify in the caption, the technique used for the determination of these concentrations.

Figure S7: Concentration units are missing (in axis and caption).

 

Tables in Suppl. Material:

-Table S1: I don't think the column "Sample quality (g)" (which I think you meant "Sample quantity (g)") makes sense, since we are talking about blank filters, and thus there is no sampled mass.

-Tables S3: A reference should be inserted in the caption.

-Table S4: A reference should be inserted in the caption.

I have introduced the class designations by Wei et al. (2015), adopted in https://doi.org/10.1016/j.ecoenv.2021.111937.

-Table S6: Attention: the AF units are not correct! (it should be mg (cm2.d)-1).

Furthermore, Ref. 25 refers AF=0.07 for adults, and not 0.7 (please verify).

-Table S7: A reference should be inserted in the caption.

-Table S8:

The mean for the whole year should be presented, including both dust and non-dust days.

The last column is redundant (please remove).

The Table is not well formatted, because it is not obvious that the Max, Min refer to Dust days (as is stated in the text).

-Table S9: Please present the concentration units.

In this Table, the global average (including both dust and non-dust periods) should be presented for each ion.

 

References section:

Please insert DOI in each reference.

 

Best regards

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Comments for author File: Comments.zip

Comments on the Quality of English Language

The attachment identifies many English language corrections that are needed.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

 The article submitted for review is a relevant and original study, since it is devoted to the study of the migration of one of the priority toxicants of our time - mercury. The authors study the atmospheric path of mercury transfer with dust particles.

This study has scientific novelty, since it introduces into scientific circulation new data on mercury concentrations in the environment and its migration channels. However, there are a number of comments that need to be eliminated in order for the study to look more holistic and be more convenient for the reader to understand.

1. It is necessary to outline the goals and objectives of the research, this can be done in the abstract section. This will allow the reader to form an idea about the content of the article, about the author’s research and determine how interesting and informative the article will be in order to decide to read it. Designating goals and objectives will allow you to track the progress of the research and the compliance of the conclusions with the objectives.

2. The authors describe in detail the sampling methodology in the materials attached to the article. However, it is not entirely clear why the samples were frozen immediately after collection - perhaps this is stated in the method of preparing samples for analysis - a link to the sample preparation method needs to be given.

3. When the authors write "dust", do they mean a dust storm? It is not entirely clear from the graph (Figure 1). Maybe that's how we should write; "dust storm"?

4. Let's pay attention to Figure 1. The graph plotting area is filled with different colors, but there is no decoding of the meaning of these color designations. It is intuitively clear that the light orange color indicates the time of the dust storm, but the authors need to supplement the figure so that there are no ambiguities.

5. Figure 3. It combines 3 drawings, which, in our opinion, can be divided and each presented independently. Of particular interest here are the regression dependencies presented in the figure "regression of PBM with ions constituents (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, SO42−, NO3−) during the sampling period". As can be assumed from the figure, the only significant coefficient was identified for the chlorine ion. However, the authors do not explain this relationship. Meanwhile, this is an interesting observation in itself. We know that there are minerals - compounds of mercury and chlorine. Perhaps , it was particles of these minerals that came in, perhaps some other sources. It would be interesting to know the opinion of the authors - as experts in this area.

6. As for the assessment of environmental risk by the authors - of course, this section has the right to be here, however, I believe that it could well be framed as a separate scientific article based on the research conducted.

7. The conclusions need to be expanded and supplemented. I believe that the authors need to highlight the scientific novelty of the study - which was done for the first time and is reflected in this article. Have the authors achieved their goals and realized their objectives? What specific new data were introduced into scientific circulation, what conclusions were drawn based on a specific study.

Comments on the Quality of English Language

English can be improved and preferably tested with a native speaker.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The presented article explores a potential source of mercury particle pollution (PBM) in Xi'an, China, particularly during dusty storms. The study includes trajectory analysis, analysis of elemental ratios in dust sources, and the evaluation of various risk assessment methods for the environment and human health. However, several shortcomings need to be addressed:

The structure of the article is not always clear, making it difficult to understand the main results and conclusions.

The aim and objectives of the research need to be more clearly formulated in the introduction to help readers better understand the issues being investigated and the expected results.

There is no critical assessment of the research methods used, their limitations, and potential result biases. It is recommended to conduct a more detailed analysis of the research methodology. Include a section that critically evaluates the methods used, their limitations, and potential result biases. Provide more detailed information on the data, analysis methods, and results obtained to ensure reproducibility and understanding of the research.

The text lacks details about the data and its analysis, hindering reproducibility and understanding of the results. It is recommended to provide more detailed information about the data and the analysis methods used.

Some sections of the article are written in a complex and unclear style, while others are more accessible and clear. It is recommended to maintain a consistent style and presentation throughout the article.

Review the introduction of the article and clarify the aim and objectives of the research to make them clearer and more specific.

For greater clarity, it is necessary to cite articles addressing air pollution both in China and other regions. Authors can refer to articles such as those listed:

https://doi.org/10.1016/j.gsf.2023.101762

https://doi.org/10.1016/j.atmosenv.2012.09.003

Overall, the article makes a valuable contribution to the field of air pollution research and deserves attention from the scientific community. With the recommended improvements, it can become an even more valuable source of information for specialists in this field.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Sirs

A significant number of corrections are still needed before the manuscript can be published in Sustainability. Please find in attachment the manuscript file with the proposed corrections.

We further note that a high proportion of the cited references belong to the authors (Refs. 27,62,21,52,66,68,34,39,44,46,48,50,60,61), which can be considered excessive self-citation. Please eliminate some of these references, in order to make sure that all contribute significantly to the manuscript scholar content. 

Best regards 

Comments for author File: Comments.zip

Comments on the Quality of English Language

Dear Sirs

A significant number of corrections are still needed before the manuscript can be published in Sustainability. Please find in attachment the manuscript file with the proposed corrections.

We further note that a high proportion of the cited references belong to the authors (Refs. 27,62,21,52,66,68,34,39,44,46,48,50,60,61), which can be considered excessive self-citation. Please eliminate some of these references, in order to make sure that all contribute significantly to the manuscript scholar content. 

Best regards 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf