Observation and analysis of speciated atmospheric mercury in Shangri-La, Tibetan Plateau, China

Zhang, H.; Fu, X. W.; Lin, C.-J.; Wang, X.; Feng, X. B.

doi:https://doi.org/10.5194/acp-15-653-2015

Articles | Volume 15, issue 2

https://doi.org/10.5194/acp-15-653-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-15-653-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 15, issue 2

Research article

|

19 Jan 2015

Research article |

| 19 Jan 2015

Observation and analysis of speciated atmospheric mercury in Shangri-La, Tibetan Plateau, China

H. Zhang, X. W. Fu, C.-J. Lin, X. Wang, and X. B. Feng

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Final revised paper (published on 19 Jan 2015)
Supplement to the final revised paper
Preprint (discussion started on 05 May 2014)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC C2691: 'Referee comments on “Observation and analysis of speciated atmospheric mercury in Shangri-la, Tibetan Plateau, China”', Anonymous Referee #1, 24 May 2014
- AC C5769: 'Response to comments from referee #1', Xinbin Feng, 12 Aug 2014
RC C3103: 'Review of "Observation and analysis of speciated atmospheric mercury in Shangri-la, Tibetan Plateau, China" by Zhang et al.', Anonymous Referee #2, 02 Jun 2014
- AC C5770: 'Response to comments from referee #2', Xinbin Feng, 12 Aug 2014
RC C3174: 'Referee Comments', Anonymous Referee #3, 03 Jun 2014
- AC C5771: 'Response to comments from referee #3', Xinbin Feng, 12 Aug 2014

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Xinbin Feng on behalf of the Authors (12 Aug 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Aug 2014) by Leiming Zhang

RR by Anonymous Referee #1 (21 Aug 2014)

Suggestions for revision or reasons for rejection

Suggestions for revisions for the revised ACPD paper:

P4-5: Description of sampling and analysis of speciated atmospheric Hg is still unclear and missing details. Please state how long was the sampling cycle and how long was the desorption/analysis cycle. It doesn’t seem feasible for the site operator to replace the GOM and PBM sampling lines every two hours at nighttime even if it takes only 10 minutes. The samples appear to be analyzed offline, but it was not stated in the paper. If it’s done offline, it doesn’t seem feasible to analyze GOM and PBM samples at nighttime (revised paper states the samples were analyzed immediately on P5, L14-15). This is why the reviewer comment suggested including the procedures for storing the denuder and quartz filter samples to minimize sampling errors and contamination.

P5, L11: The year for the Landis et al. citation is missing.

P6, L6: Should be “Negative IMI indicates northerly wind that pushes the air back to the Indian Ocean.” Please mention here that the IMI is correlated with rainfall intensity in the revised paper. This was only explained in the response to comments.

P6, L28: The order of the reference citations need to be corrected. Specify which Landis et al. 2002 reference is being referred to here. Please double check other citations with the reference list.

P8, L17: It should be mentioned in the revised paper that data were not available to support the explanations and that “It is speculated that diurnal mountain valley breezes...”

P8, L22-24: The relative humidity data provided here do not correspond with the average diurnal pattern of relative humidity in Fig. 4, which shows lower RH in the afternoon period than overnight and morning. Please revise this. I believe you wanted to show lower RH was associated with higher GOM.

P8, L22-30: Not enough data analysis has been done to rule out other factors influencing the diurnal patterns (e.g., mountain/valley breezes suggested in the reviewer comment or other factors). It should be mentioned in the revised paper that data were not available to support the explanations and that the explanations are possible theories.

P9, L14: It’s not conventional to use p = 0; it should be p<0.001 or p<0.0001. Also in P10, L3, it should be p<0.05 or some other significance level.

P9, L30 to end of paragraph: This sentence is a run-on sentence with several grammatical errors.

P10, L14-17: Despite finding weak correlation coefficients and explaining in the response to comments that weak scavenging is a possible reason, the revised paper continues to state that “This may indicate the role of increasing wet scavenge process that played in the lower GOM and PBM concentrations during the ISM period”. There are also grammatical errors in the previous sentence. The conclusion also stated, “moist air during the ISM significantly decreased GOM and PBM levels.” These statements need to be revised to reflect the statistical analysis results.

P10, L25-29: This sentence is a run-on sentence with several grammatical errors.

P10, L32: Should be “These two reasons...”

Table S1 (Supplement): This table was not mentioned anywhere in the revised paper. The statistical analysis results for the trajectory clusters should be incorporated into the discussion in section 3.4. Please clarify if these are the statistical analysis results to assess whether TGM concentrations between the trajectory clusters were statistically different. The table caption is different from the response to comment #33 for Reviewer #3. According to Table S1, the mean TGM concentrations were not statistically different between clusters 1 and 2 and between clusters 2 and 3. The discussion in section 3.4 needs to be revised to reflect these statistical analysis results.

Common issues raised by other reviewers:

More details on the manual sampling and analysis of speciated atmospheric Hg are needed

Not enough data analysis done to support explanations

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RR by Anonymous Referee #3 (04 Sep 2014)

Suggestions for revision or reasons for rejection

The authors have made some changes following reviewers’ comments and suggestion. Overall, however, the revised manuscript still lacks the integrity and quality to meet the standards for publication in Atmospheric Chemistry and Physics. One major problem is the lack of direct or indirect data to support the proposed mechanisms regarding the temporal variation in Hg concentration and speciation. The proposed emissions sources, such as biomass burning, are also highly speculative because of lack of supporting evidence, too. Considering the value of these data that could contribute to the understanding of regional and global Hg transport and cycling, I think the authors need to analyzed their data and revised the manuscript again very carefully before it can be considered for publication in Atmospheric Chemistry and Physics.

1. The manuscript needs to be proofread carefully. Errors can be found throughout the manuscript. For example, “bioaccumulates” in line 4 of page 2 should be “bioaccumulate” and “low” in line 18 of page 8 should be “high”. Some sentences are not easy to understand, for example, line 27-30 of page 7.
2. Data QA procedure is not provided. How did the authors decide if the data is OK to use or not? Or the authors just used all the data reported from the instrument without any screen criteria?
3. The description of sampling instrument is not very clear. I think the authors should prepare a figure or diagram showing how the manual GOM and PBM sampler was connected to the Tekran 2537A. Was the TGM measurement continued when analyzing the GOM and PBM samples?
4. Page 5, Line 11: Landis et al., which year?
5. Page 7, Line 7: please change “nij” to “Nij”.
6. Page 7, Line 24-26: “As a remote background site, .....” References are required to support this statement.
7. Page 8, Line 11-13: I don’t understand why the cumulus process could cause dilution of the air masses and gave lower TGM concentrations. Although the authors indicated this would be further discussed in section 3.3, I don’t see a real discussion there. Any reference to back up this statement?
8. Page 8, Line 22-24. Here the authors said that relative humidity was higher in the afternoon than at night and in the morning. However, in Figure 4, it shows clearly that RH was lower in the afternoon. Please double check which one is correct. Because of this inconsistency, the follow-up discussion is problematic.
9. Page 9, Line 19-22: The authors first suggested that the lower TGM in late fall and winter months was due to more stagnant wind that limited the regional transport. In the next sentence, however, the authors then suggested that the variation in wind speed was not likely to cause the observed TGM seasonal variation. These two sentences seemed to contradict each other.
10. Page 9, Line 33 to Page 10, Line 1: “....., therefore the GOM level at SAWRS could be effected primarily by local photochemical transformation or meteorological conditions, as compared to the subsidence of free troposphere”. If local photochemical transformation is so important why GOM level peaked in winter not summer?
11. Page 10, Line 5-6: “Therefore the local anthropogenic sources could contribute to the high PBM level at SAWRS”. What kind of local anthropogenic sources? In section 2.1, the authors indicated that SAWRS is a remote site and the closest large point sources are in Kunming, about 500 km away. This statement implies that there is no local anthropogenic source near SAWRS. Besides, if there is influence from local anthropogenic sources, I would expect to see high values of TGM and PBM, and maybe GOM, occur concurrently? Is this the case?
12. Page 10, Line 9-10: “Due to increasing consumption of resource, these areas are expected to release remarkable Hg to the atmosphere”. This is purely a guess. Please provide real data or references to support it.
13. Page 11, Line 28-29: “The most likely source region was South Asia’s biomass burning activities”. No data to support this statement.

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ED: Reconsider after major revisions (06 Sep 2014) by Leiming Zhang

AR by Xinbin Feng on behalf of the Authors (01 Nov 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Nov 2014) by Leiming Zhang

RR by Anonymous Referee #1 (11 Nov 2014)

RR by Anonymous Referee #2 (21 Nov 2014)

Suggestions for revision or reasons for rejection

Major comments
This is the third round of reviews for the manuscript “Observation and analysis of speciated atmospheric mercury in Shangri-la, Tibetan Plateau, China.” Although, some sections are much improved, unfortunately, there are still significant language issues. I have tried to point out some of them, but it is still is not in a final publishable form even after three reviews.
The authors have done a good job showing how the denuders were analyzed (for GOM) but still have not reported exactly how they analyzed the filters for PBM (e.g., were the filters removed from the filter holders, placed in a non-annular denuder and heated in a Lindberg Furnace?). Although they state that their method is identical to a Tekran speciation unit, this is not true. Having to remove a filter each time a sample is collected is not an identical analysis method, it is similar but not identical.
The manuscript could also use a reorganization. Section 3.3 and the first paragraph of Section 3.4 are well written and really work to substantiate the findings. Instead of talking about distribution and influences of potential regional sources and the backtrajectory analysis in separate sections, the results of these two parts should be integrated and the backtrajectories used to more clearly make the point. As the paper is organized right now, statements are made in Section 3.1 and seem unsubstantiated until Section 3.3 – 3.4. The paper would be much clearer if the statements were immediately justified and these discussions were combined.
Further major revisions to the language, method description, and discussion are needed before this manuscript can be published.

Specific comments
1) P2 L11: need citations after “respectively”
2) P2 L13: need citations after “respectively”
3) P2 L19: “help understand” should be “help with understanding”
4) P2 L29: should be “corner of the Tibetan”
5) P2 L30: should be “mainland” not “Mainland”
6) P2 L33: “Recently, there” should be “There”
7) P3 L5: “pollutants emissions” should be “pollutant emissions”
8) P3 L17: “aimed to establish” should be “aimed at establishing”
9) P3 L19 - 20: “The data within GMOS network provide global monitoring data…” should be “The global monitoring data within the GMOS network can be used…”
10) P3 L22: The citation Gay et al., 2013 is about AMNet. Not GMOS, I suggest a citation about GMOS.
11) P3 L31: “away from” should be “of”
12) P3 L31: “The largest point sources…” In a previous comment I asked what these were and this has not been addressed. Are they coal fired power plants? Cement manufacturing? Gold mining? Just how large are these sources?
13) P3 L33: “are to east” should be “are east” and what is the distance from Shangri-La.
14) P4 L26: “A denuder-based sampling unit was for sampling PBM and GOM and it was separated from the TGM measurements using the Hg vapor analyzer” should be “A denuder-based sampling unit (separate from the TGM sample train) was used for sampling PBM and GOM.”
15) P5 L14 – 15: “other is undergoing” should be “other was undergoing”
16) P5 L16 – 17: “samples can be collected a day.” Should be “samples were collected per day.”
17) P5 L17: “filter after air sampling were analyzed immediately” should be “filter were analyzed immediately after air sampling.”
18) P5 L19 – 28: Still not fully addressing the reviewers concerns! Specifically detail what was done to the quartz filter. On pg 5 of the SI it does not show or state how the quartz filter was handled during the analysis by saying “A separate PBM quartz trap of identical connector” does not address this concern. Was the filter placed in this “trap”? How? Were tongs used? If so were the tongs Teflon coated? I see a hollow denuder in Fig S6, was this used? Was the filter analyzed in this? If it was how was the filter placed in the denuder? These issues are the reasons the reviewers are having so many issues.
19) P5 Line: Please reference discussion in Supporting Information
20) P5 L24: “using a pyrolyzer for three heating cycles” – in Fig. S5 this is a Lindberg Blue clamshell furnace and not a “pyrolyzer”. What was a heating cycle? The cycles on the furnace would be heating to the 500 or 900 then completely cooling and heating again. This is not possible with the current set up, in order to be ready for the next sample collection.
21) P5 L26 – 27: Change “the caps were not heated and air cooling was also used to lower the temperature of caps” to “a fan was used to blow cool air on both ends of the denuder.”
22) P5 L34: Change “The blank of denuder and quartz filter” to “The denuder and quartz filter blanks”
23) P6 L2: “procedure were followed to ensure the data” should be “procedure was followed to ensure data”
24) P6 L3: “of Tekran 2537A must to be” should be “of the Tekran 2537A must be”
25) P6 L8: should be “via an automatic”
26) P6 L15: should be “by air transport of the ISM, and wet air flow from the Indian Ocean will cause high rainfall in southern and southeastern Asia.”
27) P6 L17-18: Remove “A positive IMI also indicates the wet air flow form Indian Ocean will cause high rainfall in southern and southeastern Asia.”
28) P7 L24 – 25: There is a range of months referred to, but only one spike for each period. Is this a single spike or where spikes typically this high? If they are single spikes the date the spike occurred should be given.
29) P8 L17-22: were the differences in concentration by wind direction statistically significant?
30) P8 L24: should be “dilution of an air mass”
31) P8 L26: “and therefore gave” should be “resulting in”
32) P8 L29: “located at a” should be “located on a”
33) P9 L9: should be “and photochemical”
34) P9L13-14: If statistically lower we need a p value, if not then this should be mentioned or discussion removed.
35) P9L27: should be “during the ISM” and “air masses”
36) P9L28: “flow into inland” should be “flow inland” and “In addition, the cumulus”
37) P9L29: should be “in the atmosphere”
38) P9L30: should be “from the surface” and “relatively lower”
39) P9L32: should be “August) likely due”
40) P9L33: should be “limited regional”
41) P9L33-34: So if the wind speeds weren’t different then this explanation is not supported by your data and must be deleted.
42) P10L27: This section needs incorporated earlier to make the discussion more understandable.
43) P10L29: “values IMI” should be “IMI values”
44) P10L33: What does “High TGM peaks were not observed consistently” mean?
45) P11 L13: This discussion also needs incorporated earlier
46) P11 L21: should be “moved fast, passing”
47) P12 L3: should be “from Central”
48) P12 L6: “were displayed” should be “are displayed”
49) P12 L8-10: “The winter…” This sentence says that the trajectories were cause by domestic sources, I think this should refer to mercury concentrations instead.
50) P12 L11: What does “mild air movement” mean?
51) P12 L31: should be “on the Tibetan plateau”
52) P13 L1: should be “levels by occasionally”
53) P13 L2: should be “while moist air from the ISM likely decreased”
54) P13 L7: Maybe there should be some mention of the very nice cluster analysis results here to support these statements.

Supporting Info
I have only given this a cursory look, but the text here needs a complete re-write as there are many typographical errors.
Pg 5 last paragraph: “paralyzer” should be “pyrolyzer”
Pg 5: This technique is not identical to the speciation unit, so please remove any reference to “identical.”
Fig S2: Grass should be Glass

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ED: Reconsider after minor revisions (Editor review) (23 Nov 2014) by Leiming Zhang

AR by Xinbin Feng on behalf of the Authors (03 Dec 2014) Author's response Manuscript

ED: Publish as is (08 Dec 2014) by Leiming Zhang

AR by Xinbin Feng on behalf of the Authors (10 Dec 2014)

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