Spatial and Temporal Distribution Characteristics and Source Apportionment of VOCs in Lianyungang City in 2018
Round 1
Reviewer 1 Report
Observations of VOCs are a prerequisite for evaluating the effectiveness of air pollution control policies. Based on continuous observation data of 5 sampling sites in the urban, the suburban and industrial area from April 1 to September 30, 2018, this study analyzed the spatial-temporal variation of VOCs concentration in Lianyungang City, components contribution, emission sources and their Ozone Formation Potential. The results supplied detailed data on O3 alleviation.
Line 184-187: It is well known that VOCs are key precursors in forming tropospheric O3, however, the O3 concentration isn’t perfectly consistent with the VOCs concentration, please identify and quantify metrological parameters’ role in the O3 formation and VOCs.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript entitled “Spatial and temporal distribution characteristics and source apportionment of VOCs in Lianyungang City in 2018” investigates the characteristics of VOCs and their source apportionment at five sites in Lianyungang. The study on ambient VOCs is important for the air pollution control in China. But there are some questions needed to be addressed in the manuscript.
Major comment
This study applied common methods and focused on a very local problem. How the innovation and significance of this study.
Specific comments
- Line 213-215, “The trend of VOC concentrations at the five sampling sites were relatively consistent, with the largest proportion of alkanes in spring. In summer, the proportion of aromatics and alkenes increased, and in autumn, the proportion of alkanes increased.”. Please explain them.
- There are some grammar mistakes. For example, line 116, “at least one canister should be select” should be changed to “… selected”.
- The reference (Y et al., 2006) may be wrong. Please check.
- Line 333, “Isoprene was the tracer of plant emissions, and there were certain emissions in industrial processes.”. Isoprene may also come from the vehicle emission. Please furtherly verify the factor and evaluate the results of source apportionment.
- Comparison with other cities or regions can be added to reveal the relative level of VOCs in Lianyungang City.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript describes the levels of volatile organic compounds (VOCs) in the atmosphere of different sites (urban, industrial and suburban) from China during 6 months. The results are discussed in terms of seasonality, sources and the relation with ozone levels found in the same sites. The work is too much descriptive, without a deep or novel discussion of the results. Authors analysed the common VOCs in different sites, but their results do not provide any novelty/advance in the research field. They are just the usual compounds determined in other different sites without any interesting characteristic. I would recommend working more on the data obtained in order to contribute to the knowledge of these compounds and their relationship with the formation of ozone
MAIN DRAWBACKS
I understand that authors are studying sites from China; however, the introduction must give the state-of-the-art of the research field. Looking the references (here and in others sections of the manuscript), it seems that all work done in this field have been focused on China and have been done by Chinese researchers (of the 33 cited references, 27 are from Chinese authors).
Lack of methodological details. Readers need to search for what seems a report “Canister sampling / gas chromatography-mass spectrometry for the determination of volatile organic compounds in ambient air” (HJ 759-2015), for knowing the analysed compounds, analytical procedures, MS identification and quantification. This supposed report is not included in the bibliography and no records appear if it is searched by internet. Therefore, it is difficult to assess the results of a scientific work without knowing the methods applied for their production.
Most of the results are given as average of different groups of compounds without specify which compounds are consider, so reader must trust that the results are those that the authors state. Without the raw data, it is difficult to evaluate the levels found, their reliability and compare them with other levels published in other sites. In addition, several times in the text it is stated that O3 or VOCs levels are higher/lower in different seasons/sites; however, taking into account the averages and standard deviations, one can questioned if these levels are statistically significant different (for example O3 in spring 97.76±49.9 µg m-3, autumn 88.10±42.6 µg m-3, and summer 85.64±43.0 µg m-3 ).
Authors mention some tables and figures in supporting information, but I could not find this supporting material, for example in Line 324, where can I find tables S1-S5 to check the results? Without this information, it is impossible validate if the conclusions of the work are consistent.
DETAILED COMMENTS
Line 24. What is OFP? It is not define previously.
Keywords: Two keywords are included in the title. Choose others in order to widen the search possibilities.
Line 296. How is MIR calculated? Are their values taken from the literature? Then the reference should be included
Line 303. Should be table 5?
Figure 3. Consider to draw each variable in different panels. It would be clearer if some data do not share panels. For example, it is difficult to see the fluctuations and correspondences of ozone and NO2.
Figure 4. It is very difficult to see the results for each group of VOCs in the left panel
Figure 5. I cannot understand some colours in this figure (grey, pale blue…)
Figure 7. Sort the compounds in the y-axis following the same order in all graphics, otherwise it is confusing.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
This paper analyzes the VOCs characteristics of different regions in Lianyungang city, and enriches the VOCs characteristics and source apportionment results of different types of urban atmospheric environment. However, there are some fundamental issues that need to be addressed. The major problems can be summarized as follows:
- There are many errors of expression in the manuscript; ①The full name of abbreviations should be given in the manuscript (Line 88: GC-MS/FID); ②“Ozone Formation Potential (OFP)” appears in line 63, while “O3 formation potential” appears in line 91; ③The icon title should begin with a capital letter in Figure 2; ④“Table 1-3” in line 216 should be changed to "Table 2-4"; ⑤“As shown in table 4” in line 297 should be changed to “As shown in table 5”; ⑥“According to table 2-5” in line 348 should be changed to “According to table S2-S5”；⑦The legend in Figure 5 is inconsistent with the color filling of the original picture, and the content expressed in the picture is confusing.
- The content of source apportionment by PCA model is described in the abstract is too simply.
- The analysis of PM2.5 concentration in Section 3.1 seems to have little relation to the overall content of the article.
- It can be seen that there are obvious differences between different sampling sites in the same functional area from Figure 4, but corresponding descriptions and difference analysis are missing in this paper.
- Is there any difference between VOCs characteristics of the atmospheric environment in Lianyungang city obtained in this study and those of other regions in other studies? If so, what are the reasons for the difference.
- The 116 VOC species mentioned in section 2.2 included 36 halogenated hydrocarbons and 22 oxygen-containing VOCs, but why did the subsequent analysis not include all VOC species?
- Whether the typical VOC species vary regionally and seasonally is not mentioned in the paper.
- The description of VOC source apportionment results in Section 3.5 is too simple, and there is no quantified data or chart. For sampling sites in suburban, the influence of vegetation source is not reflected.
- There are many grammatical errors in this article. I would recommend that the authors have it proofread by a native English speaker.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
All the comments are well addressed. It can be considered to be accepted.
Author Response
Thanks to the expert teachers for commenting on our manuscript entitled "Spatial and Temporal Distribution Characteristics and Source Apportionment of VOCs in Lianyungang City in 2018" (ID: 1432336).
Reviewer 3 Report
The new version does not address most of my concerns about the novelty of the study, the inclusion of more analytical details and the need of a deeper analysis of the results. In fact, almost no changes have been made in this new version in relation to the former one, therefore my recommendation about its publication is essentially the same.
Below I comment some the authors’ responses to my original questions:
Response to Point 1: First of all, I am very grateful to the expert teachers for their opinions. The focus of this article in the introduction is not that all work done in this field are carried out by Chinese researchers, but that I want to introduce the situation of VOCs in Lianyungang that this article wants to introduce by introducing the progress of other cities in China in the research of VOCs.
Comment to authors’ response: No other new reference has been included, although there several examples (in the introduction and in other sections of the manuscript) where general information of VOCs are discussed (not focused on China)
Response to Point 2: Lines 120-135 in the article describe the details of the method for collecting and analyzing VOCs samples.
Comment to authors’ response: No reference has been included for the methodology applied and no other details about experimental work have been added. For example, which compounds have been analysed, which standards have been used, MS in full scan or in selective ion monitoring mode?, and so on.
Response to Point 3: First of all, I am very grateful to the expert teachers for their opinions. If necessary, the raw data can be attached in the supporting materials. In addition, lines 180-182 in the text are just for comparing the relative size of O3 concentration in each season
Comment to authors’ response: I think it would useful to include the raw data in the supporting information. Regarding my second comment, do you think these values (for Ozone or VOCs in other sites of the manuscript) are statistically different?. Have you performed any statistical test to confirm if they are really different?
Author Response
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Author Response File: 
Author Response.docx
Reviewer 4 Report
After the last round of revision, the article has been further improved. However, there are some issues that need to be addressed clearly.
- In terms of differences between different sampling sites in the same functional area, corresponding difference analyses are still missing in this paper. Please give further details.
- The problem about the seasonal and regional variation characteristics of typical VOCs species is not supplemented.
Author Response
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Author Response File: Author Response.docx
