Source Apportionment and Risk Assessment of Soil Heavy Metals due to Railroad Activity Using a Positive Matrix Factorization Approach
Round 1
Reviewer 1 Report
Comments to sustainability-2050681
The manuscript raised critical issues that should be studied to show the potential risks of living along railway sides, which is problematic. However, the following points should be critically considered for publication.
Abstract
ü It could have been better if the authors began the abstract with one background statement that showed the problem initiating this study.
ü Line 13-14. “The results showed railway 13 operation was the dominant anthropogenic of heavy metal contents in soil, with contributions 14 ranging from 11.73% to 42.55%”. This statement should be misleading as there are no other sources studied. How much we are sure it is the dominant contributor without studying other sources too.
ü Line 23-24. “Our research could give suggestions for railway risk management and control.” Please forward your suggestion (recommendation) based on your key findings than the current statement.
Introduction
ü Line 50-57. The statements are more on approach (methodology), not a gap-filling statement. The authors had better substitute with gap-filling statements, and shift the current narrations to the method section.
ü Limitations and advantages of the models used should be specified.
Materials and Methods
ü Section 2.1. It should encompass an elaboration of the reason for selecting the four sites. Besides, the authors should indicate the sampling technique with convincing reasons. It seems purposive, but not indicated. In addition, to reach a conclusion, there had to be a site far from the railway that was used as a control.
ü Line 78…”..at various distance….” The authors should specify the exact distance from the statement currently used.
ü Difference analysis method and software used should be indicated
ü How much is the model viable to indicate the potential sources of agriculture, and automobile while the area is selected based on the railway proximity?
Results and Discussion
ü The main limitation of this study is the use of the background soil characteristics which was performed about 20 years before. Is it really possible to compare the current data with the 20-year-old data? It could have been better if the authors had control data so that it would justify more.
ü Table 4 and Table 5. What was the method of data collection for the sources?
Conclusion
ü In my view the study conclusion should be on the additional non-carcinogenic and carcinogenic risks due to rail than on the different contributors.
Author Response
1. It could have been better if the authors began the abstract with one background statement that showed the problem initiating this study.
Response 1: Abstract was rewrote and background statement was added.
2. Line 13-14. “The results showed railway 13 operation was the dominant anthropogenic of heavy metal contents in soil, with contributions 14 ranging from 11.73% to 42.55%”. This statement should be misleading as there are no other sources studied. How much we are sure it is the dominant contributor without studying other sources too.
Response 2: Abstract was rewrote.
3. Line 23-24. “Our research could give suggestions for railway risk management and control.” Please forward your suggestion (recommendation) based on your key findings than the current statement.
Response 3: Abstract was rewrote.
4. Line 50-57. The statements are more on approach (methodology), not a gap-filling statement. The authors had better substitute with gap-filling statements, and shift the current narrations to the method section.
Response 4: Information was added in introduction.
5. Limitations and advantages of the models used should be specified.
Response 5: Information was added in introduction.
6. Section 2.1. It should encompass an elaboration of the reason for selecting the four sites. Besides, the authors should indicate the sampling technique with convincing reasons. It seems purposive, but not indicated. In addition, to reach a conclusion, there had to be a site far from the railway that was used as a control.
Response 6: More details about sampling were added. The main reasons for selecting these four sampling sites were 1) the railways they close to could cover basic types of usual railway in Japan; 2) they were public green places where we could do sampling legally. In our research, some sampling areas were relative small. It couldn't find proper controlling site. In this situation, after discussed with co-authers, we determined to use Takeda's research as background value. In the future research, we will try to find better sampling sites.
7. Line 78…”..at various distance….” The authors should specify the exact distance from the statement currently used.
Response 7: Map of sampling was added.
8. Difference analysis method and software used should be indicated
Response 8: Information was added in section 2.2.
9. How much is the model viable to indicate the potential sources of agriculture, and automobile while the area is selected based on the railway proximity?
Response 9: According to uncertainty analysis(line 333-340), the PMF results in our research are acceptable.
10. The main limitation of this study is the use of the background soil characteristics which was performed about 20 years before. Is it really possible to compare the current data with the 20-year-old data? It could have been better if the authors had control data so that it would justify more.
Response 10: In Japan, Takeda's research was widely used as Japanese soil heavy metal's background. As mentioned above, some sampling areas were relative small. It couldn't find proper controlling site. In this situation, after discussed with co-authers, we determined to use Takeda's research as background value. In the future research, we will try to find better sampling sites.
11. Table 4 and Table 5. What was the method of data collection for the sources?
Response 11: The method of calculation was mentioned in section 2.4.3 and 2.5.2.
12. In my view the study conclusion should be on the additional non-carcinogenic and carcinogenic risks due to rail than on the different contributors.
Response 12: Conclusion was rewrote.
Reviewer 2 Report
This MS showed the effects of different railways on soil metals contamination. It showed some interesting results. However, due to the weak data management and English writing. It still needs to major revise. The detail comments showed as following:
Title, PLS make a novel title
Abstract, PLS rewrite it. Show your method and main results.
Lines 31-34, Grammar
Lines 43-47, Grammar
Lines 48-57, It is method, not the objectives. So PLS make the objectives clear.
Section 2.2. For the sampling, how far is from railway? How many samples for each type train? How to ensure the representativeness of your samples. Some are from urban and some are from countryside. Also, there are diesel train and electricity train. How to compare it? Why did not to take samples under both urban and countryside?
How about the background value of the sample sites?
Line 114. PLS changing Cn as italics. Similar in the following.
PLS add the statistical analysis and software
Table 3. PLS add the statistic differences.
Lines 201-206, Where is the result? Could you make a fig.
Section 3.0 Could you please show the difference of diesel versus electricity, and countryside versus urban. What is the difference between of railway soil and other soils.
Section 4.0, PLS make your conclusion much more concise. The conclusion should show your new finding and main results. It should answer your objectives.
Author Response
1. Title, PLS make a novel title
Response 1: Changed in manuscript.
2. Abstract, PLS rewrite it. Show your method and main results.
Response 2: abstract was rewrote.
3. Lines 31-34, Grammar
Response 3: Changed in manuscript.
4. Lines 43-47, Grammar
Response 4: Changed in manuscript.
5. Lines 48-57, It is method, not the objectives. So PLS make the objectives clear.
Response 5: Introduction was rewritten.
6. Section 2.2. For the sampling, how far is from railway? How many samples for each type train? How to ensure the representativeness of your samples. Some are from urban and some are from countryside. Also, there are diesel train and electricity train. How to compare it? Why did not to take samples under both urban and countryside?
7. How about the background value of the sample sites?
Response 7: In our research, some sampling areas were relative small. It couldn't find proper controlling site. In this situation, after discussed with co-authers, we determined to use Takeda's research, which was widely used in study about Japanese soil heavy metal, as background value. In the future research, we will try to find better sampling sites.
8. Line 114. PLS changing Cn as italics. Similar in the following.
Response 8: Changed in manuscript.
9. PLS add the statistical analysis and software
Response 9: Information was added in manuscript.
10. Table 3. PLS add the statistic differences.
Response 10: The statistic differences was mentioned in section 3.1.2.
11. Lines 201-206, Where is the result? Could you make a fig.
Response 11: We rewrote this sentence to avoid misunderstanding.
12. Section 3.0 Could you please show the difference of diesel versus electricity, and countryside versus urban. What is the difference between of railway soil and other soils.
Response 12: In this paper, we wanted to focus on risk assessment and contribution of railway operation to soil heavy metals. However, it still could be noticed in section 3.1.2 and 3.2.1 that there were difference between diesel and electricity railways. In our future study, we'd like to collect more samples to make a deeper analysis about these differences. In introduction, we described why we chose railway soil, not other soil as target. Because in Japan and many other places, there are residence or agriculture field in 5-10m to railway. Previous studies revealed that in that distant to railway, surface soil might have high concentration of heavy metals. In the future study, we could try to compare railway soil and other soil, even road dust to make a deeper understanding of effects of railway on environment.
13. Section 4.0, PLS make your conclusion much more concise. The conclusion should show your new finding and main results. It should answer your objectives.
Response 13: The conclusion was rewritten.
Reviewer 3 Report
Reviewer’s comments
1. The title is ambiguous. It is suggested to be as follows: “Risks assessment of soil heavy metals due to railroads activity using positive matrix factorization approach”. Or “ Evaluating the potential risks associated with soil heavy metals in the vicinity of railroads using positive matrix factorization technique".
2. Please identify terms in the abstract by name when they first appear in the text. PMF-ERA and PMF-HHRA, for instance. (Positive Matrix Factorization-Environmental Risk Assessment and Positive Matrix Factorization-Human Health Risk Assessment)
3. Add the following to the introduction (Lines 31-32):
- “Although metals are present naturally in the environment, due to volcanic eruptions, soil formation alongside river sedimentation, rainfall, and rock weathering.
- The authors are directed to the following paper: Heavy Metals and Pesticides Toxicity in Agricultural Soil and Plants: Ecological Risks and Human Health Implications (https://doi.org/10.3390/toxics9030042).
4. Were Zn, As, and Hg present in your analysis?
5. What is the ppm concentration of the “Ni, Cu, Cd and Pb” heavy metals in the soil?
6. Is there any explanation for the differences in the number of samples that were gathered for this investigation, such as the 39 samples from Niigata soil and the 47 samples from Tachikawa soil, 21 samples from each of the Datemonbetsu and Komagawa soils)?
7. How much does each sample weigh?
8. What does HF stand for in line 82?
9. Do you mean bakers or beakers in line 86?
10. In line 87, what do you mean by Milli-Q water? Is it distinct from tap water?
11. What does "EPA PMF v5.0" mean in Line 95?
12. What does RSD stand for in Line 107?
13. Kindly give the citation of Table 1, Line 118.
14. What does RI stand for in Line 135? I think it stands for risk index.
15. What is the reference for Table 2 in Line 137?
16. What does PMF-ERA stand for in Line 139? “Positive Matrix Factorization-Environmental Risk Assessment”
17. What does RfD stand for in Equation 10, Line 157?
18. What does PMF-HHRA stand for in Line 174?
19. What does "mean by P value" indicate in Line 200 when the Kruskal–Wallis H test was used?
20. In Line 215: Do you mean six sampling areas or four sampling sites?
21. Line 215, What are the four factors identified in Figure 1?
22. Figure 1, kindly show the full-name of the site and its contribution factors F1, F2, F3 & F4 on the charts.
23. Please refer to Table 3 for background values in Line 233 and Line 238.
24. In line 240, correct the word the trailway to railway.
25. Lines 244, 251 and 257: Would you please name Factor 1, Factor 4 and Factor 3 in the text that are linked to railways operation (e.g. agricultural or industrial activities).
26. Lines 287-288, the sentence should be written as follows: “Table 4, at all sampling sites, railway operation was the main anthropogenic event, contributing with 11.73% to 42.55%”.
27. Lines 288-289, “The second dominant source in Datemonbetsu and Komagawa zones was agricultural activities at 24.81% and 26.13%, respectively”.
28. Figure 2, Please use more distinct colours to represent agricultural and natural source activities.
29. Figure 4, use different colors to better represent the risk indices of heavy metals for the four sampling sites.
30. Figure 5, use distinct colors to better depict of the ecological risk of different sampling sites.
31. Line 348, Table 5 not 6.
32. Lines 353-354, “In this research, industrial and agricultural activities only showed high contributions in the two sampling areas”. This sentence needs to be revised as both industrial and agricultural activities have only high contribution in Komagawa site and agricultural activities contribute to % of ecological risk in Tachikawa.
33. Line 361 what do HQing & TH stand for?
34. Line 367, what does THQ stand for?
35. Line 368, “Table x also shows that Cr and Pb were the elements that people...”. Where is the Table?
36. What does TRC stand for?
37. Line 373, Table 7 is missing.
38. Line 380, “….while those for 379 adults and children were similar”. I think the word “adults should be deleted.
39. Lines 389-391, “For instance, at the Tachikawa sampling site, the contributions of natural sources to adult noncarcinogenic and carcinogenic risks were 56.34% and 86.06%, respectively…”. The correct site is Niigata.
40. Lines 392-394, “On the other hand, the contribution of agricultural activities to adult carcinogenic risk decreased to 6.59%, which was only approximately a quarter of the contribution to content”. This sentence should be revised as follows:
“On the other hand, at Datemonbetsu, agricultural activities contributed 17.39% of the adult non-carcinogenic risk. For adult carcinogenic risk, this percent falls to 6.59%,...
41. Line 400, change word “near” to “nearby”.
42. Line 400, “applying a positive matrix”. Please add “factorization model”.
43. Lines 403-404, “At the other two sampling sites, it was the second dominant source”. Rewrite as “It was the second most prevalent source at the other two sampling locations, Niigata and Tachikawa”.
Author Response
1. The title is ambiguous. It is suggested to be as follows: “Risks assessment of soil heavy metals due to railroads activity using positive matrix factorization approach”. Or “ Evaluating the potential risks associated with soil heavy metals in the vicinity of railroads using positive matrix factorization technique".
Response 1: Title was changed. Please see the revised version.
2. Please identify terms in the abstract by name when they first appear in the text. PMF-ERA and PMF-HHRA, for instance. (Positive Matrix Factorization-Environmental Risk Assessment and Positive Matrix Factorization-Human Health Risk Assessment)
Response 2: Changed in the revised manuscript.
3. Add the following to the introduction (Lines 31-32):
- “Although metals are present naturally in the environment, due to volcanic eruptions, soil formation alongside river sedimentation, rainfall, and rock weathering.
- The authors are directed to the following paper: Heavy Metals and Pesticides Toxicity in Agricultural Soil and Plants: Ecological Risks and Human Health Implications (https://doi.org/10.3390/toxics9030042).
Response 3: Information was added.
4. Were Zn, As, and Hg present in your analysis?
Response 4: As was one of the target elements in our study. During our search, our laboratory equipment for Hg analysis was broken, therefore Hg was not our target this time. Parameters for Zn in calculation were missed, therefore, in this paper we excluded Zn. However, in our future, we will add these two elements in.
5. What is the ppm concentration of the “Ni, Cu, Cd and Pb” heavy metals in the soil?
Response 5: In this research we used mg/kg as unit of concentration, and 1ppm=1mg/kg.
6. Is there any explanation for the differences in the number of samples that were gathered for this investigation, such as the 39 samples from Niigata soil and the 47 samples from Tachikawa soil, 21 samples from each of the Datemonbetsu and Komagawa soils)?
Response 6: Because the different areas of sampling site, in some places, we could only selected 21 samples in some small sampling sites. And in larger sampling sites, we could collected more samples.
7. How much does each sample weigh?
Response 7: In this research, wet weight of soil was around 300g. During experiment, only 1.0 g of dried sample was used.
8. What does HF stand for in line 82?
Response 8: HF was hydrofluoric acid.
9. Do you mean bakers or beakers in line 86?
Response 9: Changed in manuscript.
10. In line 87, what do you mean by Milli-Q water? Is it distinct from tap water?
Response 10: Milli-Q water is the name of ultrapure water in Japanese. Changed in manuscript.
11. What does "EPA PMF v5.0" mean in Line 95?
Response 11: EPA PMF v5.0 is software for PMF analysis.
12. What does RSD stand for in Line 107?
Response 12: RSD stands for relative standard deviation.
13. Kindly give the citation of Table 1, Line 118.
Response 13: Information was added.
14. What does RI stand for in Line 135? I think it stands for risk index.
Response 14: RI stands for risk index. Information was added.
15. What is the reference for Table 2 in Line 137?
Response 15: Information was added.
16. What does PMF-ERA stand for in Line 139? “Positive Matrix Factorization-Environmental Risk Assessment”
Response 16: PMF-ERA stands for Positive Matrix Factorization-Environmental Risk Assessment. Information was added.
17. What does RfD stand for in Equation 10, Line 157?
Response 17: Please see table S1.
18. What does PMF-HHRA stand for in Line 174?
Response 18: PMF-HHRA stands for Positive Matrix Factorization-Human Health Risk Assessment. Information was added.
19. What does "mean by P value" indicate in Line 200 when the Kruskal–Wallis H test was used?
Response 19: P-value is the possibility of assumption in Kruskal–Wallis H test.
20. In Line 215: Do you mean six sampling areas or four sampling sites?
Response 20: Changed in manuscript.
21. Line 215, What are the four factors identified in Figure 1?
Response 21: They stand for sampling sites. Changed in manuscript.
22. Figure 1, kindly show the full-name of the site and its contribution factors F1, F2, F3 & F4 on the charts.
Response 22: Changed in manuscript.
23. Please refer to Table 3 for background values in Line 233 and Line 238.
Response 23: Changed in manuscript.
24. In line 240, correct the word the trailway to railway.
Response 24: Changed in manuscript.
25. Lines 244, 251 and 257: Would you please name Factor 1, Factor 4 and Factor 3 in the text that are linked to railways operation (e.g. agricultural or industrial activities).
Response 25: Only after analysis, could we infer each factor to specific source. Therefore, during analysis, we used factors in the text.
26. Lines 287-288, the sentence should be written as follows: “Table 4, at all sampling sites, railway operation was the main anthropogenic event, contributing with 11.73% to 42.55%”.
Response 26: Changed in manuscript.
27. Lines 288-289, “The second dominant source in Datemonbetsu and Komagawa zones was agricultural activities at 24.81% and 26.13%, respectively”.
Response 27: Changed in manuscript.
28. Figure 2, Please use more distinct colours to represent agricultural and natural source activities.
Response 28: Changed in manuscript.
29. Figure 4, use different colors to better represent the risk indices of heavy metals for the four sampling sites.
Response 29: Changed in manuscript.
30. Figure 5, use distinct colors to better depict of the ecological risk of different sampling sites.
Response 30: Changed in manuscript.
31. Line 348, Table 5 not 6.
Response 31: Changed in manuscript.
32. Lines 353-354, “In this research, industrial and agricultural activities only showed high contributions in the two sampling areas”. This sentence needs to be revised as both industrial and agricultural activities have only high contribution in Komagawa site and agricultural activities contribute to % of ecological risk in Tachikawa.
Response 32: Changed in manuscript.
33. Line 361 what do HQing & TH stand for?
Response 33: Please see table S1.
34. Line 367, what does THQ stand for?
Response 34: Please see table S1.
35. Line 368, “Table x also shows that Cr and Pb were the elements that people...”. Where is the Table?
Response 35: Changed in manuscript.
36. What does TRC stand for?
Response 36: TRC should be TCR, standing for total carcinogenic risk.
37. Line 373, Table 7 is missing.
Response 37: table 7 should be table s2.
38. Line 380, “….while those for 379 adults and children were similar”. I think the word “adults should be deleted.
Response 38: Changed in manuscript.
39. Lines 389-391, “For instance, at the Tachikawa sampling site, the contributions of natural sources to adult noncarcinogenic and carcinogenic risks were 56.34% and 86.06%, respectively…”. The correct site is Niigata.
Response 39: Changed in manuscript.
40. Lines 392-394, “On the other hand, the contribution of agricultural activities to adult carcinogenic risk decreased to 6.59%, which was only approximately a quarter of the contribution to content”. This sentence should be revised as follows:
“On the other hand, at Datemonbetsu, agricultural activities contributed 17.39% of the adult non-carcinogenic risk. For adult carcinogenic risk, this percent falls to 6.59%,...
Response 40: Changed in manuscript.
41. Line 400, change word “near” to “nearby”.
Response 41: Changed in manuscript.
42. Line 400, “applying a positive matrix”. Please add “factorization model”.
Response 42: Changed in manuscript.
43. Lines 403-404, “At the other two sampling sites, it was the second dominant source”. Rewrite as “It was the second most prevalent source at the other two sampling locations, Niigata and Tachikawa”.
Response 43: Changed in manuscript.
Reviewer 4 Report
The article is interesting and relevant. The information provided is properly processed according to the scientific requirements. Conclusions are justified and reasonable.
I see one issue that needs to be specified and complemented in relation to the research methodology. Authors stated that the soil samples were collected near the railway, but a more detailed description of the principles of sampling is missing: at what distances from the railway were the samples taken? What were the distances from other roads and potential sources of anthropogenic pollution? Were the samples taken according to the principle of transects? What were the distances between sampling points? Could authors provide the simple scheme/map of the sampling area and points in section “Study area”? This would greatly complement and justify the principles of organizing field research and help to more clearly assess the results of the calculations presented below in the article.
Author Response
at what distances from the railway were the samples taken? What were the distances from other roads and potential sources of anthropogenic pollution? Were the samples taken according to the principle of transects? What were the distances between sampling points? Could authors provide the simple scheme/map of the sampling area and points in section “Study area”?
Response: More details and map of sampling were added in revised manuscript. In this research, we only collected surface soil (<3cm). Therefore, we did not apply the principle of transects in sampling. In our future study, when we do some deeper soil sampling, we will follow the principle of transects.
Round 2
Reviewer 1 Report
The manuscript is now significantly improved except for some problems in language. Please go through it once again for editorial issues, especially on the abstract section. You may use online English editing tools if necessary.
Author Response
Response: Abstract was rewrote. Please see the revised manuscript.
Reviewer 2 Report
The English of current MS has been improved a lot. However, the PMF have been used in many researches for source identification. What is the novelty? Also, it still did not summary the useful information or suggestions on soil metals pollution from railway. So, it would be hard for readers to find the significant effects of different type railways on soil metals pollution. Especial for the abstract and conclusion, it needs to rewrite.
Author Response
Response: Abstract and conclusion were rewrote. Please see the revised manuscript.
Previous studies showed railway operation had effects on concentration of soil heavy metals. Unfortunately, soil heavy metal usually originated from multiple sources. However, the contribution of railway operation to contents of heavy metals was not clear. Besides, information about how railway operation influence environment and human health was limited. In this research, we tried to answer these question by applying the PMF model. And we also made a brief comparison between diesel driven railway and electricity driven railway. Thus, we believe our novelty is that we made a deeper understanding about relationship between railway operation and the environment on the basis of previous studies.
Reviewer 3 Report
All of the comments have been addressed. No more comments are required for the authors regarding the updated manuscript.
Author Response
Response: Because there is no more comments, we have no response here.
Round 3
Reviewer 2 Report
PLS add some results about the effects of different trains and give some more detai suggestions regarding the majore metals pollution character of the diesel train and electricity train. Also，the conclusion needs to be more concise.
Author Response
PLS add some results about the effects of different trains and give some more detai suggestions regarding the majore metals pollution character of the diesel train and electricity train. Also，the conclusion needs to be more concise.
Response: Abstract and conclusion had been rewritten. English language and style had been edited once more. Comparison and discussion about two different type railways was added in section 3.2.2, 3.3.1, 3.3.2, and 3.4.1. For more details, please see the revised manuscript.
