Seasonal and Spatial Variations in Particulate Matter, Black Carbon and Metals in Delhi, India’s Megacity
and Alok Kumar Pandey 1,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsComment on “Seasonal and Spatial Variations of Particulate Matter and Metals in India's Megacity Delhi” written by Pramod Kumar et al.
This study explores the spatial pattern of particulate matter (PM) in the metropolitan city of Delhi. The spatial distribution of particulate matter of different aerodynamic diameters, black carbon (BC), and metals at six major locations in Delhi during the summer and winter seasons were analyzed to explore the air pollution problem in the city. Although a lot of work has been done on spatial distribution and seasonal differences, the article needs to explore the causes of the differences in more depth. Therefore, it is recommended that this article be published with the following revisions:
1. Lines 18-19, Should be PM10, PM2.5, PM1.0.
2. Add the practical significance of this study for Delhi in Introduction.
3. Supply the detailed sampling information (such as year of sampling, month, date, number of samples) in Mothed.
4. The limits of detections for black carbon and metals are necessary.
5. The authors mentioned that the instrument can detect 21 metals, but why only Pb, Fe, Ca, Al, Zn, Si and S were analyzed?
6. What are the particle size categories used for the black carbon and metals analyzed?
7. Redraw the Figures 2-5 like Figure 1.
8. The differences of black carbon between winter and summer are not obvious.
9. Section 3.2, only description the results of seasonal variations, lack of depth discussion.
10. The correlation analysis is not a power tool explain the contribution of emission sources, add the PMF analysis and PCA analysis.
11. Modified the Conclusion.
Comments on the Quality of English LanguageNeed to enhance the presentation of English language.
Author Response
Reviewer 1
This study explores the spatial pattern of particulate matter (PM) in the metropolitan city of Delhi. The spatial distribution of particulate matter of different aerodynamic diameters, black carbon (BC), and metals at six major locations in Delhi during the summer and winter seasons were analyzed to explore the air pollution problem in the city. Although a lot of work has been done on spatial distribution and seasonal differences, the article needs to explore the causes of the differences in more depth. Therefore, it is recommended that this article be published with the following revisions:
General Response to the Reviewer 1: The authors would like to express their gratitude to Reviewer 1 for their careful reading of the article and their valuable suggestions for improvement. We have thoroughly addressed all the concerns raised by Reviewer 1. Authors are thankful to Reviewer 1 for significantly improving the manuscript. Reviewer comments are given in ‘Black’ color and authors' responses are given in ‘Blue’ color. The detail responses on the specific comments are below:
- Lines 18-19, Should be PM10, PM2.5, PM1.0.
Response to comment 1: We corrected the PM10, PM2.5, and PM1.0, as suggested by the reviewer in the manuscript now. [Lines 18-19 of the revised manuscript]
- Add the practical significance of this study for Delhi in Introduction.
Response to comment 2: We are thankful to the reviewer for this valuable feedback. We have added the significance of this study in line 74-80.
- Supply the detailed sampling information (such as year of sampling, month, date, number of samples) in Mothed.
Response to comment 3: The study provides useful results regarding the changes occurred in air quality during two consecutive years (2016 summer and 2016-2017 winter season). We have added the sampling period duration in the methodology section now. [Lines 154-156 of the revised manuscript]
- The limits of detections for black carbon and metals are necessary.
Response to comment 4: The Aethalometer AE-51, a portable device used to measure black carbon (BC) concentration in real-time, has the detection limit of approximately 0.1 µg/m³. The same has been added in the revised manuscript lines 180-183.
- The authors mentioned that the instrument can detect 21 metals, but why only Pb, Fe, Ca, Al, Zn, Si and S were analyzed?
Response to comment 5: That’s a good question. We chose only these metals as we are focusing on specific metals due to their health risks and their presence in Delhi's air. Relevant text has been added for this in the revised manuscript [ lines 298-299].
- What are the particle size categories used for the black carbon and metals analyzed?
Response to comment 6: The particle size categories used for analyzing black carbon and metals analyzed are typically based on aerodynamic diameter i.e. PM10, PM2.5, PM1.0. [We have explained this in the lines 194-195 for BC and lines 193-194 and 217-219].
- Redraw the Figures 2-5 like Figure 1.
Response to comment 7: We understand the concern raised in this comment. However, the results obtained in Figure 2-5 are different from Figure 1. In figure 1, we only mentioned study locations in Delhi. Whereas, in Figure 2-5 kriging interpolation results are shown. We have recreated Figures 2 - 5 to better illustrate the spatial patterns. These Figures have been designed to enhance the visual representation of our results and provide a clearer understanding of the spatial relationships discussed in the manuscript.
- The differences of black carbon between winter and summer are not obvious.
Response to comment 8: Yes, we agree with the reviewer's comment regarding that winter and summer Black carbon concentration are not obvious. Therefore, we have recreated Figure 4 which clearly shows the difference between winter and summer seasons now by adding more layers. The description is added in the revised manuscript in the discussion section. [Lines 492-508].
- Section 3.2, only description the results of seasonal variations, lack of depth discussion.
Response to comment 9: We have added a separate section (Section 4) on discussion in the revised manuscript [lines 455-510]
- The correlation analysis is not a power tool to explain the contribution of emission sources, add the PMF analysis and PCA analysis.
Response to comment 10: Thanks for this valuable comment. We also agree with the reviewer's thoughts of using PCA as a strong tool. A common rule of applying PCA is to have at least 5 to 10 times as many observations (samples) as variables (features). However, due to lack of funding we were not able to get an ample number of observations which are mainly required for PCA and our dataset is comparatively small in size. That's Why, we have to use correlation analysis to show the contribution of emission sources in this research.
- Modified the Conclusion.
Response to comment 11: As suggested by the reviewer, the conclusion has been modified and improved.
Once again authors are thankful to Reviewer 1 for his encouraging comments and suggestions to improve the manuscripts.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe purpose of this study is to examine the spatial arrangement of aerosol properties and their association with harmful metals in the polluted megacity of Delhi, during the winter and summer seasons. The structure of this paper is reasonable, while the logical relationship and hierarchy are clear. In addition, the research topic chosen by the author is very specific and the theoretical basis is relatively solid. However, there are still some problems to be further improved.
1. The paper only discusses the seasonal variations in summer and winter. However, the author mentions that the majority of rainfall over the region is between July-September i.e., monsoon season. So how does the effect of it reflect?
2. The part of the instrumentation and sampling methodology focuses on the introduction of the instrument rather than the detailed description of specific operation steps.
3. In this paper, there is less discussion about the theoretical and practical significance of the study. The significance of this study is not clear.
Comments on the Quality of English LanguageSome sentences are incomplete and need to be carefully checked and corrected. Some statements in this paper need to be further modified and improved.
Author Response
Reviewer 2
Comments and Suggestions for Authors
The purpose of this study is to examine the spatial arrangement of aerosol properties and their association with harmful metals in the polluted megacity of Delhi, during the winter and summer seasons. The structure of this paper is reasonable, while the logical relationship and hierarchy are clear. In addition, the research topic chosen by the author is very specific and the theoretical basis is relatively solid. However, there are still some problems to be further improved.
General Response to the Reviewer 2: Authors are thankful to the Reviewer 2 managing time to read the manuscript and providing valuable corrections. We have modified the manuscript and addressed all the concerns pointed by Reviewer 2 in the revised manuscript. Reviewer comments are given in ‘Black’ color and authors' responses are given in ‘Blue’ color. The detail responses on the specific comments are below:
- The paper only discusses the seasonal variations in summer and winter. However, the author mentions that the majority of rainfall over the region is between July-September i.e., monsoon season. So how does the effect of it reflect?
Response to comment 1: We understand and thank the reviewer for raising their concern for this point. However, we have selected only the summer and winter seasons because the variability in the pollutant level is different and high during these two seasons. For instance, during summer, due to dust storms, the particulate matter concentration was reported high in May and June, while in winter due to atmospheric inversion and more consumption of energy resources, the air pollution levels are at peak. During July-September, the air quality in Delhi is within the standards proposed by CPCB, therefore, we have not shown these results. Additionally, we had the plan to do sampling during monsoon but due to paucity of resources we have done sampling during the winter and summer only.
- The part of the instrumentation and sampling methodology focuses on the introduction of the instrument rather than the detailed description of specific operation steps.
Response to comment 2: We are thankful to the reviewer for this valuable feedback. We have added the paragraphs in Aethalometer, an ED-XRF technique related to specific operation steps. [Lines 185-194 and 214-219 in the revised manuscript]
- In this paper, there is less discussion about the theoretical and practical significance of the study. The significance of this study is not clear.
Response to comment 3: Yes, it is very important to clear the significance of the study. We have added the lines [74-80] about the significance of this study in the Introduction section.
Comments on the Quality of English Language
Some sentences are incomplete and need to be carefully checked and corrected. Some statements in this paper need to be further modified and improved.
Response to on the Quality of English Language: We have checked and corrected all the grammatical errors throughout the manuscript now.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript describes an investigation of PM measurements in multiple sites in Delhi. The authors have measured a range of PM fractions, Black carbon and metal content in PM. The study aims to investigate the spatial distribution of same.
Specific comments:
p.2 l.48: COPD should be "... Pulmonary Disorder", not "...Coronary Disorder"
p.3, map: Please increase the font size on the axis labels
p.4, tabl1 1: please change "cum" to "come"
p.5, section 2.2.2: The AE51 manufacturer is not mentioned, but it is presumably the microaethalometer form Aethlabs. Please describe the processing of the data, e.g. was there an attempt at loading correction?
p.5 section2.4: This section is very unclear and provides absolutely no useful information about how the kriging was carried out. Please clarify and elaborate
p.5 l.223: "microscopic particulate matter" is better described as "sub-micron"
p.6 figure 2: The maps extend quite a lot beyond the periphery of the measurement sites. How can interpolation between the points (kriging) yiel;d values to the north and south of the most extreme points. The measurement locations are located in a relatively narrow band from south west to north east, but the maps extrapolate far beyond it.
figure 3, figure 4, figure 5as above
Table 2, table 3. The colours do not match the legend.
Conclusions. Very brief and does not state any new insights. Could be improved.
General comments:
The study has potential to be interesting, but the manuscript leaves the impression that more effort could be made to generate inteersting insights from the data. The kriging is not convincing, especially since it involves extrapolation outside the area covered by the stations.
Certainly more statistical analysis could be carried out and the data would probably also lend itself to multivariate analysis to extract factors/source categories.
So the data is probably worth publishing, but the manuscript does not do it justice. In my opinion it should be reanalysed and reworked before publication.
Author Response
Reviewer 3
Open Review
Comments and Suggestions for Authors
The manuscript describes an investigation of PM measurements in multiple sites in Delhi. The authors have measured a range of PM fractions, Black carbon and metal content in PM. The study aims to investigate the spatial distribution of the same.
General Response to the Reviewer 3: Authors are thankful to the Reviewer 3 for reviewing the manuscript and providing valuable suggestions. We have modified the manuscript and addressed all the concerns pointed by Reviewer 2 in the revised manuscript. Reviewer comments are given in ‘Black’ color and authors' responses are given in ‘Blue’ color. The detail responses on the specific comments are below:
Specific comments:
p.2 l.48: COPD should be "... Pulmonary Disorder", not "...Coronary Disorder"
Response to comment p.2 l.48: We are thankful to the reviewer for catching this typing error. We have changed the word “Coronary” into “Pulmonary” now.
p.3, map: Please increase the font size on the axis labels
Response to comment p.3: We have increased the font size on the axis labels now.
p.4, tabl1 1: please change "cum" to "come"
Response to comment p.4: We have changed “cum” into “and”. These site locations have two types of activities- residential and industrial.
p.5, section 2.2.2: The AE51 manufacturer is not mentioned, but it is presumably the micro aethalometer from Aethlabs. Please describe the processing of the data, e.g. was there an attempt at loading correction?
Response to comment p.5, section 2.2.2: Thank you for this important correction. We have added a paragraph regarding sampling methodology and data processing of black carbon using an aethalometer in the method now. [Lines 199-206 in the revised manuscript 180-194]
p.5 section 2.4: This section is very unclear and provides absolutely no useful information about how the kriging was carried out. Please clarify and elaborate.
Response to comment p.5, section 2.4: We agree with the reviewer that the details regarding kriging are less in the methodology section. We have clarified and elaborated section 2.4 now. [lines 226-236]
p.5 l.223: "microscopic particulate matter" is better described as "sub-micron"
Response to comment p.5, l.223: Thanks to the reviewer. It’s a good point. We have changed “microscopic particulate matter” into “sub-micron”. [Line 251 in the revised manuscript]
p.6 figure 2: The maps extend quite a lot beyond the periphery of the measurement sites. How can interpolation between the points (kriging) yield values to the north and south of the most extreme points. The measurement locations are located in a relatively narrow band from south west to north east, but the maps extrapolate far beyond it.
Response to comment p.6 figure 2: Thank you for your valuable suggestions. Considering this suggestion as one of the most important points for refining this study, we redraw Figure 2. Now, in Figure 2, we added more layers to understand the clear distinction both spatially and seasonally.
Figure 3, Figure 4, Figure 5 as above
Response to comment p.6 Figure 2: We also regenerated Figure 3, 4, and 5 to show better spatial distribution during summer and winter.
Table 2, Table 3. The colors do not match the legend.
Response to comment Table 2 and Table 3: We have corrected the legend in both tables.
Conclusions. Very brief and does not state any new insights. Could be improved.
Response to Conclusions: Thanks for suggestions. We have modified the conclusion as per the reviewer’s suggestion.
General comments:
The study has potential to be interesting, but the manuscript leaves the impression that more effort could be made to generate interesting insights from the data. The kriging is not convincing, especially since it involves extrapolation outside the area covered by the stations.
Certainly, more statistical analysis could be carried out and the data would probably also lend itself to multivariate analysis to extract factors/source categories.
So the data is probably worth publishing, but the manuscript does not do it justice. In my opinion it should be reanalysed and reworked before publication.
Response to the General Comments: Thank you for your valuable feedback on the manuscript. We have addressed all specific comments of the Reviewer 3. This work is highlighting the spatial and seasonal variations of Particulate Matter, Black Carbon and Metals over the ambient air of Megacity Delhi that is important for other urban studies too.
Author Response File: Author Response.pdf
