The Nature and Size Fractions of Particulate Matter Deposited on Leaves of Four Tree Species in Beijing, China
Round 1
Reviewer 1 Report
The study deals with the PM accumulation on leaves of tree species, and as the authors concluded, the amount of accumulated Pm increased with the increase of stomatal aperture and width, leaf length and width, and stomatal density but decrease with contact angle. The topic is very interesting, the conclusions have practical implications, the authors have explained the mechanism of deposition and also have imposed the question related to retention i.e. washing-off and blowing-off processes which occur during the atmospheric precipitation and need further investigation. I would recommend this paper for publication after minor corrections.
It seems that the lines 161/164: The amounts of PM, PM>10, PM2.5-10, and PM0.1-2.5 ranged from 3.9-14.2, 5.7-41.2, 80.0-109.1, 89.6-164.5 µg/cm2; 9.3-25.0, 15.9-51.7, 98.7-389.5, 123.9-466.2 µg/cm2, at Site 1 and site 2, respectively, do not reflect the results in the Table 1. Also, the authors should edit the text and check for punctuation and grammatical errors.
Additionally, as I have found the published paper with similar topic of the same authors ( https://doi.org/10.3390/plants10102109), I would like to suggest the authors to ensure that no paragraphs or sentences are reused, as it can be considered as plagiarism.
Author Response
Dear reviewer and editor:
Thank you very much for your hard work on our manuscript entitled “The Nature and Size Fractions of Particulate Matter Deposited on Leaves of Four Tree Species in Beijing, China” (ID: forests-1579555). The comments are all valuable and very helpful for revising and improving our manuscript. We have studied those comments carefully and have made correction which we hope meet with approval. The revisions to the manuscript are marked up using the “Track Changes” function in MS Word. We uploaded the tracked copy and clear copy of the revised manuscript.
The main corrections in the manuscript and the responses to the reviewer’s comments are as following (in BOLD type). The pages and line numbers refer to our revised manuscript (clear copy) submitted on 4 Feb., 2022.
English language and style are fine/minor spell check required. Also, the authors should edit the text and check for punctuation and grammatical errors.
Response: Considering the reviewer’s suggestion, we have tried our best to improve English writing. After revision, we use the language check provided by Beijing INCRECENCE Company (https://check.newacademic.net/#/index).
It seems that the lines 161/164: The amounts of PM, PM>10, PM2.5-10, and PM0.1-2.5 ranged from 3.9-14.2, 5.7-41.2, 80.0-109.1, 89.6-164.5 µg/cm2; 9.3-25.0, 15.9-51.7, 98.7-389.5, 123.9-466.2 µg/cm2, at Site 1 and site 2, respectively, do not reflect the results in the Table 1.
Response: We are very sorry for the mistake we have made. In the previous manuscript, the order of PM, PM>10, PM2.5-10, and PM0.1-2.5 should be in the order of PM0.1-2.5, PM2.5-10, PM>10, and PM. We have revised this in the revised manuscript (P5 L181-183).
Additionally, as I have found the published paper with similar topic of the same authors (https://doi.org/10.3390/plants10102109), I would like to suggest the authors to ensure that no paragraphs or sentences are reused, as it can be considered as plagiarism.
Response: Thanks a lot for the useful and kind suggestion. We know plagiarism is a very bad phenomenon, so we won't do such a thing. In fact, these two paper focused on different aspects of PM accumulation. In the published paper (https://doi.org/10.3390/plants
10102109), we focused on the methods for quantifying PM on leaves, and the proper index for evaluating the PM accumulation of leave surfaces of plant species. We also discussed the implications for urban planting for improving urban air quality. In the present manuscript, we focused on the differences in PM accumulation among species and between sampling sites. Furthermore, the test materials , location are both different.
We tried our best to improve the manuscript and made some changes in the manuscript.
We appreciate for Reviewer’/ Editor’ warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions.
Huixia Wang
Author Response File: 
Author Response.docx
Reviewer 2 Report
Overall this is an interesting manuscript exploring the ability of leaves from different species of trees to collect PM. Minor suggestions are included below.
A map and pictures of the sampling location would be helpful.
Providing additional detail about how many leaves were removed from each tree would help (was it 8 per tree? Inner and outer N,W,S, and E facing) If so why is there such a range in the batch numbers in section 2.3?
Further detail and the analysis is needed. So the batch samples (n=3) per tree type were used to calculate a concentration. The area of the leaf was combined total area of all leaves in the batch?
Was statistical analysis conducted on data in Table 2?
Figure 1: the letters indicated figures need to be larger, perhaps adding a column of tree species on the left would help
Section 3.4 how many leaves were used to determine this information?
Figure 2 needs to be described further, what were the main findings from it?
How did the ambient PM concentrations compare to what was captured on the leaves?
Section 4.1: Is there previous research using the same tree types to compare to?
Author Response
Dear reviewer and editor:
Thank you very much for your hard work on our manuscript entitled “The Nature and Size Fractions of Particulate Matter Deposited on Leaves of Four Tree Species in Beijing, China” (ID: forests-1579555). The comments are all valuable and very helpful for revising and improving our manuscript. We have studied those comments carefully and have made correction which we hope meet with approval. The revisions to the manuscript are marked up using the “Track Changes” function in MS Word. We uploaded the tracked copy and clear copy of the revised manuscript.
The main corrections in the paper and the responses to the reviewer’s comments are as flowing (in BOLD type). The pages and line numbers refer to our revised manuscript (clear copy) submitted on 4 Feb., 2022.
English language and style are fine/minor spell check required.
Response: Considering the reviewer’s suggestion, we have tried our best to improve English writing. After revision, we used the language check provided by Beijing INCRECENCE Company (https://check.newacademic.net/#/index).
Are the methods adequately described? (can be improved)
Response: We have tried our best to reorganize the methods. The detailed methods were provided in Section 2. (P3-5, L84-177)
Are the results clearly presented? (can be improved)
Response: We have tried our best to improve the results. Please see Section 3 Results for more information (P5-9 L178-245).
A map and pictures of the sampling location would be helpful.
Response: A map of the sampling location was added in the revised manuscript (Figure 1, P3 L94-96).
Providing additional detail about how many leaves were removed from each tree would help (was it 8 per tree? Inner and outer N, W, S, and E facing). If so why is there such a range in the batch numbers in section 2.3?
Response: Information as “Small branches with mature and healthy leaves were cut from four dimensions (N, S, E and W) at 2-6 m above ground at each site and for each species. After cutting, small branches bearing leaves were placed in labeled ziplock bags, transported to the laboratory and analyzed as soon as possible.” (P3 L102-105) was added in the revised manuscript. In total, more leaves were collected as presented in Section 2.3 because we have other experiments to do at the same time.
Further detail and the analysis is needed. So the batch samples (n=3) per tree type were used to calculate a concentration. The area of the leaf was combined total area of all leaves in the batch?
Response: For each plant species at Sites 1 and 2, three batches of leaves were initially prepared. We calculated the PM and its size fraction deposited on leaves with three replicates as the mass differences before and after filteration. The leaf areas were also three replicates. So we can get three values for each size fraction for each species at each site. So the presented data in Table 1 (P6 L190-194) were shown in Mean±SD.
Was statistical analysis conducted on data in Table 2?
Response: Yes. We have added the detailed information “The relative importance of measured leaf characteristics (stomatal density, stomatal length, stomatal width, stomatal aperture, CA upper side, CA lower side, single leaf area, specific leaf area, leaf length, leaf width, petiole length, roughness upper side, roughness lower side) on the amount of PM and its size fractions was studied using multivariate data analysis (principal component analysis) and partial least squares regression.” in Section 2.5 Data Analysis (P5 L171-176).
Figure 1: the letters indicated figures need to be larger, perhaps adding a column of tree species on the left would help.
Response: Thanks a lot for the useful suggestion. Figure 1 in the original manuscript is Figure 2 in the revised manuscript because we add a figure of location of sampling sites (Figure 1). The letters in Figure 2 are much larger than before now. And also a column of tree species on the left was added in Figure 2. Please see P7-8 L222-225 for detailed information.
Section 3.4 how many leaves were used to determine this information?
Response: PMs within cuticles were observed for F. chinensis (Figure 2m) and G. biloba (Figure 2n), but not for P. tomentosa and P. acerifolia. Encapsulation of PM within cuticles was not so common using FESEM observation. We only observed the encapsulated PM in less than 10 fields (F. chinensis and G. biloba in total) even we observed more than 50 fields of the upper and lower surfaces for each species at each site, so more than 400 SEM images were collected in this study. So we could not provide the precise number of leaves used to determine PMs whihin cuticles. But for the FESEM, we provided more information, Please see Section 2.4 Analysis of Leaf Surfaces Characteristics (P4 L135-146).
Figure 2 needs to be described further, what were the main findings from it?
Response: Figure 2 in the original manuscript is Figure 3 in the revised manuscript because we add a figure of location of sampling sites (Figure 1). More findings from Figure 3 were added in the revised manuscript. Please see Section 3.5 The Effects of Leaf Structure on PM Accumulation on P8 L233-235.
How did the ambient PM concentrations compare to what was captured on the leaves?
Response: We collected the PM2.5 and PM10 concentrations at the nearest monitoring stations (Beijing Botanical Garden and Huangcun) operated by Beijing Municipal Ecological and Environmental Monitoring Center during the growing season. The ratios of PM2.5/PM10 was calculated using the mean values of PM2.5 and PM10 concentrations (P6 L202). The ratios of PM0.1-2.5/PM0.1-10 deposited on each plant species and each site were calculated, and the mean values at each site were used in the manuscript (P6 L201).
Section 4.1: Is there previous research using the same tree types to compare to?
Response: Yes. For example, the study taken by Zhang et al. (2018) published in Forests, Reference [21], and Zhang et al. (2017) in Forests (Relationship between Leaf Surface Characteristics and Particle Capturing Capacities of Different Tree Species in Beijing, doi:10.3390/f8030092). However, we used the different methods for quantifying the amount of PM and its size fractions deposited on leaf surfaces. We discussed this in Discussion section. Please see P10 L280-284 for detailed information.
We tried our best to improve the manuscript and made some changes in the manuscript.
We appreciate for Reviewer’/ Editor’ warm work earnestly, and hope that the correction will meet with approval.
Once again, thank you very much for your comments and suggestions.
Huixia Wang
Author Response File: Author Response.docx
