The Comprehensive Reduction Capacity of Five Riparian Vegetation Buffer Strips for Primary Pollutants in Surface Runoff
Round 1
Reviewer 1 Report
The investigation that has been made by the authors is relevant to the research. I would reccomend to consider the article for pubblication. Further studies might be performed to investigate at the full-scale level.
Author Response
Response to Reviewer 1 Comments
Comments: The investigation that has been made by the authors is relevant to the research. I would recommend to consider the article for publication. Further studies might be performed to investigate at the full-scale level.
Response : Thank you very much for your comments, your encouragement gave us great comfort. Your comments has reminded us to conduct further full-scale research, which is consistent with the research direction we have planned.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The topic of this investigation is for remediation pollutants in natural resources, anyway, please consider some observations as below:
1. In the abstract, there is a lack of methods or experimental conditions to apply five riparian vegetation buffer strips for removal of the contaminants
2. The introduction part also lacks the reference related to five riparian vegetation buffer strips that were used in this study.
3. The method should describe the process to obtain and prepare vegetation buffer strips as shown in Figure 2. Moreover, it should study the physico-chemical characterization of studied vegetation buffer strips also.
4. In Table 3-7, the title bar of each table should be identified clearly with specific text names.
5. How to calculate Synthesis score in Table 8, please explain.
6. Line 232-244, the discussion mentioned Vegetation morphology and biomass that it didn’t show in the manuscript, please provide this information.
Author Response
Response to Reviewer 2 Comments
Comments to the Author
The topic of this investigation is for remediation pollutants in natural resources, anyway, please consider some observations as below:
Point 1: In the abstract, there is a lack of methods or experimental conditions to apply five riparian vegetation buffer strips for removal of the contaminants
Response 1: We have reorganized the Abstract and provided detailed information on the experimental conditions of five types of riparian herbaceous vegetation buffer strips.
Lines 19-27: In the indoor simulation experimental device designed, processed soil samples from the plain lake area were filled and herbaceous vegetation seeds in the plain lake area were quantitatively sown to simulate riparian herbaceous vegetation buffer strips. Using collected rainwater to prepare standard solutions for simulating surface runoff, which includes five water primary pollutants: Total Suspended Solids (TSS;149 mg/L), Total Nitrogen (TN;4.44 mg/L), Total Phosphorus (TP;0.67 mg/L), Ammonia nitrogen (NH3-N;0.40 mg/L), and Chemical Oxygen Demand (COD; 74.2 mg/L). The simulated herbaceous riparian buffer strip is 54cm long with a slope of 30º. The surface runoff flow rate is 0.5L/H, and the runoff time is 4 hours. Pollutant concentrations were measured after the experiments.
Point 2: The introduction part also lacks the reference related to five riparian vegetation buffer strips that were used in this study.
Response 2: The reasons for five riparian vegetation buffer strips selection and references have been added.
Lines 80-85: This study intends to compare and analyze the reduction effects of preventing and controlling non-point source pollution in surface runoff by different riparian herbaceous vegetation buffer strips. Riparian herbaceous vegetation buffer strips can simultaneously remove multiple types of water pollutants, but the actual effectiveness of their removal is greatly influenced by natural conditions. Therefore, the selection of herbaceous vegetation species in this study is based on the actual situation in the research area[33,34].
Lines 87-93: And the riparian herbaceous vegetation buffer strips should play a long-term role in reducing non-point source pollution; the plants with high temperature and cold resistance are selected, respectively. Based on the on-site investigation, three types of plants that are resistant to high temperature and drought have been identified: Zoysia matrella, Cynodon dactylon (Linn.) Pers, Dichondra repens Forst; and two types of plants that prefer cold and humid environments: Festuca elata Keng ex E. Alexeev and Lolium perenne.
Point 3: The method should describe the process to obtain and prepare vegetation buffer strips as shown in Figure 2. Moreover, it should study the physico-chemical characterization of studied vegetation buffer strips also.
Response 3: The riparian vegetation buffer strips simulation box filled with the soil particles. The soil particles were sampled form the bank slope of the river channel entering the Liangzi lake, with plant roots, stones and other impurities removed. After drying and grinding, the soil particles were sieved through a 2mm mesh screen. The moisture content of the planting was determined according to the natural water content of the soil, which is 26%, and the seeding rate of five vegetation types was controlled at 7.5 g/m2. After 60 days of natural growth, the conditions for starting the experiment have been met. During the growth process, each riparian vegetation buffer strips produced different physical and chemical characteristics. We will explore their mechanisms in the next stage of work.
Point 4: In Table 3-7, the title bar of each table should be identified clearly with specific text names.
Response 4: Thank you for your advice, the table bar of Table 3-7 has been clearly described.
Table 3. The comparison reduction capacity of five herbaceous vegetation buffer strips on TSS.
Table 4. The comparison reduction capacity of five herbaceous vegetation buffer strips on TN.
Table 5. The comparison reduction capacity of five herbaceous vegetation buffer strips on NH3-N.
Table 6. The comparison reduction capacity of five herbaceous vegetation buffer strips on TP.
Table 7. The comparison reduction capacity of five herbaceous vegetation buffer strips on COD.
Point 5: How to calculate Synthesis score in Table 8, please explain.
Response 5: Based on calculating the reduction capacity of riparian vegetation buffer strips for individual pollutants, the comprehensive reduction ability(R, %) of riparian vegetation buffer strips on five pollutants is calculated by arithmetic mean method.
Lines 141-147: The reduction ability ( , %) of riparian herbaceous vegetation buffer strips on for individual pollutants is calculated by the following Eq. (1).Based on the above calculation results, the comprehensive reduction ability(R, %) of riparian vegetation buffer strips on five pollutants is calculated by arithmetic mean method, Eq. (2).
Point 6: Line 232-244, the discussion mentioned Vegetation morphology and biomass that it didn’t show in the manuscript, please provide this information.
Response 6: Discussions and references on vegetation morphology and biomass have been added in lines 239-243 . However, due to the lack of quantitative measurement of biomass size, we only discuss the plant growth morphology and biomass generated from sowing a certain amount of vegetation seeds. In the next step, we will explore the mechanism of how quantitative biomass size affects pollutant reduction.
Lines 270-277: Physical adsorption is the most direct way to reduce pollutants, and vegetation biomass and growth morphology are the main factors affecting physical adsorption efficiency. Vegetation biomass reflects the total amount of living organisms per unit area at a certain moment. Under the same type of vegetation and external environment, the greater the biomass, the stronger its ability to reduce pollutants. In shallow surface runoff situations, vegetation with well-developed leaves and stems that grow close to or along the ground have a stronger ability to reduce pollutants.
Author Response File: Author Response.docx
Reviewer 3 Report
In this article, the author study the reduction effects of TSS, TN, TP, NH3-N, and COD by five riparian vegetation buffer strips through indoor simulation experiments. The experiment is complete, I recommend a minor revision for this article:
1. The reason why chooses these five vegetation buffer strips seems missing.
2. The discuss about the result: why one buffer strips are superior than the others is too week. The author can consider add more discussion, cite some others' work to improve.
Author Response
Response to Reviewer 3 Comments
Comments to the Author
In this article, the author study the reduction effects of TSS, TN, TP, NH3-N, and COD by five riparian vegetation buffer strips through indoor simulation experiments. The experiment is complete, I recommend a minor revision for this article.
Point 1: The reason why chooses these five vegetation buffer strips seems missing.
Response 1: The reasons for five riparian vegetation buffer strips selection and references have been added.
Lines 80-85: This study intends to compare and analyze the reduction effects of preventing and controlling non-point source pollution in surface runoff by different riparian herbaceous vegetation buffer strips. Riparian herbaceous vegetation buffer strips can simultaneously remove multiple types of water pollutants, but the actual effectiveness of their removal is greatly influenced by natural conditions. Therefore, the selection of herbaceous vegetation species in this study is based on the actual situation in the research area[33,34].
Lines 87-93: And the riparian herbaceous vegetation buffer strips should play a long-term role in reducing non-point source pollution; the plants with high temperature and cold resistance are selected, respectively. Based on the on-site investigation, three types of plants that are resistant to high temperature and drought have been identified: Zoysia matrella, Cynodon dactylon (Linn.) Pers, Dichondra repens Forst; and two types of plants that prefer cold and humid environments: Festuca elata Keng ex E. Alexeev and Lolium perenne.
Point 2: The discuss about the result: why one buffer strips are superior than the others is too week. The author can consider add more discussion, cite some others' work to improve.
Response 2: Discussions and references on vegetation morphology and biomass have been added.
The most significant factors affecting the comprehensive reduction ability of five plants are vegetation morphology and biomass. Vegetation biomass reflects the total amount of living organisms per unit area at a certain moment. Under the same type of vegetation and external environment, the greater the biomass, the stronger its ability to reduce pollutants. In shallow surface runoff situations, vegetation with well-developed leaves and stems that grow close to or along the ground have a stronger ability to reduce pollutants. Dichondra repens Forst is a small creeping herb with adventitious roots on nodes fixed to the ground; Cynodondactylon(Linn.)Pers is a low, stalking ground with a firm root spreading force, spreading widely on the ground. The above two kinds of vegetation grow fast, prostrate on the ground, and have suitable biomass during the experiment. This is the main reason for its strong ability to reduce pollutants.
Author Response File: Author Response.docx
Reviewer 4 Report
This manuscript explored the effects of vegetation buffer strips on the removal of multiple pollutants. The entire manuscript quality can be improved in the following aspects.
1. In Abstract section, show some results of the five vegetation buffer strips. The sentence of initial pollutants concentrations (lines 20-21) can be removed, while the number of each pollutant can be inserted into lines 19-20.
2. First time used acronym should be introduced. E.g., TN and TP in line 54.
3. What does superior purity indicate? >98%, 99%, or others? This is not a professional expression.
4. Double check Eq. 1. It doesn’t seem correct.
5. Add justification of the flow rate (0.5 L/h) for simulated runoff.
6. Tables 8 is a simple summary of Tables 3-7. I suggest changing the current Table 8 to be Table 3 and deleting the current Tables 3-7. In addition, subsections 3.1-3.5 offer similar result description, so they can be combined into one subsection with the new Table 3.
7. What is the soil water hold capacity? It can significantly contribute to the reduction of runoff volume.
8. The Discussion section lacks insightful discussion or comparison with previous literature. Instead, it consists of result description and very limited discussion on N and P removal. The potential mechanisms of pollutants removal should be a focus in the discussion.
9. After presenting the results for bare soil, authors should compare these with those vegetation buffer strips in Discussion.
10. The English language throughout the manuscript should be revised by an expert. E.g., lines 45-47, 97-99, 167-168.
Author Response
Response to Reviewer 4 Comments
Comments to the Author
This manuscript explored the effects of vegetation buffer strips on the removal of multiple pollutants. The entire manuscript quality can be improved in the following aspects.
Point 1: In Abstract section, show some results of the five vegetation buffer strips. The sentence of initial pollutants concentrations (lines 20-21) can be removed, while the number of each pollutant can be inserted into lines 19-20.
Response 1: We have reorganized the Abstract and provided detailed information on the results of five vegetation buffer strips.
Lines 19-26: In the indoor simulation experimental device designed, processed soil samples from the plain lake area were filled and five common vegetation seeds in the plain lake area were quantitatively sown to simulate riparian vegetation buffer strips. Using collected rainwater to prepare standard solutions for simulating surface runoff, which includes five water primary pollutants: Total Suspended Solids (TSS;149 mg/L), Total Nitrogen (TN;4.44 mg/L), Total Phosphorus (TP;0.67 mg/L), Ammonia nitrogen (NH3-N;0.40 mg/L), and Chemical Oxygen Demand (COD; 74.2 mg/L). The simulated riparian vegetation buffer strip is 54cm long with a slope of 30º. The surface runoff flow rate is 0.5L/H, and the runoff time is 4 hours. Pollutant concentrations were measured after the experiments.
Lines 31-33: During Dichondra repens Forst and Cynodon dactylon (Linn.) Pers experiments, they had high bio-mass and their vegetation was creeping on the ground with well-developed roots, showing a strong comprehensive ability to reduce pollutants.
Point 2: First time used acronym should be introduced. E.g., TN and TP in line 54.
Response 2: Thank you for the correction, we have carefully read the full manuscript again, and some of the paragraphs were optimized.
Lines 61-63: In recent years, some researchers found that riparian vegetation buffer strips can significantly reduce total nitrogen (TN), total phosphorus (TP), or other pollutants through physical, chemical, and biological actions.
Point 3: What does superior purity indicate? >98%, 99%, or others? This is not a professional expression.
Response 3: We have changed the expression to indicate that the chemical reagents used in the experiment are of Analytical Regent (AR; >99.7% ) and above grades, suitable for scientific research.
Lines 108-112: The above solutions were prepared manually using ammonium bicarbonate (NH4HCO3), potassium dihydrogen phosphate (KH2PO4), ammonium chloride (NH4Cl), and potassium hydrogen phthalate(C8H5O4K), all of which were of Analytical Regent (AR; >99.8%).
Point 4: Double check Eq. 1. It doesn’t seem correct.
Response 4: Thank you for the correction. This was a typo during translation, we have already corrected it.
Point 5: Add justification of the flow rate (0.5 L/h) for simulated runoff.
Response 5: We have added it in Lines117-121.
Lines 117-121: Based on summarizing the experience parameters of previous experiments, considering that surface runoff in farmland under natural rainfall conditions often flows slowly through riverbank vegetation buffer strips, and combining factors such as vegetation growth and container specifications, a runoff flow rate of 0.5L/H was determined.
Point 6: Tables 8 is a simple summary of Tables 3-7. I suggest changing the current Table 8 to be Table 3 and deleting the current Tables 3-7. In addition, subsections 3.1-3.5 offer similar result description, so they can be combined into one subsection with the new Table 3.
Response 6: Considering the clear demonstration of the removal ability of five types of vegetation buffer strips for individual pollutants, we conducted a separate comparison of the removal efficiency for each vegetation buffer strip. Based on the above comparison results, we further compared the comprehensive pollutant removal ability of the five types of vegetation buffer strips. Therefore, in order to maintain logical structure and clarity in our article and provide accurate data support for future research, we retained the table mentioned above.
Point 7: What is the soil water hold capacity? It can significantly contribute to the reduction of runoff volume.
Response 7: The moisture content of the planting was determined according to the natural water content of the soil, which is 26%. Then, the plants underwent 60 days of natural growth, and the simulated surface runoff was initially 2L. After the experiment ended, it decreased to 1.5L, with a portion of the runoff being reduced by the soil.
Point 8: The Discussion section lacks insightful discussion or comparison with previous literature. Instead, it consists of result description and very limited discussion on N and P removal. The potential mechanisms of pollutants removal should be a focus in the discussion.
Response 8: Discussions and references have been added. In this article, we mainly analyzed the physical and chemical processes of pollutant reduction in five types of vegetation buffer strips, explained the factors that affect the physical reduction process and the differences in chemical reactions. In the next step, we will explore the mechanism of how quantitative biomass size affects pollutant reduction.
Point 9: After presenting the results for bare soil, authors should compare these with those vegetation buffer strips in Discussion.
Response 9: In the discussion section, a comprehensive comparative analysis of vegetation buffer strips and bare soil was added. Two types of vegetation buffer strips and bare soil were selected for quantitative comparison of pollutant reduction effects.
Lines 240-246: Five types of vegetation buffer strips have significantly greater reduction effects on pollutants than bare soil, especially in terms of reducing TSS and TN pollutants. Taking the better-performing Cynodondactylon(Linn.)Pers and weaker-performing Lolium perenne as examples, Cynodondactylon(Linn.)Pers has a 21.5 times greater ability to reduce TSS than bare soil and a 6.2 times greater ability to reduce TN than bare soil, while Lolium perenne has a 9.9 times greater ability to reduce TSS than bare soil and a 3.3 times greater ability to reduce TN than bare soil.
Point 10: The English language throughout the manuscript should be revised by an expert. E.g., lines 45-47, 97-99, 167-168.
Response 10: Thank you for your advice. We have carefully read the full manuscript again, and some of the paragraphs were optimized. The current version of the manuscript has been revised by experts.
Author Response File: Author Response.docx
Reviewer 5 Report
A very interesting research. I recommend it for publication after a minor revision. The conclusions are very general, they should be more specific. My comments can be found in the manuscript.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Thank you for your response and correction.
Author Response
Thank you very much for your comments. Your previous comments on the article have made our next research goals clearer.
Reviewer 4 Report
The overall quality of this manuscript has been significantly improved. After reviewing the revised version, I have two more comments.
1. The length of Abstract exceeds what journal requires. Please refer to the “Instructions for Authors”. Authors can keep key information there, while the background or other descriptive information regarding experimental details can be redacted.
2. The issue of first-time-used acronyms wasn’t fully resolved. E.g., TSS in line 67. If TSS, TN, and TP were shown in lines 62-67, they can be directly used in line 97.
Author Response
Point 1: The length of Abstract exceeds what the journal requires. Please refer to the “Instructions for Authors”. Authors can keep key information there, while the background or other descriptive information regarding experimental details can be redacted.
Response 1: According to the “Instructions for Authors,” changes have been made by deleting the background or other descriptive information regarding experimental details. Now Abstract has 196 words, which complies with what the journal requires.
Abstract: Most studies of plant reduce pollutants in surface runoff focus on the mechanism of single pollutant elimination by single plant species. We take into account the fact that natural riparian herbaceous vegetation buffer strips remove multiple pollutants at the same time, and vegetation species need to be selected according to actual conditions. In the indoor simulation experimental device designed, processed soil samples were filled and using collected rainwater to prepare standard solutions for simulating surface runoff, which includes five primary water pollutants: Total Suspended Solids (TSS), Total Nitrogen (TN), Total Phosphorus (TP), Ammonia nitrogen (NH3-N), and Chemical Oxygen Demand (COD). Pollutant concentrations were measured after the experiments. Through indoor simulation experiments, the reduction capacity of vegetation buffer strips differs due to the differentiation of biological structure and growth characteristics. During Dichondra repens Forst and Cynodon dactylon (Linn.) Pers had high biomass, and their vegetation was creeping on the ground with well-developed roots, showing a strong comprehensive ability to reduce pollutants. The comprehensive reduction capability of five riparian herbaceous vegetation buffer strips for pollutants is ranked as follows: Dichondra repens Forst > Cynodon dactylon (Linn.) Pers > Zoysia matrella > Festuca elata Keng ex E. Alexeev > Lolium perenne.
Point 2: The issue of first-time-used acronyms wasn’t fully resolved. E.g., TSS in line 67. If TSS, TN, and TP were shown in lines 62-67, they can be directly used in line 97.
Response 2: Thank you very much for your correction; we have revised it this time.
Lines 53-55: In recent years, some researchers found that riparian herbaceous vegetation buff-er strips can significantly reduce total nitrogen (TN), total phosphorus (TP), or other pollutants through physical, chemical, and biological actions.
Lines 59-61: For instance, total suspended solids (TSS) interception and other pollutants reduction mainly happen at the front end of riparian herbaceous vegetation buffer strips.
Lines 88-89: Pollutants include TSS, TN, TP, ammonia nitrogen (NH3-N), and chemical oxygen demand (COD).
Author Response File: Author Response.pdf
