Gas Exchange Research on Plant Layers of Green Structures and Indoor Greening for Sustainable Construction

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Overall rating

The paper focuses on the gas exchange mechanism of green structures and indoor greening, providing scientific basis for sustainable buildings and meeting the current needs of carbon neutrality and ecological city development. The proposed four zone gas exchange testing method combines dynamic mixing and stratification analysis, improves the shortcomings of traditional experimental equipment, and has potential for engineering applications. Combining plant physiology, environmental engineering, and building science, this study systematically explores the role of plants in air purification and carbon sequestration.

Provided quantitative reference for the design of green roofs, vertical greening, and other related areas.

1. Introduction

The core function of the introduction is to provide background for the research, clarify the problem, articulate the objectives, and guide the reader into the main text. The introduction should:

1. Concise and clear: avoid being lengthy and highlight key points.
2. Clear logic: from the background to the problem, and then to the goals and methods, it progresses layer by layer.

The introduction should avoid being too long

Lack of focus on research gaps, adding a "research gap" paragraph to clarify the limitations of current methods, and thus highlighting the necessity of this study.

2.Materials and Methods

Detailed description of the dimensions, materials, and sealing testing methods for the 4-zone system.

Explain the reasons for choosing Chlorophytum comosum and Ligustrum vulgare.

3.Results

Clarify the testing conditions for Ligustrum vulgare.

4. Conclusion

Propose a design guideline based on the 4-zone method.

Suggest expanding the research scope to include plant species and mixed planting systems under different climatic conditions. Propose to optimize the airflow design of green structures through CFD simulation.

5. Other issues
6. Some of the images are unclear and have inconsistent fonts or are not labeled with coordinate axes (Figure 2, Figure 6, Figure 10, Figure 11). It is recommended to modify or redraw them.
7. Pay attention to the title format

Author Response

Dear Editor and Reviewers,

 

We would like to thank the you for careful reading, critical and constructive comments on this manuscript, by the Reviewer. The comments have been very thorough and useful in improving the manuscript. We strongly believe that the comments and suggestions have increased the scientific value of revised manuscript by many folds. We have taken them fully into account in revision. We are submitting the corrected manuscript with the suggestion incorporated the manuscript. Suggested changes to the text are marked in red.

Below, we included the point-to-point response to the Reviewer’s comments.

 

Review 1.

The paper focuses on the gas exchange mechanism of green structures and indoor greening, providing scientific basis for sustainable buildings and meeting the current needs of carbon neutrality and ecological city development. The proposed four zone gas exchange testing method combines dynamic mixing and stratification analysis, improves the shortcomings of traditional experimental equipment, and has potential for engineering applications. Combining plant physiology, environmental engineering, and building science, this study systematically explores the role of plants in air purification and carbon sequestration. Provided quantitative reference for the design of green roofs, vertical greening, and other related areas.

Many thanks for the high estimation of the manuscript

Some suggestions are included to benefit the manuscript:

 

• Introduction

The core function of the introduction is to provide background for the research, clarify the problem, articulate the objectives, and guide the reader into the main text. The introduction should:

1. Concise and clear: avoid being lengthy and highlight key points.
2. Clear logic: from the background to the problem, and then to the goals and methods, it progresses layer by layer.

The introduction should avoid being too long.

Lack of focus on research gaps, adding a "research gap" paragraph to clarify the limitations of current methods, and thus highlighting the necessity of this study.

 

Thank you for your valuable comments and recommendations regarding the introduction. In response to your feedback, this section has been completely revised. It now clearly outlines the background of the study, defines the problem, establishes the objectives, and logically guides the reader into the main text. The introduction is concise and focused on the key aspects, eliminating unnecessary details. The structure of the chapter progresses consistently from the general background to the specific issues, objectives, and methods of the study. Additionally, a paragraph describing the research gap has been added, highlighting the limitations of current methods and emphasizing the need for this study. The updated Introduction section can be found in the manuscript (lines 36-278).

 

• Materials and Methods

1. Detailed description of the dimensions, materials, and sealing testing methods for the 4-zone system.

Thank you for your valuable comment. The materials and methods are carefully revised. We added all dimensions of all parts of the setup (lines 297, 338, 396-397, 400-401, 403, 405-406, 447-448, 453, 472) and described the tightness monitoring method  (lines 552-568).

 

2. Explain the reasons for choosing Chlorophytum comosum and Ligustrum vulgare.

Thank you for your question regarding the selection of Chlorophytum comosum and Ligustrum vulgare for the experiment. The choice of these plants is based on several key criteria that allow us to explore different aspects of the study effectively. Firstly, we aimed to distinguish between indoor and outdoor plants to compare their efficiency in absorbing pollutants under varying conditions. Chlorophytum comosum is one of the most studied plants for indoor air phytoremediation. This species is known for its ability to effectively absorb a wide range of pollutants, including formaldehyde, nitrogen dioxide, carbon monoxide, ozone, benzene, toluene, cigarette smoke, and ammonia. Therefore, Chlorophytum comosum was selected as a model plant to evaluate the capacity of indoor plants to purify the air. Secondly, we considered the ecological significance of Ligustrum vulgare, which is one of the most common species used for creating hedges in urban areas of Ukraine. The proportion of Ligustrum vulgare among plantings in green spaces within large cities exceeds 85%, highlighting its high adaptability to urban environments. Additionally, this type of hedge is recognized for its ability to absorb harmful substances from the air while actively producing oxygen, contributing to improved urban air quality. Moreover, the selected plants exhibit differences in photosynthetic biomass, allowing us to study the impact of this parameter on air purification efficiency. Given these considerations, Chlorophytum comosum and Ligustrum vulgare serve as optimal representatives for a comparative analysis of the phytoremediation properties of plants in both indoor and outdoor environments. (Lines 629-635).

 

• Results

Clarify the testing conditions for Ligustrum vulgare.

Thank you for your valuable comment. The testing conditions are described in lines 799-800.

 

• Conclusion

Propose a design guideline based on the 4-zone method.

Suggest expanding the research scope to include plant species and mixed planting systems under different climatic conditions. Propose to optimize the airflow design of green structures through CFD simulation.

Thank you for your comment. We include the conclusion that we develop the method in line 880. We refer to the new standard developed and describe the main features of it in lines 838-844. The extending of plant species and climatic conditions are included in lines 845-851. It’s impossible to perform them using single laboratory. The goal of the new standard is to grow a lab network and involve investments for such task. CFD-simulation of plants require leaf-by-leaf models. Such a task is now tried to perform in Aladdin Energy Performance of Buildings software to simulate illumination, but for CFD it will require high precision of the models and very high number of mesh elements. A large data centre required will consume a lot of energy, which is unreasonable for the task.

 

• Other issues

1. Some of the images are unclear and have inconsistent fonts or are not labeled with coordinate axes (Figure 2, Figure 6, Figure 10, Figure 11). It is recommended to modify or redraw them.
2. Pay attention to the title format

Thank you for your comment on the quality of the images and the formatting of the titles. As the introduction has been changed, the following figures (Figure 2, Figure 6, Figure 10, Figure 11) have been removed. All other images have been carefully checked and adjusted according to your recommendations.

With best,

Authors teams

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Abstract

Suggestion: "Green structures, buildings incorporating living plants, offer numerous benefits, including carbon sequestration and improved indoor air quality. (1) However, the effective design and analysis of these structures are hindered by a lack of standardized methodologies. (2)..."

Suggestion: "This work proposes a novel 4-zone method for instantaneous gas exchange testing in green structures. (2) The method involves estimating gas exchange by measuring gas content at the plant zone's entrance and exit, with individual CO₂ content measurements within the zone to account for inertia and stratification effects exacerbated by mixing. (3) This method has been adopted into a national standard."  Enhance the Results and Conclusion:

Suggestion: "(4) The developed method provides formulas and data on CO₂ absorption/release for use in designing green structures and indoor greening systems. Results show that Chlorophytum comosum can consume over 23 μg/s of CO₂ per square meter of foliage, with a light saturation threshold for CO₂ absorption between 8500 and 20000 phlx, depending on CO₂ levels."

Materials and Methods:

• Provide a more detailed description of the experimental setup, including the dimensions of the chambers, environmental conditions (temperature, humidity, etc.), and the lighting system used.
• Explain the rationale behind the choice of specific plant species (Chlorophytum comosum and Ligustrum vulgare) for the study.
• Provide additional information about the measurement instruments used, such as gas analyzers, flow meters, and lux meters, including their accuracy and calibration.
• Describe the experimental procedure step by step, including the duration of the experiments, the frequency of measurements, and any additional controls or treatments included.
• Justify the modifications made to the experimental bench and explain how these modifications improved the accuracy and reliability of the results.
• Include a schematic diagram or flowchart to illustrate the experimental procedure and data flow.

Results:

• Present the results clearly and concisely, using visual aids such as tables and figures to complement the text.
• Provide informative captions or titles for tables and figures, explaining the content and main conclusions.
• Use appropriate and consistent units for all measurements.
• Highlight the main trends and relationships observed in the data.
• Consider including statistical analyses to support your conclusions and determine the significance of observed differences.

Discussion:

• Interpret the results in the context of existing literature and highlight the main contributions of your research.
• Discuss the implications of your findings for the design and application of green structures and indoor vegetation to improve air quality and sustainability.
• Address any limitations or uncertainties in your study and suggest areas for future research.
• Consider comparing your results with those of other studies and discuss any similarities or differences.
• Provide a more in-depth discussion of the underlying mechanisms of gas exchange in plants and how factors such as lighting and CO2 concentration affect these processes.

Author Response

Dear Editor and Reviewers,

 

We would like to thank the you for careful reading, critical and constructive comments on this manuscript, by the Reviewer. The comments have been very thorough and useful in improving the manuscript. We strongly believe that the comments and suggestions have increased the scientific value of revised manuscript by many folds. We have taken them fully into account in revision. We are submitting the corrected manuscript with the suggestion incorporated the manuscript. Suggested changes to the text are marked in red.

Below, we included the point-to-point response to the Reviewer’s comments.

 

Review 1.

The paper focuses on the gas exchange mechanism of green structures and indoor greening, providing scientific basis for sustainable buildings and meeting the current needs of carbon neutrality and ecological city development. The proposed four zone gas exchange testing method combines dynamic mixing and stratification analysis, improves the shortcomings of traditional experimental equipment, and has potential for engineering applications. Combining plant physiology, environmental engineering, and building science, this study systematically explores the role of plants in air purification and carbon sequestration. Provided quantitative reference for the design of green roofs, vertical greening, and other related areas.

Many thanks for the high estimation of the manuscript

Some suggestions are included to benefit the manuscript:

 

• Introduction

The core function of the introduction is to provide background for the research, clarify the problem, articulate the objectives, and guide the reader into the main text. The introduction should:

1. Concise and clear: avoid being lengthy and highlight key points.
2. Clear logic: from the background to the problem, and then to the goals and methods, it progresses layer by layer.

The introduction should avoid being too long.

Lack of focus on research gaps, adding a "research gap" paragraph to clarify the limitations of current methods, and thus highlighting the necessity of this study.

 

Thank you for your valuable comments and recommendations regarding the introduction. In response to your feedback, this section has been completely revised. It now clearly outlines the background of the study, defines the problem, establishes the objectives, and logically guides the reader into the main text. The introduction is concise and focused on the key aspects, eliminating unnecessary details. The structure of the chapter progresses consistently from the general background to the specific issues, objectives, and methods of the study. Additionally, a paragraph describing the research gap has been added, highlighting the limitations of current methods and emphasizing the need for this study. The updated Introduction section can be found in the manuscript (lines 36-278).

 

• Materials and Methods

1. Detailed description of the dimensions, materials, and sealing testing methods for the 4-zone system.

Thank you for your valuable comment. The materials and methods are carefully revised. We added all dimensions of all parts of the setup (lines 297, 338, 396-397, 400-401, 403, 405-406, 447-448, 453, 472) and described the tightness monitoring method  (lines 552-568).

 

2. Explain the reasons for choosing Chlorophytum comosum and Ligustrum vulgare.

Thank you for your question regarding the selection of Chlorophytum comosum and Ligustrum vulgare for the experiment. The choice of these plants is based on several key criteria that allow us to explore different aspects of the study effectively. Firstly, we aimed to distinguish between indoor and outdoor plants to compare their efficiency in absorbing pollutants under varying conditions. Chlorophytum comosum is one of the most studied plants for indoor air phytoremediation. This species is known for its ability to effectively absorb a wide range of pollutants, including formaldehyde, nitrogen dioxide, carbon monoxide, ozone, benzene, toluene, cigarette smoke, and ammonia. Therefore, Chlorophytum comosum was selected as a model plant to evaluate the capacity of indoor plants to purify the air. Secondly, we considered the ecological significance of Ligustrum vulgare, which is one of the most common species used for creating hedges in urban areas of Ukraine. The proportion of Ligustrum vulgare among plantings in green spaces within large cities exceeds 85%, highlighting its high adaptability to urban environments. Additionally, this type of hedge is recognized for its ability to absorb harmful substances from the air while actively producing oxygen, contributing to improved urban air quality. Moreover, the selected plants exhibit differences in photosynthetic biomass, allowing us to study the impact of this parameter on air purification efficiency. Given these considerations, Chlorophytum comosum and Ligustrum vulgare serve as optimal representatives for a comparative analysis of the phytoremediation properties of plants in both indoor and outdoor environments. (Lines 629-635).

 

• Results

Clarify the testing conditions for Ligustrum vulgare.

Thank you for your valuable comment. The testing conditions are described in lines 799-800.

 

• Conclusion

Propose a design guideline based on the 4-zone method.

Suggest expanding the research scope to include plant species and mixed planting systems under different climatic conditions. Propose to optimize the airflow design of green structures through CFD simulation.

Thank you for your comment. We include the conclusion that we develop the method in line 880. We refer to the new standard developed and describe the main features of it in lines 838-844. The extending of plant species and climatic conditions are included in lines 845-851. It’s impossible to perform them using single laboratory. The goal of the new standard is to grow a lab network and involve investments for such task. CFD-simulation of plants require leaf-by-leaf models. Such a task is now tried to perform in Aladdin Energy Performance of Buildings software to simulate illumination, but for CFD it will require high precision of the models and very high number of mesh elements. A large data centre required will consume a lot of energy, which is unreasonable for the task.

 

• Other issues

1. Some of the images are unclear and have inconsistent fonts or are not labeled with coordinate axes (Figure 2, Figure 6, Figure 10, Figure 11). It is recommended to modify or redraw them.
2. Pay attention to the title format

Thank you for your comment on the quality of the images and the formatting of the titles. As the introduction has been changed, the following figures (Figure 2, Figure 6, Figure 10, Figure 11) have been removed. All other images have been carefully checked and adjusted according to your recommendations.

With best,

Authors teams

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper’s subject matter aligns well with important sustainability topics, and the research offers tangible practical value. Nonetheless, there is room for improvement in terms of rigor and systematic methodology. By strengthening the following three aspects, the overall quality of the manuscript could be significantly enhanced to meet journal publication standards:

1.While the paper provides a relatively detailed design for the plant gas exchange experiment, it should more explicitly emphasize the scientific rigor and repeatability of the method. It is advisable to add an evaluation of experimental uncertainty and potential sources of error, explaining how measurement errors are quantified and minimized. In the data analysis section, a more detailed comparison between experimental and control groups would help illustrate the differences more vividly. Ideally, results from multiple batches of experiments or from real-world case studies should also be included to reinforce the credibility and persuasiveness of the data.

2.The current literature review thoroughly addresses urban environments, air pollution, and the role of green roofs (and walls) in carbon sequestration and air purification. However, it would be beneficial to strengthen the theoretical innovation of this study. In the conclusion or discussion, consider contrasting your findings with those of similar research to highlight the unique technical approaches or practical design contributions of your work. When citing references, incorporating more recent publications (from the past three to five years) in high-impact international journals could better demonstrate the relevance of the latest research trends to your study.

3.Although the paper covers essential components such as the literature review, experimental process, and results analysis, the overall structure is somewhat scattered. It is recommended to reaffirm the central objectives in both the introduction and conclusion. Meanwhile, using clearer subheadings or illustrations in the methodology and results/discussion sections would help readers quickly grasp the key points. It may also be prudent to condense any overly lengthy technical background in order to spotlight the most critical findings and underscore the practical implications of your research.

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Dear Editor and Reviewers,

 

We would like to thank the you for careful reading, critical and constructive comments on this manuscript, by the Reviewer. The comments have been very thorough and useful in improving the manuscript. We strongly believe that the comments and suggestions have increased the scientific value of revised manuscript by many folds. We have taken them fully into account in revision. We are submitting the corrected manuscript with the suggestion incorporated the manuscript. Suggested changes to the text are marked in red.

Below, we included the point-to-point response to the Reviewer’s comments.

 

The paper’s subject matter aligns well with important sustainability topics, and the research offers tangible practical value. Nonetheless, there is room for improvement in terms of rigor and systematic methodology. By strengthening the following three aspects, the overall quality of the manuscript could be significantly enhanced to meet journal publication standards:

1) While the paper provides a relatively detailed design for the plant gas exchange experiment, it should more explicitly emphasize the scientific rigor and repeatability of the method. It is advisable to add an evaluation of experimental uncertainty and potential sources of error, explaining how measurement errors are quantified and minimized. In the data analysis section, a more detailed comparison between experimental and control groups would help illustrate the differences more vividly. Ideally, results from multiple batches of experiments or from real-world case studies should also be included to reinforce the credibility and persuasiveness of the data.

Thank you for your comments and recommendations. A new section “2.5. The error estimation” has been added in lines 682-707.

 

2) The current literature review thoroughly addresses urban environments, air pollution, and the role of green roofs (and walls) in carbon sequestration and air purification. However, it would be beneficial to strengthen the theoretical innovation of this study. In the conclusion or discussion, consider contrasting your findings with those of similar research to highlight the unique technical approaches or practical design contributions of your work. When citing references, incorporating more recent publications (from the past three to five years) in high-impact international journals could better demonstrate the relevance of the latest research trends to your study.

Thank you for your comments and recommendations. In response to them, the Introduction section has been completely revised to clearly outline the background of the study, formulate the problem, define the objectives, and logically direct the reader to the main text. Also, a paragraph describing the research gap was added to the text, emphasizing the limitations of current methods and the need for the study.

Regarding the literature review, the entire bibliography has been updated to include recent research publications, mostly from the last three to five years, published in influential international journals.

And we didn’t find works devoted to the task. Most works used single-leaf method, which gives the possibility to deeply understand the mechanisms of photosynthesis. The works didn’t consider the relative arrangement of the foliage, where some leaves can partially shadow other; the true CO₂ concentration around the leaf tested; the influence of non-photosynthetic biomass and ground; plants with foliage without stalks (Chlorophytum comosum, Sansevieria, etc.). Thus, the comparison is meaningless (Lines 845-857).

 

3) Although the paper covers essential components such as the literature review, experimental process, and results analysis, the overall structure is somewhat scattered. It is recommended to reaffirm the central objectives in both the introduction and conclusion. Meanwhile, using clearer subheadings or illustrations in the methodology and results/discussion sections would help readers quickly grasp the key points. It may also be prudent to condense any overly lengthy technical background in order to spotlight the most critical findings and underscore the practical implications of your research.

Thank you for your comments and recommendation. We carefully revise and change the structure of the article.

 

 

Best regards, Authors.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

the manuscript can be published