Study on the Relationship between Indoor Vertical Greening and Oxygen Content in High-Rise Buildings
Hiroshi Matsumoto
Round 1
Reviewer 1 Report
Review
This paper deals with an important subject, i.e., the effect of plants on the indoor oxygen content and the factors that influence the functionality of these plants in different indoor spaces. An improvement is made as to how oxygen content in the air can be inferred indirectly by using a simple instrumental setup which avoids air pollution generated by previous methods of computing oxygen content in the air. Below are the shortcomings of this paper and study which merit major revisions before it can be considered for publication.
General comments:
- Use line numbers throughout the draft otherwise it is difficult to comment, v2 does not contain it
- Change gas collection bottle/cylinder to gas bottle throughout the draft
- Any supposition about how occupants/inhabitants in the high-rise apartment would affect the oxygen content? Were there actually any participants involved in the study?
- No mention anywhere in the manuscript about which plants were used in the study! This should be added.
Abstract:
- Specify what is gas collection cylinder?
- You mention ‘positive correlation between indoor oxygen content and vertical greening placement in high-rise buildings’ but there is actually no statistic in the paper to warrant such a term. If there is a statistical term/measure that can be added that would be good, e.g., R value. Otherwise re-phrasing the sentence to get around ‘positive correlation’ would be ok.
Intro:
- ‘With the rapid development of urbanization’ à rewrite: ‘With rapid urbanization occurring worldwide’
- Add this reference for populations spending 90% of their time indoors: Klepeis, N. et al. The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. J Expo Sci Environ Epidemiol 11, 231–252 (2001)
- CO2 is not defined as a term first but the chemical name is directly mentioned! à Human activities produce a large amount of carbon dioxide (CO2) indoors…
- ‘Thus, the study of oxygen content in high-rise buildings cannot be ignored’ à ….in high-rise buildings warrants further investigation.
- ‘In addition, by installing vertical greenery…’ à any examples for vertical greenery?
- ‘…and visual comfort, etc. [18–20].’ à do not use etc., it makes it sound lazy
- The basic method of igniting red phosphorous is not described, e.g., what happens, how is it measured? Subsequent improvements for the basic method are, however, described.
Experimental Section:
- Fig. 3: Is there any picture for the new apparatus besides the diagram? Please show.
- In Sec. 2.3. term gas collection bottle is wrong à change to gas bottle
Results and Discussion:
3.1. Indoor Oxygen Content with Vertical Greening under different Ventilation Conditions
A table or two tables listing results for burning time with different window states (open / closed) should be added. Currently there is a lot of text describing the different window states and the reader will get lost what are the main results and subsequent conclusions drawn by the authors.
Conclusion:
‘In addition, the windows should not be left open for too long: 5~10 min in the winter, 10~15 min in the spring and autumn, and 15~20 min in the summer’ à why? What is the basis for this?
Author Response
We greatly appreciate the reviewer for your helpful comments and corrections on our manuscript. We have made revisions following closely to your comments. Please see our point-by-point responses below. Our responses are in blue. We also attached the manuscript on the website, and the revised contents are in red.
General comments:
1. Use line numbers throughout the draft otherwise it is difficult to comment, v2 does not contain it
We accepted the suggestions of reviewer, and have used the line numbers throughout the new manuscript.
2. Change gas collection bottle/cylinder to gas bottle throughout the draft
We accepted the suggestions of reviewer, and have changed gas collection bottle/cylinder to gas bottle throughout the draft.
3. Any supposition about how occupants/inhabitants in the high-rise apartment would affect the oxygen content? Were there actually any participants involved in the study?
In this study, we used green dill which is favored by most Chinese residents to test the relationship between green plants and oxygen content in the indoor space. In order to avoid interference factors such as human activities, inhabitants were not in the apartment during the experimental test. We added the explanation from line 128 to 130.
4. No mention anywhere in the manuscript about which plants were used in the study! This should be added.
We accepted the suggestions of reviewer, and added the information and the reference of green dill from line 139 to 143.
Abstract:
5. Specify what is gas collection cylinder?
We have described the gas bottle in line 154.
6. You mention ‘positive correlation between indoor oxygen content and vertical greening placement in high-rise buildings’ but there is actually no statistic in the paper to warrant such a term. If there is a statistical term/measure that can be added that would be good, e.g., R value. Otherwise re-phrasing the sentence to get around ‘positive correlation’ would be ok.
We accepted the suggestions of reviewer, and have changed “positive” to “potential” in line 20 of the abstract.
Introduction:
7. With the rapid development of urbanization’ à rewrite: ‘With rapid urbanization occurring worldwide’
We accepted the suggestions of reviewer, and have modified this sentence in line 30.
8. Add this reference for populations spending 90% of their time indoors: Klepeis, N. et al. The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. J Expo Sci Environ Epidemiol 11, 231–252 (2001)
We accepted the suggestions of reviewer, and have added the reference in line 32.
9. CO2 is not defined as a term first but the chemical name is directly mentioned! à Human activities produce a large amount of carbon dioxide (CO2) indoors.
We accepted the suggestions of reviewer, and have added the carbon dioxide before CO2 in line 34.
10. Thus, the study of oxygen content in high-rise buildings cannot be ignored’ à ….in high-rise buildings warrants further investigation.
We accepted the suggestions of reviewer, and have defined the high-rise buildings and added the reference from line 30 to 31.
11. ‘In addition, by installing vertical greenery…’ à any examples for vertical greenery?
We have reviewed more papers about vertical greenery, there are few studies on indoor oxygen content and vertical greening, especially fewer studies and experiments on indoor oxygen content of high-rise buildings as research objects. Therefore, we have added some research cases on the relationship between indoor oxygen content and vertical greening from line 44-47.
12. ‘…and visual comfort, etc. [18–20].’ à do not use etc., it makes it sound lazy
We accepted the suggestions of reviewer, and have canceled etc. in line 63.
13. The basic method of igniting red phosphorous is not described, e.g., what happens, how is it measured? Subsequent improvements for the basic method are, however, described.
We accepted the suggestions of reviewer, and have added the description of red phosphorus experimental process and measurement method from line 70 to 75.
Experimental Section:
14. Fig. 3: Is there any picture for the new apparatus besides the diagram? Please show.
We accepted the suggestions of reviewer, and have added Figure 4 of the equipment and the process of the experiment in line 186.
15. In Sec. 2.3. term gas collection bottle is wrong à change to gas bottle
We accepted the suggestions of reviewer, and have changed gas collection bottle to gas bottle.
Results and Discussion:
16. A table or two tables listing results for burning time with different window states (open / closed) should be added. Currently there is a lot of text describing the different window states and the reader will get lost what are the main results and subsequent conclusions drawn by the authors.
We accepted the suggestions of reviewer, and have added Table 2 for test times with different window opening states in line 231.
Conclusion:
17. ‘In addition, the windows should not be left open for too long: 5~10 min in the winter, 10~15 min in the spring and autumn, and 15~20 min in the summer’ à why? What is the basis for this?
We accepted the suggestions of reviewer. In order to enhance the preciseness of the conclusion, the conclusion is revised as “the window opening status determines the window opening time according to the latitude and seasonal changes of the region, taking into account the temperature, wind direction and wind speed.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper deals with a very interesting research theme, but the following questions remain, so please consider them.
1. There are many methods for measuring the oxygen content in air with different principles, such as the zirconia method, magnetic method, laser spectroscopy, and electrode method. Please explain why you chose the oxygen content measurement method by burning red phosphorus in this study, including the advantages of your method over other methods, such as accuracy and reliability.
2. The oxygen content is evaluated by the burning time of red phosphorus, but it is somewhat difficult to understand. It is easier to understand if the time is converted to the oxygen content and the absolute amount is compared.
3. The indoor and outdoor temperature, humidity, oxygen concentration, wind direction and speed, illuminance, and the number of people in the room at the time of measurement, which affects oxygen consumption, are unknown, so it is desirable to clearly describe them.
4. The indoor oxygen content is greatly affected by the amount of outside air introduced and indoor mutual ventilation. These ventilation volumes can be measured by the tracer decay method, etc., and it is desirable to measure them during the experiment period to achieve the purpose of the study.
5. Since the plant mass of vertical greening soft partition used in the experiment shown in Figure 2 is quite small, it is estimated that the effect of oxygen supply by photosynthesis of the plant on indoor oxygen concentration is negligible. Experiments with more plants seem necessary.
6. As mentioned above, there is no clear data on the ventilation route and ventilation volume in this study, so it must be said that the validity and reliability of the findings inferred from the experimental data on the oxygen content are somewhat weak.
Author Response
We greatly appreciate the reviewer for your helpful comments and corrections on our manuscript. We have made revisions following closely to your comments. Please see our point-by-point responses below. Our responses are in blue. We also attached the manuscript on the website, and the revised contents are in red.
1. There are many methods for measuring the oxygen content in air with different principles, such as the zirconia method, magnetic method, laser spectroscopy, and electrode method. Please explain why you chose the oxygen content measurement method by burning red phosphorus in this study, including the advantages of your method over other methods, such as accuracy and reliability.
This study is an improved method which is different from red phosphorus. Because the red phosphorus combustion will produce phosphorus pentoxide gas, which will pollute the air and affect the health of operators, we use the method of burning candles in the gas collecting cylinder to measure the oxygen content. Compared with zirconia method, magnetic method, laser spectroscopy, and electrode method the measurement method, this method is easier to operate and has lower cost. It is suitable for operation in non-laboratory conditions and more general environments.
2.The oxygen content is evaluated by the burning time of red phosphorus, but it is somewhat difficult to understand. It is easier to understand if the time is converted to the oxygen content and the absolute amount is compared.
In this study, the oxygen content was measured by the burning time of the candle in the gas collecting cylinder. Since the oxygen content is closely related to the burning time, the high oxygen content supports the long burning time of the candle, while the low oxygen content supports the short burning time of the candle. So the amount of oxygen in a candle can be determined by how long it burns. The object of this study is common household living space, and the study on oxygen content focuses more on improving indoor air quality through the use of green plants, rather than achieving absolute oxygen content value.
3.The indoor and outdoor temperature, humidity, oxygen concentration, wind direction and speed, illuminance, and the number of people in the room at the time of measurement, which affects oxygen consumption, are unknown, so it is desirable to clearly describe them.
We accepted the suggestions of reviewer, and have added the environment conditions in Table 1 and the descriptions from line 121 to 130. In order to avoid confounding factors such as human activities, inhabitants were not present in the apartment during the experimental test.
4.The indoor oxygen content is greatly affected by the amount of outside air introduced and indoor mutual ventilation. These ventilation volumes can be measured by the tracer decay method, etc., and it is desirable to measure them during the experiment period to achieve the purpose of the study.
We accepted the suggestions of reviewer, and have added the discussion from line 412 to 416. In this study, an external environment with a gentle breeze (wind speed: 1.6-3.3 m/s) was selected. Throughout the experiment, the indoor air flow rate was relatively stable, and the flame of the candle burning was always in a vertical upward state. Therefore, the air flow rate in this study was not used as an important reference index, and weather with a high wind speed will be chosen for further in-depth study in subsequent research.
5.Since the plant mass of vertical greening soft partition used in the experiment shown in Figure 2 is quite small, it is estimated that the effect of oxygen supply by photosynthesis of the plant on indoor oxygen concentration is negligible. Experiments with more plants seem necessary.
We accepted the suggestions of reviewer. The number of plants in this study is set according to the number of commonly cultivated plants in the general living space. Through experiments, we can figure out the impact of plants on the oxygen content in the air and improve the relationship in the home life, rather than creating a home living space with high oxygen content through a large number of plants. If a few plants can affect the indoor oxygen content, the indoor air quality will become better with the increase of plants.
6.As mentioned above, there is no clear data on the ventilation route and ventilation volume in this study, so it must be said that the validity and reliability of the findings inferred from the experimental data on the oxygen content are somewhat weak.
We accepted the suggestions of reviewer. and have added the discussion of relevant contents from line 412 to 416 of the discussion section. In the follow-up study, the weather with high wind speed will be selected for further in-depth study.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Thanks, comments were adequately addressed.
Please add a practical implications and limitations section, this will make it easier for the reader to understand the scope of the research.
Author Response
We greatly appreciate your helpful comments and corrections on our manuscript. We have made revisions following closely to the comments. Please see our point-by-point responses below. We also attached the manuscript on the website, and the revised contents are in red.
1.Please add a practical implications and limitations section, this will make it easier for the reader to understand the scope of the research.
We accepted the suggestions, and have add the practical implications and limitations section from line 451 to 461, in the conclusion part, the main research results are refined again.
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors' responses and their revised proposals to my comments were not fully satisfactory, so I regrettably decided that rejection was appropriate.
Although the authors' measurement method is said to be simpler and less costly than other methods, it must be said that there are problems with the accuracy and credibility of the measurement results. In particular, the amount of foliage plants used in the experiment produced only a very small amount of oxygen through photosynthesis, which is far less than the amount of oxygen generated indoors and outdoors by ventilation, and it is assumed that there is no significant effect on changes in indoor oxygen concentration.
The burning time of a candle is used to evaluate the oxygen content, but it is difficult to imagine, so physical indices such as volume concentration and weight concentration should have been used instead of such a relative index.
Also, it is difficult to understand because it is not specified in the experimental conditions, but it seems that oxygen consumption is due to the breathing and cooking of the residents, but there is no description of the residents.
Author Response
We greatly appreciate the edit’s helpful comments and corrections on our manuscript. We have made revisions following closely to the comments. Please see our point-by-point responses below. We also attached the manuscript on the website, and the revised contents are in red.
1. Although the authors' measurement method is said to be simpler and less costly than other methods, it must be said that there are problems with the accuracy and credibility of the measurement results. In particular, the amount of foliage plants used in the experiment produced only a very small amount of oxygen through photosynthesis, which is far less than the amount of oxygen generated indoors and outdoors by ventilation, and it is assumed that there is no significant effect on changes in indoor oxygen concentration.
Accepted, in this study, we measured the relative value of oxygen content, and the number of plants in the experiment was based on the number of commonly cultivated plants in the general families. We made a supplementary explanation about the plant number from line 149 to 152. In the experiment, we tested the changes of oxygen content before and after placing green plants in the living room under seven states, including closing Windows and opening different numbers of Windows, in order to get the influence of plants and different opening windows on oxygen content in the indoor space. We added the discussion of the limitations and subsequent studies of this study from line 451 to 461. In the conclusion part, the main research results are refined again.
2. The burning time of a candle is used to evaluate the oxygen content, but it is difficult to imagine, so physical indices such as volume concentration and weight concentration should have been used instead of such a relative index.
Accepted, we added the discussion of test methods from line 121 to 139, and added the discussion about the physical indicators of oxygen content from line 196 to 201.
3. Also, it is difficult to understand because it is not specified in the experimental conditions, but it seems that oxygen consumption is due to the breathing and cooking of the residents, but there is no description of the residents.
We accepted the suggestions, we added descriptions of residents' living activities during the experiment from line 154 to 156.
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
There are polite comments and minor revisions from the authors in response to my comments, and I can understand the research purpose, measurement method, analysis / evaluation method, etc. However, it is still hard to say that they are essential corrections, so I hope that the manuscript will be resubmitted as a more complete manuscript with higher quality.
Author Response
We greatly appreciate the reviewer’s helpful comments and corrections on our manuscript. We have made revisions following closely to the comments. The revised contents are in green.
We accepted the suggestions, and revised the research method, discussion, and conclusion again in order to make the manuscript more rigorous.
Author Response File: 
Author Response.docx
