Effects of Iron Nanoparticles Addition on Bacterial Community and Phytotoxicity in Aerobic Compost of Pig Manure

Round 1

Reviewer 1 Report

From our point of view, to be able to accept this work, the following major revisions must be made:

1.- AC-200 and AC-500 must be modified and expressed throughout the article by its equivalent in mg Fe /Kg compost. The expression of 200 and 500 mL / Kg compost is not allowed.

2. Attach a comparative study of the two solutions incorporated into the compost and explain in detail section 3.1 and the differences between the two solutions studied by SEM, XPS, size of the nanoparticles and mapping in the two cases...and improve the figure 2.

3. More clearly specify the Temporal Changes in pH, ORP, and FTIR during composting for the two solutions used. It is not explained why the first solution works better vs the second one and the problem is that the differences in sizes are not shown, mapping of both solutions....

4. Neither is the mechanism clearly explained for both solutions and their influence on the composting process... and the VS changes for the two solutions based on their characterization by SEM, XPS, mapping and size of the nanoparticles.

5. Sections 3.3, 3.4 and 3.5 should be improved with SEM characterization studies of the two solutions

6.- The expressions of the lines that are cited below must be redrafted to facilitate their understanding:

123, "cooling. vs. and vs"[....]

174, (Figure 1A), After [....]    change to  (Figure 1A), after

180, 1) AC-C (Control–aerobics.... [....] change to (control-aerobics

Author Response

-Reviewer #1 (Red colour)

From our point of view, to be able to accept this work, the following major revisions must be made:

R: Thank for all the comments, and these comments have been addressed in following section.

1. AC-200 and AC-500 must be modified and expressed throughout the article by its equivalent in mg Fe /Kg compost. The expression of 200 and 500 mL / Kg compost is not allowed.

R: Thanks for your advice. When we designed the experiment, we directly added G-nFe solution to the experiment, because on the one hand, further preparation of dried nanoparticles by filtration and drying will increase the cost of subsequent industrial application; and on the other hand, we also need to add water to the compost to adjust the moisture content to 55%. However, your timely advice is really important. The synthesis experiment was conducted again and the effective dry weight of G-nFe was calculated and marked in the paper. It has been revised as suggested. Please see L11 and L172-176.

2. Attach a comparative study of the two solutions incorporated into the compost and explain in detail section 3.1 and the differences between the two solutions studied by SEM, XPS, size of the nanoparticles and mapping in the two cases...and improve the figure 2.

R: Thanks for your advice. It has been revised as suggested in section 3.1 and figure 2. Please see L203-205, L209-210 and 220-223.

We're sorry that only XPS characterization of G-nFe particles was performed in this paper (W. Yang, Q. Zhuo, Q. Chen, Z. Chen, Effect of iron nanoparticles on passivation of cadmium in the pig manure aerobic composting process, Sci. Total Environ., 690 (2019) 900-910.). Since the composting experiment period is long, please allow us to conduct more in-depth research on XPS analysis of different composting times in the future.

3. More clearly specify the Temporal Changes in pH, ORP, and FTIR during composting for the two solutions used. It is not explained why the first solution works better vs the second one and the problem is that the differences in sizes are not shown, mapping of both solutions....

R: Thank you. It has been revised as suggested. Please see L237-240.

For FTIR, we only characterized the promoting effect of G-nFe on humification of pig manure before and after composting. please allow us to conduct more in-depth research in the future.

4. Neither is the mechanism clearly explained for both solutions and their influence on the composting process... and the VS changes for the two solutions based on their characterization by SEM, XPS, mapping and size of the nanoparticles.

R: Thank you. It has been revised as suggested. Please see L268-272, L277-280.

We will make continuous efforts to explore the mechanism, thank you for your valuable advice.

5. Sections 3.3, 3.4 and 3.5 should be improved with SEM characterization studies of the two solutions

R: Thanks for your advice. We will improve it in the future work.

6. The expressions of the lines that are cited below must be redrafted to facilitate their understanding:

123, "cooling. vs. and vs"[....]

174, (Figure 1A), After [....]    change to  (Figure 1A), after

180, 1) AC-C (Control–aerobics.... [....] change to (control-aerobics

R: Thank you. I’m sorry for the confusion, it has now been revised. Please see L123, L166 and L172.

Author Response File: Author Response.pdf

Reviewer 2 Report

It is interesting and useful that authors have investigated the effects of added iron nanoparticles on bacterial community and phytotoxicity in aerobic compost of pig manure. In total, the MS was written sound. Hence, it is recommended to be published after some revisions.

1.       Title, it is better to change to “effects of iron nanoparticles addition on bacterial community and phytotoxicity in aerobic compost of pig manure”;

2.         The experiment design had 3 treatments, but there were only 6 reactors. Why not use 3 replications?

3.         In M&M, add a sub-section of statistical analysis at the end of this section.

4.       In Results and Discussions, need to more emphasize on comparison between treatments (ie. added iron nanoparticles and no-added).

Author Response

We have completely revised the manuscript to clarify the points addressed by the reviewers. The responses to the reviewers’ specific comments are listed below, where the line numbers cited refer to those in the “Marked revision” manuscript.

Reviewer #2: (green colour)

It is interesting and useful that authors have investigated the effects of added iron nanoparticles on bacterial community and phytotoxicity in aerobic compost of pig manure. In total, the MS was written sound. Hence, it is recommended to be published after some revisions.

R: Thanks for the positive comments.

1. Title, it is better to change to “effects of iron nanoparticles addition on bacterial community and phytotoxicity in aerobic compost of pig manure”;

R: Thanks for your advice. It has been revised as suggested. Please see L2-L3.

2. The experiment design had 3 treatments, but there were only 6 reactors. Why not use 3 replications?

R: Thanks for your advice. We will use 3 smaller replications in future work. The reasons for using 2 replications in this experiment are: 1) The experiment was performed by sampling multiple points at the top and middle of the reactor and reducing the collected samples to the required compost sample weight using the quadrat method, therefore, the use of 3 or 2 replications in the same culture environment has little effect on the results. 2) Six reactors are just enough to fill one incubator, and the same culture environment is important for our experiments.

3. In M&M, add a sub-section of statistical analysis at the end of this section.

R: Thank you. The sub-section of statistical analysis has been added as suggested. Please see L190-L199.

4. In Results and Discussions, need to more emphasize on comparison between treatments (ie. added iron nanoparticles and no-added).

R: Thank you. It has been revised as suggested. Please see L465-L475.

Finally, we thank the editor and the reviewers for their valuable comments and suggestions to help improving this manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

It would have been desirable for the authors to have introduced the requested modifications, but nevertheless the work can be accepted and that they take it into account for other works in the future.