Photodegradation of Decabrominated Diphenyl Ether in Soil Suspensions: Kinetics, Mechanisms and Intermediates

Round 1

Reviewer 1 Report

The photodegradation of BDE-209 in soil suspensions was analyzed in order to determine the PBDEs transformation in the environment. Pollution caused by PBDE has great importance due to its bioaccumulation, persistence, and carcinogenicity. The paper provided results that BDE-209 could be degraded during sun irradiation in soil suspension. Having in mind that it was reported that PBDEs can be the reason for reproductive toxicity, neurotoxicity and endocrine system disruption and that was detected in air, water, soil, sediment, etc. and can be transformed in the environment, I would like to emphasize the importance of the presented research.

The introduction should contain the novelty and academic significance of the work. It is not clear the motivation of the presented study. I would like that Authors provide refences related to the similar problem and possible similar approaches for the analysis.

Authors should provide the structure of the paper in the end of Introduction section.

Before Materials and Methods, Authors should provide a comparison discussing the results of other used methods. Why is the proposed method suited for this study? 

Results and Discussion should be separated in order to better present the findings of the research.

Also, the strengths and weaknesses of applied approach should be highlighted.

The limitation of study should be addressed, and future research guidelines need to be provided in Conclusions.

Author Response

Response to Reviewer #1:

The photodegradation of BDE-209 in soil suspensions was analyzed in order to determine the PBDEs transformation in the environment. Pollution caused by PBDE has great importance due to its bioaccumulation, persistence, and carcinogenicity. The paper provided results that BDE-209 could be degraded during sun irradiation in soil suspension. Having in mind that it was reported that PBDEs can be the reason for reproductive toxicity, neurotoxicity and endocrine system disruption and that was detected in air, water, soil, sediment, etc. and can be transformed in the environment, I would like to emphasize the importance of the presented research.

Response: Thank you

1. The introduction should contain the novelty and academic significance of the work. It is not clear the motivation of the presented study. I would like that Authors provide refences related to the similar problem and possible similar approaches for the analysis.

Response: Thank you. In the “Introduction”, we have mentioned the reasons of us to do this work and the novelty of our studies. The last sentence of each paragraph also shows the necessity of our work. Simply put, our work wants to investigate the photodegradation behaviors of BDE-209 in the condition of being closer to the natural. The most PBDEs molecules were absorbed on the soil particles, and few study focused on this. Hence, their photodegradation on soil suspensions should be investigated.

We have provided refences of PBDEs photodegradation on solid surface in the page 1, lines 62-63 as below:

In addition, some studies have investigated the PBDEs photodegradation on the solid surface[21, 22], but in previous studies, few people have studied the photochemical process of PBDEs in soil suspension. Therefore, the photodegradation of PBDEs in soil suspension should be investigated.

2. Authors should provide the structure of the paper in the end of Introduction section.

Response: Thank you. we have provided the main structures of our study in the end of Introduction section, and the content as below:

The kinetics of BDE-209 photodegradation with different light sources, as well as the effects of soil concentration, pH, and organic matter were investigated. In addition, the products of BDE-209 were analyzed by GC-MS and LC-TOF-MS and the photodegradation pathway was proposed.

3. Before Materials and Methods, Authors should provide a comparison discussing the results of other used methods. Why is the proposed method suited for this study? 

Response: Thank you. The methods used in this study, such as GC-MS, LC-TOF-MS and HPLC, are commonly used for the detection of PBDEs concentration and products. Our experimental results also show that these experimental methods are suitable for this study. IC is also a conventional method for the detection of bromine ions. ESR is the most common method for free radical characterization. We don't think it's necessary to compare these methods before choosing them.

4. Results and Discussion should be separated in order to better present the findings of the research.

Response: Thank you for your proposal. We think it is better for this article to put the results together with the discussion. In this way, the structure of our article is more compact, the results and analysis can confirm each other, and the repeated description of the results can be reduced

5. Also, the strengths and weaknesses of applied approach should be highlighted.

Response: Thank you. We studied the photochemical degradation of PBDEs in soil suspension. This paper attempts to reveal its photochemical transformation process in the real environment. In addition, the We also mentioned some shortcomings of this study in the last paragraph of this paper as below:

In addition, our research is not a natural environmental, in the future, we should explore the photochemical transformation process of PBDEs contaminated soil suspension by sunlight irradiation.

6. The limitation of study should be addressed, and future research guidelines need to be provided in Conclusions.

Response: Thank you. we have added “In addition, our research is not a natural environmental, in the future, we should explore the photochemical transformation process of PBDEs contaminated soil suspension by sunlight irradiation.” in Conclusions.

Reviewer 2 Report

The article „Photodegradation of decabrominated diphenyl ether in soil suspensions: kinetics, mechanisms and intermediates“ from authors Kaibo Huang, Haozhong Lin, Xueqin Tao, Mengyao Zou and Guining Lu describes research results dealing with photochemical debromination of perbrominated diphenyl ether adsorbed on soil. The effect of humic acid and common metal ions is discussed and explained in this article utilizing HPLC, LC-TOF-MS, GC-MS, IC and ESR analysis.

This article serves as very interesting for Processes journal readers.

The submitted article still needs few revisions:

1. Page 2, line 73: Please, explain the abbreviations DMPO and TEMP.
2. Page 3, Table 1: Please, explain the abbreviation cmol.
3. Page 3, line 113: Please, correct or discuss in more details the claim: „… prepared soil solution…“. It is not simple to dissolve aluminosilicates.
4. Page 4, line 189, ESR analysis: Could you explain in more details the procedure used for irradiation-produced radicals detection?
5. Page 4, line 191: Please, correct or explain the claim: „… as the capture agent of .oh and…“.
6. Page 6, Figure 1a: Please, correct the description: „Dark contral“.
7. Page, line 273: Please, explain „ROS“ abbreviation.
8. Page 11, line 353: Please, correct the claim: „strep-by-step“.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer #2:

The article „Photodegradation of decabrominated diphenyl ether in soil suspensions: kinetics, mechanisms and intermediates“ from authors Kaibo Huang, Haozhong Lin, Xueqin Tao, Mengyao Zou and Guining Lu describes research results dealing with photochemical debromination of perbrominated diphenyl ether adsorbed on soil. The effect of humic acid and common metal ions is discussed and explained in this article utilizing HPLC, LC-TOF-MS, GC-MS, IC and ESR analysis.

This article serves as very interesting for Processes journal readers.

The submitted article still needs few revisions:

Response: Thank you.

1. Page 2, line 73: Please, explain the abbreviations DMPO and TEMP.

Response: Thank you. We have explained them as “2,3-Dimethylpyridine-N-oxide (DMPO) (purity>97%), and 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMP) (purity>97%)” .

2. Page 3, Table 1: Please, explain the abbreviation cmol..

Response: Thank you. The cmol/kg is a common unit of ion exchange capacity, and 1 cmol=10 mmol. We have changed it to mmol/kg.

3. Page 3, line 113: Please, correct or discuss in more details the claim: „… prepared soil solution…“. It is not simple to dissolve aluminosilicates..

Response: Thank you. We have corrected this sentence to “The 15 mL prepared soil suspension solutions were added in the 22 mL foil-wrapped quartz tubes and a magnetic rotor is added at the same time.”

4. Page 4, line 189, ESR analysis: Could you explain in more details the procedure used for irradiation-produced radicals detection?

Response: Thank you. The details were added as below “The soil suspension solutions were irradiated by 500 W mercury lamp, and the 1 mL sample was taken into the 1.5 mL sharp bottom tube containing 20 μL DMPO/TEMP after 10 min irradiation. The filtered solutions were detected by ESR.”

5. Page 4, line 191: Please, correct or explain the claim: „… as the capture agent of .oh and…“.

Response: Thank you. We have corrected this sentence to “DMPO was used as the capture agent of •OH· oh and TEMP was used as the capture agent of ¹O₂.”

6. Page 6, Figure 1a: Please, correct the description: „Dark contral“.

Response: Thank you. We have corrected the “contral” to “control”

7. Page, line 273: Please, explain „ROS“ abbreviation.

Response: Thank you. The ROS abbreviation have been explained in the Page 7, lines 261-262.

8. Page 11, line 353: Please, correct the claim: „strep-by-step“.

Response: Thank you. We have changed the “strep-by-step” to “step-by-step”