Exploration of Influencing Factors and Generation Mechanism of EPFRs in Polycyclic Aromatic Hydrocarbon-Contaminated Soil

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript by Liu et al describes the light-induced formation of environmentally persistent free radicals (EPFRs) from polycyclic aromatic hydrocarbons (PAHs) under a range of conditions that simulate environmental conditions. Of highest importance is their study of the influence of various transition metal cations, and (ii) the differences in the EPFR formation in mixture of PAHs vs anthracene monomers. The manuscript contributes with relevant results, but crucial information is missing and additional experimental data needs to be reported.

1: They carry out photochemistry experiments under natural light, but nowhere can I find information on the light intensity. This information is absolutely crucial in order to assess how their findings translate to other (geographic) settings with different natural light intensities.

2: For similar reason, what is the impact of temperature on their findings?

3: I would also like them to discuss how the electron transfer from a PAH depends on the structure of the PAH. ANT is an acene where the radical cation gains maximum stabilization when at the C9 and C10 as it can delocalize into the two terminal benzene rings. How extensively are EPFRs formed from phenanthrene, an isomeric PAH to anthracene, under the conditions explored for ANT?

4: In Figure 6 and in the text above the figure, it is unclear why radical A (1,3-di-tBu-benzene radical cation) forms upon electron transfer from ANT to Cu2+. From where comes the 1,3-di-tBu-benzene?

Furthermore, why is radical B drawn as saturated? Then going from Product 1 to Products 2 in Figure 6, from where comes the methyl group that replaces a H atom in the para-position to the OH group? The mechanistic discussion is weak and handwavy, and likely incorrect to some extent.

5: Finally, they never tell that the acronym ANT stands for anthracene when it appears for the first time on page 2.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript is “Exploration of influencing factors and generation mechanism of EPFRs in polycyclic aromatic hydrocarbon contaminated soil”. Some detailed comments are as follows:

(1) What is the relationship between this research and sustainable development?

(2) Abstract: There is a lack of research background introduction and research objectives here.

(3) Abstract: “These findings align with existing research, highlighting that metal ions with greater oxidizing potential enhance EPFRs formation.” Where is the innovation of this research?

(4) Introduction: What is the problem or important research objective addressed by the research institute?

(5) Materials and Methods, Preparation of soil with various transition metal ion loading: Is there a lack of explanation for the preparation conditions of soil samples here?

(6) Materials and Methods: The introduction of data processing is not detailed enough.

(7) Results: The Results section should be revised to Results and Discussion. The discussion content in this chapter is clearly insufficient.

(8) Conclusions: The research conclusions need to be further summarized, and this section needs to highlight innovative content.

(9) The format of table 1 does not meet the requirements of the journal.

(10) The format of the references did not meet the requirements of the journal, and the journal names in the references were not abbreviated as required.

(11) A proof reading by a native English speaker should be carefully conducted to improve both language and organization quality.

Comments on the Quality of English Language

The English language of this manuscript needs improvement.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I am more or less satisfied with their revisions, except for two items:

Comment on revision wrt my earlier comment 1: In a paper on photodegradation I want to see relevant information on the irradiation conditions in the paper itself, not in the Supporting Information. Thus, please move that information to the manuscript section “2. Materials and Methods”.

Comment on revision wrt to my earlier comment 2: The added sentences on temperature are odd. It should be obvious that one cannot determine the temperature variation at room temperature, i.e., at one single temperature. It is better that the authors write that the temperature variation will be explored in a follow-up study.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf