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Open AccessArticle
Peer-Review Record

Analysis of Migration of Polycyclic Aromatic Hydrocarbons from Sewage Sludge Used for Fertilization to Soils, Surface Waters, and Plants

Water 2019, 11(6), 1270; https://doi.org/10.3390/w11061270
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Water 2019, 11(6), 1270; https://doi.org/10.3390/w11061270
Received: 4 April 2019 / Revised: 7 June 2019 / Accepted: 9 June 2019 / Published: 18 June 2019
(This article belongs to the Section Wastewater Treatment and Reuse)

Round 1

Reviewer 1 Report

Page 1 line42: aromatic rings instead rings

Page 2 line 87: what are the limits?

Page 2 line89: “situated in the south of Poland”, too generic, remove from the text.

Page 2 line 91-93: briefly, aerobic stabilization

Page 3 line 95: grain size of sandy soil?

Page 3 line 97: Mg = megagrams, why not use tons/hectare? mg/kg…..?

Page 3 line 108: water content?

Page 3 line 124: and groundwater , not only surface water

Page 3 line 129-130: already mentioned on page 2 line 84-85

Page 3 line 131: what are the permissible values?

Page 3 line 131: IUNG??

Page 3 line 132-133: remove element symbols (or name)

Page 4 table 1: add: permissible limits, water content. What is the "Hh" value?

Page 4 table 2: "total 16 PAHs" but there are 17PHs

Page 5 table 3: not fertilizer “K”, in the text is reported “C”. 

Chrysene increases compared to “K”, how is it possible?  Moreover missing initial data (start of the experiments)

Page 6 table 4: nanograms or micrograms?

Page 7 table 5: biomass instead of bomass. If the chrysene increases in “K” it should also increase in biomass. “n.d.” not detected or below the instrument limits?

Table 3, 4 and 5: what about the heavy metals (and other parameters) reported in table 1?

Page 8 line 189-195: it is not clear and, moreover, the references are not in English language

Page 8 line 199-200: naphthalene dominant: it is not clear the comparison, naphthalene is more abundant simply because there is so much in the starting materials. Furthermore, if the starting values are missing, it is not possible to make comparisons.

Page 8 line203: in table 4 are reported ng/l (or μg/l)

Page 8 line 205:what are the characteristic concentrations?

Page 8 line 214: class 1=international classification?clarify

Page 8 line 217: what are the hydrogeological background values?

Page 9 line 228: what are the safe values?

Page 9 line 244: benzo(a) pyrene never used in the text as B(a)P

Page 9 line 258: missing values

Line 264 species in italic text

 

General consideration

It would be advisable to use a single unit. Moreover make comparisons between Mg / hectare (surface) and micrograms / kg d.m. (mass) is not correct.

It would be appropriate to report the initial concentrations to make comparisons regarding the presence of the single compounds.

The admissible values are also missing, even though comparisons are abundantly cited.

although the values of heavy metals are reported (tab 1) they are not treated in the text.

The parameters reported in table 1 (including heavy metals) are no longer considered in the txt: what is table 1 for?

Part of the references are not written in English


Author Response

Dear Reviewer,

I would like to thank you very much for your detailed comments on my paper. They were extremely valuable and helped me improve the study. I have made all the recommended revisions in the text. I marked them in yellow to make it easy to notice.

Some explanations concerning the text:

1.       Heavy metals are the main contaminants in soil and sewage sludge which are standardized in Poland and determine the possibility of their use. The limits for heavy metals contents in soils (which can be fertilized with sewage sludge) and sewage sludge (used for agricultural purposes) are given in the text and explained. They were not entered in Table 1. Their contents in soil and sewage sludge were presented in order to characterise these materials and to demonstrate the absence of contamination with other compounds before the experiment was set up.  Migration of heavy metals was not analysed in the study. The study focused on the analysis of polycyclic aromatic hydrocarbons in the environments studied.

2.       The contents of heavy metals in sewage sludge made it possible to use the sludge for agricultural purposes. The permissible quantities of heavy metals for such use are: for cadmium - 20 mg/kg, copper - 1000 mg/kg, nickel - 300 mg/kg, lead - 750 mg/kg, zinc - 2500 mg/kg, mercury - 16 mg/kg and chromium - 500 mg/kg of dry matter of sludge.

3.       The composition of the water used for watering was not analysed because it was tap water approved for human consumption, which met the recommended standards.

4.       The control soil showed an increase in the content of chrysene during the experiment. It is possible that this was caused by changes in the external environment (air), despite experimentation in conditions that limited access of contaminants. As stated in the paper, the research was carried out in a foil tunnel, which prevented the access of precipitation and contaminants, e.g. those contained in rain.

5.        I agree with the comment of the Reviewer that the data from the start of the experiment are missing.

6.       Page 6 table 4: nanograms or micrograms?

The values for the water tested were given in nanograms per litre.

7.       Page 7 table 5: biomass instead of bomass. If the chrysene increases in “K” it should also increase in biomass. “n.d.” not detected or below the instrument limits?

Despite the increase in the content of chrysene in the control soil in the 2nd year of the experiment, no increase in the accumulation of this compound in plant biomass was observed. It may have been leached from the soil or microbiologically transformed into other compounds.

8.       The abbreviation n.d. (“not detected”) means that a given compound was not detected in the examined material due to the detection capabilities of the equipment used for determinations.

9.       Table 3, 4 and 5: what about the heavy metals (and other parameters) reported in table 1?

The contents of heavy metals shown in Table 1 was to present the characteristics of the materials tested used in the experiment. In sewage sludge and fertilized soils, the content of these elements determines how they are used and how they can be fertilized.  The amount of heavy metals and other components, including biogenic compounds, will be presented in another study. This paper focuses only on the migration of polycyclic aromatic hydrocarbons to soils and groundwater.

10.   Page 8 line 199-200: naphthalene dominant: it is not clear the comparison, naphthalene is more abundant simply because there is so much in the starting materials. Furthermore, if the starting values are missing, it is not possible to make comparisons.

I agree with the reviewer's comment. However, the authors wanted to emphasize which compound was dominant.

11.   Page 8 line 205: what are the characteristic concentrations?

These are average background concentrations.  More specifically, these are the average contents of a given component in a non-contaminated environment (geochemical background).

12.   Page 8 line 217: what are the hydrogeological background values?

Hydrogeochemical background is a range of concentrations of the substances tested or range of values of hydrochemical features, characteristic for the examined environment, unit or fragment of a hydrogeological unit homogeneous in hydrogeochemical terms. The background is bounded by the lower and upper limits of the concentrations beyond which anomalous values (hydrogeochemical anomaly) occur.

13.   Page 9 line 228: what are the safe values?

In accordance with the Commission Regulation (EU) No 835/2011 of 19 August 2011 on maximum levels for polycyclic aromatic hydrocarbons in foodstuffs, the maximum permissible content of benzo(a)pyrene, e.g. for smoked meat and smoked meat products is 2 µg/kg. The Regulation also introduced a criterion concerning a maximum permissible level for the total of benzo(a)pyrene, benzo(a)anthracene, benzo(b)fluoranthene and chrysene for the above foodstuffs up to 12.0 µg/kg. For foods produced for children under 5 years of age, the maximum permitted levels of benzo(a)pyrene and of the total of benzo(a)pyrene, benzo(a)anthracene, benzo(b)fluoranthene and chrysene are 1 µg/kg.

Yours faithfully

Ewa Stańczyk-Mazanek


Author Response File: Author Response.doc

Reviewer 2 Report

Your manuscript (Ms.) focuses on the contamination of ground, superficial waters and plant biomass with PAHs from wastewaters sludge used as fertilizer in soils. Albeit the importance of your research (results obtained in 3 years are scarce) and the fact that was proper conducted, the Ms. must be improved in its clarity and objectivity to be of scientific interest. In particular, the results must be more improved in their presentation and exploration. Please considerer my suggestions, advices or hints as contributions to improve your work.


General comments:

The Ms. is written in a confusing way, needing edition: e.g. cut off repetitions of sentences and/or ideas, integrating “solitary” phrases (e.g. the last phrase e.g. the last one in section 2, “Material and Methods”), replacing words or terms with more appropriate ones (e.g. “examinations” or experiments?; “application in nature, e.g. in agriculture” – just put “application in agriculture /forestry”, line 29). Avoid or cut vague terms (e.g. “growing season”, in abstract – do you meant a season, time frame? Use a date or time unit), simply the sentences, cut unnecessary words – e.g. “very strong” per strong (line 38); line 92 – “sludge was composted in sludge drying beds” – per “sludge was composted in drying beds”. If abbreviations are introduced (such as PAHs), use them, along the text.

Do not initiate sentences with numbers (e.g. line 116). A species name is full written (in italic) when it is introduced, but should be abbreviated after (D. glomerata). Use the same abbreviations in all data tables (S, for soil; SS for sewage sludge) but explain them in all table legends. Correct the English.


Specific comments, by section:

a) “Introduction” – considerer rewrite the section. Pay attention to the sequence of ideas and topics. Present continuous story-line.

Line45/46 – rephrase it

Line 48 – “that transform PAHs to forms that are not very hazardous” – try “that degrade PAHs to less hazardous forms” or molecules(?)

Lines 54/55 – use “anaerobic degradation” instead “fermentation”.

Paragraphs between lines 53/63 – rephrase

Include, in the end of the section, a paragraph with the objectives of this research


b) “Material and Methods (M&M)” – Organize the text; clarify or be more objective some aspects: did you analyze the soil granulometry? Describe it. The physico-chemical chtractrization of the sludge and its heavy metal composition are presented. But the methods are missing. Describe them all the parameters (or give the references to them). Explain better the field assays (when, time frame, conditions) and the determination of PAHs (10 for “recommendation” – what do you mean? The plant species was choose for any particular reason?


c) “Results” – considerer joint this section with the “Discussion”. In fact you discussed some of the results (lines 129-130). You have some phrases or ideas repeated from introduction.

Introduce the tables and explored more the results.

Line 131 – “IUNG” – explain

Line 137 – “PAH content does not represent a legal” – “PAH content does not have a legal”

Line 138 – “11 PAHs (indicated in the table*)” – “11 PAHs (marked with an asterisk in Table 2)”

Tables 2, 3, 4 and 5– explain d.m. (dry mass?); the values are means (put the number of repetitions)? The error values are standard-deviation?

Tables 3, 4 and 5 – what is K? control? In line 98 it was mentioned that control was “C”


d) “Discussion” – considerer joint this section with the “results”.

 

e) “Conclusions” – “pure soil values”; substitute “pure”; point 3 – safeguard “for the PAHs measured”

 

(f) “References” – references 21, 22, 29 and 30 are indispensable? If yes translate the title and give complete the references (source, link, if any)


Good work

Author Response

Dear Reviewer,

Thank you very much for your valuable and insightful comments, which have helped me improve my paper.  I have modified the text according to your recommendations.  Changes have been made to the text in green to make it easier to find.

Some explanations concerning the text:

1. The authors did not analyse in detail the granulometric composition of soil.

2. Dactylis glomerata is a fast-growing plant that produces an extensive root system. It is used for plant toxicological tests to assess soil quality.

3. The authors performed the tests in 3 repetitions and the presented results are the mean of these repetitions.  This has been corrected in the text.

4. The authors presented all the results of the research.

5. References to the methodology of determination of heavy metals have been introduced in the text.

 

Yours faithfully

Ewa Stańczyk-Mazanek


Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

THE PAPER "ANALYSIS OF MIGRATION OF POLYCYCLIC AROMATIC HYDROCARBONS FROM SEWAGE SLUDGE USED FOR FERTILIZATIOn TO SOIL, surface water and plants" can be accepted for publication.

page 9 line216:  75 t/ha instead of Mg.ha-1 

Author Response

Dear Reviewer,

 

Thank you very much for your valuable comments, which have helped me improve my paper.

 

Yours faithfully

Ewa Stańczyk-Mazanek


Author Response File: Author Response.doc

Reviewer 2 Report

Your manuscript (Ms.) focuses on the contamination of ground, superficial waters and plant biomass with PAHs from wastewaters sludge used as fertilizer in soils. Albeit the importance of your research (results obtained in 3 years are scarce), ant the effort to clarify the methodology and the overall Ms. reading, the results must be more explored.

 

General comments:

The introductions of abbreviations (e.g. PAHs), are useful to use them, except when they are in the beginning of a phrase.

The first time a species name is written is the full name (Dactylis glomerata) afterwards, is abbreviated (D. glomerata). Justify the use of this plant species in the manuscript (you did in the cover letter, which will not be available to the readers).

 

Specific comments, by section:

a) “Abstract” – needs a paragraph with the main results and conclusions, both mission in the present “abstract”.

 

b) “Material and Methods (M&M)”

Line 141 – “The results are represented by mean levels from these repetitions” – considerer substitute by “The results are represented by arithmetic mean 2 from these repetitions”

Explain the use of this plant species.

 

c) “Results” – considerer joint this section with the “Discussion”.

Introduce the tables and explored more the results. You present lots of data that are not explored in a 3-year time frame experiment. Explore better the differences in leachate from soil mixtures among the years (e.g. PCA), and analyze more profoundly, that is statistically some parameters (PAHs, for example)

Analyze and discussed the plant response; For instance leachate from soil mixtures have metals in 2nd and 3rd years, but were not detected in plant biomass. Any explanation? Other plants would respond in a similar way?

 

Table 1. – enlarge column 1 from the table to accommodate all words in the same line

 

d) “Discussion”

Line 272 – “Other results were obtained by Kipopoulou et al. [28], who found that even 8-9 years after sewage sludge fertilization, biomass yields may accumulate excessive amounts of PAHs.” – other results most probably different plant species were used. Physiologically different from D. glomerata? Different field/soil conditions?

 

Line 285  – “control objects” – substitute by “control plants”

 

Be careful with terms such as “risk” (your work did not measured the risk). 

Author Response

Dear Reviewer

I would like to thank you very much for your detailed comments on my paper. They are extremely valuable and will help me improve the study in future. I have made all the recommended revisions in the text. I marked them in green to make it easy to notice.

Some explanations concerning the text:

 

As recommended by the Reviewer, I have used the full name of Dactylis glomerata throughout the paper.

The migration of pollutants (including polycyclic aromatic hydrocarbons) in the soil is influenced by the soil type, soil pH and organic matter. The products of its decomposition affect the properties of the soil sorption complex. If it is extended, the buffering properties of the soil do not allow for a rapid migration of PAHs. The paper did not analyse all properties of soils fertilized with sewage sludge.

I agree with the Reviewer's suggestion that this is an important issue and this will be taken into account in future studies and publications.

 

 Results

The authors of the paper did not investigate the migration of heavy metals to soil leachate. We analysed only the amount of polycyclic aromatic hydrocarbons in soil, soil leachate and plant biomass fertilized with sewage sludge. The heavy metal contents presented in table 1 were used to characterize the soil properties and to determine its suitability for sewage sludge fertilization. An excessive amount of these elements in soils can make it impossible to fertilize them with sewage sludge. In Poland, the permissible amounts of heavy metals in sewage sludge used for fertilizing purposes and in soils to which they can be applied are specified in the Regulation of the Minister of the Environment of 6 February 2015 on municipal sewage sludge [20].

 

Yours faithfully

Ewa Stańczyk-Mazanek


Author Response File: Author Response.doc

Round 3

Reviewer 2 Report

Your manuscript (Ms.) focuses on the contamination of ground, superficial waters and plant biomass with PAHs from wastewaters sludge used as fertilizer in soils. Albeit the importance of your research (results obtained in 3 years are scarce), ant the effort to clarify the methodology and the overall Ms. reading, the results must be more explored.

 

General comments:

The first time a species name is written is the full name (Dactylis glomerata) afterwards, it should be abbreviated (D. glomerata). Justify the use of this plant species in the manuscript (you did in the cover letter, which will not be available to the readers).

 

Specific comments, by section:

 

a) “abstract” – correct “resaearch"

lines 24 and 25 – the phrase “In resaearch increase in the content of 10 polycyclic aromatic hydrocarbons in soils was 24 observed with the increase in fertilizing doses of sewage sludge” does not make any sense. It seems that something is missing.

b) “Results” – joint this section with the “Discussion”; that is, a one section named “Results and Discussion” and not transferred results from “results” section to “discussion”. 

c) “Discussion”

Lines 275-281 – regarding the correlation determinations – stated which results; round the correlation values (e.g. 0.96 instead 0.956793686!); same observation to lines 307 and 317;

Line 318 – “a very high correlation”, a “high correlation”

Line 331 – “The authors of the cited research” – which research? From reference 28? If yes, considerer substitute by “These authors also analyzed…"


Author Response

              Dear Reviewer,


I would like to thank you very much for your detailed comments on my paper. They were extremely valuable and helped me improve the study.


Yours faithfully,

Ewa Stańczyk-Mazanek


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