Copper Contamination Affects the Biogeochemical Cycling of Nitrogen in Freshwater Sediment Mesocosms
Round 1
Reviewer 1 Report
Title: Copper contamination affects the biogeochemical cycling of nitrogen in freshwater sediment mesocosms.
Publish after minor revisions noted.
In order to test the effect of increasing copper load on nitrogen in freshwater sediment, river sediment and water were collected and analyzed, and the mesocosm experiment was conducted using treated sediment with different copper concentrations as independent variables. The existing forms and concentration depth distributions of trace elements and nitrogen were measured with diffusive gradients in thin-films (DGT) and diffusive equilibria in thin-films (DET) sediment probes. The nitrogen cycle with increasing copper concentration and the effect of iron and manganese on the nitrogen cycle were analyzed.
Some questions are as follows:
P1-L22: There should be punctuation before “this”.
P2-L80: “(pseudo)total” should be changed to “pseudo-total”, consistent with the other two parts of the article.
P4-L136: The writing format of “CuCl2.2H2O” is not correct.
P6-L235: The “~” before “4 cm” is not formal expression, and other similar issues also need to be modified.
P7-L256: The writing format of “(µg L-)” is not correct.
P9-L364: “µg/L” should be changed to “µg⋅L-1”, please change other similar issues in the article.
P10-L400: “(2.39 mg L-1 ± 0.06)” should be changed to “(2.39 ± 0.06 mg⋅L-1)”.
P13-L519: The charge of nitrite ion should be superscript.
Author Response
Please see attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is an interesting work, however, there are no evidences that the results are valid.
1. It was mentioned that the content of C and N was determined by using an CN analyzer. There are no proofs regarding the trueness of these results.
2. In addition, the content of Cu, P, S, Fe and Mn was measured after the wet digestion of the samples. Although, the authors wrote that "The accuracy of the sediment trace element digestion (Cu, Fe, Mn) and subsequent analysis was confirmed with a certified reference material (Montana 2710, NIST® SRM® , New Zealand), ..." they added that "recovery rates of the three analytes were within 10% of reported values", which means that not valid results were obtained.
3. What about other elements, i.e., C, N, S and P. How was the trueness of their results verified?
Author Response
Please see attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript of Tomoiye et al., “Copper contamination affects the biogeochemical cycling of nitrogen in freshwater sediment mesocosms”
The authors presented new data about effect of Cu excess on nitrogen biogeochemistry
Some minor recommendation listed below:
- In references used many ancient articles it will be better refresh the references
- Table 1. For the first time used the T5 and T20, need the description. In section 2.1.2 described that the sediment was divided into three parts with different Cu content, but according the Table 1. The variant T5 and T20 also did not contain P, S, as well as no information about organic matter and total C and N content. It seems rather different with Tc
- The discussion started with effect of Cu on microbial. In present work as I understand did not detected the microbial community. But it can contain bacteria or nitrogen-fixing bacterium as well as some micro alga that capable to nitrogen-fixing. The species composition can explain some of presented results.
- Discussion 4.2. It is well known that disbalance with NH4 and NO3 caused a decrease in pH that can affect on translocation elements and higher NH4 concentration resulted in Mn and Ca content. According to this maybe the Cu not primary affected on the Mn drop.
- The result of mesocosm experiment can be different with data from natural (without control) condition
- The conclusion need to make closer to described results gotten during present work
Comments for author File: Comments.pdf
Author Response
Please see attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
In my opinion, the authors have revised quite well their work. Its present form deserves the publication. Well done.
Reviewer 3 Report
All recomendations were accepted
English language required
