Suspended Sediment Metal and Metalloid Composition in the Danube River Basin, Croatia
Round 1
Reviewer 1 Report
This is the review of the article entitled “Suspended Sediment Metal and Metalloid Composition in the 2 Danube RB, Croatia” in which the authors calculate the daily values of chemical elements in the transmission of the suspended sediment and its accumulation in the suspended matter collected at some hydrological stations in the Danube River Basin during high flow events. This work is interesting since the authors perform chemical analysis of Danube suspended sediment, suggesting the need of a permanent sediment quality monitoring program.
However, I suggest the publication of article after minor revisions:
1) In equation 1 it should be mentioned that Q is the flow rate.
2) In Figures 3, 6 and 7, I suggest the rivers to be mentioned on the graph in order to be clearer.
3) I suggest part of the conclusions to be moved in the discussion section.
Comments for author File: 
Comments.docx
Author Response
All corrections and explanations are in the attached file Reviewer_1_answers
Author Response File: Author Response.docx
Reviewer 2 Report
Table 1 has an extensive list of 47 chemicals, but in line 53 of the document, you state that 33 priority substances and 8 other pollutants which tend to accumulate in sediments are addressed. Maybe only include in Table 1 those specific pollutants.
Somewhere in the background give a physical description of the watershed that is being monitored so that the reader knows if it flows through rural, agricultural, forest, urban, industrial settings and if there are any dams. Later in the discussion of results, relate the results to this description. This will help explain why certain pollutants were observed and it sets a framework for reduction. Provide a somewhat detailed map of the river flows with their connections.
For American and British readers, state that 1000 kg = 1 ton so that the conversion factor 0,0864 makes sense.
Make the font sizes in figure 1 bigger so that they are readable.
Under results 3.2, in line 266, you list Mn twice. Did you mean Mg and Mn?
Figure 3 will need to be in color with higher resolution
Under section 4.1, explain what positive and negative correlations are in the context of pollutant concentrations
Make font in Figure 8 bigger
Author Response
All corrections and explanations are in the attached file Reviewer_2_answers
Author Response File: Author Response.docx
Reviewer 3 Report
Please address the following:
- the article does not respect the main sections accepted by Water: Introduction, Materials & Methods, Results, Conclusions. The Materials and Method part is missing. please rearrange the article in order to comply with the imposed requirements.
- please clearly state the main importance of this study, at what will serve the obtained results, what is the main goal of the study.
- what is the main process that affected the content of the studied pollutants in the water?
- Table 1 needs to be rearranged: either 4 columns (1,2,3,4) or renounce at table heather
-in Table 1, 4.2. is identical to 4.5.
-row 81- "concentrations" is repeated
- are necessary both table 3 and Figure 6, table 4 and Figure 7?
- row 230-231- please explain boiled at 50 °C for 6 hours - The samples in the glasses were sealed with parafilm, placed in a Grant JB Academy JBA5 water bath, put in a fume cupboard, and boiled at 50 °C for 6 hours with occasional stirring.
- is it possible to assess the potential sediment toxicity due to metal pollution in the study area?
Author Response
First of all, we want to thank Rev 3 for helpful comments and suggestions. All suggestions by Rev 3 were accepted and implemented in the text of the manuscript.
Below the authors give their explanations:
Rev 3: the article does not respect the main sections accepted by Water: Introduction, Materials & Methods, Results, Conclusions. The Materials and Method part is missing. please rearrange the article in order to comply with the imposed requirements.
Authors: Corrected. The article has been rearranged according to the guidelines.
Rev 3: please clearly state the main importance of this study, at what will serve the obtained results, what is the main goal of the study.
Authors: Corrected. A paragraph at the end of the Introduction has been added. – Ln – 75-82.
In the Introduction, the objectives of this research are clearly defined, and in conclusions they are related to the results.
Rev 3: what is the main process that affected the content of the studied pollutants in the water?
Authors:
In chapter 4. Discussion – Ln – 310-327; 389-404 and 4.2 – Ln – 435-469 are discuss possible sources of the discovered contamination in suspended sediments.
After the results of chemical analysis two hypothesis appeared:
- Hypothesis is that in conditions of high flow, contaminated sediment in upstream reservoirs is triggered old settled fine sediment.
- Second Hypothesis is that heavy rain flushes floodplains and possible landfills from which toxic substances are washed into the watercourse and transported via sediment.
These hypotheses need to be confirmed by a longer-term monitoring program to be able to conclude with certainty what the real cause is.
Rev 3: Table 1 needs to be rearranged: either 4 columns (1,2,3,4) or renounce at table heather
Authors: Corrected. Ln - 71
Rev 3: in Table 1, 4.2. is identical to 4.5.
Authors: Corrected. – Ln 71
Rev 3: row 81- "concentrations" is repeated
Authors: Corrected.
Rev 3: are necessary both table 3 and Figure 6, table 4 and Figure 7?
Authors: The authors decided for tabular and graphical representations due to a more precise presentation of values because it is not possible to see the exact values of individual elements on the graph.
Rev 3: row 230-231- please explain boiled at 50 °C for 6 hours - The samples in the glasses were sealed with parafilm, placed in a Grant JB Academy JBA5 water bath, put in a fume cupboard, and boiled at 50 °C for 6 hours with occasional stirring.
Authors: Corrected - Ln 262
Rev 3: is it possible to assess the potential sediment toxicity due to metal pollution in the study area?
Authors: The answer is in Conclusion:
Based on several individual samples, it is impossible to conclude the origin of the high concentration of mercury and other heavy metals at the analysed location. Since heavy metals are highly toxic, a continuous monitoring program with a specific spatial and temporal resolution is required to monitor this phenomenon adequately. According to Environmental Quality Standards Directive recommendations (2008/105/EC), this research could be the starting point for defining a preliminary sampling program which can be useful in providing relevant information.
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
The authors have addressed all my observations.
The article can be published.
