Occurrence and Ecological Risk Assessment of Heavy Metals from Wuliangsuhai Lake, Yellow River Basin, China

Round 1

Reviewer 1 Report

This paper is interesting and quite comprehensive and adequate. This paper deals with the problem of sediment interstitial water, surface sediments, and sediment cores of Wuliangsuhai Lake (China) for evaluating heavy metal contaminants level (Cr, Ni, Cu, Zn, As, Cd, Hg and Pb). The bioavailability of heavy metals of the surface sediments were evaluated by calculating the ratio of chemical fractions of heavy metals. This study aimed to investigate the contaminant characteristics, pollution levels, and ecological risks.

 

Strengths : The paper provides a comprehensive analysis of three matrices to examine the various entry points for a large panel of elements (Cr, Ni, Cu, Zn, As, Cd, Hg and Pb) into the environment and thereby demonstrate possible exposure and potential ecological risk. Enrichment factor (EF), geo-accumulation index (Igeo), toxic units (ΣTUs) and toxic risk index (TRI), risk assessment code (RAC) and potential ecological risk index (RI) were calculated.

 

Weakness :­ The conclusions. The authors state that “Based  on the pollution assessment results, Cd and Hg are the primary pollutants in WLSH Lake, which deserve attention.” but no contributions are reported to overcome or solve these problems.

Abstract – the information given is adequate and concise.

1. Introduction – The aim of paper is adequately exploited.

2.. Materials and Methods – adequate

Equipment, experimental design, sampling collection and analytical methods and pollution assessment methods – adequate

3. Results and discussion- Adequate discussion well documented by tables and figures.

Figure 2 – values should be presented with only three significant figures (for instance for Cr instead of 21.94-26.05 write 21.9-26.1 ….), figure will be more legible.

English should be improved. For instance, lines 248, 352, 375, 383, 440/441

and grammar in general.

Lines 342 The average enrichment degree decreased  in the order of Cd>Hg>As>Cu>Ni >Pb> Cr >Zn. is not correct according to mean values of table 4.

Insert reference for CMC and CCC values in Table 1.

Insert reference for TEL, PEL, ERL and BV values in Table 2.

Therefore in my opinion this paper should be accepted with minor revision.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This is an interesting paper that I think merits publication.  There are a number of revisions that need to be made before the paper is ready for publication, however, as I indicate in the following specific comments. Each comment is linked to a particular page and line number (s) in the manuscript.

1. Page 3, Lines 130-131. It would be helpful here to clearly indicate where the sediment samples were collected. Are they coming from lake bottom sediments?
2. Page 4, Line 141. I am confused about the measurement of metal concentrations from interstitial water. Does this represent the dissolved content of metals? Could be clarified.
3. Page 4, Line 170. Is the enrichment factor (EF) a measure devised by the authors, or has it been used in other studies?  If the latter, then the other studies need to be noted here.
4. Page 5, Line 184. What is the date of publication for the Mueller paper?  Also, it is not in the list of references at the end of the manuscript.
5. Page 5, Between Lines 187 and 188. What is the number in the brackets to the right of the equation?
6. Page 5, Line 192. Similar to the enrichment factor noted above, what is the source for potential ecological risk index? Is it devised by the authors or has it been used in other studies?
7. Page 5, Lines 202-203.  TEL and PEL were first used by MacDonald et al. (2000). That work needs to be referenced here. 
8. Page 5, Line 212. Need a date for the Singh et al. paper.
9. Page 8, Lines 277-278. This is the first mention of soil background values. Since they are being used as a basis for determining the anthropogenic enrichment of metals, background values and the source for them should be discussed in the Methods section.  Why were those from inner Mongolia chosen?  Are there other possible ways to determine background values in the study area?
10. Page 8, Lines 284-285. Here TEL and PEL are referred to as Threshold Effect Concentrations and Probable Effect Concentrations. Earlier on page 5, they were called Threshold Effect Levels and Probable Effect Levels. I believe the latter is correct, as used by MacDonald et al. (2000).
11. Page 8, Lines 299-300. What is the basis for the comparison of heavy metals concentrations in developed area lakes vs. those in economically developing areas? Are the lakes listed in Table 3 in developed areas or developing areas?  This section needs to be clarified.
12. Page 10, Lines 337-339. When is something "minimal enrichment"? When is the concentration defined as "significant enrichment"?  Are these designations developed by the authors or do they come from the literature?
13. Page 13, Line 389. I assume these are aquatic species listed in italics here?  Could the common name also be provided?
14. Page 15, Line 444.  I think the reference here should be to Fig. 6, not to Fig. 4.
15. Page 15, Line 448. What is the source for the sedimentation rate calculation? 
16. Page 15, Line 451. How do the concentrations in the "background layer" compare to the background values presented on page 8?

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

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Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx