Spatial Distribution and Ecological Risk Assessment of Potentially Harmful Trace Elements in Surface Sediments from Lake Dali, North China

Round 1

Reviewer 1 Report

Comments to the Authors:

The manuscript is written clearly and the reader can follow the research very easily. Nevertheless, there should be some changes included, especially in the discussion part:

line 23: specify which endogenous factors

line 33: rephrase in - to understand the history and consequential risk...

line 35: add - of lake sediments

line 37: please add other HM (heavy metals) main sources; e.g. the traffic is also very important anthropogenic source of HM

line 53: add - in Lake Dali sediments

line 111: why did you choose Ti? Why not Al? Explain. 

Discussion part

Specify very precisely: are these outcrops of arsenopyrite just outcrops or is this an mining area? If they are outcrops, you can define this as natural/geogenic source of As, otherwise no. 

Why is natural origin only a part source for Pb? Completely missing is the discussion about Pb. And, if there is reported that you have Pb-Zn mine, how do you interpret the Zn? Specify. 

Atmospheric deposition... is this true, or you just anticipate that there should be an atmospheric deposition? On the other hand, if you have Pb-Zn mine in the catchment area, maybe you have also enhanced values of Cu, Cd and Ni there (in the mining area). Why only atmospheric deposition? Please consider also other options or other natural options. It is very confusing. 

Lines from 224-239: you should make sequential extractions (chemical speciations) of HM from lake sediments, then you can accurately say, which part of the lake should be in priority for management. And, your citation number 5 - is Lake Dalinouer actually lake Dali? If yes, why are you not comparing your results from the 2013 study? This is urgent. 

Talking about spatial distribution of HM: specify precisely where your inflows are, where the groudwater is influencing on your sediments and finally, you should check if this spatial distribution (of all HM) is induced by inflows or groundwater. It is not clear. 

Check again the background geology, your HM values there and then compare. 

line 210: Gonnger and Shali river

You should write the Discussion part more clearly and much more supported by facts.

There are not remote lakes only in China, there are everywhere in the planet. Please use worldwide references.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The problems raised in the manuscript are very interesting, but are local character. The conclusions concern only one lake. They should be treated more broadly, present more general conclusions.

In the manuscript is stated that natural factor and anthropogenic disturbance can lead to the enrichment of heavy metals. But these factors and disturbances is not described. They should be presented in Study area chapter. It concern 1) location of the outcrops of arsenopyrite and lead-zinc and the probability of this element reaching Lake Dali, 2) the lithology of rocks building the lake catchment area which has an impact on the chemistry on lacustrine sediments. 3) No evidence also was provided for the atmospheric origin of heavy metal pollution.

The authors analyse the relationship between heavy metal content and lake depth but there is no accurate bathymetric analysis in manuscript.

It is not true that the PCA from Figure 4 proves that As pollution was mainly owing to natural source with high As concentrations in the groundwater.

The manuscript does not contain mineralogical, chemical and sedimentological characteristics of lacustrine deposits, which are very important for assessing the causes of heavy metal content.

The map with the location of the research area in the background of China is not clear

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript has been improved and I think it can be accepted for publication. But I have one comment:

The information in Table 1 should be supplemented because there is no information on what statistics are presented. Average?