Particulate Mercury and Particulate Organic Matter in the Itenez Basin (Bolivia)
Round 1
Reviewer 1 Report
The presented work contains exciting information on the Itenez River's mercury pollution, associated lakes in the Amazon rainforest area. The researchers sought to determine the contamination source and determine the relationship between particulate mercury and particulate organic carbon.
Critical remarks below:
- The authors present data from 2007. These are rather archival data and do not describe the current pollution of the river by mercury. In terms of methodology, the analysis of samples from only two dates of 2007 is incorrect (the lack of repetitions in time intervals eliminates one of the most critical determinants of pollution). It affects the statistical inference. I am afraid that experimenting is not appropriate despite the interesting results, translating into the results and conclusions. Please explain why these are such out-of-date data, and the authors did not repeat these studies in the following years?
- Please explain what is innovative in research. The authors largely confirm the published data, which in some cases are much more recent than those presented in the article. In the Results and Discussion section, the authors write: (lines 178-179), "No increase in [Hg]v was observed in sample points nearest to the mining sites. These results agree with those obtained by Roulet et al. [21]." Firstly, the authors confuse the citation order – it should be Roulet et al. [23]. Secondly, they refer their archival results to even older ones from 1998, i.e., to almost historical data: (lines 197-200) "In both seasons, the values for [Hg]w in Itenez river and its lakes were comparable to those obtained by Roulet et al. [17] for fine particulate matter and organomineral components in Tapajos and to those reported by Vieira et al. [19] for suspended matter in clear waters of the Madeira basin." The authors confirmed the data again. The reference is to the publication from 2001 and the publication from 2018, in which the data comes from the years (2009-2012). In the latter case, you compare your results for 2007 with more recent data for the four years.
- Figure 1 is blurry – it is impossible to locate all the sampling sites first of all. The map should have a scale that is missing here. The authors should also provide the source based on which they drew the sampling sites for analyzes.
- In the case of submitting a revised manuscript, I suggest that you split the RESULTS AND DISCUSSION section. In the discussion, please show the research's uniqueness by first comparing it with the data in the Itenez River area. If you do not find any, please compare similar ecosystems exposed to similar threats. Please systematize and expand the literature.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This MS describes PHg in correlation with POC in a Bolivian freshwater basin. MS was written in straightforward manner and is understandable.
Specific comments:
Line 61: Authors stated: “Most of Hg in the water column is aggregated on suspended particulate matter (SPM)”, with citing reference [11]. This reference deals with Hg(0), while authors refer on Hg in general. It should be commented accordingly.
Some references were not written correctly (such as ref no. 23). Check it.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
178/5000 I thank the authors for the corrections made in the text. I have no more comments. The article has application and cognitive values, therefore I am applying for publication in the Applied Sciences journal