Selective Speciation of Inorganic Selenium [Se(IV)] in Water Samples by Inductively Coupled Plasma Mass Spectrometry after Solid Phase Extraction: Blood and Mokolo Rivers, South Africa
Round 1
Reviewer 1 Report
The manuscript “Speciation of inorganic selenium [Se(IV)] in water samples by inductively coupled plasma mass spectrometry after solid phase extraction: Blood and Mokolo rivers, South Africa” by Meldred Mmakoena Matjena et al is devoted to the examination of the concentrations of Se(IV) in water samples from Blood and Mokolo Rivers using ICP-MS analysis. Interesting work deserves publication in the Water Journal.
Below are some of the reviewer's comments.
The English text should be corrected. There are some grammatical and syntactical errors (word order, omission of articles, implicit meaning, etc.). For example,
p.4.1 “In general, water with a pH lower than 7 is acidic and with a pH greater than 7 is basic.” Water cannot be alkaline or acidic, only a water solution, or an aqueous system such as surface water.
“Low pH levels cause organisms like fish to be more vulnerable to diseases [23].” – the sentence should be changed.
“The low pH maybe due to the river passing through the vicinity of the Grootegeluk Coal Mine.” The sentence should be reformulated.
reagent blanks = blank reagents
instrumental setup and conditions. Conditions of the experiment
"Selenite, Se(IV) is the main selenium valence for water soluble selenium and the most toxic inorganic selenium." Pointless repetitions
“Findings from this study on the levels of inorganic selenium specie [Se(IV)] from Blood River indicates that the river is not heavily polluted by pollutants from anthropogenic activities and natural activities as the levels are very low.” The sentence should be reformulated.
“The pH of 6 was selected as optimum as it yields an excellent percentage recovery.” Why is pH 6 and not 5 chosen as optimal? The figure shows that at pH = 5 percentage recovery is higher.
It is necessary to give a transcript of the abbreviations from Table 5 (WHO etc.)
In Figure 5, the presentation of the data should be optimized, for example using a break in the y scale. Due to the difference in values, the diagram does not give the correct graphical representation without reading the text fragment.
The English text should be corrected. There are some grammatical and syntactical errors (word order, omission of articles, implicit meaning, etc.). For example,
p.4.1 “In general, water with a pH lower than 7 is acidic and with a pH greater than 7 is basic.” Water cannot be alkaline or acidic, only a water solution, or an aqueous system such as surface water.
“Low pH levels cause organisms like fish to be more vulnerable to diseases [23].” – the sentence should be changed.
“The low pH maybe due to the river passing through the vicinity of the Grootegeluk Coal Mine.” The sentence should be reformulated.
reagent blanks = blank reagents
instrumental setup and conditions. Conditions of the experiment
"Selenite, Se(IV) is the main selenium valence for water soluble selenium and the most toxic inorganic selenium." Pointless repetitions
“Findings from this study on the levels of inorganic selenium specie [Se(IV)] from Blood River indicates that the river is not heavily polluted by pollutants from anthropogenic activities and natural activities as the levels are very low.” The sentence should be reformulated.
etc.
Author Response
Comments and Suggestions for Authors
The manuscript “Speciation of inorganic selenium [Se(IV)] in water samples by inductively coupled plasma mass spectrometry after solid phase extraction: Blood and Mokolo rivers, South Africa” by Meldred Mmakoena Matjena et al is devoted to the examination of the concentrations of Se(IV) in water samples from Blood and Mokolo Rivers using ICP-MS analysis. Interesting work deserves publication in the Water Journal.
Below are some of the reviewer's comments.
The English text should be corrected. There are some grammatical and syntactical errors (word order, omission of articles, implicit meaning, etc.).
Response: The manuscript has been revised thoroughly. Corrections of grammatical and syntactical errors have been conducted throughout the manuscript.
For example,
- “In general, water with a pH lower than 7 is acidic and with a pH greater than 7 is basic.” Water cannot be alkaline or acidic, only a water solution, or an aqueous system such as surface water
Response: The sentence has been rephrased as “In general, surface water can be acidic or basic depending on the environment.”
- “Low pH levels cause organisms like fish to be more vulnerable to diseases [23].” – the sentence should be changed.
Response: The sentence has been rephrased as “The lower pH levels can cause water-based organisms like fish to be more vulnerable to diseases [23].”
- “The low pH maybe due to the river passing through the vicinity of the Grootegeluk Coal Mine.” The sentence should be reformulated.
Response: The sentence has formulated as “The measured pH value of 4.55 in water sample from Mokolo River site 9 is below the permitted pH range of 6.5 to 8.5. The low pH is presumably attributed to the river passing through the vicinity of the Grootegeluk Coal Mine.”
- reagent blanks = blank reagents
Response: “blank reagents” is used consistently as recommended by the reviewer.
- instrumental setup and conditions. Conditions of the experiment
Response: “conditions of the experiment” was used as suggested by the reviewer.
- "Selenite, Se(IV) is the main selenium valence for water soluble selenium and the most toxic inorganic selenium." Pointless repetitions
Response: The sentence has been deleted.
- “Findings from this study on the levels of inorganic selenium specie [Se(IV)] from Blood River indicates that the river is not heavily polluted by pollutants from anthropogenic activities and natural activities as the levels are very low.” The sentence should be reformulated.
Response: The sentence has been reformulated under conclusion, last paragraph. “According to the results of this study, the levels of inorganic selenium specie [Se(IV)] in Blood River are relatively low, indicating that the river is not severely contaminated by pollutants from anthropogenic and natural activities”
- “The pH of 6 was selected as optimum as it yields an excellent percentage recovery.” Why is pH 6 and not 5 chosen as optimal? The figure shows that at pH = 5 percentage recovery is higher.
Response: As shown in Figure 5, acceptable percentage recovery was obtained at pH greater than 5 ranging from 87% to 114%. The pH of 6 was selected as optimum pH as it yields an excellent percentage recovery (104%) which is much closer to 100% than other percentage recoveries with the less deviation of +4% from 100%. However, at pH 5 the percentage recovery is 87% with the higher deviation of -13% compared to the percentage recoveries at most pH values. The sentence has been rephrased in the revised manuscript.
- It is necessary to give a transcript of the abbreviations from Table 5 (WHO etc.)
Response: The transcript of the abbreviations were included throughout the manuscript in first usage of abbreviations/acronyms including WHO.
- In Figure 5, the presentation of the data should be optimized, for example using a break in the y scale. Due to the difference in values, the diagram does not give the correct graphical representation without reading the text fragment.
Response: Figure 5 was redone to make the data visible.
Comments on the Quality of English Language: Response: The below highlighted comments are repeat and have been addressed above.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Authors reported the selenium content of Blood and Mokolo Rivers by solid phase extraction and then ICP. The report does not contain new finding since the selenium in Blood and Mokolo Rivers was reported previously.
Author Response
Response to Reviewer 2 Comments
Point 1: Authors reported the selenium content of Blood and Mokolo Rivers by solid phase extraction and then ICP. The report does not contain new finding since the selenium in Blood and Mokolo Rivers was reported previously.
Response : To the best of our knoweledge, speciation analysis of Se(IV) in water samples from Blood and Mokolo Rivers has not been published except MSc dissertation submitted to University of Limpopo by Ms MM Matjena.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The manuscript is acceptable for publishing. I suggest to the authors to improve the reference section by adding some invaluable references in this area like "https://doi.org/10.1007/BF01734294".
