Pollution Evaluation of the El Pueblito River in Queretaro, Mexico, Using the Water Quality Index
Round 1
Reviewer 1 Report (Previous Reviewer 2)
The manuscript is improved in relation to its initial version. The authors should calculate the p-values and present them in Table 4.
Regards,
Author Response
Answers to reviewer 1.
Reviewer comment :
The manuscript is improved in relation to its initial version. The authors should calculate the p-values and present them in Table 4.
Answer to reviewer:
P value was calculated for a bilateral and the value was 1 x 10-32, now it appear reported in the table.
Reviewer 2 Report (New Reviewer)
My queries and suggestions are as follows:
Materials and methods
· According to the authors “all the sites were chosen in places where changes in water quality were perceived to result from discharges” - which site will be selected as reference site?
· Why samples were collected only during June to August? Pollution status of a river cannot be evaluated just by one season data as water quality changes with time and space. Seasonal variations have a great role.
· It seems sampling was done in each site without replicates in each week. Seven weeks were considered. For any scientific study replicate sampling is must.
· Samples were collected weekly for seven consecutive weeks or alternate weeks?
· Sampling procedure for BOD 5 is not written.
· Software used for statistical analyses is not mentioned.
Results
· Discussion is written with results. But in the heading it is omitted.
· Whether spatial variations in different physico-chemical parameters were statistically significant. ANOVA/ Kruskal- Wallis test or other parametric or non parametric test should be performed.
· Why Spearman’s rank correlation coefficient analysis was used? It is a nonparametric method. Have you checked normality?
· Spearman’s rank correlation table –significance not marked.
· Sample size is too small for Spearman’s rank correlation coefficient analysis. Statistical analysis with few data will never give a robust result.
· In the text supplementary table no. should be provided.
Water quality rating according to National Sanitation Foundation Water Quality Index is given twice in SS material and also in the manuscript.
Author Response
Answers to reviewer 2.
Reviewer comment :
According to the authors “all the sites were chosen in places where changes in water quality were perceived to result from discharges” - which site will be selected as reference site?
Answer to reviewer:
From the 7 locations, three of them correspond a discharges (PIR, RAS, MAN), there are two after these points (PUE,BAR) and before are located BAT and STA. Whit this points and their location it is possible to stablish the state after and before the discharge points. This information can be reeded in the text as follows (line 156-165)
Document:
Seven locations were selected; the sites were chosen in places where changes in water quality were perceived to result from discharges. Also, the last two sampling sites were selected because they were in the most accessible area, closest to the end of the riverbed. Sites’ details and coordinates are presented in Table 1, and Figure 1 illustrates their locations. Sampling sites were named after their location and are as follows: Batan (BAT), Manantial (MAN), and Santa barbara (STA), there are two river water contribution point near the Piramides (PIR) and Rastro (RAS) sites. Then two other sites follow and are called Puente (PUE) and Barrera (BAR). Each sample consisted of 2 L of water, collected by hand in clean and sterile plastic bottles. All the bottles were previously rinsed with river water of the corresponding sampling site; after taking the sample it was transported at 4º C.
Reviewer comment :
Why It seems sampling was done in each site without replicates in each week. Seven weeks were considered. For any scientific study replicate sampling is must.
Answer to reviewer:
In this case a judgmental sampling was selected according to the knowledge of the area, using the knowledge of the site and the observation of the discharge points. The characteristics of the river make it change with time, for this reason the selection fo a discrete sample, the sampling time was performed for consecutive weeks.
Reviewer comment :
Samples were collected weekly for seven consecutive weeks or alternate weeks?
Answer to reviewer:
Samples were collected weekly.
Reviewer comment :
Sampling procedure for BOD 5 is not written
Answer to reviewer:
More specific details are in the document now in line 193
“Biological oxygen demand (BOD5) was determined five days of incubation at 20°C in the dark and measuring the difference in the dissolved oxygen according to Mexican normative [29].”
Reviewer comment :
- Software used for statistical analyses is not mentioned
Answer to reviewer:
All the formulas used for the calculus are specified in each section. Software was not used to perform data analysis.
Reviewer comment :
Discussion is written with results. But in the heading it is omitted.
Answer to reviewer:
The document has been changed now the line 242 can be read as follows:
“3. Results and discussion”
Reviewer comment :
Whether spatial variations in different physico-chemical parameters were statistically significant. ANOVA/ Kruskal- Wallis test or other parametric or non parametric test should be performed. Why Spearman’s rank correlation coefficient analysis was used? It is a nonparametric method. Have you checked normality?
- Spearman’s rank correlation table –significance not marked.
- Sample size is too small for Spearman’s rank correlation coefficient analysis. Statistical
analysis with few data will never give a robust result.
Answer to reviewer:
The following questions will be answered simultaneously. In this case the main objective of the analysis. For this reason, statistical tools were not proposed in the title or any section of the document. The focus of the document was stablishing the levels of pollution on the river across its flow throw city.
Reviewer comment :
In the text supplementary table no. should be provided
Answer to reviewer:
The text was modified and in line 256 now the supplementary material is referenced.
“A summary of the results is presented in Table 3, and complete information is presented as supplementary material SM 1 to SM 10.”
And line 353-354 were also modified
“Please find the complete results in supplementary information (SM 11 and SM 12).”
Reviewer comment :
Water quality rating according to National Sanitation Foundation Water Quality Index is given twice in SS material and also in the manuscript.
Answer to reviewer:
Supplementary material was modified, deleting the table; which was keeped in the manuscript.
Reviewer comment :
More updated references were added to the document
Answer to reviewer:
In the introduction section, the information was actualized, and the follow citations are now included in the new version of the document.
Reviewer 3 Report (New Reviewer)
Please see attachment
Comments for author File: 
Comments.pdf
Author Response
Answers to reviewer 3.
Reviewer comment :
The literature well supports the introduction section but lacks mention of the potential impact of seasonality (seasons) on the quality of surface and deep Water. Many studies confirm such a relationship, and I think it is worth including this in a few sentences of the introduction theory. You can use the following items: https://doi.org/10.3390/en15030981 ; https://doi.org/10.1016/j.jhazmat.2020.124018 ; https://doi.org/10.1007/s12403-020-00357-6
Answer to reviewer:
References are now included in the manuscript
https://doi.org/10.3390/en15030981 in line 54
https://doi.org/10.1016/j.jhazmat.2020.124018 in line 58, and
https://doi.org/10.1007/s12403-020-00357-6 in line 72
Reviewer comment :
At the end of the Introduction section, you need to include a brief description of the other structure of the manuscript - this will improve its clarity.
Answer to reviewer:
The last paragraph of introduction was modified and now it can be read as follows (line 131-137):
“In this sense, the main objective of this work is to compare the water quality obtained by physicochemical parameters with bioassays. The monitoring of water quality employing physicochemical parameters of El Pueblito River will be translated to WQI. Bioassays such as Daphnia magna survival rate and Sorghum bicolor seeds germination rates are carried out. Finally, an analysis of data is performed to establish the interrelation between physicochemical parameters, the relation between physicochemical parameters and bioindicators, and the relation of WQI and bioindicators throughout the river. “
Reviewer comment :
At the end of the Conclusion section, please include the limitations of the manuscript and the possibilities for future research in this area.
Answer to reviewer:
The conclusion now can be readed as follows (lines 441-443):
“One of the limitations of this work is that the sampling was performed in rainy season, for futures researches it will be important to consider the whole year in the study.”
Reviewer comment :
Please adapt the style of the literature list to the guidelines of the journal Water
Answer to reviewer:
The style was modified in the manuscript, and now corresponds to Water format.
Author Response File: 
Author Response.docx
Reviewer 4 Report (New Reviewer)
Please see the attached file for comments
Comments for author File: Comments.pdf
Author Response
Answers to reviewer 4.
Reviewer comment :
- There is no correspondence between Figure 1 and Table 1. The table shows "SAN" in the figure "STA".
Answer to reviewer:
There was a mistake in Table 1, it was modified and now it says STA as shows in line 173 of the manuscript.
|
Place |
Coordinates |
Altitude, ft |
||
|
North |
West |
|||
|
1 |
BAT |
20° 30.845' |
100° 25.881' |
6053 |
|
2 |
MAN |
20° 30.776' |
100° 26.065' |
6047 |
|
3 |
STA |
20° 31.573' |
100° 26.774' |
6023 |
|
4 |
PIR |
20° 32.951' |
100° 27.300' |
6096 |
|
5 |
RAS |
20° 32.986' |
100° 27.336' |
6096 |
|
6 |
BAR |
20° 30.827' |
100° 25.952' |
6095 |
|
7 |
PUE |
20° 33582' |
100° 28.006' |
6097 |
Reviewer comment :
Also, check the altitudes, "SAN" and "MAN" have a much lower quota than "BAT", if it is correct, it should be explained.
Answer to reviewer:
Data of altitude is correct. In fact the place STA act as a reservoir where the water is more abundant that in the rest of the river, but how it is a natural river, altitude is the obtained in measurements on field and confirmed employing google maps to answer this question.
Reviewer comment :
You provide Table 3 with the summary results of the obtained parameters. However, a better comparison of the latter with the legislation about surface water of the reference territory and / or with international criteria should be made, to better frame whether the river is polluted or not, and how much it is polluted with respect to reference values.
Answer to reviewer:
In table 3, values corresponding to polluted water in water bodies according to Mexican normativity are indicated.
Table 3. Summary results of the obtained parameters of the water from El Pueblito river.
|
Parameter |
Average |
Maximum |
Minimum |
|
Temperature (°C) |
23.12 ± 1.40 |
24.80 |
21.10 |
|
pH |
7.82 ± 0.32 |
8.39 |
7.24 |
|
TDS (ng/L) |
786.27 ± 386.69 |
1570.00 |
360.00 |
|
VSS (mg/L) |
279.54 ± 228.64 |
885.00 |
5.00 |
|
TS (mg/L) |
722.35 ± 410.06 |
1575.00 |
5.00 |
|
Conductivity (S/cm) |
1.11 ± 0.58 |
2.23 |
0.12 |
|
CDO (mg/L) |
337.33 ± 395.53* |
1289.00* |
ND |
|
BOD (mg/L) |
352.97 ± 397.75* |
1248.00* |
ND |
|
Fecal coliforms (MPN/100 mL) |
1081.00 ± 1164.60* |
2400.00* |
0.3 |
Abbreviations: ND, No Detectable. Quantification Limits: COD 4mg/L. *Values corresponding to polluted water according to Mexican regulations.
Reviewer comment:
Authors are encouraged to provide a graphical representation of the analysis of biological factors.
Answer to reviewer:
It is an interesting way to present some results; however, in this case we believe that it is more appropriate the way the results are presented, due to the results show intermedial values due to the dilutions used for the analysis.
Reviewer comment :
Table 5 should be reported as a color-coded (or heatmap colored) correlation matrix. See for example: Figure 2 - https://doi.org/10.3390/jmse9121415
Answer to reviewer:
Agree. We have modified the table and this change emphasize the differences in values, and now appears as follows in the manuscript.
|
Parameter |
Conductivity |
COD |
BOD |
VSS |
Sorghum |
LC50 |
TDS |
PT |
TS |
Total coliforms |
|
Conductivity |
1.00 |
|
|
|
|
|
|
|
|
|
|
COD |
0.69 |
1.00 |
|
|
|
|
|
|
|
|
|
BOD |
0.55 |
0.65 |
1.00 |
|
|
|
|
|
|
|
|
VSS |
0.77 |
0.73 |
0.51 |
1.00 |
|
|
|
|
|
|
|
Sorghum |
-0.19 |
-0.32 |
-0.35 |
-0.22 |
1.00 |
|
|
|
|
|
|
LC50 |
0.37 |
0.68 |
0.36 |
0.38 |
-0.19 |
1.00 |
|
|
|
|
|
TDS |
0.98 |
0.80 |
0.62 |
0.71 |
-0.31 |
0.50 |
1.00 |
|
|
|
|
PT |
0.81 |
0.83 |
0.71 |
0.66 |
-0.21 |
0.51 |
0.87 |
1.00 |
|
|
|
TS |
0.36 |
0.30 |
0.23 |
0.62 |
0.18 |
0.04 |
0.36 |
0.37 |
1.00 |
|
|
Total coliforms |
0.74 |
0.67 |
0.69 |
0.82 |
-0.21 |
0.46 |
0.76 |
0.81 |
0.19 |
1.00 |
Reviewer comment :
Please provide a graphical representation of WQI. I suggest making at least two maps in GIS, with respectively average and standard deviation of the WQI, similar in shape to Figure 1 on the right but with different colors based on the WQI.
This type of representation would help to understand how the WQI varies from upstream to downstream. From what reported: "The WQI average follows the trend of RAS <BAR <PIR
<PUE <STA <BAT <MAN", it would seem that there is no net trend of the WQI from upstream to downstream. If so, explain this aspect further. For example: Figures 6 and 7 - https://doi.org/10.3390/w13091173
Answer to reviewer:
In this case we believe that it is more appropriate the way the results are presented, due to the results obtained show a good quality in upstream points and polluted water downstream.
Reviewer comment :
Based on the conclusion section, what is further research direction?
Answer to reviewer:
In conclusion section was modified showing information about the limitations and future directions, it is presented in lines 439 to 444.
“Otherwise, in the conditions of our experiments there is not a good numerical correlation index to associate WQI values with LC50 perhaps, a clear correlation could be performed by increasing the number of dilutions at the LC50 assays allowing to obtain more information about it. One of the limitations of this work is that the sampling was performed in rainy season, for futures researches it will be important to consider the whole year in the study.”
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report (New Reviewer)
I find that the authors have revised the manuscript according to the comments except one.
I am not fully satisfied with the response of the following comment.
Whether spatial variations in different physico-chemical parameters were statistically significant. ANOVA/ Kruskal- Wallis test or other parametric or non parametric test should be performed. Why Spearman’s rank correlation coefficient analysis was used? It is a nonparametric method. Have you checked normality?
- Spearman’s rank correlation table –significance not marked.
- Sample size is too small for Spearman’s rank correlation coefficient analysis. Statistical
analysis with few data will never give a robust result.
Answer to reviewer:
The following questions will be answered simultaneously. In this case the main objective of the analysis. For this reason, statistical tools were not proposed in the title or any section of the document. The focus of the document was stablishing the levels of pollution on the river across its flow throw city.
Author Response
The main idea of this work is to have information able to describe the state of pollution in El Pueblito river, by generating information about its quality. One complementary analysis of data in this study was the correlation of the obtained parameters. In this case, it is not our goal to avoid monitoring task by predicting employing data from correlation like the study performed by Bhandary and col. [1], for this reason the Spearman correlation is adequate for the analysis.
Besides, different studies have employed Spearman rank in their correlation for physicochemical parameters, some examples are presented.
In one approach Spearman rank is used for the analysis of three river basins performed by Diamantini and col. [2]. Another example, was the employed in the estuary of Merbok for parameters as pH, DO, salinity, EC, NO3-, NH3, PO43-, BOD [3]. As before, Lenart-Borón used Spearman correlation to find the correlation between physicochemical parameters and biological parameters [4].
References
- Bhandari, N.S.; Nayal, K. Correlation Study on Physico-Chemical Parameters and Quality Assessment of Kosi River Water, Uttarakhand. Curr. World Environ. 2008, 5, 342–346, doi:10.12944/cwe.4.1.12.
- Diamantini, E.; Lutz, S.R.; Mallucci, S.; Majone, B.; Merz, R.; Bellin, A. Driver Detection of Water Quality Trends in Three Large European River Basins. Sci. Total Environ. 2018, 612, 49–62, doi:10.1016/j.scitotenv.2017.08.172.
- Maznah O, W.; Mat Isa, M. Spatial and Temporal Variation of Physico-Chemical Parameters in the Merbok Estuary , Kedah, Malaysia. Trop. Life Sci. Res. 2014, 25, 1–19.
- Lenart-Boroń, A.; Wolanin, A.; Jelonkiewicz, Ł.; Chmielewska-Błotnicka, D.; Zelazny, M. Spatiotemporal Variability in Microbiological Water Quality of the Białka River and Its Relation to the Selected Physicochemical Parameters of Water. Water. Air. Soil Pollut. 2016, 227, doi:10.1007/s11270-015-2725-7.
Author Response File: Author Response.docx
Reviewer 4 Report (New Reviewer)
The authors improved the quality of the manuscript. However, they did not adequately answer the following question:
Please provide a graphical representation of WQI. I suggest making at least two maps in GIS, with respectively average and standard deviation of the WQI, similar in shape to Figure 1 on the right but with different colors based on the WQI.
This type of representation would help to understand how the WQI varies from upstream to downstream. From what reported: "The WQI average follows the trend of RAS <BAR <PIR <PUE <STA <BAT <MAN", it would seem that there is no net trend of the WQI from upstream to downstream. If so, explain this aspect further
I expect a graphic representation or, at the very least, a more in-depth discussion. The graphical representation however is strongly recommended
Author Response
A graphical representation was added to the manuscript, as mentioned the reviewer it shows in a better way how changes the pollution across the river.
Changes in document.
Figure 2 was added, mention of the figure appears in line 398 and 399 of the manuscript.
Author Response File: Author Response.docx
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
General comments
This paper apply the new parameters (bioassays using Daphnia magna, sorghum seeds) and evaluate and compare with water quality index.
In abstract, author indicated "This study also shows the utility of the WQI as a practical method to estimate the global water quality and verifies its application to the El Pueblito River.". However, Water Quality Index is widely used in the water quality evaluation and WQI was regularly used in US EPA regulatory impact analysis. Utility of WQI was already known.
In this study, author should be discussed why apply the bioassays using Daphnia magna, sorghum seeds as new parameters.
In addition, beneficial results obtained from this study should indicate. What is the new findings by using the above parameters?
Suggestion: Better to reform the story of this article.
1. Indication of the clear meanings and benefit to use the new parameter.
2. Result should be explained by using Figure and almost detail values (Table) should change to supplementary.
3. Main discussion points should be "3.2 Biological parameters and bioassays" and "3.3 Parameters correlation". (Please indicate the obtained useful information based on the using of new parameter)
Line 88-100
Author should indicate the reasons for the using the bioassays using Daphnia magna, sorghum seeds as new parameters. Only apply the new parameters, compare the several parameters used in WQI and success to obtained the good correlation is not environmental study.
Should be indicate the meaning and usefulness to use the new parameters.
Fig. 1
Author should indicate more detail and high-resolution image map. Especially, detail map. Please re-prepare such as bellow article.
[Water] Water, Sanitation and Hygiene Conditions in Kenyan Rural Schools: Are Schools Meeting the Needs of Menstruating Girls?
https://www.mdpi.com/2073-4441/6/5/1453
In addition, sampling points should indicate as plot on the map such as bellow article.
[Water] Climate Change and Classic Maya Water Management
https://www.mdpi.com/2073-4441/3/2/479/htm
Table 1
Table 1 should indicate in supplementary.
Table 4
Table 4 should be indicated in one page (should not separate in two page)
Table 5
Table 5 should indicate in supplementary.
Author Response
In abstract, author indicated "This study also shows the utility of the WQI as a practical method to estimate the global water quality and verifies its application to the El Pueblito River.". However, Water Quality Index is widely used in the water quality evaluation and WQI was regularly used in US EPA regulatory impact analysis. Utility of WQI was already known.
In this study, author should be discussed why apply the bioassays using Daphnia magna, sorghum seeds as new parameters.
In addition, beneficial results obtained from this study should indicate. What is the new findings by using the above parameters?
It was added to the manuscript information to support the recommendations of the reviewer about the importance of the bioassays their similarity with WQI and that bioassays can be an important tool to calculate WQI with less parameters and supported with this easy and cheap analysis.
Modifications to the document.
Abstract
“This study evaluated the water quality of the El Pueblito River by employing physicochemical parameters and biological indicators; monitoring was conducted weekly for three months at seven sampling sites. The water quality index (WQI) was calculated to interpret the obtained information in the analysis. The results obtained by physicochemical analysis show the same trends as that of the analysis performed with bioassays using Daphnia magna, sorghum seeds and the WQI, showing the importance of these bioassays in the evaluation of the water quality. The WQI values presented an evident deterioration of water quality from upstream to downstream due to input of discharges into the river as it passed through the city of Corregidora. The WQI values shifted from indicating a good (83.00 ± 7.40) water quality to a poor (27.00 ± 0.85) water quality. This study also shows the utility of the bioassays and their correlation with WQI as a practical method to estimate the global water quality and verifies its application to the El Pueblito River; where is probed the depletion in the quality when it runs through the urban area.”
Conclusions
“It is essential to mention that the selection of bioassay with Daphnia magna is a practical method, economic and the results have the same behavior as WQI. We believe this assay can aid in determining WQI with fewer parameters and be a tool to corroborate the information about water quality. Regarding pollution in the river, the results in this study indicate that the upstream analyzed sites in the El Pueblito River presented good quality at sites MAN, BAT, and STA, but downstream of RAS, PIR, BAR, and PUE, the water quality decreased slightly.”
Suggestion: Better to reform the story of this article.
- Indication of the clear meanings and benefit to use the new parameter.
- Result should be explained by using Figure and almost detail values (Table) should change to supplementary.
- Main discussion points should be "3.2 Biological parameters and bioassays" and "3.3 Parameters correlation". (Please indicate the obtained useful information based on the using of new parameter)
The three points discussed above were addressed in the document, emphasizing the importance of biological assays and they relationship with WQI.
Line 88-100
Author should indicate the reasons for the using the bioassays using Daphnia magna, sorghum seeds as new parameters. Only apply the new parameters, compare the several parameters used in WQI and success to obtained the good correlation is not environmental study.
The idea of the document is to analyze separately the bioassays, no to include them in the calculation on WQI. The idea of the study is present the bioindicators as a contrast of WQI.
Should be indicate the meaning and usefulness to use the new parameters.
Fig. 1
Author should indicate more detail and high-resolution image map. Especially, detail map. Please re-prepare such as bellow article.
[Water] Water, Sanitation and Hygiene Conditions in Kenyan Rural Schools: Are Schools Meeting the Needs of Menstruating Girls?
https://www.mdpi.com/2073-4441/6/5/1453
In addition, sampling points should indicate as plot on the map such as bellow article.
[Water] Climate Change and Classic Maya Water Management
https://www.mdpi.com/2073-4441/3/2/479/htm
Figure 1 was modified considering the sugestions
Table 1
Table 1 should indicate in supplementary.
Table 1 now appear as a supplementary information
Table 4
Table 4 should be indicated in one page (should not separate in two page)
Table 4 is in only one page
Table 5
Table 5 should indicate in supplementary.
Table 5, was changed of section
Author Response File: Author Response.docx
Reviewer 2 Report
The topic of the paper is of interest to the readers of Water. It is within the scope of the journal. The authors have to answer if this paper meets the impact and innovation criteria of this journal. Additional scientific editing is required (e.g., there are sentences with syntax problems). In other words, the discussion section should be reworked, highlighting the relevance of this topic worldwide. The conclusions section is not very successful and should be revised. Additional comments are presented in the annotated .pdf file.
Regards,
Comments for author File: Comments.pdf
Author Response
The changes were performed and the new version is attached
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
There are still some major points that require revision. Please see the annotated .pdf file for further comments.
Regards,
Comments for author File: Comments.pdf
