the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Feb 2021
Influence of land use and occupation on the water quality of a microbasin in the southwestern Amazon
Abstract. Water resource management in Brazil is constantly evolving, and greater knowledge about this resource allows better planning and more sustainable uses. In Brazil, the improvement of water resource management faces the difficulty of implementing the instruments of the National Water Resources Policy, such as classification of water bodies. Thus, to help improve the water management instruments in the country's northern region, the objective of the present study was to diagnose the influence of land use and occupation on the water quality of the Igarapé Nazaré microbasin. For this purpose, indirect methods of landscape analysis were applied based on the processing of remote sensing images in a GIS. For the water quality analysis, 10 collection points were selected in the watershed, with samples collected at each one in four periods (high water; HW/LW transition; low water; LW/HW transition). In the collected samples, 14 parameters were analyzed, namely: temperature, pH, electrical conductivity; turbidity; water transparency and depth; dissolved oxygen; chlorophyll a, ammonia, nitrite, nitrate, total phosphorus and dissolved phosphorus; total coliforms and E. coli. The spatial analysis showed that the microbasin has about 84 % anthropized territory, with emphasis on agriculture, and sources of pollution from industries, fish farming and domestic sewage. Parameter analyses showed high values of total phosphorus (0.005–27.55 mg.L−1), total coliforms (4,103–1,09,106 CFU) and E. coli (0–5.8,105 CFU), and low DO concentration (0.0–8.33 mg.L−1), below the official limit established in all periods analyzed The water quality of the Igarapé Nazaré microbasin was found to suffer strong anthropic interference, requiring improvement of the sanitary infrastructure of city of Ji-Paraná, for maintenance of the watershed in class 2.
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RC1: 'Comment on bg-2020-485', Anonymous Referee #1, 02 Apr 2021
The manuscript presented the results from a basin-scale water quality survey conducted through four seasons in the southwestern Amazon. Continuous progression of anthropogenic disturbance in the area has developed serious deterioration of water environments and scientists are highly expected to provide insights for resolving and managing/controlling the problems. In this context, the authors only reported the measured values for several parameters, failed to identify research questions based on knowledge previously accumulated (known and unknown) and, accordingly, were unable to emphasise the impacts of this study on academia and society. Hence, I evaluate the manuscript is not at the level of publication in Biogeosciences as an original article with a decision of Rejected.
Major comments:
- In Abstract and Introduction, what do you mean by “diagnose”? The objectives have not been specified due to lack of establishing the research question.
- Explanation on the methodology introduced by the authors to analyse “influence of land use and occupation” is critically insufficient and illogical throughout the manuscript.
- L130-142: What is this analysis on temperature for in the relationship with the following water quality parameters?
- L148, 197, 230, 251, 259: For all of transparency, phosphorus, nitrite, EC, Chl.a and bacteria, no significant seasonality was examined. Was it as the authors expected or unexpected before the analyses? What does “objective of identifying possible temporal variations” mean by? What was the hypothesis originally?
- L148-152, 168-173, 184-185: The authors tried to discuss on the pollution source by using concentration data only, however, need another analysis on pollutant loading (concentration and river flow) for that purpose.
- L153-155, 238-240: Those descriptions on phosphorus and Chl.a are not discussions deduced from the obtained results in this study, and should not appear in Discussion section.
- L193-196: What would be a logical relationship between “significant increase in the LW for ammonia” and “highest nitrate in HW and HW/LW”? I do not understand the mechanism of “a longer time interval for contamination”.
- L208-2009: I do not agree “As can be observed” and “This result can be correlated” in Figure 5a.
- L210-212, 221-224: For insisting those conclusions, the authors need to present TOC and its correlation with transparency.
- PCA in L260-272: The meanings/interpretations for Axis1 and Axis2 are necessary at minimum in basic discussion on PCA. The two obvious groups (P1,P2,P3 and P4) should be first assessed by comparing to the interpretations for the axes. “These results are similar to those reported” makes no sense without detailed discussion.
Minor comments:
- L85 “using 95% ethanol”: Not explaining the correspondent analytical method appropriately.
- “3.1 Land use and occupation” should be moved to Study Area in Methods section.
- L108: figure 3 > Figure 3
- Figure 2: What are “Colorful Composition RGB” for? This figure can be combined with Figure 1.
- Table 2: Errors should be added for each.
- Table 3: What is this figure for?
- Figure 6: Please confirm if F1 and F2 were switched.
Citation: https://doi.org/10.5194/bg-2020-485-RC1 -
AC1: 'Reply on RC1', Alan Mendonça, 18 May 2021
The manuscript presented the results from a basin-scale water quality survey conducted through four seasons in the southwestern Amazon. Continuous progression of anthropogenic disturbance in the area has developed serious deterioration of water environments and scientists are highly expected to provide insights for resolving and managing/controlling the problems. In this context, the authors only reported the measured values for several parameters, failed to identify research questions based on knowledge previously accumulated (known and unknown) and, accordingly, were unable to emphasise the impacts of this study on academia and society. Hence, I evaluate the manuscript is not at the level of publication in Biogeosciences as an original article with a decision of Rejected.
Major comments:
- In Abstract and Introduction, what do you mean by “diagnose”? The objectives have not been specified due to lack of establishing the research question.
The basin diagnosis refers to the state of land use and occupation of the Igarapé Nazaré basin and its influence on water quality. This diagnosis is a methodological step taken from the Brazilian National Water Resources Policy to classify bodies of water into classes. In order to fit a body of water in a certain class, a complete study of the hydrographic basin is necessary, where the diagnosis of the basin is the first stage of this process.
- Explanation on the methodology introduced by the authors to analyse “influence of land use and occupation” is critically insufficient and illogical throughout the manuscript.
The method used to analyze the influence of land use and occupation, was to establish a relationship between the form and the characteristics of use within the basin under study. The basin had its natural area converted into an urban and rural area. Then, the most significant point sources of pollution were identified, among other information, and data from an article already published by the same author and on the same basin according to the DOI were used: https://doi.org/10.22478/ufpb .1981-1268.2020v14n3.52610 relating the use and occupation data with the water quality data found for the basin. The process is carried out in this way due to the methodology defined by the Brazilian National Water Resources Policy for framing water bodies. This study was carried out in view of the need to improve water management in the Amazon region, which does not have a framed river, as determined by the National Water Resources Policy. Thus, it was analyzed whether the characteristics of use, are affecting or not the water quality of this stream from the data of use and occupation of the soil and the quality parameters analyzed in the stream in different periods.
- L130-142: What is this analysis on temperature for in the relationship with the following water quality parameters?
The analysis of the temperature variable is extremely important in studies that analyze the presence / absence of vegetation cover in a basin, considering mainly that this variable is strictly related to environmental variables such as dissolved oxygen and depth, and with a high influence on the aquatic biota.
- L148, 197, 230, 251, 259: For all of transparency, phosphorus, nitrite, EC, Chl.a and bacteria, no significant seasonality was examined. Was it as the authors expected or unexpected before the analyses? What does “objective of identifying possible temporal variations” mean by? What was the hypothesis originally?
As a main result, the authors expected that differences in water quality parameters would show differences between the hydrological periods analyzed. Thus, we inserted a hypothesis at the end of the introduction section in order to better present the results of this research.
“we hypothesized that the water quality parameters vary between the seasons of the hydrological cycle, in a microbasin in southwestern Amazonia. Following the premise that for each period of the hydrological cycle, the environment changes its environmental conditions due to differences in water volume and depth, which consequently influences the concentration and availability of limnological variables.”
- L148-152, 168-173, 184-185: The authors tried to discuss on the pollution source by using concentration data only, however, need another analysis on pollutant loading (concentration and river flow) for that purpose.
For this manuscript, the objective was to present data on water quality and the influence of land use under them in the Igarapé Nazaré watershed. However, we believe it is very important studies that, through flow data, can contribute to a better understanding of the dynamics of pollutants in this basin, which was not possible in this research.
- L153-155, 238-240: Those descriptions on phosphorus and Chl.a are not discussions deduced from the obtained results in this study, and should not appear in Discussion section.
The portion of the text in question has been removed as requested.
- L193-196: What would be a logical relationship between “significant increase in the LW for ammonia” and “highest nitrate in HW and HW/LW”? I do not understand the mechanism of “a longer time interval for contamination”.
One of the consequences of being a microbasin with a strong anthropic influence, is that we are unable to observe the chemical transformations of chemical substances (nitrate, nitrite and ammonia) as in a non-anthropized environment. In the Nazaré stream microbasin, effluents are discharged with different concentrations of nitrogenous substances, which makes some interpretations of the results unfeasible over a hydrological cycle. Because regardless of the flow, the effluents continue to be released.
- L208-2009: I do not agree “As can be observed” and “This result can be correlated” in Figure 5a.
P4 is the sampling point where the values observed for dissolved oxygen were the lowest. For the last three sampled periods (HW / LW; LW; LW / HW) the presence of dissolved oxygen was not identified in P4, pulling the lower limit of the box-splot graph downwards. However, the values of Electrical Conductivity and Turbidity for the same point and period will be added in the text for better visualization and interpretation.
- L210-212, 221-224: For insisting those conclusions, the authors need to present TOC and its correlation with transparency.
It was not possible to perform this analysis.
- PCA in L260-272: The meanings/interpretations for Axis1 and Axis2 are necessary at minimum in basic discussion on PCA. The two obvious groups (P1,P2,P3 and P4) should be first assessed by comparing to the interpretations for the axes. “These results are similar to those reported” makes no sense without detailed discussion.
The discussion was expanded to better characterize the results of this article with other articles in the same area, as follows:
These results are similar to those found by Toledo and Nicolella (2002) and Oliveira et al. (2017) where for microbasins with rural and urban influence they presented the highest values of correlation coefficient between the same variables presented in this axis. The authors observed a great influence downstream of the analyzed streams, after urban areas, of extensive cattle breeding on water quality and the influence of heavily impacted tributaries, as is the case of the P4 analyzed in this research.
We emphasize that the sampling points were grouped and purchased with the indications for each axis of the PCA.
Minor comments:
- L85 “using 95% ethanol”: Not explaining the correspondent analytical method appropriately.
For the analysis of chlorophyll a, a volume of 100mL of sample was filtered through a glass microfiber filter, 0.45 µm porosity (Whatman AP – 20). Subsequently, the filters were added to Falcon tubes protected from light, and 5mL of 95% ethanol was added. The tubes were then taken to a water bath until reaching a temperature of 75 ° C, and kept under these conditions for 5 minutes. Then the tubes were cooled and kept protected from light for 6 hours. Subsequently, the samples were centrifuged, removing the supernatant from which the spectrophotometric measurements were obtained at 664 and 750nm ((Kasuaki, IL-226-NM).
- “3.1 Land use and occupation” should be moved to Study Area in Methods section.
The cited section will be removed to the study area.
- L108: figure 3 > Figure 3
The correction will be accepted and changed in the article.
- Figure 2: What are “Colorful Composition RGB” for? This figure can be combined with Figure 1.
The caption indicating the composition R (RED) G (GREEN) and B (BLUE), indicates the coloring process of the satellite image used. It is preferred not to combine the two figures due to different information contained in the maps, Figure 1 addresses the water sampling points and Figure 2 highlights the main point sources of pollution, identified within the hydrographic basin, which would make the map “ polluted ”with so much information.
- Table 2: Errors should be added for each.
A new table will be added with the errors, as requested, with a new title: Table 2: Environmental variables (mean ± SD) in the Igarapé Nazaré microbasin for the four periods sampled. Depth (cm) and transparency (cm).
- Table 3: What is this figure for?
These values serve as a comparison for results observed in hydrographic basins close to the Igarapé Nazaré basin, and which have similar characteristics of use and occupation.
- Figure 6: Please confirm if F1 and F2 were switched.
They were not exchanged. F1 (38.86%), F2 (13.01%).
Citation: https://doi.org/10.5194/bg-2020-485-AC1
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AC1: 'Reply on RC1', Alan Mendonça, 18 May 2021
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RC2: 'Comment on bg-2020-485', Anonymous Referee #2, 27 Apr 2021
The manuscript presents data on water quality parameters of a watershed in the Brazilian Amazon. These data are rare and extremely important for the knowledge of Amazonian aquatic systems. However, these are presented and discussed in a regional view and can be valuable for local monitoring. I suggest reconsidering after major revisions or rejected.
Abstract
The abstract has a very regional view of the data and conclusions. I suggest rewriting it to demonstrate how the findings of this study in the Igarapé Nazaré basin can be extrapolated to other streams around the world (or at least in tropical/equatorial systems).
Introduction
Like the abstract, the introduction is also very local. It discusses the problem of water quality and its management in Brazil. I suggest thinking how that occurs worldwide. For example, I put some questions bellow that can be thought of to enrich the introduction:
- Are there National Policies in other countries? Brazil has the PNRH (line 34), and other countries have similar programs. This could be mentioned in the introduction, giving a more global aspect to the study.
- The implementation of water quality monitoring is cited (line 41). Is there effective monitoring anywhere in the world? Why? Why hasn’t in Brazil?
- The aim is very regional and fits well in a local journal. With these findings in Nazaré, is it possible to understand other streams in the Amazon or in the tropical/equatorial biomes?
Material and Methods
In lines 49-51, the manuscript says that there are rainy and dry seasons. In lines 72-73, the manuscript says that water sampling occurred in high-water and low-water seasons. Are these same stations? Are these aquatic systems subject to the flood-pulse of the main river? Is there water fluctuation in sampling points due to the season? This is not described in the Study area section.
The methods can be briefly described. Example:
- lines 73-76: Are these places of discharge accounted for? When they were seen, did the water collection take place upstream or downstream from discharge points?
- lines 83-85: These methods can be briefly described.
- Total nitrogen was not measured in unfiltered water? Why?
Results and discussion
- There is a lack of correlation between the parameters evaluated and land use. The data was presented extensively with a temporal perspective, but not a spatial one (and that was the primary objective of the work).
- Like the other sections of the paper, I suggest putting in a global perspective. What is the relationship of your results with global parameters observed in anthropized streams?
- There is a discussion about the parameters listed by CONAMA. Does being within the limits established by CONAMA mean that the water is from a preserved site? And on the contrary? Does being off limits mean that the environment is anthropic or that the water is not fit for human use? Ex: very acidic pH may indicate a black water river, and not that the environment has been modified.
This discussion should be added to the discussion section since the work gave a lot of emphasis to CONAMA.
- Results were compared using ANOVA, but a post hoc test was not done to identify the different group(s) – example: lines198-199.
Final considerations
The authors summarized the findings. It would be more interesting to relate these findings to others in the world. Are such changes commonly seen in anthropic environments? What is the most frequent type of anthropization (e.g., sewage or pasture)?
Figure 2: It is difficult to see the dots (sewage, food and frigorific industries) in the picture. I suggest increasing them.
Citation: https://doi.org/10.5194/bg-2020-485-RC2 -
AC2: 'Reply on RC2', Alan Mendonça, 18 May 2021
The manuscript presents data on water quality parameters of a watershed in the Brazilian Amazon. These data are rare and extremely important for the knowledge of Amazonian aquatic systems. However, these are presented and discussed in a regional view and can be valuable for local monitoring. I suggest reconsidering after major revisions or rejected.
Abstract
The abstract has a very regional view of the data and conclusions. I suggest rewriting it to demonstrate how the findings of this study in the Igarapé Nazaré basin can be extrapolated to other streams around the world (or at least in tropical/equatorial systems).
Introduction
Like the abstract, the introduction is also very local. It discusses the problem of water quality and its management in Brazil. I suggest thinking how that occurs worldwide. For example, I put some questions bellow that can be thought of to enrich the introduction:
- Are there National Policies in other countries? Brazil has the PNRH (line 34), and other countries have similar programs. This could be mentioned in the introduction, giving a more global aspect to the study.
Countries such as South Africa (Koppen and Schreiner, 2013), Australia (Byrnes et al. 2006), Malaysia (Afroz et al., 2016), China (Shuzhong et al., 2017), United Arab Emirates (Paleologos et al. ., 2018) and others, present policies for the conservation, management, equal distribution of water resources. Although Brazil has a well-intentioned National Water Resource Policy (PNRH in the Portuguese acronym), specifying various instruments for management of watersheds, these instruments have proved hard to implement in the majority of cases.
- The implementation of water quality monitoring is cited (line 41). Is there effective monitoring anywhere in the world? Why? Why hasn’t in Brazil?
Therefore, more information is necessary to hasten progress in water management. This can be promoted by the use of 40 geoprocessing tools (Flauzino et al., 2010), implementation of effective water quality monitoring, como é realizado em outros países (Ighalo and Adeniyi, 2018; Chen and Han, 2018; Wilson et al., 2018; Altenburger et al., 2019; Li et al., 2020) , and production of information to support policymakers’ decisions regarding sustainable water use and ecological restoration of watersheds (Avila, 2016; Vigiak, 2016; Britto, 2018).
- The aim is very regional and fits well in a local journal. With these findings in Nazaré, is it possible to understand other streams in the Amazon or in the tropical/equatorial biomes?
Looking toward the establishment of these initiatives in the country’s North region, our objective in this study was to diagnose the influence of land use and occupation on the water quality of the Igarapé Nazaré microbasin.
Our research promotes a better understanding of the impacts of changes in land use in microbasins in the Amazon region, as well as for several tropical biomes
The information cited in the previous responses will be present in the text of the article.
Material and Methods
In lines 49-51, the manuscript says that there are rainy and dry seasons. In lines 72-73, the manuscript says that water sampling occurred in high-water and low-water seasons. Are these same stations? Are these aquatic systems subject to the flood-pulse of the main river? Is there water fluctuation in sampling points due to the season? This is not described in the Study area section.
The term used as flood periods represents the wettest seasons. The ebb period represents the transition period from the rainy to the dry period, where there is a decrease in the flow of this stream. The sampling took place in 4 periods, being in the rainy and dry seasons (popularly called winter and Amazonian summer, respectively), and in the transition periods between one and the other. There is a variation in water fluctuation in all periods.
The methods can be briefly described. Example:
- lines 73-76: Are these places of discharge accounted for? When they were seen, did the water collection take place upstream or downstream from discharge points?
The most relevant point sources, such as industries and sanitary sewage, were counted as shown in figure 2. Diffuse sources were not counted due to the difficulty of measuring these sources. The collections were carried out both upstream and downstream of the discharge points mentioned in the article, since the observed sources of pollution observed maintain a constant discharge flow.
- lines 83-85: These methods can be briefly described.
Samples were also taken to the laboratory under refrigeration for other analyses, as described by the Standard Methods for the Examination of Water and Wastewater (APHA, 2015) and the National Guide for Collection and Preservation of Samples (2011). The turbidity was measured with a portable turbidimeter (Hach model 2100P). The dissolved oxygen (DO) was measured according to the Winkler method (APHA, 2015) and the transparency was determined in the field using a Secchi disk. The concentrations of dissolved nutrientes, ammonia, nitrite, nitrate, total phosphorus and dissolved phosphorus were ascertained by spectrophotometry, according to the analytic methods described in APHA (2015).
The analyzes of the dissolved nutrients were performed with water samples previously filtered through glass microfiber filters, 0.45 µm porosity (Whatman AP – 20). Only the analysis of total phosphorus was performed on unfiltered samples. All nutrient analyzes were preceded by a calibration curve with standard solutions. After adding specific solutions for each analysis, absorbances were measured on a spectrophotometer (Kasuaki, IL-226-NM). For the analysis of ammonia, samples containing solutions containing phenol, sodium nitroprusside, hypochlorite and sodium hydroxide were added to the samples. Absorbance measurements were performed at 630nm. Nitrite analyzes were performed using 1% sulfanilamide solutions and 0.1% n-naphthyl alcoholic solution. Absorbances were measured at 543 nm. For the nitrate analysis, 1% brucine solution, sulfanilic acid and hydrochloric acid were added to the samples. Absorbance measurements were performed at a wavelength of 410nm. The analysis of dissolved phosphorus was performed by adding the samples ammonium molybidate solution, 15% sulfuric acid solution, ascorbic acid solution and atymone and potassium tartrate solution, followed by the reading of the absorbance at 882 nm. For the analysis of total phosphorus, unfiltered samples were added to supersaturated solution of ascorbic acid, then the samples were autoclaved. After the samples were reaffirmed, the method used for the analysis of dissolved phosphorus was carried out.
- Total nitrogen was not measured in unfiltered water? Why?
The analyzes of this parameter were not carried out because we do not have all the material devices necessary for it.
Results and discussion
- There is a lack of correlation between the parameters evaluated and land use. The data was presented extensively with a temporal perspective, but not a spatial one (and that was the primary objective of the work).
We emphasize that the data of our research were presented in a spatial perspective. We agree with the Reviewer that the time scale analysis was more emphasized, however the spatial variation of the analyzed variables was also demonstrated and discussed. Below we highlight some parts of the "Results and discussion" that indicate such a placement.
“Points P1, P2 and P3, located in a relatively well preserved rural APP, were the only ones to present concentrations below 0.1 mg.L-1 in all the periods. The others (P4 to P10) all had levels greater than 0.1 mg.L-1, with highlight on P4, which in the low water period had total phosphorus concentration of 27.55 mg.L-1. The highest concentrations of total phosphorus were found in the low water period at all the points sampled.”
“The lowest concentrations of dissolved phosphorus were also found at points P1, P2 and P3, while the highest concentrations were found at P4 (2.06 mg.L-1) and P7 (0.12 mg.L-1). These values can reflect the presence of aquatic flora, since this is the main form of phosphate assimilated by aquatic plants (Esteves, 2011).”
“With respect to the dissolved oxygen levels (Figure 5a), only at P2 was the concentration higher than the limit set by CONAMA Resolution 357/2005 (5 mg.L-1) in all the periods. Only the points in the microbasin located in rural areas (P1, P2 and P3) had values below the regulatory threshold, in periods HW (P1 and P2), HW/LW (P2), LW (P2 and P3) and LW/HW (P1, P2 and P3).”
“The sampling points located in the urban area of Ji-Paraná (P4 to P8), in the periods HW, HW/LW and LW, had values below the regulatory limit, with the exception of P7 in the period HW/LW (5.33 mg.L-1). In the LW/HW period, there were higher DO concentrations, which can be explained by the strong rainfall on the collection day, contributing to the aeration of the water.”
“In periods HW and LW, the presence of E. coli was not found at points P2 and P3, and P1 and P3, respectively. The water at all the other points had values above the limits stipulated in CONAMA Resolution 357/2005, of 1,000 coliforms per 100 mL of water. With respect to total coliforms, no point presented values greater than that threshold.”
- Like the other sections of the paper, I suggest putting in a global perspective. What is the relationship of your results with global parameters observed in anthropized streams?
This suggestion was accepted and a survey on research with similar objectives from different locations on the planet was raised for purposes of comparison with the present work and will be incorporated into the text.
- There is a discussion about the parameters listed by CONAMA. Does being within the limits established by CONAMA mean that the water is from a preserved site? And on the contrary? Does being off limits mean that the environment is anthropic or that the water is not fit for human use? Ex: very acidic pH may indicate a black water river, and not that the environment has been modified.
Within CONAMA (National Council for the Environment) there is a classification that is called special class, class 1, class 2, class 3 and class 4. These classes define the way in which these waters are used and the degree of quality in which they are used. find. As an example the special class, are waters destined to the preservation of the aquatic environments in integral protection conservation units; preserving the natural balance of aquatic communities. In short, waters that must be protected to maintain their original characteristics. Starting from class 1, these are waters that can be used for public supply, recreation, up to class 4, which has its use only for navigation; and landscape harmony. This classification is used so that the forms of use around this body of water are controlled to prevent the parameters that classified it in this way from maintaining these characteristics. However, there are discussions in the scientific environment in which CONAMA observes this in general, not taking into account the different natural characteristics of water bodies, especially in the Amazon, which has rivers with different characteristics.
This discussion should be added to the discussion section since the work gave a lot of emphasis to CONAMA.
This information will be added to the discussion session.
- Results were compared using ANOVA, but a post hoc test was not done to identify the different group(s) – example: lines198-199.
“The nitrate parameter when applied to the Tukey test obtained differences in almost all periods except when comparing the periods LW and LW / HW (HW and HW / LW p = 0.001575; LW and HW p = 3.90E-06; HW / LW and LW p = 2.02E-11; HW and LW / HW p = 5.58E-08; HW / LW and LW / HW p = 3.87E-13). The ammonia parameter for the same test obtained significant differences for the period of HW and LW (p = 0.005775); HW / LW and LW (0.006708); LW and LW / HW (p = 0.008358); showing that the highest concentration of this parameter occurred in the period with the lowest volume of water in the stream.”
These were the only nutrient parameters that showed a significant relationship when the Tukey test was applied.
Final considerations
The authors summarized the findings. It would be more interesting to relate these findings to others in the world. Are such changes commonly seen in anthropic environments? What is the most frequent type of anthropization (e.g., sewage or pasture)?
As mentioned in previous answers, we performed analyzes of other studies for comparison purposes where we found the following information (briefly):
“The concern with water management on a global scale is growing and current. Several studies similar to this one happen in several locations in an attempt to maintain the quality of the water for its different uses. Authors like Rimoldi (2018); Wei et al. (2020); Buonocore et al. (2021); Lei et al. (2021); Ni et al. (2021); Shehab et al. (2021); Spicer et al. (2021) seek in their work to report the importance of analyzing land uses in different regions of the planet (Argentina; China; Iberian Peninsula; Germany; United States of America; Malaysia; New Zealand) on water quality, having as a similarity in all of them changes in water quality in anthropic environments, whether rural or urban. These studies demonstrate the importance of analyzes such as the one carried out by this article, in regions with little information about their waters and the changes in them caused by anthropic action, in this case, the Amazon region. All of these studies had the objective of paying attention to the planning of water resources management in the studied region and in the adjacent regions. ”
DOI of the cited articles:
https://doi.org/10.1016/j.jclepro.2020.122249
https://doi.org/10.1016/j.ecolind.2020.106940
https://doi.org/10.1016/j.scitotenv.2021.146034
https://doi.org/10.1016/j.catena.2020.105055
https://doi.org/10.1016/j.landusepol.2020.105200
https://doi.org/10.1016/j.ecolind.2020.107254
https://doi.org/10.1016/j.ecolind.2018.01.063
Regarding the most frequent types of anthropization, in most part we highlight the agricultural areas, where the pasture fits. However, urban areas tend to impact as much as agricultural areas due to the large load of domestic and industrial sewage in bodies of water, as mentioned by the articles cited above.
Figure 2: It is difficult to see the dots (sewage, food and frigorific industries) in the picture. I suggest increasing them.
The change was made as requested.
Citation: https://doi.org/10.5194/bg-2020-485-AC2
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AC2: 'Reply on RC2', Alan Mendonça, 18 May 2021
Status: closed
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RC1: 'Comment on bg-2020-485', Anonymous Referee #1, 02 Apr 2021
The manuscript presented the results from a basin-scale water quality survey conducted through four seasons in the southwestern Amazon. Continuous progression of anthropogenic disturbance in the area has developed serious deterioration of water environments and scientists are highly expected to provide insights for resolving and managing/controlling the problems. In this context, the authors only reported the measured values for several parameters, failed to identify research questions based on knowledge previously accumulated (known and unknown) and, accordingly, were unable to emphasise the impacts of this study on academia and society. Hence, I evaluate the manuscript is not at the level of publication in Biogeosciences as an original article with a decision of Rejected.
Major comments:
- In Abstract and Introduction, what do you mean by “diagnose”? The objectives have not been specified due to lack of establishing the research question.
- Explanation on the methodology introduced by the authors to analyse “influence of land use and occupation” is critically insufficient and illogical throughout the manuscript.
- L130-142: What is this analysis on temperature for in the relationship with the following water quality parameters?
- L148, 197, 230, 251, 259: For all of transparency, phosphorus, nitrite, EC, Chl.a and bacteria, no significant seasonality was examined. Was it as the authors expected or unexpected before the analyses? What does “objective of identifying possible temporal variations” mean by? What was the hypothesis originally?
- L148-152, 168-173, 184-185: The authors tried to discuss on the pollution source by using concentration data only, however, need another analysis on pollutant loading (concentration and river flow) for that purpose.
- L153-155, 238-240: Those descriptions on phosphorus and Chl.a are not discussions deduced from the obtained results in this study, and should not appear in Discussion section.
- L193-196: What would be a logical relationship between “significant increase in the LW for ammonia” and “highest nitrate in HW and HW/LW”? I do not understand the mechanism of “a longer time interval for contamination”.
- L208-2009: I do not agree “As can be observed” and “This result can be correlated” in Figure 5a.
- L210-212, 221-224: For insisting those conclusions, the authors need to present TOC and its correlation with transparency.
- PCA in L260-272: The meanings/interpretations for Axis1 and Axis2 are necessary at minimum in basic discussion on PCA. The two obvious groups (P1,P2,P3 and P4) should be first assessed by comparing to the interpretations for the axes. “These results are similar to those reported” makes no sense without detailed discussion.
Minor comments:
- L85 “using 95% ethanol”: Not explaining the correspondent analytical method appropriately.
- “3.1 Land use and occupation” should be moved to Study Area in Methods section.
- L108: figure 3 > Figure 3
- Figure 2: What are “Colorful Composition RGB” for? This figure can be combined with Figure 1.
- Table 2: Errors should be added for each.
- Table 3: What is this figure for?
- Figure 6: Please confirm if F1 and F2 were switched.
Citation: https://doi.org/10.5194/bg-2020-485-RC1 -
AC1: 'Reply on RC1', Alan Mendonça, 18 May 2021
The manuscript presented the results from a basin-scale water quality survey conducted through four seasons in the southwestern Amazon. Continuous progression of anthropogenic disturbance in the area has developed serious deterioration of water environments and scientists are highly expected to provide insights for resolving and managing/controlling the problems. In this context, the authors only reported the measured values for several parameters, failed to identify research questions based on knowledge previously accumulated (known and unknown) and, accordingly, were unable to emphasise the impacts of this study on academia and society. Hence, I evaluate the manuscript is not at the level of publication in Biogeosciences as an original article with a decision of Rejected.
Major comments:
- In Abstract and Introduction, what do you mean by “diagnose”? The objectives have not been specified due to lack of establishing the research question.
The basin diagnosis refers to the state of land use and occupation of the Igarapé Nazaré basin and its influence on water quality. This diagnosis is a methodological step taken from the Brazilian National Water Resources Policy to classify bodies of water into classes. In order to fit a body of water in a certain class, a complete study of the hydrographic basin is necessary, where the diagnosis of the basin is the first stage of this process.
- Explanation on the methodology introduced by the authors to analyse “influence of land use and occupation” is critically insufficient and illogical throughout the manuscript.
The method used to analyze the influence of land use and occupation, was to establish a relationship between the form and the characteristics of use within the basin under study. The basin had its natural area converted into an urban and rural area. Then, the most significant point sources of pollution were identified, among other information, and data from an article already published by the same author and on the same basin according to the DOI were used: https://doi.org/10.22478/ufpb .1981-1268.2020v14n3.52610 relating the use and occupation data with the water quality data found for the basin. The process is carried out in this way due to the methodology defined by the Brazilian National Water Resources Policy for framing water bodies. This study was carried out in view of the need to improve water management in the Amazon region, which does not have a framed river, as determined by the National Water Resources Policy. Thus, it was analyzed whether the characteristics of use, are affecting or not the water quality of this stream from the data of use and occupation of the soil and the quality parameters analyzed in the stream in different periods.
- L130-142: What is this analysis on temperature for in the relationship with the following water quality parameters?
The analysis of the temperature variable is extremely important in studies that analyze the presence / absence of vegetation cover in a basin, considering mainly that this variable is strictly related to environmental variables such as dissolved oxygen and depth, and with a high influence on the aquatic biota.
- L148, 197, 230, 251, 259: For all of transparency, phosphorus, nitrite, EC, Chl.a and bacteria, no significant seasonality was examined. Was it as the authors expected or unexpected before the analyses? What does “objective of identifying possible temporal variations” mean by? What was the hypothesis originally?
As a main result, the authors expected that differences in water quality parameters would show differences between the hydrological periods analyzed. Thus, we inserted a hypothesis at the end of the introduction section in order to better present the results of this research.
“we hypothesized that the water quality parameters vary between the seasons of the hydrological cycle, in a microbasin in southwestern Amazonia. Following the premise that for each period of the hydrological cycle, the environment changes its environmental conditions due to differences in water volume and depth, which consequently influences the concentration and availability of limnological variables.”
- L148-152, 168-173, 184-185: The authors tried to discuss on the pollution source by using concentration data only, however, need another analysis on pollutant loading (concentration and river flow) for that purpose.
For this manuscript, the objective was to present data on water quality and the influence of land use under them in the Igarapé Nazaré watershed. However, we believe it is very important studies that, through flow data, can contribute to a better understanding of the dynamics of pollutants in this basin, which was not possible in this research.
- L153-155, 238-240: Those descriptions on phosphorus and Chl.a are not discussions deduced from the obtained results in this study, and should not appear in Discussion section.
The portion of the text in question has been removed as requested.
- L193-196: What would be a logical relationship between “significant increase in the LW for ammonia” and “highest nitrate in HW and HW/LW”? I do not understand the mechanism of “a longer time interval for contamination”.
One of the consequences of being a microbasin with a strong anthropic influence, is that we are unable to observe the chemical transformations of chemical substances (nitrate, nitrite and ammonia) as in a non-anthropized environment. In the Nazaré stream microbasin, effluents are discharged with different concentrations of nitrogenous substances, which makes some interpretations of the results unfeasible over a hydrological cycle. Because regardless of the flow, the effluents continue to be released.
- L208-2009: I do not agree “As can be observed” and “This result can be correlated” in Figure 5a.
P4 is the sampling point where the values observed for dissolved oxygen were the lowest. For the last three sampled periods (HW / LW; LW; LW / HW) the presence of dissolved oxygen was not identified in P4, pulling the lower limit of the box-splot graph downwards. However, the values of Electrical Conductivity and Turbidity for the same point and period will be added in the text for better visualization and interpretation.
- L210-212, 221-224: For insisting those conclusions, the authors need to present TOC and its correlation with transparency.
It was not possible to perform this analysis.
- PCA in L260-272: The meanings/interpretations for Axis1 and Axis2 are necessary at minimum in basic discussion on PCA. The two obvious groups (P1,P2,P3 and P4) should be first assessed by comparing to the interpretations for the axes. “These results are similar to those reported” makes no sense without detailed discussion.
The discussion was expanded to better characterize the results of this article with other articles in the same area, as follows:
These results are similar to those found by Toledo and Nicolella (2002) and Oliveira et al. (2017) where for microbasins with rural and urban influence they presented the highest values of correlation coefficient between the same variables presented in this axis. The authors observed a great influence downstream of the analyzed streams, after urban areas, of extensive cattle breeding on water quality and the influence of heavily impacted tributaries, as is the case of the P4 analyzed in this research.
We emphasize that the sampling points were grouped and purchased with the indications for each axis of the PCA.
Minor comments:
- L85 “using 95% ethanol”: Not explaining the correspondent analytical method appropriately.
For the analysis of chlorophyll a, a volume of 100mL of sample was filtered through a glass microfiber filter, 0.45 µm porosity (Whatman AP – 20). Subsequently, the filters were added to Falcon tubes protected from light, and 5mL of 95% ethanol was added. The tubes were then taken to a water bath until reaching a temperature of 75 ° C, and kept under these conditions for 5 minutes. Then the tubes were cooled and kept protected from light for 6 hours. Subsequently, the samples were centrifuged, removing the supernatant from which the spectrophotometric measurements were obtained at 664 and 750nm ((Kasuaki, IL-226-NM).
- “3.1 Land use and occupation” should be moved to Study Area in Methods section.
The cited section will be removed to the study area.
- L108: figure 3 > Figure 3
The correction will be accepted and changed in the article.
- Figure 2: What are “Colorful Composition RGB” for? This figure can be combined with Figure 1.
The caption indicating the composition R (RED) G (GREEN) and B (BLUE), indicates the coloring process of the satellite image used. It is preferred not to combine the two figures due to different information contained in the maps, Figure 1 addresses the water sampling points and Figure 2 highlights the main point sources of pollution, identified within the hydrographic basin, which would make the map “ polluted ”with so much information.
- Table 2: Errors should be added for each.
A new table will be added with the errors, as requested, with a new title: Table 2: Environmental variables (mean ± SD) in the Igarapé Nazaré microbasin for the four periods sampled. Depth (cm) and transparency (cm).
- Table 3: What is this figure for?
These values serve as a comparison for results observed in hydrographic basins close to the Igarapé Nazaré basin, and which have similar characteristics of use and occupation.
- Figure 6: Please confirm if F1 and F2 were switched.
They were not exchanged. F1 (38.86%), F2 (13.01%).
Citation: https://doi.org/10.5194/bg-2020-485-AC1
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AC1: 'Reply on RC1', Alan Mendonça, 18 May 2021
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RC2: 'Comment on bg-2020-485', Anonymous Referee #2, 27 Apr 2021
The manuscript presents data on water quality parameters of a watershed in the Brazilian Amazon. These data are rare and extremely important for the knowledge of Amazonian aquatic systems. However, these are presented and discussed in a regional view and can be valuable for local monitoring. I suggest reconsidering after major revisions or rejected.
Abstract
The abstract has a very regional view of the data and conclusions. I suggest rewriting it to demonstrate how the findings of this study in the Igarapé Nazaré basin can be extrapolated to other streams around the world (or at least in tropical/equatorial systems).
Introduction
Like the abstract, the introduction is also very local. It discusses the problem of water quality and its management in Brazil. I suggest thinking how that occurs worldwide. For example, I put some questions bellow that can be thought of to enrich the introduction:
- Are there National Policies in other countries? Brazil has the PNRH (line 34), and other countries have similar programs. This could be mentioned in the introduction, giving a more global aspect to the study.
- The implementation of water quality monitoring is cited (line 41). Is there effective monitoring anywhere in the world? Why? Why hasn’t in Brazil?
- The aim is very regional and fits well in a local journal. With these findings in Nazaré, is it possible to understand other streams in the Amazon or in the tropical/equatorial biomes?
Material and Methods
In lines 49-51, the manuscript says that there are rainy and dry seasons. In lines 72-73, the manuscript says that water sampling occurred in high-water and low-water seasons. Are these same stations? Are these aquatic systems subject to the flood-pulse of the main river? Is there water fluctuation in sampling points due to the season? This is not described in the Study area section.
The methods can be briefly described. Example:
- lines 73-76: Are these places of discharge accounted for? When they were seen, did the water collection take place upstream or downstream from discharge points?
- lines 83-85: These methods can be briefly described.
- Total nitrogen was not measured in unfiltered water? Why?
Results and discussion
- There is a lack of correlation between the parameters evaluated and land use. The data was presented extensively with a temporal perspective, but not a spatial one (and that was the primary objective of the work).
- Like the other sections of the paper, I suggest putting in a global perspective. What is the relationship of your results with global parameters observed in anthropized streams?
- There is a discussion about the parameters listed by CONAMA. Does being within the limits established by CONAMA mean that the water is from a preserved site? And on the contrary? Does being off limits mean that the environment is anthropic or that the water is not fit for human use? Ex: very acidic pH may indicate a black water river, and not that the environment has been modified.
This discussion should be added to the discussion section since the work gave a lot of emphasis to CONAMA.
- Results were compared using ANOVA, but a post hoc test was not done to identify the different group(s) – example: lines198-199.
Final considerations
The authors summarized the findings. It would be more interesting to relate these findings to others in the world. Are such changes commonly seen in anthropic environments? What is the most frequent type of anthropization (e.g., sewage or pasture)?
Figure 2: It is difficult to see the dots (sewage, food and frigorific industries) in the picture. I suggest increasing them.
Citation: https://doi.org/10.5194/bg-2020-485-RC2 -
AC2: 'Reply on RC2', Alan Mendonça, 18 May 2021
The manuscript presents data on water quality parameters of a watershed in the Brazilian Amazon. These data are rare and extremely important for the knowledge of Amazonian aquatic systems. However, these are presented and discussed in a regional view and can be valuable for local monitoring. I suggest reconsidering after major revisions or rejected.
Abstract
The abstract has a very regional view of the data and conclusions. I suggest rewriting it to demonstrate how the findings of this study in the Igarapé Nazaré basin can be extrapolated to other streams around the world (or at least in tropical/equatorial systems).
Introduction
Like the abstract, the introduction is also very local. It discusses the problem of water quality and its management in Brazil. I suggest thinking how that occurs worldwide. For example, I put some questions bellow that can be thought of to enrich the introduction:
- Are there National Policies in other countries? Brazil has the PNRH (line 34), and other countries have similar programs. This could be mentioned in the introduction, giving a more global aspect to the study.
Countries such as South Africa (Koppen and Schreiner, 2013), Australia (Byrnes et al. 2006), Malaysia (Afroz et al., 2016), China (Shuzhong et al., 2017), United Arab Emirates (Paleologos et al. ., 2018) and others, present policies for the conservation, management, equal distribution of water resources. Although Brazil has a well-intentioned National Water Resource Policy (PNRH in the Portuguese acronym), specifying various instruments for management of watersheds, these instruments have proved hard to implement in the majority of cases.
- The implementation of water quality monitoring is cited (line 41). Is there effective monitoring anywhere in the world? Why? Why hasn’t in Brazil?
Therefore, more information is necessary to hasten progress in water management. This can be promoted by the use of 40 geoprocessing tools (Flauzino et al., 2010), implementation of effective water quality monitoring, como é realizado em outros países (Ighalo and Adeniyi, 2018; Chen and Han, 2018; Wilson et al., 2018; Altenburger et al., 2019; Li et al., 2020) , and production of information to support policymakers’ decisions regarding sustainable water use and ecological restoration of watersheds (Avila, 2016; Vigiak, 2016; Britto, 2018).
- The aim is very regional and fits well in a local journal. With these findings in Nazaré, is it possible to understand other streams in the Amazon or in the tropical/equatorial biomes?
Looking toward the establishment of these initiatives in the country’s North region, our objective in this study was to diagnose the influence of land use and occupation on the water quality of the Igarapé Nazaré microbasin.
Our research promotes a better understanding of the impacts of changes in land use in microbasins in the Amazon region, as well as for several tropical biomes
The information cited in the previous responses will be present in the text of the article.
Material and Methods
In lines 49-51, the manuscript says that there are rainy and dry seasons. In lines 72-73, the manuscript says that water sampling occurred in high-water and low-water seasons. Are these same stations? Are these aquatic systems subject to the flood-pulse of the main river? Is there water fluctuation in sampling points due to the season? This is not described in the Study area section.
The term used as flood periods represents the wettest seasons. The ebb period represents the transition period from the rainy to the dry period, where there is a decrease in the flow of this stream. The sampling took place in 4 periods, being in the rainy and dry seasons (popularly called winter and Amazonian summer, respectively), and in the transition periods between one and the other. There is a variation in water fluctuation in all periods.
The methods can be briefly described. Example:
- lines 73-76: Are these places of discharge accounted for? When they were seen, did the water collection take place upstream or downstream from discharge points?
The most relevant point sources, such as industries and sanitary sewage, were counted as shown in figure 2. Diffuse sources were not counted due to the difficulty of measuring these sources. The collections were carried out both upstream and downstream of the discharge points mentioned in the article, since the observed sources of pollution observed maintain a constant discharge flow.
- lines 83-85: These methods can be briefly described.
Samples were also taken to the laboratory under refrigeration for other analyses, as described by the Standard Methods for the Examination of Water and Wastewater (APHA, 2015) and the National Guide for Collection and Preservation of Samples (2011). The turbidity was measured with a portable turbidimeter (Hach model 2100P). The dissolved oxygen (DO) was measured according to the Winkler method (APHA, 2015) and the transparency was determined in the field using a Secchi disk. The concentrations of dissolved nutrientes, ammonia, nitrite, nitrate, total phosphorus and dissolved phosphorus were ascertained by spectrophotometry, according to the analytic methods described in APHA (2015).
The analyzes of the dissolved nutrients were performed with water samples previously filtered through glass microfiber filters, 0.45 µm porosity (Whatman AP – 20). Only the analysis of total phosphorus was performed on unfiltered samples. All nutrient analyzes were preceded by a calibration curve with standard solutions. After adding specific solutions for each analysis, absorbances were measured on a spectrophotometer (Kasuaki, IL-226-NM). For the analysis of ammonia, samples containing solutions containing phenol, sodium nitroprusside, hypochlorite and sodium hydroxide were added to the samples. Absorbance measurements were performed at 630nm. Nitrite analyzes were performed using 1% sulfanilamide solutions and 0.1% n-naphthyl alcoholic solution. Absorbances were measured at 543 nm. For the nitrate analysis, 1% brucine solution, sulfanilic acid and hydrochloric acid were added to the samples. Absorbance measurements were performed at a wavelength of 410nm. The analysis of dissolved phosphorus was performed by adding the samples ammonium molybidate solution, 15% sulfuric acid solution, ascorbic acid solution and atymone and potassium tartrate solution, followed by the reading of the absorbance at 882 nm. For the analysis of total phosphorus, unfiltered samples were added to supersaturated solution of ascorbic acid, then the samples were autoclaved. After the samples were reaffirmed, the method used for the analysis of dissolved phosphorus was carried out.
- Total nitrogen was not measured in unfiltered water? Why?
The analyzes of this parameter were not carried out because we do not have all the material devices necessary for it.
Results and discussion
- There is a lack of correlation between the parameters evaluated and land use. The data was presented extensively with a temporal perspective, but not a spatial one (and that was the primary objective of the work).
We emphasize that the data of our research were presented in a spatial perspective. We agree with the Reviewer that the time scale analysis was more emphasized, however the spatial variation of the analyzed variables was also demonstrated and discussed. Below we highlight some parts of the "Results and discussion" that indicate such a placement.
“Points P1, P2 and P3, located in a relatively well preserved rural APP, were the only ones to present concentrations below 0.1 mg.L-1 in all the periods. The others (P4 to P10) all had levels greater than 0.1 mg.L-1, with highlight on P4, which in the low water period had total phosphorus concentration of 27.55 mg.L-1. The highest concentrations of total phosphorus were found in the low water period at all the points sampled.”
“The lowest concentrations of dissolved phosphorus were also found at points P1, P2 and P3, while the highest concentrations were found at P4 (2.06 mg.L-1) and P7 (0.12 mg.L-1). These values can reflect the presence of aquatic flora, since this is the main form of phosphate assimilated by aquatic plants (Esteves, 2011).”
“With respect to the dissolved oxygen levels (Figure 5a), only at P2 was the concentration higher than the limit set by CONAMA Resolution 357/2005 (5 mg.L-1) in all the periods. Only the points in the microbasin located in rural areas (P1, P2 and P3) had values below the regulatory threshold, in periods HW (P1 and P2), HW/LW (P2), LW (P2 and P3) and LW/HW (P1, P2 and P3).”
“The sampling points located in the urban area of Ji-Paraná (P4 to P8), in the periods HW, HW/LW and LW, had values below the regulatory limit, with the exception of P7 in the period HW/LW (5.33 mg.L-1). In the LW/HW period, there were higher DO concentrations, which can be explained by the strong rainfall on the collection day, contributing to the aeration of the water.”
“In periods HW and LW, the presence of E. coli was not found at points P2 and P3, and P1 and P3, respectively. The water at all the other points had values above the limits stipulated in CONAMA Resolution 357/2005, of 1,000 coliforms per 100 mL of water. With respect to total coliforms, no point presented values greater than that threshold.”
- Like the other sections of the paper, I suggest putting in a global perspective. What is the relationship of your results with global parameters observed in anthropized streams?
This suggestion was accepted and a survey on research with similar objectives from different locations on the planet was raised for purposes of comparison with the present work and will be incorporated into the text.
- There is a discussion about the parameters listed by CONAMA. Does being within the limits established by CONAMA mean that the water is from a preserved site? And on the contrary? Does being off limits mean that the environment is anthropic or that the water is not fit for human use? Ex: very acidic pH may indicate a black water river, and not that the environment has been modified.
Within CONAMA (National Council for the Environment) there is a classification that is called special class, class 1, class 2, class 3 and class 4. These classes define the way in which these waters are used and the degree of quality in which they are used. find. As an example the special class, are waters destined to the preservation of the aquatic environments in integral protection conservation units; preserving the natural balance of aquatic communities. In short, waters that must be protected to maintain their original characteristics. Starting from class 1, these are waters that can be used for public supply, recreation, up to class 4, which has its use only for navigation; and landscape harmony. This classification is used so that the forms of use around this body of water are controlled to prevent the parameters that classified it in this way from maintaining these characteristics. However, there are discussions in the scientific environment in which CONAMA observes this in general, not taking into account the different natural characteristics of water bodies, especially in the Amazon, which has rivers with different characteristics.
This discussion should be added to the discussion section since the work gave a lot of emphasis to CONAMA.
This information will be added to the discussion session.
- Results were compared using ANOVA, but a post hoc test was not done to identify the different group(s) – example: lines198-199.
“The nitrate parameter when applied to the Tukey test obtained differences in almost all periods except when comparing the periods LW and LW / HW (HW and HW / LW p = 0.001575; LW and HW p = 3.90E-06; HW / LW and LW p = 2.02E-11; HW and LW / HW p = 5.58E-08; HW / LW and LW / HW p = 3.87E-13). The ammonia parameter for the same test obtained significant differences for the period of HW and LW (p = 0.005775); HW / LW and LW (0.006708); LW and LW / HW (p = 0.008358); showing that the highest concentration of this parameter occurred in the period with the lowest volume of water in the stream.”
These were the only nutrient parameters that showed a significant relationship when the Tukey test was applied.
Final considerations
The authors summarized the findings. It would be more interesting to relate these findings to others in the world. Are such changes commonly seen in anthropic environments? What is the most frequent type of anthropization (e.g., sewage or pasture)?
As mentioned in previous answers, we performed analyzes of other studies for comparison purposes where we found the following information (briefly):
“The concern with water management on a global scale is growing and current. Several studies similar to this one happen in several locations in an attempt to maintain the quality of the water for its different uses. Authors like Rimoldi (2018); Wei et al. (2020); Buonocore et al. (2021); Lei et al. (2021); Ni et al. (2021); Shehab et al. (2021); Spicer et al. (2021) seek in their work to report the importance of analyzing land uses in different regions of the planet (Argentina; China; Iberian Peninsula; Germany; United States of America; Malaysia; New Zealand) on water quality, having as a similarity in all of them changes in water quality in anthropic environments, whether rural or urban. These studies demonstrate the importance of analyzes such as the one carried out by this article, in regions with little information about their waters and the changes in them caused by anthropic action, in this case, the Amazon region. All of these studies had the objective of paying attention to the planning of water resources management in the studied region and in the adjacent regions. ”
DOI of the cited articles:
https://doi.org/10.1016/j.jclepro.2020.122249
https://doi.org/10.1016/j.ecolind.2020.106940
https://doi.org/10.1016/j.scitotenv.2021.146034
https://doi.org/10.1016/j.catena.2020.105055
https://doi.org/10.1016/j.landusepol.2020.105200
https://doi.org/10.1016/j.ecolind.2020.107254
https://doi.org/10.1016/j.ecolind.2018.01.063
Regarding the most frequent types of anthropization, in most part we highlight the agricultural areas, where the pasture fits. However, urban areas tend to impact as much as agricultural areas due to the large load of domestic and industrial sewage in bodies of water, as mentioned by the articles cited above.
Figure 2: It is difficult to see the dots (sewage, food and frigorific industries) in the picture. I suggest increasing them.
The change was made as requested.
Citation: https://doi.org/10.5194/bg-2020-485-AC2
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AC2: 'Reply on RC2', Alan Mendonça, 18 May 2021
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