Evaluation of Water Quality in the Tamiš River in Serbia Using the Water Pollution Index: Key Pollutants and Their Sources

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I suggest a good justification in the introduction. The results were well presented, but information about the uses of the basin in question could be included in the discussion. The conclusions deserve to be readjusted precisely because the data are from more than 10 years ago. Suggestions in the manuscript.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

I believe that English revision could happen to further improve the manuscript.

Author Response

Once every year? Was the information from a database?

The study utilized a robust database provided by the Serbian Environmental Protection Agency. Specifically, water quality data was collected based on approximately 11 measurements per year at both hydrological stations, Jaša Tomić and Pančevo, within the time frames 2011–2016 and 2018–2022. These measurements were part of systematic sampling campaigns conducted by the Agency. Therefore, the evaluation is based on comprehensive and consistent datasets, ensuring the reliability of the Water Pollution Index (WPI) analysis applied in the study.

Why cite 2009? It's confusing.

We appreciate the reviewer’s observation regarding the reference to the year 2009. Upon further consideration, we agree that this information may appear unnecessary and potentially confusing in the context of our study, as it does not significantly contribute to the presentation of our results. Therefore, we have decided to remove this detail from the manuscript to ensure clarity and focus on the core findings of our research.

The Tamiš River, has been affected by various anthropogenic influences, necessitating regular monitoring and assessment. Which?

Thank you for pointing out the need for further specification. To address this, we have added a Table 1 entitled "Anthropogenic Pollution Sources" in Section 2.1. Study Area, within the Materials and Methods chapter. This table provides a clear overview of the main anthropogenic influences affecting the Tamiš River, as discussed in our study. We hope this addition enhances the clarity and comprehensiveness of the manuscript.

I think you could explain why you should do this study if each area has data from different years and what is the justification for making this information public after 10 years.

We appreciate the reviewer’s thoughtful comment. The inclusion of studies conducted more than 10 years ago, such as Lujić et al. [44], serves to highlight the historical context and underline the persistent challenges regarding pollution in the Tamiš River. These references provide important insights into the types and sources of pollution identified in the past and are valuable for understanding the progression of water quality issues over time.

The current study aims to fill the gap in recent data and offers an updated perspective on the state of the Tamiš River's water quality. By presenting both historical and contemporary findings, we aim to provide a comprehensive view of pollution trends in the river and emphasize the need for continuous and coordinated cross-border efforts to address these issues.

Furthermore, we included this information to underscore that water quality research on the Romanian section of the river has also been conducted, highlighting the diversity of pollution sources affecting the Tamiš. This study therefore contributes not only to updating scientific knowledge but also to fostering better understanding and management of transboundary water resources.

We used data from Pančevo hydrological station in period 2011–2015, because, this hydrological station ceased to work, and there is no monitoring after 2015. However, pollution sources still exsists, as it is presented in Table 1.

We hope this clarifies the importance and justification of our approach and the relevance of making this information publicly available now, to benefit both the scientific community and environmental management initiatives.

and 2010?

Before our research, Serbian section of the Tamiš river has been studied in 2009 by Babović et al. (2011). This paper was published 2011, but study was conducted 2009. This is reference 43.

Jasa Tomić 2011-2022 (table 3).

Pancevo 2011 a 2015?

I don't understand.

 

Thank you for your comment regarding the time periods analyzed in the study. We selected two five-year periods (2011–2015 and 2018–2022) to provide a systematic and balanced approach to assessing water quality trends. Unfortunately, monitoring at the Pančevo hydrological station ceased in 2015, and water quality parameters have not been measured since there. For this reason, WPI calculations for this station are limited to the first period (2011–2015).

Additionally, the selected periods reflect the unique characteristics and pollution influences at the two stations. The Jaša Tomić station captures upstream pollution from Romania, predominantly from industrial facilities, agricultural runoff, and urban wastewater. In contrast, the Pančevo station, positioned near the confluence of the Tamiš and the Danube, integrates upstream pollution from Romania alongside additional contributions from urban, industrial, and agricultural sources within Serbia. These distinctions make both stations essential for understanding the broader pollution dynamics affecting the Tamiš River.

We believe this selection of timeframes provides meaningful insights into the water quality challenges faced by the Tamiš River, while remaining within the constraints of available data.

Suggestion: present in a table the differences and anthropic actions of each season.

Thank you for the valuable suggestion. While we do not have data segmented by seasons, the sources of anthropogenic pollution listed in the Table 1 are considered to contribute to water pollution throughout the year. The continuous nature of these activities, such as industrial operations, agricultural runoff, and municipal waste, suggests that their impact is not confined to specific seasons.

Additionally, we have created and included the Table 1 titled "Anthropogenic Pollution Sources" in the manuscript to further illustrate these continuous pollution influences. This addition was made in response to your suggestion, ensuring greater clarity and comprehensiveness.

We hope this explanation addresses your suggestion and clarifies the scope of our data and analysis.

Suggestion: insert a location map with Europe as a whole, and from this, the smaller map indicating Serbia, Romania, Croatia, or the map that is presented.

Thank you for the suggestion. In response, we have created and included a new cartographic supplement in the manuscript. This addition provides a map highlighting the location of the Tamiš River near Pančevo, close to its confluence with the Danube, on a European scale. Pančevo hydrological station is presented on European map. Additionally, we have incorporated a more detailed map that illustrates the river's position within Serbia and its neighboring countries, including Romania and Croatia. We believe these updates address the suggestion effectively and enhance the geographical clarity of the study.

In the years 2016 and 2017 were no measurements made at the Jasa Tomić station?

For Jaša Tomić hydrological station, data were available for 2016 and 2017. However, we chose to focus our analysis on two five-year periods (2011–2015 and 2018–2022) to align with the study's scope and objective. This approach ensures consistency and comparability across the dataset.

Suggestion: present in a table the differences and anthropogenic actions of each station.

Thank you for your thoughtful suggestion. For the Pančevo station, we have provided information about the anthropogenic influences in the table titled "Anthropogenic Pollution Sources" within the manuscript. This table highlights the key pollution sources impacting the Tamiš River at this location in Serbia.

For the Jaša Tomić station, situated near the border with Romania, a comprehensive presentation of anthropogenic actions would require access to official data from the Romanian territory. Unfortunately, within the scope and timeline of this study, we were unable to obtain reliable and verified data from Romania to include in this research. As a result, we have focused on presenting the data available for the Serbian section of the river.

We believe this approach ensures the integrity and reliability of the information presented, while remaining within the constraints of the study. We hope this clarification addresses your comment.

Although the TDS reduced the clarity of the water, limiting the penetration of light, what happened to the DO? Could it have actually affected photosynthesis?

Thank you for this important question. Increased levels of suspended solids (TDS) can significantly reduce water clarity, thereby limiting light penetration essential for photosynthesis in aquatic ecosystems. Reduced light availability can negatively affect primary production processes, including photosynthesis, which in turn may influence the levels of dissolved oxygen (DO), as photosynthesis is a key process in oxygen production in water. Additionally, elevated concentrations of suspended solids may physically cover benthic plants and algae, further impairing their ability to perform photosynthesis.

Numerous scientific studies, such as Bilotta and Brazier (2008), have extensively analyzed the influence of suspended solids on water quality and aquatic biota. This topic certainly opens avenues for further research into the dynamic interactions between TDS, photosynthesis, and DO.

Comment with more emphasis on the land use of these locations

Thank you for your comment. We add information about land use impact on water quality (last paragraph in 3.1).

But that was 10 years ago? And now? Could the situation be different? It is strange to comment on a situation from more than 10 years ago.

Thank you for your comment. As it is previous mentioned, official monitoring of water quality on Pančevo hydrological station ceased and there is no data after 2015. However, pollution sources are still active and we could not conclude that situation is now different, comparing with 10 years ago.

Include as a suggestion: what actions could be taken with the riverside population? And water quality management actions with authorities.

with permanent monitoring: suggestion.

Thank you for your valuable suggestions. We have taken your comments into account and have supplemented the conclusion accordingly. We have included a section addressing specific actions that could be taken in collaboration with the riverside population, as well as measures for water quality management in cooperation with relevant authorities. Additionally, we have emphasized the importance of permanent monitoring. We hope these modifications have enhanced the conclusions of the paper. We would be happy to consider any further suggestions you may have.

Reviewer 2 Report

Comments and Suggestions for Authors

Please see the attachment. 

Comments for author File: Comments.pdf

Author Response

1.  

The discussion is limited to data from two hydrological stations, but it would be good to compare these results with other rivers, e.g. neighboring rivers or sections of the same river (e.g. above and below the source of pollution)

Thank you for your valuable suggestion regarding the inclusion of comparisons with other rivers. We have updated the manuscript to address this point. Specifically, we have added a discussion comparing the WPI results of the Tamiš River with those of nearby rivers, including the Danube River and the Karaš River. These comparisons demonstrate that the pollution levels in the Tamiš River align with regional trends, highlighting the importance of integrated water resource management across the area. The revised section is included in the Discussion and provides further context to the findings.

2.  

The work lacks an analysis of trends and seasonality in the context of WPI, which allows monitoring changes in water quality over time, identifying factors influencing these changes, predicting periods of water quality deterioration and implementing appropriate protective measures. Presently, the analysis gives possible causes of an increased indicators, however they are just general reasons. Seasonality analysis could be helpful in more accurate identification of the causes.

Thank you for your insightful suggestion regarding the incorporation of trend and seasonality analysis in the context of WPI. We have carefully considered this point and have included a seasonal analysis in the revised manuscript. By examining WPI variations across different seasons, we have been able to monitor changes in water quality over time and identify factors influencing these changes with greater accuracy.

The seasonal analysis has provided additional depth to our discussion, allowing for a clearer identification of periods of potential water quality deterioration and offering critical insights for implementing targeted protective measures.  We appreciate your suggestion, which has been instrumental in refining the scope and robustness of our analysis

3. As far as I understand, Table 3 provides the ratios of the value of a given index and the reference value for class I. It would be good to clearly describe this in the methodology.

Description of Table 3 Table 3 presents the ratio of mean annual concentrations of the analyzed water quality parameters to the standard values for Class I water quality in Serbia. These parameters are the same as those used in the calculation of the Water Pollution Index (WPI). The ratios provide an indication of how much the annual average concentration of each parameter deviates from the benchmark values set for high-quality water (Class I). A ratio greater than 1 indicates that the mean annual concentration exceeds the standard for Class I, highlighting potential exceedances or pollution issues, whereas a ratio below 1 suggests compliance with the Class I standard.

This table does not compare individual index values directly to reference values but rather focuses on the averaged concentrations of parameters such as nitrites, ammonium, orthophosphates, heavy metals, and other key indicators. The purpose of this analysis is to provide a comprehensive annual perspective of water quality status, which complements seasonal variations captured elsewhere in the study.

4.  
5. a) Line 175: the WPI formula, the formula would look better if 1/n was placed before the sum.

Thank you for the suggestion regarding the placement of 1/n in the WPI formula. We appreciate your attention to detail. However, we have opted to maintain the current representation of the formula as it aligns with how we have presented it in our previous publications. Consistency in formatting across our work is important to avoid potential confusion among readers who are familiar with our earlier studies. Additionally, the formula in its current form accurately conveys the calculation process, and we believe it fulfills its intended purpose effectively.

201. b) Table 3: the DO data from 2014 was given as 201.013? Line 208 discussed the value of 1.013?

Thank you for your comment. Yes, it was mistake and we correct it (1.013 is correct value).

4. c) Line 340: it is not clear how the average annual WPI values were calculated in Table 4.

Calculation of WPI Values in Table 4

The Water Pollution Index (WPI) values presented in Table 4 were calculated using the formula outlined in the methodology section:

WPI =

where Ci represents the mean annual concentration of each analyzed parameter, SFQS_denotes the standard value for Class I water quality in Serbia, and n is the total number of analyzed parameters (18 in this study).

The calculation involved the following steps:

1. Annual Averages of Parameters: For each hydrological station, the annual mean concentrations of the 18 analyzed parameters (e.g., dissolved oxygen, nitrites, ammonium) were computed based on data provided by the Serbian Environmental Protection Agency (SEPA) for the respective years.
2. Ratios to Class I Standards: The mean annual concentration of each parameter (Ci) was divided by its corresponding Class I standard value (SFQS) as listed in Table 1 (Methodology section). For example:
• For nitrites (standard value: 0.01 mg/L), if the mean annual concentration was 0.02 mg/L, the ratio would be 2.
3. Summation and Averaging: The individual ratios for all 18 parameters were summed, and the total was divided by the number of parameters (n) to yield the WPI value for the given year and station.
4. Classification: Based on the resulting WPI value, the water quality classification was assigned according to the criteria in Table 2 (Methodology section). For example:
• A WPI value of 0.93 at Jaša Tomić in 2011 corresponds to Class II ("Pure"), while a WPI value of 9.1 at Pančevo in 2015 indicates Class VI ("Heavily Impure").

Note: In cases where data for certain parameters were missing due to monitoring limitations, the WPI calculation included only the available parameters, and n was adjusted accordingly.

This rigorous computational approach ensures that the WPI values accurately reflect the overall water quality for each year and station, providing a clear indicator of ecological conditions.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors,
since all suggestions were accepted and justified, this manuscript can be published and will contribute to water management and to the realization of other similar works.