Nitrate Monitoring in Semi-Urban Groundwater of Northeastern Saudi Arabia
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsAfter detailed readings of the manuscript entitled: “Comparative Assessment of Field and Laboratory Techniques for Nitrate Monitoring in Semi-Urban Groundwater of Northeastern Saudi Arabia”, It should be noted that nitrate levels in water are necessary to protect public health and ensure compliance with regulatory standards. I emphasize that the study provides a comprehensive assessment of four analytical techniques—test strips, and ISE—has enabled the identification of shallow wells located in northern regions that exceed the World Health Organization (WHO) limit of 50 mg/L, thus indicating the presence of localized critical contamination points, enabling better decision-making, which would attract the attention of Journal readers. However, in order to be published, the manuscript requires major corrections, such as:
1 - I suggest that the title: “Comparative Assessment of Field and Laboratory Techniques for Nitrate Monitoring in Semi-Urban Groundwater of Northeastern Saudi Arabia”, Be modified to: “Nitrate Monitoring in Semi-Urban Groundwater of Northeastern Saudi Arabia”. It would make the manuscript clearer and spark the interest of the Journal's readers.
2 - At the end of the “Abstract,” I suggest highlighting the overall importance of the study for society.
3 - On page 2, lines 53 to 65. Together with lines 67 to 70, there are no references. In this section, you use strong terms; you should insert more bibliographic references to consolidate the arguments used.
4 - There are some confusing passages in the introduction: “These innovations demonstrate the growing need for rapid nitrate measurement techniques that can be used in the field.” This should be rewritten.
5 - I highlight the presence of passages with strong arguments without references, which therefore do not support the arguments:
- (page 3, lines 99 to 101) “The ultraviolet spectrophotometric method detects nitrate by measuring the amount of ultraviolet light absorbed by nitrate ions, a simple process that indicates the presence of nitrate in the sample”.
- (page 3, lines 111 to 118) “This approach involves the reduction of nitrate to ammonia using a reducing agent, typically Devarda alloy. Ammonia was then distilled and collected in a boric acid solution. The collected ammonia was subsequently titrated against a standardized acid, usually hydrochloric or sulfuric acid, using a suitable indicator, such as methyl red or bromocresol green. The quantity of acid necessary to neutralize ammonia is directly proportional to the nitrate concentration present in the initial water sample. This method offers high accuracy and precision, making it suitable for use in environmental monitoring and research”
- (page 3, lines 121 to 132)
6 - At the end of the introduction, it is necessary to highlight the overall importance of the manuscript to society.
7 - The methodology needs to be better grounded with references from the literature, enabling greater methodological consolidation.
8 - The resolution of the figures is adequate. Congratulations to the authors.
9 - 30 bibliographic references is too few; increase this number to make the manuscript more attractive.
10 - The results need to be discussed further in relation to the literature; there is no research without discussion of results.
11 - The conclusion is appropriate. Congratulations.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors compare various analytical techniques used to measure nitrates in water. This comparison does not contribute anything new to the general knowledge of analytical techniques. It is widely known that analytical techniques should be selected individually for the type of medium being tested and the concentration range of the indicator being tested. Therefore, the purpose of the study should be changed (lines 143-150).
General note: The use of specialised equipment (e.g. electrodes, Line 96) is not a disadvantage of the method. Similarly, it can be said that the use of a UV-VIS spectrophotometer is a disadvantage of this method. These statements should be changed throughout the article. A disadvantage of a method may be its negative impact on the measurement of other components (ions) dissolved in water, which may react with reagents to form coloured compounds that interfere with absorbance measurement or interact with the ion-selective electrode. Alternatively, these matters should be described in more detail – what interferes with the measurement of nitrates in particular methods and how this negative impact can be eliminated. Were there no interfering substances/ions in the tested waters?
The lack of testing for other components in water reduces the quality of the research conducted. Nitrites are more harmful than nitrates (standards in drinking water are 0.5 and 50 mg/L, respectively). Comparing these two parameters would be more valuable for assessing the health safety of the local community.
Section 2.3.4. The reasons for using hydrochloric acid in some cases and sulphuric acid in others should be explained.
Why did the authors not take into account the methods for determining nitrates recommended by the APHA (Standard Methods for Examination of Water and Wastewater; American Public Health Association: Washington, DC, USA)?
I consider the lowest concentration of the diluted standard (15.75 mg/L), which the authors consider extremely low, to be very high. Nitrate concentrations recorded in surface waters are often below 1 mg/L, and the calibration range used by the authors does not allow for the measurement of such low nitrate concentrations. In the UV-VIS method, the authors certainly exceeded the maximum absorbance that can be measured by a spectrophotometer (usually 3, which is already achieved at nitrate concentrations below 5 mg/L). This needs to be clarified. Were additional dilutions used after the colour reaction?
L482 – correct the concentration value (880 or 980?).
The strength of the article lies in the results described from line 537 onwards. It is only for this reason that this article can be published in Urban Science as an exception.
Line 609 – correct the following sentence: Conversely, if a sample is a nitrate solution that undergoes oxidation to nitrite, the nitrate concentration increases over time as the nitrate transforms into nitrite. (nitrates are reduced to nitrites).
L730 – specify the depth ranges for shallow and deep wells.
L750-785 – add more information about the chemical composition of these geological formations; what kind of rocks they are (sedimentary, volcanic, calcareous or other). Explain how the chemical composition of the rocks could have affected the nitrate concentrations in the water from individual wells.
Section 3.7 contains many repetitions and could be added as a SUPPLEMENT.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Editor
My recommendations have been addressed. I suggest ACCEPTING the manuscript for publication.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors addressed all questions approprietly and manuscript has improved its quality. It is acceptable for me.
