Spatial and In-Depth Distribution of Soil Salinity and Heavy Metals (Pb, Zn, Cd, Ni, Cu) in Arable Irrigated Soils in Southern Kazakhstan

Round 1

Reviewer 1 Report

The references in the text are not in accordance with the instructions, namely [1].

Instead of Fig.  should be noted Figure.

73. The citations of the authors in parentheses are listed in descending order

124. Leymus multicaulis, Phragmites australiss hould be noted in italics. There are other underlined species that need to be written in italics. Isn't the paragraph from 116 about the types of vegetation identified in the investigated areas correct to be presented in the description of the study area?

 

241. The explanations under fig. 4 should be listed separately as a table and written in 1 row. 648. Small retouches to the bibliography according to the guide. The journal in which the article is published must be written in italics.
     

 

 

Comments for author File: Comments.pdf

Author Response

Thank you very much for all your comments and comments. Regarding individual comments:

The references in the text are not in accordance with the instructions, namely [1].

Instead of Fig.  should be noted Figure.

Was changed

73. The citations of the authors in parentheses are listed in descending order

Was changed

124. Leymus multicaulis, Phragmites australiss hould be noted in italics. There are other underlined species that need to be written in italics.

The names of underlined plant species are changed into italics

 Isn't the paragraph from 116 about the types of vegetation identified in the investigated areas correct to be presented in the description of the study area?

Yes, however, the description is related rather to natural vegetation, but study sites cover both cultivated and no cultivated areas

The explanations under fig. 4 should be listed separately as a table and written in 1 row. 648.

Unfortunately, for technical reasons, it is not possible to put the explanation in the table

Small retouches to the bibliography according to the guide. The journal in which the article is published must be written in italics.

Was changed

 

Reviewer 2 Report

Review: Spatial and in-depth distribution of soil salinity and heavy 2 metals (Pb, Zn, Cd, Ni, Cu) in arable irrigated soils in Southern 3 Kazakhstan

Manuscript Number: 1699877

In my opinion, the paper is a good quality work. However, although the reviewer basically judges the paper to be a significant, some changes are suggested, in order to improve the overall quality of the paper. Therefore, the Authors are asked to consider the following comments and to add the suggested modifications.

1. In the introduction, the authors have poorly substantiated the topic.
2. There is no description of how the individual parameters were determined?
3. What was the criterion for selecting the research site?
4. At exactly what depth the samples were taken, only layers are given in the paper?

 Alongside with the above major points, some minor comments follow.

L 24 there are two dots at the end of the sentence

L 99 give literature?

L 202 correct the headings in table 1?

in figure 3 give the unit of the graph.

 

I hope the following comments are informative for the authors when improving the manuscript further.

Author Response

In my opinion, the paper is a good quality work. However, although the reviewer basically judges the paper to be a significant, some changes are suggested, in order to improve the overall quality of the paper. Therefore, the Authors are asked to consider the following comments and to add the suggested modifications.

1. In the introduction, the authors have poorly substantiated the topic.

 

Thank you for all your comments and remarks. Regarding individual comments.

The research is monitoring, and the aim is to show the diversity of soil contamination and secondary salinity of soils in the context of the monitoring of arable soils.

 

 Recently, it seems to us that the main purpose of the article has been well recorded. It sounds like:

Considering the importance of proper soil quality in the Syr Darya river basin and the fact that simultaneous assessment of soil secondary salinity and contamination with heavy metals at the regional scale allows specification of the metals’ sources in different soil horizons, the primary goal of this study was to determine salinity and content of selected heavy metals (Pb, Zn, Cd, Ni, Cu) in irrigated arable soils.  We compared the concentration of salts and heavy metals (both total and mobile forms) in different soil types in three functional depths of soil profiles. To identify the potential source of soil pollution, we analyzed the relationships between physical and chemical properties and the content of heavy metals in the studied soils.

 

1. There is no description of how the individual parameters were determined.

 

Was added: SOM was determined by oxidizing it with potassium dichromate (K₂Cr₂O₇) according to the Tiurin method. The Na⁺, K⁺, and Ca⁺ content were determined on a flame spectrophotometer, while a measuring of Mg²⁺ was performed with an atomic absorption spectrometer AA-6200 (Shimadzu, Japan). The anions content was measured using the colorimetric methods.

The chemical analyzes were carried out according to the methodology mentioned in the literature list (below)

1. Methodological recommendations for conducting field and laboratory studies of soils and plants in the control of environmental pollution by metals. Moscow, Publishing house: Hidrometeoizdat, 1981, 107 p.
2. Methodological guidelines for the determination of heavy metals in soils of farmland and crop production. Moscow, Gosagroprom USSR, 1989, 62 p.

 

1. What was the criterion for selecting the research site?

Soil samples from 348 soil profiles from irrigated pastures and arable fields in the Shauldara massif were representative of this region.

 

 

1. At exactly what depth the samples were taken, only layers are given in the paper?

An explanation of the depth of sampling has been added to the description.: “soil samples were taken from the middle level of each of the three determined levels of soil profiles”.

 

 Alongside with the above major points, some minor comments follow.

L 24 there are two dots at the end of the sentence

Was changed

L 99 give literature?

Was added

L 202 correct the headings in table 1?

Was corrected

in figure 3 give the unit of the graph.

The unit is % and is visible on the Y axis

 

Reviewer 3 Report

Dear authors,

The paper is very interesting and for a real worldwide interest are the studies to avoid salinization and to preserve the soil fertility.

General comment:

The term of "Heavy metals" should be avoided and replace with a term more adequate, there are many papers that sustain this controversy.

All the decimal numbers should be separated by point : see table 2, lines 349-350, Fig 5.

Review the page set up and remove all the free spaces, as well lines 64-65 with different fonts; as well as the subscript or superscript function for ions or others equations.

Specific comments:

Line 17- from the abstract talk about "soil pollution" without having a conclusion of the results about contamination of pollution of the area.

Figure 1, line 90 - there is missing the explanations of red and green dots.

To the section 2.1. a short geological background of soil formation is missing; this information can be used to explain the presence of some elements in the soil.

To Field sampling section, there horizons are described, but further the authors mention first, second and third layers -in this case it should mention the soil horizon to which they refer to.

At Laboratory analyses you should describe the digestion methods, as well to mention the reference materials used for analyses validation and the water type used  for sample dilutions. Some references can be added.

Explain the mention of "t" beside chemical symbols from Table 1, as well the different notation from Table 2  as "tot"/"mob". Make a difference between these notations and use only one.

For soil contamination assessment, the authors may used one or more geochemical indices to evidence the grade or the source of contamination/pollution. The part of "spatial distribution" from the title was not evidenced in the study.

Good luck with the paper!

 

Author Response

Thank you very much for all your comments and comments. Regarding individual comments:

General comment:

The term of "Heavy metals" should be avoided and replace with a term more adequate, there are many papers that sustain this controversy.

“The term heavy metal refers to any metallic chemical element that has a relatively high density (mostly above 4,5 g/cm³ > ). The term heavy metals are generally used to refer to elements that are used in industry and are toxic to humans or the environment at the same time. Heavy metals include metals (e.g. mercury, lead, cadmium, chromium, nickel, copper, zinc ect.).

According to this definition (Pb, Zn, Cd, Ni, Cu), all elements mentioned in the article meet these criteria.

All the decimal numbers should be separated by point : see table 2, lines 349-350, Fig 5.

Was changed

Review the page set up and remove all the free spaces, as well lines 64-65 with different fonts;

Was changed

as well as the subscript or superscript function for ions or others equations.

The ion symbols have been represented according to the chemical nomenclature

Specific comments:

Line 17- from the abstract talk about "soil pollution" without having a conclusion of the results about contamination of pollution of the area.

 The sentence below was added

“The soil contamination with heavy metal was low and, in most cases, except for cadmium, it was below the limits developed for arable soils in most countries.  Soil contamination with cadmium is the result of contamination of the water used for irrigation of farmland.”

Figure 1, line 90 - there is missing the explanations of red and green dots.

Explanations were added:” Cultivated soils are marked with green dots, not cultivated soils with red dots”

To the section 2.1. a short geological background of soil formation is missing; this information can be used to explain the presence of some elements in the soil.

The short geological settings were added

“For many geological epochs, the modern deserts of Kazakhstan have been areas of the earth's crust immersion. As a result, strong unconsolidated marine and continental sediments have accumulated there. The complexity of the geological structure of Kazakhstan is due to the participation of various rock complexes. The major ore deposits were formed in the Middle and Late Paleozoic, whereas the Early Paleozoic deposits are few. Many of the ore deposits, especially those formed in the post-collisional stage, are associated with the granitoid intrusion”

To Field sampling section, there horizons are described, but further the authors mention first, second and third layers -in this case it should mention the soil horizon to which they refer to.

The terminology soil profile layers/horizons were clarified in the field sampling section.

At Laboratory analyses you should describe the digestion methods, as well as mention the reference materials used for analysis validation and the water type used for sample dilutions. Some references can be added.

Was added: “ultrapure reagents were used for all analyzes and deionized water for dilutions”

The analyzes were carried out according to the methodology mentioned in the literature list (below)

1. Methodological recommendations for conducting field and laboratory studies of soils and plants in the control of environmental pollution by metals. Moscow, Publishing house: Hidrometeoizdat, 1981, 107 p.
2. Methodological guidelines for the determination of heavy metals in soils of farmland and crop production. Moscow, Gosagroprom USSR, 1989, 62 p.

An ISO method has been added regarding the use of aqua regia in the determination of total content of studied metals in soil samples

ISO 11466. International Organization for Standardization; , Geneva, Switzerland: 1995. Soil Quality – Extraction of Trace Elements Soluble in Aqua Regia.

Explain the mention of "t" beside chemical symbols from Table 1, as well the different notation from Table 2  as "tot"/"mob". Make a difference between these notations and use only one.

t means total, that is, oversight has been highlighted in table 1 on tot

For soil contamination assessment, the authors may use one or more geochemical indices to evidence the grade or the source of contamination/pollution. The part of "spatial distribution" from the title was not evidenced in the study.

The assumption of the research was to demonstrate the differentiation of the soil contamination with heavy metals. As the soil pollution levels were below the limits except for cadmium, no spatial variation was demonstrated, even though the sampling plan was in line with the spatial variation between cultivated and non-cultivated land. It should be noted that the sampling plan also concerned the spatial differentiation of soil salinity and in this sense, the title corresponds to the obtained results.

 

Round 2

Reviewer 3 Report

Dear authors,

I was expected that the new version of the manuscript to be carefully checked for mistyping, page set up and references list according to the journal requirements.

 A part of these can be seen at: line 132; line 182 Cl-;  lines 228,231: word "za";line 297, correct the order;line 308 Cl-; line 339 Table 2, "tot" as subscribed; lines 367, 374, 367 as well for subscribe function.

The symbol for total or mobile form of the elements should be mention in the manuscript before to be used.

The Introduction section presents the context of salinization, but the part of toxicity of the metals are not integrated; this can be extracted from the section 4.2. Soil contamination with heavy metals.

Line 98- the title of Fig 1 present cultivated and non-cultivated soils; non-cultivated soils are arable or pasture (or any other land use category)?

Line 109 - the indicated link for climatic data is missing from the References {Title of Site. Available online: URL (accessed on Day Month Year)}

Line 118- which types of rocks are part of geological structure of the area?

Line 171 - there is a sign " at the end of new introduced sentence. Here, the authors should mention the depth of each sample collected from the soil profile.

Line 180 - "laboratory analyses" should be replaced with "materials and methods"

Line 184- describe Tiurin method and add reference;

Line 187 - describe colorimetric methods for each anion and add references.

Line 202 - before to use a shortcut,  the entire name should be written - MEPRK and EU.

Line 547- references.

Line 588- references.

For the increase/decrease of total of mobile form of the studied element for different soil type, the authors should give an geochemical explanation. They only compare the studied  soil types and makes an inventory of increasing/decreasing without a correlation with physico-chemical parameters of soils and the bedrock from the region.

The journal requirement is "References must be numbered in order of appearance in the text (including table captions and figure legends) and listed individually at the end of the manuscript." As well, the references list should be check and written as indicated in the " Instructions for Authors".

From my previous review, I am still not agree with authors explanations about "heavy metals" term and "spatial distribution" from the manuscript title.

The definition given by the authors is out of the context of present work, because they do not refers to  "elements that are used in industry and are toxic to humans or the environment at the same time." For this reason, I suggest  the following papers to clarify the terminology: https://doi.org/10.1007/s11631-021-00468-0  https://doi.org/10.1351/pac200274050793

The sampling plan is not enough  if there is no discussion about spatial extended or no presence of a distribution map based on GIS applications. Therefore I have to keep my first decision.

Kind regards and good luck with the paper!

 

 

Author Response

Dear Reviewer

Thank you very much for your comments. Below you will find our responses. As far as the last two comments, please allow us to stick to our opinion on the issue raised.

Thank you very much and best regards,

Authors

------------------------------------------------

 A part of these can be seen at: line 132; line 182 Cl-;  lines 228,231: word "za";line 297, correct the order;line 308 Cl-; line 339 Table 2, "tot" as subscribed; lines 367, 374, 367 as well for subscribe function.

was changed

The symbol for total or mobile form of the elements should be mention in the manuscript before to be used.

was added

The Introduction section presents the context of salinization, but the part of toxicity of the metals are not integrated; this can be extracted from the section 4.2. Soil contamination with heavy metals.

Line 98- the title of Fig 1 present cultivated and non-cultivated soils; non-cultivated soils are arable or pasture (or any other land use category)?

'Un-cultivated' means that the area was primarily cultivated in the past but is now abandoned, mainly due to the high secondary salinity of the soil.

 The detailed description was added in section 2.2. "Abandoned fields are characterized by a typical and recognizable vegetation succession, starting with the recovery of annual and multiyear herbaceous species, perennial woody species such as shrubs (e.g., Tamarix spp.) and some trees".

Line 109 - the indicated link for climatic data is missing from the References {Title of Site. Available online: URL (accessed on Day Month Year)}

Was added to the Reference

RSE «KAZHYDROMET» MINISTRY OF ECOLOGY, GEOLOGY AND NATURAL RESOURCES OF THE REPUBLIC OF KAZAKHSTAN. Available from: https:// www. kazhydromet.kz/en/klimat/kyzylorda [Accessed 17.03.2022].

Line 118- which types of rocks are part of the geological structure of the area?

The area is agricultural, and, to our knowledge, there is no precise geology setting of the area in which the research was carried out. As mentioned in the text, the rocks are various, and the only available geological data are on a large scale covering the whole of southern Kazakhstan. However, we added more detailed information:

From the southwest of the Kazakhstan- Central Asian territory, a significant depression appeared, accumulated gypsiferous lagoon and purely continental red-carbonate sandy-clayey sediments (Baibatscha, 2016).

Line 171 - there is a sign " at the end of new introduced sentence. Here, the authors should mention the depth of each sample collected from the soil profile.

Added: Soil samples were taken from the middle level of each of the three determined levels of soil profiles.

Line 180 - "laboratory analyses" should be replaced with "materials and methods"

The main section no 2 is "Study sites, materials and methods" and has been divided into subsections, one of which is a description of laboratory methods. In our opinion, such a division is more precise and more logical.

Line 184- describe Tiurin method and add Reference;

Turin's method of determining organic carbon in the soil gives results practically identical to the results of the dry combustion method. The procedure should be well known to all soil specialists. In our study, since the paper is not a methodical paper, in our opinion, there is no need to describe in detail this method, as well as other classical techniques used by soil scientists. We have added a reference Aleksandrova and Naidenova, 1976. This article details this method as below:

The Turin's titrimetric (classical) method is a wet combustion method, where SOM is oxidized by 0.2 M potassium dichromate solution with sulphuric acid and heated at boiling point for precisely 5 min. The oxidation reaction of organic carbon with a chromium mixture proceeds according to the equation: 2K2Cr2O7 + 8H2SO4 + 3C (organic carbon) = 2Cr2(SO4)3 + 2K2SO4 + 8H2O + 3CO2.  After oxidation, excess dichromate is determined by titration with ammonium ferrous sulphate FeSO4(NH4)2SO4 (Mohr's salt solution) and SOM calculated by multiplying the SOC content by the alteration factor f =1.724 (Aleksandrova and Naidenova 1976).

Aleksandrova, L.N. and Naidenova, O.A. (1976) Laboratory Practice in Soil Science;Kolos (in Russian):

Line 187 - describe colorimetric methods for each anion and add references.

The citation was added  to the sentence: All analyses were performed at the laboratory of the Kazakh Research Institute of Soil Science and Agrochemistry according to the standard analytical procedures recommended by the Ministry of Environment in Kazakhstan (Arinushkina <1962)

Arinushkina, E. V.  Handbook on the Chemical Analysis of Soils (Mosk. Gos. Univ., Moscow, 1962 [in Russian]

Line 202 - before to use a shortcut,  the entire name should be written - MEPRK and EU.

These are the official abbreviations for the European Union and the Ministry of Environmental Protection of Kazakhstan. The entire name of MEPRK is also visible in references,

1. MEPRK (Ministry of Environmental Protection of the Republic of Kazakhstan), 2004. The norms of maximum permissible concentrations of hazardous substances, organisms and other biological substances polluting the soil. Consignment Order No. 99 of the Ministry of Health of the Republic of Kazakhstan and No. 21 of the MEPRK, Astana, Kazakhstan.

For the increase/decrease of total of mobile form of the studied element for different soil type, the authors should give an geochemical explanation. They only compare the studied  soil types and makes an inventory of increasing/decreasing without a correlation with physico-chemical parameters of soils and the bedrock from the region.

In our opinion, the discussion related to the geochemical background does not contribute essential elements to the main goal of the work.

The journal requirement is "References must be numbered in order of appearance in the text (including table captions and figure legends) and listed individually at the end of the manuscript."

As well, the references list should be check and written as indicated in the " Instructions for Authors".

changed

From my previous review, I am still not agree with authors explanations about "heavy metals" term and "spatial distribution" from the manuscript title.

The definition given by the authors is out of the context of present work, because they do not refers to  "elements that are used in industry and are toxic to humans or the environment at the same time." For this reason, I suggest  the following papers to clarify the terminology: https://doi.org/10.1007/s11631-021-00468-0  https://doi.org/10.1351/pac200274050793

It is entirely legitimate and well-established, both from the chemical and toxicological point of view, to use the terminology of heavy metals concerning the examined elements. There is also a wealth of literature to prove this.

The sampling plan is not enough if there is no discussion about spatial extended or no presence of a distribution map based on GIS applications. Therefore I have to keep my first decision.

The sampling plan was dictated, among other things, by the monitoring plan implemented under the project financed by the Ministry of Agriculture. The presented map of sampling points (Fig. 1) was made in the GIS system, i.e., each point is defined by geograph