Geochemical Factors as a Tool for Distinguishing Geogenic from Anthropogenic Sources of Potentially Toxic Elements in the Soil

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Presented manuscript by Brenko et al. Is focused on potentially toxic elements (PTE) in the soil in Kalinovac district in Croatia. This study shows results of three different methods conventionally used for evaluation of the degree of soil pollution. Namely enrichment factor (EF), geoaccumulation index (Igeo) and contamination factor (CF), besides spatial distribution, results were also used to distinguish between two potential origins of pollution, either geogenic or anthropogenic.

The overall impression from the manuscript is good, the manuscript is very well structured, and written in high English proficiency level with good styling, which makes it a very reader-friendly.

I would suggest several things to improve, please see below:

Generally, you used three different methods for evaluation of the pollution level. However, all these methods are extremely sensitive to parameters used and the chosen normalization elements. Usually, you would normalize to some element that is unaffected by environmental changes and is a natural part of the lithogenic background composition, and is present in the most prevailing granulometric fraction, such as Al, SI, or Ti. However, you have chosen Fe, which is generally recommended to be used only in a sedimentary or soil environments with changes of a redox potential which can led to release of risk elements bound to the Fe-oxyhydroxides. I was not sure from you description of the study area, starting on the line 87 to line 102, from which part of this terraces you have obtain your samples. Were all the samples obtained from there older terraces or from the floodplain/wetland? Please add this information.

Line 116 – You drilled 5 holes at each spot, and then how were the samples processed? As a batch sample so you have five samples per sampling spot, or did you distinguish the top and the bottom layers and measured the concentration separately? Or did you put the all five samples together?

Line 117 – Regarding removal of the 10cm of topsoil - Could this lead to lose of some information about atmospheric deposition of your study elements, or what if the results of an agricultural treatment of soil had already migrated downwards?

Line 202 – We usually do not report that we measured zero concentration but we say that few samples were below the detection limit, as is shown in table in SI, for example in Cd values for sample K-HG 7-5 says b.d.l., or you just show the range of min and max values shown in the last four lines. In this table, could you please add the units under each element? Like Al units and clay and sand units are not obvious. And I believe “maksimum” is a typo.

Line 240, Figure 2 – I was a bit confused what figure is a,b ,d because the legend itself is very small, could you please add some marks to distinguishing the A, B, C and D part of the Figures?

Line 246 - Regarding the risk element concentrations, does your country have something like legislation limits for elements concentrations in soils (or maybe you can use some international environmental limits)? That would support your conclusions about the pollution level. In ArcGis, you can define several categories of pollution level based on coloring of the categories, such as you have in the distribution map, where the red color implies some bad news, but then you can find that for example up to 30 mg/kg of Cu is still considered to be “normal, natural” values.

Line 260 – Did you do also some granulometric analysis? Positive correlation of risk elements with Al or with Si can sometimes reflect their affinity towards the clay or sand parts of the sample matrix.

Line 400 - Discussion and conclusions are a bit too similar and repetitive, could you improve the conclusion part please? What method of evaluation you found to be most descriptive and recommendable for local use in this part of Croatia?

Author Response

Dear Reviewer, thank you for your time and useful comments. They have greatly improved the overall quality of the manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

By determining the concentration and distribution of PTEs in the agricultural soils of Podravina, distinguishing between geological and anthropogenic sources, and determining the correlation between the PTEs analyzed in the soils, the paper provides a basis for the effective development of measures to reduce the metal inputs and to protect the agricultural soils from the long-term accumulation of PTEs. Overall, the article is well structured, logically rigorous, and the evaluation results are objective and reasonable, but there are still areas that need to be improved and supplemented, and specific suggestions for revision are as follows.

1. The introductory section needs more references, such as“Nowadays, with the accelerated progress of technology and society, the components of the environment, such as soil and groundwater, can be endangered. Certain toxic substances can cause serious problems if they enter the environment, especially the soil. Potentially toxic elements (PTEs) are among the substances that can potentially endanger the soil."

2. The authors refer to Halamić and Miko's study on PTEs in Podravina in the introduction, please elaborate on the similarities and differences between the two articles and explain the significance of the research in this paper?

3. In section 3.1 Soil Sampling, the authors state that the depth of sampling is 10-30 cm, what is the specific depth of sampling for each sampling site, and if the depth of sampling is not consistent, is the data reliable?

4. It is recommended that the high value areas of Figures 2-7 be set to dark colors and the low value areas to light colors.

5. Figure 7 shows that only the western part of the study area is characterized by high Zn concentrations, while Halamić and Miko found elevated Zn concentrations in the Podravina area, and asked the authors to provide an explanation.

6. In the statistical analysis section of 4.3, the authors do not indicate where the Fe, pH, Clay, Silt, Sand, TC, Si, Al, CEC data were obtained.

7. Figure 9 is not aesthetically pleasing.

8. In the discussion section of 5.1, it is recommended that authors indicate the basis for judging the origin of each PTEs.

9. In the discussion section of 5.1, "The spatial distribution of Cu (Figure 3) corresponds to the distribution of Cd and can possibly be related to the use of agrochemicals" ,it should read Figure 4.In addition, Cu is more concentrated in the northern, western and central parts of the study area, while Cd is more concentrated in only a small part of the western and central parts of the study area; is it reasonable that the spatial distribution of Cu corresponds to the spatial distribution of Cd?

10. In the summary section of 6, the analysis of Zn is not covered and it is recommended that the authors add it.

 

Author Response

Dear Reviewer, thank you for your time and useful comments. They have greatly improved the overall quality of the manuscript.

Author Response File: Author Response.pdf