Evaluation of Environmental Contamination by Toxic Elements in Agricultural Soils and Their Health Risks in the City of Arequipa, Peru

Round 1

Reviewer 1 Report

The Manuscript entitled “Ecological risk assessment of heavy metals in agricultural soils in the countryside of Arequipa, Peru” is within the aim and copes of Sustainability journal. The manuscript investigates the soil pollution implications on the environment and human health risk assessment based on the element concentrations in soil samples from 6 districts in Arequipa in Peru.

The manuscript needs major revision before the publishing in Sustainability journal. In the following text are given main comments and specific comments to each subtitle in the manuscript.

First of all, the term “heavy metals” should be replaced with “potentially toxic elements”, because the term heavy metal is not proper for all investigated elements in the manuscript. Also, the ecological risk is not a proper term for describing enrichment factor (EF), geoaccumulation index (Igeo) and integrated ecological risk index (RI). The more correct is environmental implication formulas or environmental pollution assessment.

Abstract: The abstract can be rewritten to be more concise without details about the calculation of some environmental implications or some name of some specific details of results comparison which will be given in detail in the main text (e.g. “compared with the quality standards for agricultural soils (D.S. 011-2017-MINAM)”), and 17 toxic elements which were investigated should be listed in the abstract. Also, somewhere authors use the term “heavy metal” and somewhere toxic element. They should choose one term and I suggest potentially toxic elements or toxic elements.

Introduction:

The introduction should be improved. The description of this topic should be more detailed. Some nowadays scientific about the same topic papers should be cited (eg. Milićević et al., 2018a, 2018b, 2021 and many other scientific papers published on this topic investigating the environmental implications and human health risk assessment based on the potentially toxic elements in the different soils)

Milićević, Т., Aničić Urošević, М., Relić, D., Jovanović, G., Nikolić, D., Vergel, K., Popović, A. Environmental pollution influence to soil-plant-air system in organic vineyard: bioavailability and biomonitoring, Environmental Science and Pollution Research, 2021, 28, 3361–3374;

Milićević T., Aničić Urošević M., Relić D., Vuković G., Škrivanj S., Popović A., Integrated approach to environmental pollution investigation – spatial and temporal patterns of potentially toxic elements and magnetic particles in vineyard through entire grapevine season, Ecotoxicology and Environmental Safety, 2018b, 163, 245–254.

Milićević T., Aničić Urošević M., Relić D., Vuković G., Škrivanj S., Popović A., Bioavailability of potentially toxic elements in soil−grapevine (leaf, skin, pulp and seed) system and environmental and health risk assessment, Science of the Total Environment, 2018a, 626, 528–545.

Methodology:

2.1 Description of the study area

The coordinates of the sampling sites should be given. Also, the figure 1 can be improved to be more visible where are the investigated locations comparing to the World and country maps.

2.2 Method used in the analysis of samples

Again the elements are named metals and in the list of elements is As which is metalloid (it is not metal, especially not heavy). Change the name metals to potentially toxic elements, toxic elements or chemical elements.

2.3 Toxicity evaluation

Table 1: Translate the unit of RfD in English and in the proper way (not mg.Kg-1.dia-1; day not dia and -1 should be in superscript or  mg/kg×day)

It is not necessary to have subtitles 2.4, 2.5, with one sentence in the subtitle. All these subtitles should be one and can be named Human health risk assessment. Subtitles 2.6 and 2.7 can be one subtitled which can be named Environmental implication formulas or Environmental pollution assessment.

3. Results

Table 3 and Table 4. The results should be circled on two significant digits.

Discussion: This section should be improved by discussing the obtained results in more detail and by comparing them to other published studies.

The Conclusion should be improved. The main aim of the study should be mentioned at the beginning and then the main results and conclusion with suggesting the benefits of this type of study.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This is a valuable work investigating the ecological risk of heavy metals in agricultural soils in the countryside of Arequipa in Peru, which was specially explored from a spatial perspective. This work is helpful for soil healthy assessment, and it can also provide references for mitigating and preventing soil pollution in croplands. The manuscript can be refined in following ways.

1) The novelty of the paper should be more clearly stated. In the introduction part, authors focused mentioning rarity of the study, but they should also more clearly point out the novelty and significance of the study.

2) The authors need provide the full name of the abbreviations in the note of the figures and tables. As you known, the readers generally get the full story from the figures and tables.

3) The discussion was kind of simple, authors could say a bit more about the possible improvements and shortcomings of this study. This can enhance the reliability of the paper.

4) The conclusion should be improved. Authors should summarize the major findings or not just some simple words.

6) The 2.5 and 2.6 should be merged into 2.4, which makes the structure clear. In the Methodology, the authors should tell the readers why only choose the seven sites.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

I read the manuscript interestingly and the authors have worked on very important question. However, there are still some issues that have to be addressed by the authors before considering the manuscript for publication. Authors have serious concept problems; which are observed in relation to the different “risk” indices used; heavy metal definition criteria; “content” and “level” vs concentration; etc. My comments are detailed below.

The English language should be improved to ensure that an international audience can clearly understand your text. There are some grammatical errors and the writing is not fluent in manuscript.

In the “Title”, “Abstract”, and throughout the manuscript, authors should review the use of the terms “heavy metal” and “metal”. For example, arsenic is not a heavy metal, or even a metal; arsenic is a metalloid. Authors can use the term “metal(loid)s” to represent both metals and metalloids. When authors want to refer specifically to heavy metals, and also want to include elements such as arsenic, then they should write “heavy metals and metalloids”.

The “enrichment factor”, “geoaccumulation index” and “integrated ecological risk index” are of interest, but chemistry is generally only part of the triad used to assess risk in soil or sediment. No biology is invoked here. Chemical levels are not risk assessments – they are hazard assessments – risk is a function of hazard and exposure. While looking at total concentration elements is part of that overall assessment, the authors do not really engage in what their data mean in terms of the concepts of risk (and risk assessment or risk management). Throughout the manuscript, authors should review the use of the term “risk”.

There is a big problem of the sample representativeness. The number of samples is too low (7) and then the number of samples in which they could compare results is too reduced. Do the authors really consider that this short number of samples would allow evaluating the hazard in the agricultural fields of six different districts? From my point of view this scarce design does not allow to fulfil the objectives of the manuscript.

Authors should rephrase keywords. Do not use words or terms in the title as keywords: the function of keywords is to supplement the information given in the title. Words in the title are automatically included in indexes, and keywords serve as additional pointers.

About study area, this sub-section needs more information. Please provide information on climatic parameters, namely precipitation and temperature. It should be provided a map with geological information and the location of the sampling points.

The location on the map of Peru should be provided. In addition, all maps (and satellite images) must indicate scale and orientation.

Authors should present the coordinates of the sampling sites.

Readers need more information about the sampling. For example: What was the area of each sampling point? How many subsamples were collected at each site?

The “2.2 Method used in the analysis of samples” section should also give more details about Quality Assurance and Quality Control. Authors should indicate the obtained accuracy values. Were used reference materials? If so, these should be listed. It would be also interesting to provide the reader with limits of detection/determination of analysed elements.

In addition, the “Materials and methods” section needs a subsection on statistical tests. Although the use of statistics in the study is obvious, the statistical methods should be clearly described in appropriate sub-section.

Are normally distributed the metal(loid)s concentration in the soil? Usually it is very difficult to find a normal distribution, because metal and metalloid distributions are polymodal and highly right skewed. For this reason, I’ afraid that the selection of the Pearson test is not right.

Line 81: The authors refer to “Total metals”. However, they used a digestion method with nitric acid and hydrochloric acid. Therefore, no hydrofluoric acid was used, so the silicates were not dissolved and therefore the measured concentrations are not total. They are only pseudo-totals. This is the EPA Method 3051. In fact, if the authors read carefully the description of the method, is mentioned the following: “Since this method is not intended to accomplish total decomposition of the sample, the extracted analyte concentrations may not reflect the total content in the sample.” Therefore, if the authors intended to obtain the total concentrations, the samples digestion method was poorly chosen.

Overall, as presented, the ideas, results and discussion provided in the manuscript are not entirely original or attractive, and in particular the results do not seem to advance in the direction the authors imply (besides, there are alternative explanations for most of the relationships found). The research is purely descriptive and, although I do not see that as a problem per se what-so-ever, it provides no solid evidence to support the discussion on ecological risk.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors revised manuscript within the comments and in this form I suggest it for publication.

Reviewer 2 Report