Spatial Distribution and Soil-to-Fungus Transfer of Cadmium, Copper, and Zinc in Urban and Rural Green Spaces of Leicestershire, UK

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Hereby I give my review of the revised version of the manuscript which is now entitled „Spatial distribution and soil-to-fungus transfer of cadmium, copper, and zinc in urban and rural green spaces of Leicestershire, UK “ (Environments 2026, 13, x)  co-authored by Jagdev et al.

The manuscript treats distribution of three selected ‘heavy metals’ in soil and their transfer to various tissues of mushrooms from urban and rural areas of Leicestershire in the UK. The tested soil samples as well as mushroom samples were taken according to the usual procedures. The analyses of the selected elements (Cd, Cu, and Zn) were carried out by means of ICP-MS in the digestates prepared by microwave-assisted wet digestion procedures: soil samples were (partially) digested with aqua regia, while digestion procedures of the mushroom consisted of mineralisation of the samples by employing HNO₃―H₂O₂ mixture. The soil samples were also characterised by various physicochemical methods (such as pH, EC, moisture content, etc.). The results were treated by various statistical methods. Soil-to-mushroom transfer was assessed by bioconcentration factor (BCF). Assessment of dietary exposure safety was done by EWI-estimated weakly intake.

I consider that the topic of this research is sound and the research was well organised and the experiments were well done. However, there are some questions and objections on it.

1.) First of all, why the authors have analysed only these three elements (Cd, Cu, and Zn) and not the other toxic elements (Pb, As, Ni) that are – as the authors state in the rows 1171/1172 – also relevant for risk assessment. Especially if they work with using ICP-MS. (Of course, this technique is not so appropriate for analysis of Hg, that is why I have not mentioned it in the previous sentence.)

2.) I find the text too long and extensive. Moreover, some parts are redundant. For instance, the first paragraph of the subsection 3.1. was also written in the rows 351-357.

Then, the section 4.10. – in fact – represents conclusions of the work. So, the subsection 4.10. should be combined with section 5.

3.) The part of the section 3. Results, namely rows 503-522 would belong to the Experimental section.

4.) I feel free to suggest authors to check if merging of the sections Results and Discussion would make the text easier to follow. (According to the Instruction-to-authors of this journal, such an approach would be acceptable.)

5.) Displaying of the results (especially of the mass fraction, i.e. concentration, values of the analysed elements) should be thoroughly revised! Namely, it is not important the number of decimal digits, but the number of significant digits. The results of such analyses should be displayed in three or maximum four significant digits. So, for examples (taken from Table 1) 48.121 should be presented as 48.1, while 488.703 should become 489. Or instead of 9.580 should stand 9.58. The values below 1 are well presented: with three decimal digits after the decimal point. So, the presentation of the values should be revised throughout the text, both in tables and in the body of the text.

6.) Figure 1 should be technically improved; I am afraid. It seems to be strengthened. Also, caption-to-Figure 1 should stand under the figure.

7.) The description of the mushroom samples preparation should be revised:

     a) more details on the MW-assisted digestion procedure should be given: make of the  MW-oven, duration of procedure,

     b) The description of filtration (rows 304-306 is not clear. Were the digestates two times filtered?

8.) In the row 346 the word ‘calculation’ should be changed with ‘expression’.

9.) In some places in the text there is the typo: mg kg−1, instead of mg kg⁻¹.

10.) The heads of the tables should be improved in a manner that measuring units are
(mg kg⁻¹) are written in a row above the data.

Author Response

Reviewer 1

 

Hereby I give my review of the revised version of the manuscript which is now entitled „Spatial distribution and soil-to-fungus transfer of cadmium, copper, and zinc in urban and rural green spaces of Leicestershire, UK “ (Environments 2026, 13, x)  co-authored by Jagdev et al.

The manuscript treats distribution of three selected ‘heavy metals’ in soil and their transfer to various tissues of mushrooms from urban and rural areas of Leicestershire in the UK. The tested soil samples as well as mushroom samples were taken according to the usual procedures. The analyses of the selected elements (Cd, Cu, and Zn) were carried out by means of ICP-MS in the digestates prepared by microwave-assisted wet digestion procedures: soil samples were (partially) digested with aqua regia, while digestion procedures of the mushroom consisted of mineralisation of the samples by employing HNO₃―H₂O₂ mixture. The soil samples were also characterised by various physicochemical methods (such as pH, EC, moisture content, etc.). The results were treated by various statistical methods. Soil-to-mushroom transfer was assessed by bioconcentration factor (BCF). Assessment of dietary exposure safety was done by EWI-estimated weakly intake.

I consider that the topic of this research is sound and the research was well organised and the experiments were well done. However, there are some questions and objections on it.

1.) First of all, why the authors have analysed only these three elements (Cd, Cu, and Zn) and not the other toxic elements (Pb, As, Ni) that are – as the authors state in the rows 1171/1172 – also relevant for risk assessment. Especially if they work with using ICP-MS. (Of course, this technique is not so appropriate for analysis of Hg, that is why I have not mentioned it in the previous sentence.)

We thank the reviewer for this important comment. We agree that Pb, As and Ni are environmentally and toxicologically relevant and that ICP-MS enables multi-element determination. The present manuscript, however, was deliberately restricted to Cd, Cu and Zn to preserve a focused soil–fungus transfer framework. These three elements were selected because they combine toxicological relevance, contrasting biological roles and sufficient paired topsoil–mushroom coverage for spatial, species-level and apparent transfer interpretation. We have now expanded Section 2.1 to clarify that the study derives from a broader PhD environmental biomonitoring programme covering eleven metal(loid)s, and that Pb, As and Ni were outside the scope of the present focused analysis because their interpretation would require additional regulatory, toxicological and element-specific frameworks.

2.) I find the text too long and extensive. Moreover, some parts are redundant. For instance, the first paragraph of the subsection 3.1. was also written in the rows 351-357.

Then, the section 4.10. – in fact – represents conclusions of the work. So, the subsection 4.10. should be combined with section 5.

We agree with the reviewer. Section 4.10 has been removed as a separate subsection because it largely represented an interpretative conclusion. Its key message has been incorporated into the final paragraph of the Conclusions, where it now summarises the broader value and interpretative limits of paired topsoil–wild mushroom datasets. We have also revised the structure of the Results section by moving methodological and dataset-construction information to the Materials and Methods section, including the description of the retained mushroom analytical subsets and the handling of additional Bradgate Park tissue-specific records. As a result, the Results section is now more concise and focuses more clearly on the reported analytical findings.

3.) The part of the section 3. Results, namely rows 503-522 would belong to the Experimental section.

We agree. The text describing the retained mushroom analytical subsets, sampling structure and exclusion of additional Bradgate Park tissue-specific records has been moved from the Results to the Materials and Methods, where it more appropriately describes dataset construction and analytical grouping. The Results section now only summarises the final retained dataset and refers to the corresponding tables. The relevant text has been moved from Section 3.1 to the Materials and Methods, and Section 3.1 has been shortened accordingly.

4.) I feel free to suggest authors to check if merging of the sections Results and Discussion would make the text easier to follow. (According to the Instruction-to-authors of this journal, such an approach would be acceptable.)

We thank the reviewer for this helpful suggestion. We considered merging the Results and Discussion. However, because the manuscript includes several interconnected but distinct levels of analysis — topsoil concentrations, mushroom concentrations, species-specific accumulation, tissue-specific distribution, apparent BCFs and dietary screening — we believe that keeping Results and Discussion as separate sections improves traceability and allows readers to distinguish clearly between statistical findings and interpretation. Nevertheless, we have revised the manuscript to reduce repetition between the two sections and to improve cross-referencing.

5.) Displaying of the results (especially of the mass fraction, i.e. concentration, values of the analysed elements) should be thoroughly revised! Namely, it is not important the number of decimal digits, but the number of significant digits. The results of such analyses should be displayed in three or maximum four significant digits. So, for examples (taken from Table 1) 48.121 should be presented as 48.1, while 488.703 should become 489. Or instead of 9.580 should stand 9.58. The values below 1 are well presented: with three decimal digits after the decimal point. So, the presentation of the values should be revised throughout the text, both in tables and in the body of the text.

We thank the reviewer for this important observation and agree that numerical presentation should avoid implying unwarranted analytical precision. We have carefully checked the numerical formatting throughout the manuscript. However, after consideration, we have retained three decimal places for concentration values in the main statistical tables because these values are generated from the same censored-data-aware statistical workflow used throughout the study, including Kaplan–Meier/NADA-based summaries, confidence intervals, interquartile ranges and BCF calculations. Maintaining a consistent number of decimal places across tables improves traceability between descriptive statistics, censored-data treatment, supplementary datasets and derived transfer estimates.

We emphasise that these decimal places are not intended to imply greater instrumental precision than justified analytically, but to preserve internal consistency, reproducibility and comparability across matrices, concentration ranges and derived calculations. To address the reviewer’s concern, we have reviewed the body text to ensure that numerical interpretation remains appropriately cautious and that the tables clearly indicate the analytical units and statistical nature of the reported values.

The numerical presentation has been checked for consistency. Concentration values in the statistical tables have been retained with three decimal places to preserve traceability with the censored-data statistical workflow, confidence intervals, IQRs and BCF calculations, while the text has been reviewed to avoid overinterpretation of numerical precision.

6.) Figure 1 should be technically improved; I am afraid. It seems to be strengthened. Also, caption-to-Figure 1 should stand under the figure.

Figure 1 has been replaced by a technically improved version with clearer resolution, improved readability and more appropriate visual balance. The figure caption has also been placed below the figure, following journal formatting requirements.

Manuscript change: Figure 1 has been improved and the caption has been positioned below the figure.

7.) The description of the mushroom samples preparation should be revised:

1.    a) more details on the MW-assisted digestion procedure should be given: make of the  MW-oven, duration of procedure,
2.    b) The description of filtration (rows 304-306 is not clear. Were the digestates two times filtered?

We thank the reviewer for this helpful comment. We have revised the mushroom mineralisation section to avoid ambiguity. Mushroom samples were not mineralised by microwave-assisted digestion. Instead, they were digested using a conventional closed-vessel acid mineralisation procedure in pre-cleaned Teflon digestion vessels, using concentrated nitric acid and hydrogen peroxide. This has now been explicitly stated in the revised manuscript.

 

We have also clarified the digestion and filtration sequence. Briefly, approximately 0.500 g of dry homogenised mushroom powder was digested with concentrated HNO₃ and H₂O₂ in Teflon digestion vessels. The samples were left to pre-digest at room temperature and were then heated at approximately 96 °C for 12 h. After cooling, the digestates were filtered through Whatman™ Grade 42 ashless quantitative filter paper and made up to 25 mL with Milli-Q ultrapure water. A second filtration step through a 0.45 µm PTFE syringe filter was performed immediately before ICP-MS analysis as a precautionary step to remove any residual fine particulate material and protect the sample introduction system. Therefore, the digestates were filtered twice, but for different purposes: first for post-digestion clarification and volume preparation, and subsequently for instrumental protection before ICP-MS measurement.

8.) In the row 346 the word ‘calculation’ should be changed with ‘expression’.

Done

9.) In some places in the text there is the typo: mg kg−1, instead of mg kg⁻¹.

Done

10.) The heads of the tables should be improved in a manner that measuring units are
(mg kg⁻¹) are written in a row above the data.

Table headings have been revised so that measurement units are clearly indicated in the table header rather than only in the table footnote. This improves readability and reduces ambiguity, especially in tables containing dry-weight mushroom concentrations and topsoil concentrations.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear author,

The paper entitled “Spatial distribution and soil-to-fungus transfer of cadmium, copper, and zinc in urban and rural green spaces of Leicester-shire, UK” is very interesting to the reader, containing valuable information on bioaccumulation of contaminants (heavy metals cadmium, copper and zinc) in topsoil and wild mushrooms samples from public green spaces in Leicester-shire, UK. However, some points in the methods-session need to be taken into consideration:

Please explain:

• Do authors have data on the particle size of the “sieved through a 2 mm stainless-steel mesh” of topsoil samples? If so, they should include this data to the text
• Why did authors use aqua regia for the digestion of the topsoil? Apparently, the efficiency of such digestion is not suitable to give the total metal concentration (filtration afterwards is needed). Please explain. Perhaps, the common way to become clear solution after digestion is the use of aqua regia and addition of hydrofluoric acid. Authors should point this in their MS
• On the contrary, I believe that the digestion of mushroom samples using a solution of nitric acid and hydrogen peroxide leads to clear solutions and the following double filtration of samples is done only for precautionary reasons. Therefore, in this case, we have total metal concentrations determination. Please include a phrase in the MS
• The authors should write a paragraph about exactly how they managed the glass and plastic labware used for the analysis

In summary, I suggest the reviewed paper in the Journal “Environments” after author’s consideration of the above mentioned comment.

Author Response

Reviewer 2

Dear author,

The paper entitled “Spatial distribution and soil-to-fungus transfer of cadmium, copper, and zinc in urban and rural green spaces of Leicester-shire, UK” is very interesting to the reader, containing valuable information on bioaccumulation of contaminants (heavy metals cadmium, copper and zinc) in topsoil and wild mushrooms samples from public green spaces in Leicester-shire, UK. However, some points in the methods-session need to be taken into consideration:

Please explain:

• Do authors have data on the particle size of the “sieved through a 2 mm stainless-steel mesh” of topsoil samples? If so, they should include this data to the text

We thank the reviewer for this comment. We have revised the Methods to clarify that the analysed topsoil material corresponded to the <2 mm fine-earth fraction. Material retained on the 2 mm stainless-steel sieve, including stones and coarse fragments, was discarded. We have also clarified that particle-size distribution within the <2 mm fraction was characterised separately as soil texture using the Bouyoucos hydrometer method, as described in the soil physicochemical characterisation section.

• Why did authors use aqua regia for the digestion of the topsoil? Apparently, the efficiency of such digestion is not suitable to give the total metal concentration (filtration afterwards is needed). Please explain. Perhaps, the common way to become clear solution after digestion is the use of aqua regia and addition of hydrofluoric acid. Authors should point this in their MS

We agree with the reviewer and have revised the manuscript to clarify the analytical meaning of the topsoil digestion. The topsoil samples were digested using a microwave-assisted nitric acid–hydrochloric acid procedure to determine the environmentally relevant acid-extractable, or pseudo-total, Cd, Cu and Zn fraction in the <2 mm topsoil material. Hydrofluoric acid was not used because complete dissolution of refractory silicate minerals was not required for the objectives of this study, which focused on environmental distribution, mushroom accumulation and apparent soil-to-fungus transfer rather than full geochemical characterisation of the silicate lattice.

We have therefore clarified that the topsoil concentrations should not be interpreted as complete geochemical totals including silicate-bound residues. Filtration after digestion was performed to remove any remaining fine mineral residue prior to dilution and ICP-MS analysis. Importantly, analytical recovery for Cd, Cu and Zn in the soil certified reference material was satisfactory, supporting the suitability of the procedure for the three elements considered in this study.

• On the contrary, I believe that the digestion of mushroom samples using a solution of nitric acid and hydrogen peroxide leads to clear solutions and the following double filtration of samples is done only for precautionary reasons. Therefore, in this case, we have total metal concentrations determination. Please include a phrase in the MS

We agree with the reviewer. The mushroom matrix was digested using concentrated nitric acid and hydrogen peroxide in closed Teflon digestion vessels, which is appropriate for oxidation of the organic matrix and determination of total Cd, Cu and Zn concentrations in the digested mushroom material. The revised manuscript now clarifies that the second filtration through 0.45 µm PTFE syringe filters was performed only as a precautionary step before ICP-MS analysis, to protect the nebuliser and remove any residual fine particulates, rather than because incomplete digestion was expected.

• The authors should write a paragraph about exactly how they managed the glass and plastic labware used for the analysis

We thank the reviewer for this helpful suggestion. We have expanded the Quality Assurance and Quality Control section to describe the handling and cleaning of laboratory ware used for sampling, preparation, digestion, dilution and storage. The revised text now specifies the use of polypropylene materials where appropriate, the acid-washing procedure for reusable plasticware, Teflon digestion vessels and glassware when required, and the inclusion of procedural blanks to monitor possible contamination during sample preparation and digestion.

In summary, I suggest the reviewed paper in the Journal “Environments” after author’s consideration of the above mentioned comment.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Hereby I give my review of the revised version of the manuscript entitled „Spatial distribution and soil-to-fungus transfer of cadmium, copper, and zinc in urban and rural green spaces of Leicestershire, UK “ (Environments 2026, 13, x)  co-authored by Jagdev et al.

After a thorough reading of the authors' answers as well as the revised manuscript, my conclusions are as follows:

1) The manuscript has been notably improved and now is better than it was before in the sense of conciseness and clearness of the certain parts.

2) Even though the authors, in the Point 5 of their answers, have claimed that „The numerical presentation has been checked for consistency. Concentration values in the statistical tables have been retained with three decimal places to preserve traceability with the censored-data statistical workflow, confidence intervals, IQRs and BCF calculations, while the text has been reviewed to avoid overinterpretation of numerical precision.“, I can only state that I see that the numbers in the text remained the same, namely, expressed as they were before – with three decimal places. If we accept the reasons that authors have for displaying of the numbers with three decimal places in the table, I do not see why the numbers in the text have been left as they were.

Author Response

We thank the reviewer for this careful observation. We agree that, although three decimal places may be justified in the statistical tables to preserve traceability with the censored-data workflow, confidence intervals, IQRs and BCF calculations, the same level of numerical precision is not necessary in the running text. Therefore, we have revised the manuscript again and rounded the numerical values reported in the narrative text, generally to two decimal places, or expressed them qualitatively where appropriate.

This revision has been applied throughout the Abstract, Results and Discussion sections, including the descriptions of topsoil concentrations, mushroom concentrations, species-specific medians, tissue-specific ratios, apparent BCFs and dietary exposure estimates. The statistical tables have retained three decimal places for consistency with the underlying calculations and to preserve reproducibility and traceability. Analytical, regulatory, statistical and bibliographic values, such as p-values, certified reference material values and DOIs, have been retained with their appropriate original precision where necessary.

We believe that this revised presentation addresses the reviewer’s concern by avoiding an unnecessary impression of precision in the running text while maintaining full numerical transparency in the tables.