Towards Sustainable Air Quality in Coal-Heated Cities: A Case Study from Astana, Kazakhstan

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article is very interesting, well-articulated and well-reasoned as to why the issue was chosen. From the analysis of the text, the multidisciplinarity of the topic and its scientific importance is evident.

I recommend it for publication major revisions as reported below.

inserte reference relative to relation between pollution and 

• I suggest improving the quality of Figure 1. Specifically, the two figures on the left are only partially visible. Indicate clearly in the legend the different pat
• I suggest making the differentiation between the two colours clearer. Overall, it is visually unclear to the reader.
• The title could be more focused on the topic of the article. This can provide more information about the content of the article and will increase citations in the future.
• Correct the word Cladosporium in Figure 4.
• Check whether European Directive 2008/105/EC (2008) is really the latest legislation. I would suggest readingDirective 2024/3019, which appears to be the most recent.
• I suggest that the authors better articulate the conclusions section so that the reader can assimilate the key concepts.
• I suggest including this section “7. Study Limitations, Future Research” in the conclusions rather than as a separate paragraph.
• If you decide to use APA style, standardise your bibliography according to the journal's guidelines:

APAStyle
Mróz, A., Łukasik, J. M., Jagielska, K., & Pikuła, N. G. (2025). Creativity of Pre-Service Teachers in the Context of Education for Sustainable Development: Evidence from a Study Among Teacher Education Students in Poland. Sustainability, 17(20), 9116. https://doi.org/10.3390/su17209116

Sampling was carried out at a single site, which is acceptable, but this was not well described or characterised, and the representativeness of the site with respect to the city of Astana was not indicated (it should perhaps be calculated using a model).

 

The sampler used, a dichotomous sampler, separates fraction 2.5 (which approximates the end) from the remaining 10-2.5 (which approximates the coarse fraction).

 

 

 

At least for comparisons, the reference values should be presented as PM10 concentrations, but in the article (page 8), the values of 10-25 are erroneously compared with the WHO standard for PM10 (NB: there is no WHO standard for coarse PM).

 

The *introduction* indicates the size of PM in “diameter, d”, but since it is an inertial sampler (the dichotomous one), what they collected was separated according to aerodynamic diameter (Da), so this needs to be corrected.

 

In *Materials and methods*, the sampling period should be better described, and it should be explained if and how temporal representativeness was assessed. Why are the sampling durations in the four seasons not homogeneous? This needs to be justified.

In general, the figures in Table S1 do not add up if we compare the total days per season (which would have been better explained so as not to force the reader to count them) and the number of samples.

It is understandable that there are fewer samples than days (some have been discarded, but why? This needs to be explained), but more samples than days does not seem possible to me.

Figure 1 is unclear; the boxes should be labelled, and a caption should explain what is in the first, second and third boxes. The caption says “coal-fired power stations (CHPP-1 and CHPP-2)”, but they are so small in the right-hand part of the figure that I had to enlarge the image to find them. They should be better indicated and mentioned in the text regarding the representativeness of the site. They are only mentioned twice, without explaining their contribution in the results chapter.

*Results and discussion*: The dichotomous sampler takes two samples per day, but presenting the total number of samples without mentioning this (342 here, for 171 days) is misleading and suggests a coverage period twice as long.

Why is it not clearly stated (and I have to go and look it up) that sampling began in October 2021 and ended on 13 June 2023? Thus, the only full summer was that of 2022.

In this way, winter, with its higher average values, risks weighing too heavily (unless there is a clear explanation of the choice, which I cannot find here).

Paragraph 3.1 also mentions the Air Quality Index (AQI). Which one was used? AQI is a generic acronym that covers a range of different approaches and formulas: please specify, explain and provide bibliographical references. In the second paragraph of section 3.1, there is a casual shift from AQI to API (Air Pollution Index). Again, it is not clear what is being referred to.

What is the formula?  Specify, explain and provide bibliographical references. The same applies to these “GR criteria”.

Paragraph 3.3 and more generally in the introduction and conclusions. It does not seem clear to me. How the analyses and mass measurement of suspended particulate matter are linked to the characterisation of snow and rainwater

It is appropriate to add the analysis of deposits to the analysis of air quality, but the dynamics of contamination, permanence and consequently the effects on human health are different.

Perhaps it should be better explained how these two types of sampling and analysis are integrated, which, now, seem to me to be just one more thing added to enrich the study (which perhaps should have been better addressed in the design of the sampling campaign).

Comments on the Quality of English Language

I suggest to improve English language to help the reader

Author Response

Thank you for your time and effort in reviewing our manuscript. Please find our responses attached. We hope that the revised version of our manuscript conforms to your expectations. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents a timely and comprehensive investigation of particulate matter (PM) characteristics and their associated toxicological risks in Astana, Kazakhstan of a region with limited previous air quality studies. The combination of PM morphology, precipitation chemistry, and bioaccessibility assessment is a significant strength. However, major revision is required as there are many recommendations from me.

 

The title of the manuscript is long. Provide a short title. 

 

In the abstract the sentence “expanding city with intense winter heating” is grammatically incorrect and should read: “a rapidly expanding city with an intense winter heating season.”

 

The literature overview is extensive but sometimes too general, listing studies (e.g., “Michael et al., 2013; Xiao et al., 2014; Wu et al., 2018…”) without synthesizing them. It reads like a review rather than a rationale for the current study.

 

While the Introduction provides a comprehensive overview of global studies on particulate matter (PM) toxicity and chemical composition, it relies predominantly on Asian and North American sources. To strengthen the international relevance and comparative context of the paper, I recommend giving more attention to recent European research on air and soil pollution interrelations. In particular, the authors could integrate the findings from Račić & Malvić DOI:10.33271/mining17.02.112 who analyzed the spatial and statistical relationship between airborne and soil-deposited heavy metals (Ni and Pb) in Zagreb, Croatia. Their study clearly demonstrated how long-term atmospheric emissions and deposition processes shape the distribution of toxic elements in urban soils.

 

The paragraph beginning “Morphological features of PM (e.g., size, shape, and surface characteristics)…” repeats basic information widely known to the audience of Sustainability and could be shortened by half.

 

When stating “Health risk assessment of PM-bound PTEs often relies on total concentrations... potentially overestimating actual exposure,” the authors should provide a short numerical or literature example demonstrating such overestimation.

 

The final paragraph  of introduction section effectively identifies the research gap, but it would be clearer to state the novelty in one sentence

 

Section 2.1 Coordinates are given twice (“51°10’N, 71°26’E’ E”) “E’ E”???

 

The choice of sampling location (“Nazarbayev University Campus”) is reasonable, but the authors should justify why it is representative of urban Astana, since the campus may not reflect areas near main emission sources.

 

There is a minor inconsistency between “30 samples collected” and “selected samples (n = 5) underwent a second filtration” the rationale for this selection must be discussed.

 

Section 3.2. Chain-like scoot clusters and their agglomerates… scoot??? Maybe soot?

 

The authors conclude “average pH 7.11 indicates neutral character,” yet this is inconsistent with the earlier claim of “acid rain concerns.” Clarify whether precipitation is alkaline or slightly acidic overall.

 

Section 3.3. The sentence “Finally, the presence of Co may be attributed to coal combustion, industrial emissions, vehicular traffic, and mining activities (Mihajlidi-Zelić et al., 2006)” could be considerably strengthened by incorporating a broader regional context and the specific evidence on ash and slag residues recently published for Kazakhstan.

I recommend the authors expand this discussion to include findings from Nurpeisova et al. (2023) https://doi.org/10.33271/mining17.03.102 who analyzed the chemical and phase composition of ash and slag wastes from local coal-fired power plants. Their study demonstrated elevated concentrations of transition metals including Co, Cr, and Ni in the fine ash fractions and confirmed their persistence when such residues are reused in construction materials.

 

 

Section 3.5 The use of bioaccessible concentrations for HQ and CR is appropriate, but the extremely high HQ values (up to 6.07 for V) require validation. Provide uncertainty ranges or sensitivity analysis.

 

Section 3.5 “bBoaccessible” in the section title ???

 

Section 3.6 - The four identified factors are plausible. However, Factor 4 (“power plant emissions and traffic-related non-exhaust sources”) combines two unrelated categories; consider separating or explaining why they overlap statistically.

 

PMF identified four factors (Figure S5) S5???

 

The recommendation to “establish regulatory guidelines for elemental and ionic content in rain and snow” is interesting but falls outside the paper’s data scope; perhaps phrase as “future policy consideration.”

 

Study Limitations - the first limitation (“lack of comparison with Gamble’s solution”) should note that many studies use both ALF and GS for lung regions; citing those examples would strengthen the justification.

 

Overall, the paper is publishable after major revision and will be recommended for publication once the authors adequately address the indicated comments and incorporate the suggested improvements.

Author Response

Thank you for your time and effort in reviewing our manuscript. Please find our responses attached. We hope that the revised version of our manuscript conforms to your expectations. 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper focuses on examining the climatic characteristics, energy supply patterns, and air pollution status of cities. The study holds significant practical relevance and urgency in rapidly urbanizing, cold-climate cities with inadequate monitoring infrastructure. Nevertheless, there remains room for refinement in certain details.

 

1. In the Introduction section, it is recommended to introduce the current status of air pollution monitoring and management in similar urban environments internationally, in order to better highlight the innovative aspects of this study.

 

2. It is recommended to supplement the article with some methods for addressing air pollution to make it more comprehensive. such as Advanced Materials, 2020, 32, 2002361、Nature Geoscience, 16, 930、ACS Nano, 16, 17687.

 

3. In the Human Health Risk Assessment section, it is suggested that a more in-depth discussion be included regarding the variations in risk sensitivity across different age groups and health conditions. This would enhance the specificity and practicality of the assessment. Moreover, analyzing the relationship between particulate matter pollution and meteorological conditions, such as wind speed, wind direction, and humidity, could provide a more comprehensive understanding of the causes and transport mechanisms of this pollution.

Author Response

Thank you for your time and effort in reviewing our manuscript. Please find our responses attached. We hope that the revised version of our manuscript conforms to your expectations. 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I have carefully reviewed the revised version of your manuscript. I am satisfied with the revisions made and impressed by the depth and quality of your improvements.
Congratulations on the excellent work.