the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 May 2025
Insight into the size-resolved markers and eco-health significance of microplastics from typical sources in northwest China
Abstract. Research on atmospheric microplastics (MPs) from typical sources is limited, constraining the targeted management of pollution. Here, the characteristics and source profiles of eight types of common MPs and three classes of plasticizers (phthalates, benzothiazole and its derivatives, bisphenol A) emitted from plastic burning (PB), fruit bag burning (FB), road traffic (RT), agricultural film (AF) and livestock breeding (LB) sources were determined in PM2.5 and PM10 in the Guanzhong Plain, northern China. PB features high proportions of poly(methyl methacrylate) and 2-hydroxy benzothiazole, with poly(methyl methacrylate) being more abundant in coarse particles (PMcoarse). FB exhibits the higher proportion of di-n-octyl phthalate in PMcoarse than PM2.5. RT shows a distinguishable profile with high abundances of rubber. The abundance of 2-benzothiazolyl-N-morpholinosulfide in PMcoarse was twice that in PM2.5 for RT. Polystyrene is the most abundant MP in AF. LB shows the distinguishing feature of benzothiazoles, especially 2-benzothiazolyl-N-morpholinosulfide and N-cyclohexyl-2-benzothiazolesulfenamide. The eco-health risk assessments reveal combustion-derived MPs (PB and FB) pose the highest ecological risk (Level III). Elevated hazard indices to human health were observed in LB and PB, primarily attributed to bis(2-ethylhexyl) phthalate. Notably, poly(methyl methacrylate, polyethylene terephthalate, polyethylene, bisphenol A and phthalates emerged as key drivers of oxidative stress. This study advances the understanding of atmospheric MPs, offering critical insights for source tracking and risk assessment to mitigate their eco-health effects.
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Status: closed
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RC1: 'Comment on egusphere-2025-1821', Anonymous Referee #1, 12 May 2025
Focusing on atmospheric microplastic pollution in the Guanzhong Plain of China, this paper investigates the characteristics of microplastics and plasticizers emitted from five typical sources of microplastics (plastic burning, fruit bag burning, road traffic, agricultural films, and animal husbandry) and their ecological health impacts, to provide a comprehensive perspective for a deeper understanding of atmospheric microplastic pollution. It is recommended that this manuscript be published with minor revisions.
- Line 152: OBSand CBS all appear for the first time in the abstract, and it is recommended that the abbreviations be labelled on the first occurrence.
- Line 175: note the font of the concentration units.
- Why choose BT, PAE, and BPA as plastic additives for in-depth research in this study?
- Please supplement QAQC in the Methods section for the analysis of DTT, need to know the accuracy and precision of the analysis.
- How is the Source Pathway Decoder model developed? Is there an operation based on some data? Input of basic information? Or is it just a conceptual model? What is the main purpose in this study?
- Lines 210 and 429: It is suggested that there should be consistency throughout the text as to whether P should be capitalized or lower case.
- Line 296: It is recommended that further discussion of the reasons why the results in this study are contrary to other studies.
- Line 438: It is recommended that an outlook for future research be included. For example, there may be a variety of other MPs in the environment that were not detected in this study, which may pose a risk, and it is recommended that the need to expand the range of substances assessed be mentioned in the outlook for future studies to improve the health risk assessment system.
- Line 584: note the format of references.
- You can add this newly reference: The hidden threat of microplastics in the bloodstream. The Innovation Life 3:100130.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC1 - AC1: 'Reply on RC1', Hongmei Xu, 02 Jul 2025
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RC2: 'Comment on egusphere-2025-1821', Anonymous Referee #2, 12 May 2025
This study aims to determine the characteristics of microplastics and plasticizers from five typical sources in the Guanzhong Plain of China and their associated ecological and health impacts. The objectives are clear and the comprehensive analysis of atmospheric microplastic supports the significance of conducting this study. However, a few grammatical mistakes and typos are found in the data presentation and elaborations. This manuscript can be accepted for publication after revisions.
General comments
The authors must be aware of using past and present tense. Many places are inconsistent with using the correct tense.
Abstract
Line 19: Add “i.e.,” in front of phthalates
Line 21: Add a comma after (AF).
Line 22: Replace the verb ” features”.
Keyword
Line 36: Spell out ROS to keep consistency.
Specifically comments
Introduction
Line 43: in a range of “ five millimeters to one micrometer”
Line 53: It is recommended to change “results” to “result” because the subject is plural.
Line 59: Define PMs.
Line 77: rephrase the words in the presentation.
Line 81-83: The sentence must be advanced.
Line 84: Add “Most of the” at the start of the sentences.
Line 91: Remove “primary”
Methods
The First and Second paragraphs must be combined with a reasonable logic. It should start with the sample collection place and time.
Line 102: ” The term of “PB burned plastics” is not an appropriate term.
Table 1: The format of the table must be advanced. The alignment of the first line in each block must be on the top.
Line 122” A missing space for ‘at -20°C’.
Figure 1: It is recommended that the error bars should be thickened to increase the clarity.
Section 2.2.
Line 147: More advanced information on the procedures of the GC/MS analysis must be shown (i.e. capillary column used, and MSD setting), not just referring to a reference.
More detailed QC/QA procedures must be given for all analyses.
Section 2.5
Consider renaming it as “Data Analysis and Statistical Method.
Results and Decision
Section 3.1
Line 216: The data must be tabulated instead of shown in a figure. The values are more appropriate to demonstrate the actual circumstances.
The values and percentages must be presented in the form of mean plus standard deviation. Check out all these in all sections.
The uses of PM10 and PMcoarse are confusing Standardize to use one term.
Line 230: The verb “crushed” is inappropriate.
Line 274: What is the meaning of “greenhouses” here?
Line 281-284: The presentation could not be fully understood.
Line 286: ” Relative: is an inappropriate word used here.
Line 297: Is it should be shown in a new Sub-Section? Please verify that.
Figure 5 should use legends in the figure to clarify all symbols rather than explanation in the captions (“sections marked in red”)
The DTT included in this study was reported in volume-base. What is the reason for choosing this DTT to describe the toxicity of PMs?
The future research directions must be advanced. For example, it is recommended to consider coupling the multiple ecological health assessment methods mentioned in this study, measure the weights of different methods, and provide comprehensive evaluation indices.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC2 - AC2: 'Reply on RC2', Hongmei Xu, 02 Jul 2025
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RC3: 'Comment on egusphere-2025-1821', Anonymous Referee #3, 24 May 2025
Liu et al. investigated the characteristics, source profiles, and health risks of airborne microplastics and plasticizers emitted from plastic burning, fruit bag burning, road traffic, agricultural film, and livestock breeding sources in Guanzhong Plain, Northern China. Knowledge on the characteristics of atmospheric microplastics in Northern China is currently limited. This study provides important insights for source tracking and risk assessment of these emerging contaminants. I recommend this paper to be published after minor revisions.
- Many plasticizers were used in the manufacturing of plastics. The focus of this study is PAEs, BPs and BPA. Please provide the reason for selecting these three groups of plastics to study.
- The authors mention ROS formation in the text for several times. You use DTT consumption rate to represent oxidative potential. Note that DTT consumption rate is not equal to ROS formation. Some chemicals can consume DTT without the formation of ROS during interaction.
- It is interesting that PMMA, PET, PE, PAEs, and BPA showed a positive correlation with oxidative potential. I encourage the authors to further discuss the possible mechanism which would help readers to understand their health impact.
- Figure 2 shows that the composition profile of PM2.5 and PMcoarse from different sources can be very different. Did you consider the impact of particle size in risk assessment?
- Line 51, Agricultural activities are also a significant contributor to atmospheric MPs?
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC3 - AC3: 'Reply on RC3', Hongmei Xu, 02 Jul 2025
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RC4: 'Comment on egusphere-2025-1821', Anonymous Referee #4, 24 May 2025
In this study, particles emitted from five typical sources (plastic burning, fruit bag burning, road traffic, agricultural film, livestock breeding) in the Guanzhong Plain, northwest China were collected. The authors investigate characteristics and eco-health risks of microplastics (MPs) and plasticizers (phthalates, benzothiazoles, bisphenol A) in PM2.5 and PM10. It identifies source-specific markers and reveals that combustion-derived MPs pose the highest ecological risks, while livestock breeding and plastic burning exhibit elevated human health hazards. The topic is within the scope of ACP. Overall, I recommend this paper to be accepted after revisions.
My comments:
- Please be aware of the tense.
- Please define PMcoarse at its first appearance in Abstract and Introduction. Also, maybe PM2.5-10 could be better for understanding than PMcoarse.
- In this paper, five sources of MPs are analyzed, but excluding emerging sources like industrial emissions, construction, or textile abrasion, which may contribute significantly to atmospheric MPs.
- It is recommended that a separate QC/QA section can be added in Methods section, which could provide more QC/QA details for collection and analyses.
- Section 2.2, what is the size of the filter membranes you cut for pyro-GC/MC analysis?
- Figure 2, the caption of Y-axis, is it the proportion of MPs in “PMs”? Or “MPs”.
- Figure 2, what does the slash lines stands for?
- Line 198, the health risk assessment uses U.S. EPA-derived exposure parameters, which may not fully align with Chinese population characteristics.
- References are sometimes listed without page ranges. Also, there are some wired words (i.e., PM2.5) in Line 614 and 617.
- Introduction section Line 45, please consider adding these references: Micro/nanoplastics in the Shenyang city atmosphere: Distribution and sources, Environ. Pollut., 2025, 372, 126027; Characterization of atmospheric microplastics in Hangzhou, a megacity of the Yangtze river delta, China, Environ. Sci.: Atmos., 2024, 4, 1161-1169.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC4 - AC4: 'Reply on RC4', Hongmei Xu, 02 Jul 2025
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RC5: 'Comment on egusphere-2025-1821', Anonymous Referee #5, 28 May 2025
This paper describes the microplastics in the coarse and fine aerosol fractions from five different sources in northern China, quantified using pyrolysis GC/MS. A selection of common plastic additives were also detected. The oxidative potentials of filter extracts were determined using a DTT assay. Livestock breeding and plastic burning were found to produce the largest potential hazards of the five sources tested. This work represents an important study in a growing area of interest in atmospheric science, and I would recommend publication if the authors can add clarity to their methodology, QA/QC protocols, and data analysis.
Specific comments:
Line 39 “Global plastic production has gradually increased” – has it gradually or exponentially increased?
Line 43 “Current research on MPs pollution sources have primarily focused on aquatic and terrestrial ecosystems..” – I would argue that current research has started to focus much more on airborne plastics, thus, I would recommend rewording this line.
Line 50 – I would add a qualifier in this line as the Yang et al. (2021) study used a cutoff size of 50 µm, thus, there are likely many more plastic particles produced than the values reported in the study.
Line 99 – Section 2.1, can the authors provide sampling dates and a map of where sampling took place (with long and lat)? This would be very helpful for future modelling studies.
Line 121 – what was the material of the air cassettes used? And did it influence the final results?
Line 122 – did filter weighing follow any published standard and was static electricity neutralised prior to weighing?
Line 124 – please provide more detailed information on how the field blanks were treated/collected.
Line 125 – Several studies have found that nitrile gloves can potentially influence pyrolysis GC/MS analysis of polymers, particularly PE. Please discuss.
Line 138 – Please provide explicit details of preparation of samples, instrument configurations, and QA/QC protocols in this manuscript rather than referring to another paper. In regards to QA/QC, please provide information on positive and negative controls, the amount of analytes detected in background samples, and any subtractions that were completed to produce the final values. Addition to the supplemental would be a satisfactory placement for this information.
Line 140 – please provide manufacturer information on the thermal desorption unit used.
Line 142 (and elsewhere) – please provide supplier information and purity for all chemicals used in the study.
Line 154 – the extraction and concentration procedures need to be provided in detail.
Line 158 – please provide method details instead of referring to a different paper.
Line 167 – please discuss potential for interferences with detection or any specificity testing that was completed.
Line 168 – was quantification completed using an internal standard or external standard method?
Section 2.3. – With regard to the FB filters, presumably many combustion products would be produced that no longer resemble the chemical structure of the original plastic. Please discuss the potential of these compounds to influence the oxidative testing.
Line 221 – since wax coatings often contain a mixture of alkanes, please discuss any potential interferences of the wax on the pyrolysis GC/MS results (e.g. PE quantification).
Line 223 – the MPs in PB and LB were 50% of the PM, was this by mass? Please clarify and also present the percentage of PM that was attributed to plastic in all scenarios.
Line 226 – how was the reported uncertainty calculated?
Line 261 – Please discuss the details of the flyover? How was this sample collection done?
Line 394 – please cite where these compounds are accepted as carcinogens.
Line 432 – does correlation in this testing confirm causation of oxidative stress? Please discuss.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC5 - AC5: 'Reply on RC5', Hongmei Xu, 02 Jul 2025
-
RC6: 'Comment on egusphere-2025-1821', Anonymous Referee #6, 02 Jun 2025
This paper investigates emitted microplastics aerosols from five sources in northwest China. The authors present a comprehensive characterization of the sources and plasticizer profiles. An eco-health risk assessment was conducted, providing key details like daily exposure risks. These findings are especially valuable for informing risk-mitigation policies and protecting individuals who are often close to sources like those in rural households which burn plastics, agricultural workers or incineration plant workers. This paper merits publication in ACP after some minor revisions.
General comments:
- The current manuscript misses some clarification and details on the different source categories. For example, it only became apparent in Table 1 that the plastic burning occurred in a household setting not in an industrial one. This distinction is important, as emissions from household and industrial plastic burning may differ significantly, and readers should not conflate the two. Thus, this point should be clarified and emphasized in the Introduction. While it appears that fruit bags were not included in the household plastic burning, it would be helpful to define ‘fruit bags’ more thoroughly. What polymer types are they made out of - line 105 only states ‘also containing some plastics components’. How do they differ from common household plastic waste? Clarifying this will help the readers to better understand why you chose the two categories ‘fruit bag’ vs ‘plastic burning’ and their differences.
- Details on the collection of field blanks are limited and would benefit from further clarification. Line 118: How were the field blanks collected? By synchronously, do the authors mean that the blank was taken at the same location, same duration, and same time as the samples?
- Line 128: Why were phthalates, benzothiazole and its derivatives, and bisphenol A chosen to be the 3 classes for in-depth analysis? What criteria guided this choice?
- Near the source you may have metals and other aerosols depositing onto the filter, were these non-plastic sources accounted for in your analysis? How was the mass contribution from microplastics determined?
- The manuscript uses too many abbreviations, some of which are uncommon or used only once, making the text hard to follow. I recommend writing out PB, FB, RT, AF, and LB, and remove single-use abbreviations like FL (line 166). Replace OP with "oxidation potential" throughout. Limiting abbreviations to widely recognized terms like the different microplastics and plasticizers will improve clarity and readability.
Specific comments:
- Line 89: Can you elaborate why is the UV so strong in this area and why does it matter for this study? MPs emitted in this area may undergo increased photooxidation, is that something that can be discussed with your results? Or is that something that needs to be explored further in future studies?
- Line 113: State what type of sampler MiniVol samplers are (e.g. impinger, impactor, etc.)
- Figure 1: errors bars used represent standard deviation of PM10 however the figure is plotting PM5 and PMcourse. Is that error representation suitable for this plot? Consider just focusing on PM2.5 and PMcourse throughout the paper and removing PM10 to be more consistent with how results are discussed.
- Figure 1: I would suggest increasing the spacing between (a) and (b) to improve readability. The secondary y-axis for (a) is very close the first y-axis of (b).
- Line 282: In addition to the most abundant plasticizer, I would suggest the authors list the next two most abundant plasticizer types detected in PB.
- Line 288-289 and Figure 5: Use consistent spelling of tire or tyre throughout the paper.
- Figure 3: Redefine abbreviations when they appear in captions e.g., PAE and BT
- Figure 4: Consider adding visual cues (e.g. labels by the arrow, highlighted section or color cues) to help guide the reader’s eye from the black arrow to the corresponding source marker on the x-axis. In the main text, please expand the discussion for these identified markers. How confident are these marker classifications? Have previous studies reported the same markers?
- Figure 6: Please add a legend to define the colour groupings.
Technical corrections:
- Line 19: (phthalates, benzothiazole and its derivatives, and bisphenol A)
- Line 31: missing closing bracket: poly(methyl methacrylate)
- Line 122: missing space: …frozen at -20°C
- Line 180: and absorbance was measured at 412 nm using a microplate reader
- Line 246: This is because plastic products...
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC6 - AC6: 'Reply on RC6', Hongmei Xu, 02 Jul 2025
Status: closed
-
RC1: 'Comment on egusphere-2025-1821', Anonymous Referee #1, 12 May 2025
Focusing on atmospheric microplastic pollution in the Guanzhong Plain of China, this paper investigates the characteristics of microplastics and plasticizers emitted from five typical sources of microplastics (plastic burning, fruit bag burning, road traffic, agricultural films, and animal husbandry) and their ecological health impacts, to provide a comprehensive perspective for a deeper understanding of atmospheric microplastic pollution. It is recommended that this manuscript be published with minor revisions.
- Line 152: OBSand CBS all appear for the first time in the abstract, and it is recommended that the abbreviations be labelled on the first occurrence.
- Line 175: note the font of the concentration units.
- Why choose BT, PAE, and BPA as plastic additives for in-depth research in this study?
- Please supplement QAQC in the Methods section for the analysis of DTT, need to know the accuracy and precision of the analysis.
- How is the Source Pathway Decoder model developed? Is there an operation based on some data? Input of basic information? Or is it just a conceptual model? What is the main purpose in this study?
- Lines 210 and 429: It is suggested that there should be consistency throughout the text as to whether P should be capitalized or lower case.
- Line 296: It is recommended that further discussion of the reasons why the results in this study are contrary to other studies.
- Line 438: It is recommended that an outlook for future research be included. For example, there may be a variety of other MPs in the environment that were not detected in this study, which may pose a risk, and it is recommended that the need to expand the range of substances assessed be mentioned in the outlook for future studies to improve the health risk assessment system.
- Line 584: note the format of references.
- You can add this newly reference: The hidden threat of microplastics in the bloodstream. The Innovation Life 3:100130.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC1 - AC1: 'Reply on RC1', Hongmei Xu, 02 Jul 2025
-
RC2: 'Comment on egusphere-2025-1821', Anonymous Referee #2, 12 May 2025
This study aims to determine the characteristics of microplastics and plasticizers from five typical sources in the Guanzhong Plain of China and their associated ecological and health impacts. The objectives are clear and the comprehensive analysis of atmospheric microplastic supports the significance of conducting this study. However, a few grammatical mistakes and typos are found in the data presentation and elaborations. This manuscript can be accepted for publication after revisions.
General comments
The authors must be aware of using past and present tense. Many places are inconsistent with using the correct tense.
Abstract
Line 19: Add “i.e.,” in front of phthalates
Line 21: Add a comma after (AF).
Line 22: Replace the verb ” features”.
Keyword
Line 36: Spell out ROS to keep consistency.
Specifically comments
Introduction
Line 43: in a range of “ five millimeters to one micrometer”
Line 53: It is recommended to change “results” to “result” because the subject is plural.
Line 59: Define PMs.
Line 77: rephrase the words in the presentation.
Line 81-83: The sentence must be advanced.
Line 84: Add “Most of the” at the start of the sentences.
Line 91: Remove “primary”
Methods
The First and Second paragraphs must be combined with a reasonable logic. It should start with the sample collection place and time.
Line 102: ” The term of “PB burned plastics” is not an appropriate term.
Table 1: The format of the table must be advanced. The alignment of the first line in each block must be on the top.
Line 122” A missing space for ‘at -20°C’.
Figure 1: It is recommended that the error bars should be thickened to increase the clarity.
Section 2.2.
Line 147: More advanced information on the procedures of the GC/MS analysis must be shown (i.e. capillary column used, and MSD setting), not just referring to a reference.
More detailed QC/QA procedures must be given for all analyses.
Section 2.5
Consider renaming it as “Data Analysis and Statistical Method.
Results and Decision
Section 3.1
Line 216: The data must be tabulated instead of shown in a figure. The values are more appropriate to demonstrate the actual circumstances.
The values and percentages must be presented in the form of mean plus standard deviation. Check out all these in all sections.
The uses of PM10 and PMcoarse are confusing Standardize to use one term.
Line 230: The verb “crushed” is inappropriate.
Line 274: What is the meaning of “greenhouses” here?
Line 281-284: The presentation could not be fully understood.
Line 286: ” Relative: is an inappropriate word used here.
Line 297: Is it should be shown in a new Sub-Section? Please verify that.
Figure 5 should use legends in the figure to clarify all symbols rather than explanation in the captions (“sections marked in red”)
The DTT included in this study was reported in volume-base. What is the reason for choosing this DTT to describe the toxicity of PMs?
The future research directions must be advanced. For example, it is recommended to consider coupling the multiple ecological health assessment methods mentioned in this study, measure the weights of different methods, and provide comprehensive evaluation indices.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC2 - AC2: 'Reply on RC2', Hongmei Xu, 02 Jul 2025
-
RC3: 'Comment on egusphere-2025-1821', Anonymous Referee #3, 24 May 2025
Liu et al. investigated the characteristics, source profiles, and health risks of airborne microplastics and plasticizers emitted from plastic burning, fruit bag burning, road traffic, agricultural film, and livestock breeding sources in Guanzhong Plain, Northern China. Knowledge on the characteristics of atmospheric microplastics in Northern China is currently limited. This study provides important insights for source tracking and risk assessment of these emerging contaminants. I recommend this paper to be published after minor revisions.
- Many plasticizers were used in the manufacturing of plastics. The focus of this study is PAEs, BPs and BPA. Please provide the reason for selecting these three groups of plastics to study.
- The authors mention ROS formation in the text for several times. You use DTT consumption rate to represent oxidative potential. Note that DTT consumption rate is not equal to ROS formation. Some chemicals can consume DTT without the formation of ROS during interaction.
- It is interesting that PMMA, PET, PE, PAEs, and BPA showed a positive correlation with oxidative potential. I encourage the authors to further discuss the possible mechanism which would help readers to understand their health impact.
- Figure 2 shows that the composition profile of PM2.5 and PMcoarse from different sources can be very different. Did you consider the impact of particle size in risk assessment?
- Line 51, Agricultural activities are also a significant contributor to atmospheric MPs?
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC3 - AC3: 'Reply on RC3', Hongmei Xu, 02 Jul 2025
-
RC4: 'Comment on egusphere-2025-1821', Anonymous Referee #4, 24 May 2025
In this study, particles emitted from five typical sources (plastic burning, fruit bag burning, road traffic, agricultural film, livestock breeding) in the Guanzhong Plain, northwest China were collected. The authors investigate characteristics and eco-health risks of microplastics (MPs) and plasticizers (phthalates, benzothiazoles, bisphenol A) in PM2.5 and PM10. It identifies source-specific markers and reveals that combustion-derived MPs pose the highest ecological risks, while livestock breeding and plastic burning exhibit elevated human health hazards. The topic is within the scope of ACP. Overall, I recommend this paper to be accepted after revisions.
My comments:
- Please be aware of the tense.
- Please define PMcoarse at its first appearance in Abstract and Introduction. Also, maybe PM2.5-10 could be better for understanding than PMcoarse.
- In this paper, five sources of MPs are analyzed, but excluding emerging sources like industrial emissions, construction, or textile abrasion, which may contribute significantly to atmospheric MPs.
- It is recommended that a separate QC/QA section can be added in Methods section, which could provide more QC/QA details for collection and analyses.
- Section 2.2, what is the size of the filter membranes you cut for pyro-GC/MC analysis?
- Figure 2, the caption of Y-axis, is it the proportion of MPs in “PMs”? Or “MPs”.
- Figure 2, what does the slash lines stands for?
- Line 198, the health risk assessment uses U.S. EPA-derived exposure parameters, which may not fully align with Chinese population characteristics.
- References are sometimes listed without page ranges. Also, there are some wired words (i.e., PM2.5) in Line 614 and 617.
- Introduction section Line 45, please consider adding these references: Micro/nanoplastics in the Shenyang city atmosphere: Distribution and sources, Environ. Pollut., 2025, 372, 126027; Characterization of atmospheric microplastics in Hangzhou, a megacity of the Yangtze river delta, China, Environ. Sci.: Atmos., 2024, 4, 1161-1169.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC4 - AC4: 'Reply on RC4', Hongmei Xu, 02 Jul 2025
-
RC5: 'Comment on egusphere-2025-1821', Anonymous Referee #5, 28 May 2025
This paper describes the microplastics in the coarse and fine aerosol fractions from five different sources in northern China, quantified using pyrolysis GC/MS. A selection of common plastic additives were also detected. The oxidative potentials of filter extracts were determined using a DTT assay. Livestock breeding and plastic burning were found to produce the largest potential hazards of the five sources tested. This work represents an important study in a growing area of interest in atmospheric science, and I would recommend publication if the authors can add clarity to their methodology, QA/QC protocols, and data analysis.
Specific comments:
Line 39 “Global plastic production has gradually increased” – has it gradually or exponentially increased?
Line 43 “Current research on MPs pollution sources have primarily focused on aquatic and terrestrial ecosystems..” – I would argue that current research has started to focus much more on airborne plastics, thus, I would recommend rewording this line.
Line 50 – I would add a qualifier in this line as the Yang et al. (2021) study used a cutoff size of 50 µm, thus, there are likely many more plastic particles produced than the values reported in the study.
Line 99 – Section 2.1, can the authors provide sampling dates and a map of where sampling took place (with long and lat)? This would be very helpful for future modelling studies.
Line 121 – what was the material of the air cassettes used? And did it influence the final results?
Line 122 – did filter weighing follow any published standard and was static electricity neutralised prior to weighing?
Line 124 – please provide more detailed information on how the field blanks were treated/collected.
Line 125 – Several studies have found that nitrile gloves can potentially influence pyrolysis GC/MS analysis of polymers, particularly PE. Please discuss.
Line 138 – Please provide explicit details of preparation of samples, instrument configurations, and QA/QC protocols in this manuscript rather than referring to another paper. In regards to QA/QC, please provide information on positive and negative controls, the amount of analytes detected in background samples, and any subtractions that were completed to produce the final values. Addition to the supplemental would be a satisfactory placement for this information.
Line 140 – please provide manufacturer information on the thermal desorption unit used.
Line 142 (and elsewhere) – please provide supplier information and purity for all chemicals used in the study.
Line 154 – the extraction and concentration procedures need to be provided in detail.
Line 158 – please provide method details instead of referring to a different paper.
Line 167 – please discuss potential for interferences with detection or any specificity testing that was completed.
Line 168 – was quantification completed using an internal standard or external standard method?
Section 2.3. – With regard to the FB filters, presumably many combustion products would be produced that no longer resemble the chemical structure of the original plastic. Please discuss the potential of these compounds to influence the oxidative testing.
Line 221 – since wax coatings often contain a mixture of alkanes, please discuss any potential interferences of the wax on the pyrolysis GC/MS results (e.g. PE quantification).
Line 223 – the MPs in PB and LB were 50% of the PM, was this by mass? Please clarify and also present the percentage of PM that was attributed to plastic in all scenarios.
Line 226 – how was the reported uncertainty calculated?
Line 261 – Please discuss the details of the flyover? How was this sample collection done?
Line 394 – please cite where these compounds are accepted as carcinogens.
Line 432 – does correlation in this testing confirm causation of oxidative stress? Please discuss.
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC5 - AC5: 'Reply on RC5', Hongmei Xu, 02 Jul 2025
-
RC6: 'Comment on egusphere-2025-1821', Anonymous Referee #6, 02 Jun 2025
This paper investigates emitted microplastics aerosols from five sources in northwest China. The authors present a comprehensive characterization of the sources and plasticizer profiles. An eco-health risk assessment was conducted, providing key details like daily exposure risks. These findings are especially valuable for informing risk-mitigation policies and protecting individuals who are often close to sources like those in rural households which burn plastics, agricultural workers or incineration plant workers. This paper merits publication in ACP after some minor revisions.
General comments:
- The current manuscript misses some clarification and details on the different source categories. For example, it only became apparent in Table 1 that the plastic burning occurred in a household setting not in an industrial one. This distinction is important, as emissions from household and industrial plastic burning may differ significantly, and readers should not conflate the two. Thus, this point should be clarified and emphasized in the Introduction. While it appears that fruit bags were not included in the household plastic burning, it would be helpful to define ‘fruit bags’ more thoroughly. What polymer types are they made out of - line 105 only states ‘also containing some plastics components’. How do they differ from common household plastic waste? Clarifying this will help the readers to better understand why you chose the two categories ‘fruit bag’ vs ‘plastic burning’ and their differences.
- Details on the collection of field blanks are limited and would benefit from further clarification. Line 118: How were the field blanks collected? By synchronously, do the authors mean that the blank was taken at the same location, same duration, and same time as the samples?
- Line 128: Why were phthalates, benzothiazole and its derivatives, and bisphenol A chosen to be the 3 classes for in-depth analysis? What criteria guided this choice?
- Near the source you may have metals and other aerosols depositing onto the filter, were these non-plastic sources accounted for in your analysis? How was the mass contribution from microplastics determined?
- The manuscript uses too many abbreviations, some of which are uncommon or used only once, making the text hard to follow. I recommend writing out PB, FB, RT, AF, and LB, and remove single-use abbreviations like FL (line 166). Replace OP with "oxidation potential" throughout. Limiting abbreviations to widely recognized terms like the different microplastics and plasticizers will improve clarity and readability.
Specific comments:
- Line 89: Can you elaborate why is the UV so strong in this area and why does it matter for this study? MPs emitted in this area may undergo increased photooxidation, is that something that can be discussed with your results? Or is that something that needs to be explored further in future studies?
- Line 113: State what type of sampler MiniVol samplers are (e.g. impinger, impactor, etc.)
- Figure 1: errors bars used represent standard deviation of PM10 however the figure is plotting PM5 and PMcourse. Is that error representation suitable for this plot? Consider just focusing on PM2.5 and PMcourse throughout the paper and removing PM10 to be more consistent with how results are discussed.
- Figure 1: I would suggest increasing the spacing between (a) and (b) to improve readability. The secondary y-axis for (a) is very close the first y-axis of (b).
- Line 282: In addition to the most abundant plasticizer, I would suggest the authors list the next two most abundant plasticizer types detected in PB.
- Line 288-289 and Figure 5: Use consistent spelling of tire or tyre throughout the paper.
- Figure 3: Redefine abbreviations when they appear in captions e.g., PAE and BT
- Figure 4: Consider adding visual cues (e.g. labels by the arrow, highlighted section or color cues) to help guide the reader’s eye from the black arrow to the corresponding source marker on the x-axis. In the main text, please expand the discussion for these identified markers. How confident are these marker classifications? Have previous studies reported the same markers?
- Figure 6: Please add a legend to define the colour groupings.
Technical corrections:
- Line 19: (phthalates, benzothiazole and its derivatives, and bisphenol A)
- Line 31: missing closing bracket: poly(methyl methacrylate)
- Line 122: missing space: …frozen at -20°C
- Line 180: and absorbance was measured at 412 nm using a microplate reader
- Line 246: This is because plastic products...
Citation: https://doi.org/10.5194/egusphere-2025-1821-RC6 - AC6: 'Reply on RC6', Hongmei Xu, 02 Jul 2025
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