ACEIC: a comprehensive anthropogenic chlorine emission inventory for China

Li, Siting; Liu, Yiming; Zhu, Yuqi; Jin, Yinbao; Hong, Yingying; Shen, Ao; Xu, Yifei; Wang, Haofan; Wang, Haichao; Lu, Xiao; Fan, Shaojia; Fan, Qi

doi:https://doi.org/10.5194/egusphere-2023-1448

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https://doi.org/10.5194/egusphere-2023-1448

Preprints

21 Jul 2023

| 21 Jul 2023

ACEIC: a comprehensive anthropogenic chlorine emission inventory for China

Siting Li, Yiming Liu, Yuqi Zhu, Yinbao Jin, Yingying Hong, Ao Shen, Yifei Xu, Haofan Wang, Haichao Wang, Xiao Lu, Shaojia Fan, and Qi Fan

Abstract. Reactive chlorine species play a crucial role as precursors to Cl radicals, which can significantly impact the atmospheric oxidation capacity and influence the levels of trace gases related to climate and air quality. However, their anthropogenic sources remain uncertain and require further investigation. In previous studies, we developed the Anthropogenic Chlorine Emission Inventory for China (ACEIC) for the years 2012 and 2014. This inventory focused solely on the emissions of hydrogen chloride (HCl) and chlorine gas (Cl₂) from coal combustion and prescribed waste incineration. In the present study, we updated this inventory to include data from a more recent year (2018) and expanded the range of species considered (HCl, fine particulate Cl^-, Cl₂, and hypochlorous acid (HOCl)) as well as the number of anthropogenic sources (41 specific sources). The emission factors used in this updated inventory were primarily based on localized survey data. The total emissions of HCl, fine particulate Cl^-, Cl₂, and HOCl in mainland China for the year 2018 were estimated to be 454 (-48 %~45 %), 238 (-59 %~89 %), 17 (-44 %~58 %), and 73 (-44 %~79 %) Gg, respectively. To facilitate analysis, we aggregated the chlorine emissions from various sources into five economic sectors: power, industry, residential, agriculture, and biomass burning. HCl emissions were primarily derived from biomass burning (45 %), industry (35 %), and residential (15 %) sectors. The biomass burning and industry sectors accounted for 78 % and 14 % of the fine particulate Cl^- emissions, respectively. Residential and industry sectors contributed 59 % and 31 % of the total Cl₂ emissions. HOCl emissions were predominantly from the residential sector, constituting 90 % of the total emissions. Notably, the usage of chlorine-containing disinfectants was identified as the most significant source of Cl₂ and HOCl emissions in the residential sector. Geographically, regions with high HCl and fine particulate Cl^- emissions were found in northeast China, the North China Plain, and the Sichuan Basin, whereas the Pearl River Delta, Yangtze River Delta, and Beijing-Tianjin-Hebei regions exhibited elevated levels of Cl₂ and HOCl emissions. Regarding monthly variation, emissions of HCl and fine particulate Cl^- were relatively higher during early summer (June–July) and October due to intensified agricultural activities, while Cl₂ and HOCl emissions were higher in the summer months due to increased demand for water disinfection. This updated inventory contributes to a better understanding of anthropogenic sources of reactive chlorine species and can aid in the formulation of emission control strategies to mitigate secondary pollution in China.

Received: 29 Jun 2023 – Discussion started: 21 Jul 2023

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16 Oct 2024

ACEIC: a comprehensive anthropogenic chlorine emission inventory for China

Siting Li, Yiming Liu, Yuqi Zhu, Yinbao Jin, Yingying Hong, Ao Shen, Yifei Xu, Haofan Wang, Haichao Wang, Xiao Lu, Shaojia Fan, and Qi Fan

Atmos. Chem. Phys., 24, 11521–11544, https://doi.org/10.5194/acp-24-11521-2024,https://doi.org/10.5194/acp-24-11521-2024, 2024

Short summary

Siting Li, Yiming Liu, Yuqi Zhu, Yinbao Jin, Yingying Hong, Ao Shen, Yifei Xu, Haofan Wang, Haichao Wang, Xiao Lu, Shaojia Fan, and Qi Fan

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-1448', Anonymous Referee #1, 09 Aug 2023
This work compiled a comprehensive anthropogenic chlorine emission inventory for China. It improved the authors’ previous ACEIC inventory by including the sources from cooking, usage of disinfectant, and pesticide. The paper provides valuable data for chlorine emissions in China. Some parts of the calculation and discussion are not very clear and need improvement.
Major comments:
I would suggest to rearrange the introduction to make it clearer. Paragraph 2-5 have some overlaps and inconsistent, making the logic confusing.

The most significant finding of this work that differs from previous studies may be a large source of HOCl and Cl2 from the usage of chlorine-containing disinfectants. It seems that the estimate of this part of emissions (section 2.2.6) assumes that chlorine gases volatilized from the water will be directly released to the atmosphere. However, many water treatment plants, hospitals, and swimming pools are indoors, some of the waste gases are also treated. This needs more discussion.

For the part of comparing with other works, the authors frequently attributed the difference to the use of different methods without other explanation. Please provide a clearer discussion. For instance, why different methods are used? which one is better? suggestions to reduce the uncertainties of the methodology ....

Please make sure all the numbers used in the calculations have proper references.

Specific comments:
- For the name RCEI and statement such as in line 46, it is hard to say whether HCl and pCl can be grouped into reactive chlorine species as they are not that reactive and fast producing Cl radicals in the atmosphere.
- Paragraph 2, you said research on anthropogenic chlorine emission in China is very limited and rarely considered in air quality simulations, but later you provide a series of examples in paragraph 3 and 4. I would suggest removing those statements and merging them with paragraph 4.
- Paragraph 3, this part starts with saying emission inventory in foreign countries, but no related information are introduced.
- line 87, which sources were overlooked, such as?
- line 89, you may want to summarize the pros and cons of these studies at least briefly before this statement. Why did the previous estimates differ so largely? What are the uncertainties?
- line 92, what is basic data? Do you mean activity data?
- line 116, please provide references for the release ratio.
- line 144, based on your statement, MM should equal to 0.5 for Cl2 as you defined it as the ratios of the molar mass of chlorine atom to the molecular weight of chlorine species.
- line 177-178, please provide references for the chlorine removal efficiencies.
- Section 2.2.6, the whole part involves assumptions that the water in the facilities (water treatment plant, hospital, swimming pool, etc.) are open to the atmosphere and the waste gases are released without any treatment. This doesn’t sound very true.
- Section 2.2.6b, it is not clear how the calculation was conducted.
- line 496, why are the emission factors and control technologies different? Are your estimations better? Same for the entire section 4.1, when you said different results were due to different calculation methods, could you please elaborate more and maybe demonstrate that your methods are more appropriate?
- Figure 2 provides the same information as Figure 1d. Why put it as an individual figure? Also, it looks like the proportion of chlorine emissions from different sources of disinfection, not the proportion of actives as the figure title described.
- Figure 4: please introduce the green line in the label or figure captain.
- Figure 5: it is quite strange to use the unit of Mg/grid/yr, especially when no grid information is provided in figure captain. I would suggest using a unit of Mg/m2/yr or something similar.
- Table 6: could you please also include emission numbers or ranges? I am not clear what useful information can be provided by comparing uncertainties with different studies.
Citation: https://doi.org/10.5194/egusphere-2023-1448-RC1
- AC1: 'Reply on RC1', Yiming Liu, 09 Nov 2023
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1448/egusphere-2023-1448-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2023-1448-AC1
RC2:
'Comment on egusphere-2023-1448', Anonymous Referee #2, 12 Aug 2023

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1448/egusphere-2023-1448-RC2-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2023-1448-RC2
- AC2: 'Reply on RC2', Yiming Liu, 09 Nov 2023
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1448/egusphere-2023-1448-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2023-1448-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-1448', Anonymous Referee #1, 09 Aug 2023
This work compiled a comprehensive anthropogenic chlorine emission inventory for China. It improved the authors’ previous ACEIC inventory by including the sources from cooking, usage of disinfectant, and pesticide. The paper provides valuable data for chlorine emissions in China. Some parts of the calculation and discussion are not very clear and need improvement.
Major comments:
I would suggest to rearrange the introduction to make it clearer. Paragraph 2-5 have some overlaps and inconsistent, making the logic confusing.

The most significant finding of this work that differs from previous studies may be a large source of HOCl and Cl2 from the usage of chlorine-containing disinfectants. It seems that the estimate of this part of emissions (section 2.2.6) assumes that chlorine gases volatilized from the water will be directly released to the atmosphere. However, many water treatment plants, hospitals, and swimming pools are indoors, some of the waste gases are also treated. This needs more discussion.

For the part of comparing with other works, the authors frequently attributed the difference to the use of different methods without other explanation. Please provide a clearer discussion. For instance, why different methods are used? which one is better? suggestions to reduce the uncertainties of the methodology ....

Please make sure all the numbers used in the calculations have proper references.

Specific comments:
- For the name RCEI and statement such as in line 46, it is hard to say whether HCl and pCl can be grouped into reactive chlorine species as they are not that reactive and fast producing Cl radicals in the atmosphere.
- Paragraph 2, you said research on anthropogenic chlorine emission in China is very limited and rarely considered in air quality simulations, but later you provide a series of examples in paragraph 3 and 4. I would suggest removing those statements and merging them with paragraph 4.
- Paragraph 3, this part starts with saying emission inventory in foreign countries, but no related information are introduced.
- line 87, which sources were overlooked, such as?
- line 89, you may want to summarize the pros and cons of these studies at least briefly before this statement. Why did the previous estimates differ so largely? What are the uncertainties?
- line 92, what is basic data? Do you mean activity data?
- line 116, please provide references for the release ratio.
- line 144, based on your statement, MM should equal to 0.5 for Cl2 as you defined it as the ratios of the molar mass of chlorine atom to the molecular weight of chlorine species.
- line 177-178, please provide references for the chlorine removal efficiencies.
- Section 2.2.6, the whole part involves assumptions that the water in the facilities (water treatment plant, hospital, swimming pool, etc.) are open to the atmosphere and the waste gases are released without any treatment. This doesn’t sound very true.
- Section 2.2.6b, it is not clear how the calculation was conducted.
- line 496, why are the emission factors and control technologies different? Are your estimations better? Same for the entire section 4.1, when you said different results were due to different calculation methods, could you please elaborate more and maybe demonstrate that your methods are more appropriate?
- Figure 2 provides the same information as Figure 1d. Why put it as an individual figure? Also, it looks like the proportion of chlorine emissions from different sources of disinfection, not the proportion of actives as the figure title described.
- Figure 4: please introduce the green line in the label or figure captain.
- Figure 5: it is quite strange to use the unit of Mg/grid/yr, especially when no grid information is provided in figure captain. I would suggest using a unit of Mg/m2/yr or something similar.
- Table 6: could you please also include emission numbers or ranges? I am not clear what useful information can be provided by comparing uncertainties with different studies.
Citation: https://doi.org/10.5194/egusphere-2023-1448-RC1
- AC1: 'Reply on RC1', Yiming Liu, 09 Nov 2023
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1448/egusphere-2023-1448-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2023-1448-AC1
RC2:
'Comment on egusphere-2023-1448', Anonymous Referee #2, 12 Aug 2023

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1448/egusphere-2023-1448-RC2-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2023-1448-RC2
- AC2: 'Reply on RC2', Yiming Liu, 09 Nov 2023
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1448/egusphere-2023-1448-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2023-1448-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Yiming Liu on behalf of the Authors (09 Nov 2023) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (08 Dec 2023) by Lea Hildebrandt Ruiz

RR by Anonymous Referee #2 (17 Dec 2023)

Suggestions for revision or reasons for rejection

The most important of this study is to provide more accurate chlorine emission inventory (with significantly reduced uncertainties) than previous studies. The authors also pointed out that some modeling studies have used the anthropogenic chlorine emission as inputs and found that the simulated concentrations of chlorine species (HCl and pCl) were underestimated against the observations, suggesting that there are large uncertainties or missing sources for the current emission estimation. Therefore, the chlorine emission inventory shall be proved to be more reasonable and has been cross-checked. Otherwise, any study is just a big homework to duplicate or compile previous works. Unfortunately, I do see this study is lack of solid basis or significant improvement in terms of more accurate emissions factors, etc. This flaw makes this study less meaningful.

When comparing with other works, the authors frequently attributed the difference to the use of different methods / different emission factors, without further in-depth explanations. The authors emphasize frequently that this updated inventory considered more anthropogenic sources, used more localized emission factors, and adopted more refined estimation methods. However, which one is better? Can the authors prove that the current emission factors / methods are more accurate? Can the authors prove that the uncertainties have been significantly reduced? For example, comparing results with observations?

There also exist large uncertainties or ever errors in the methodology. For example:
1. In all the formulars, there are even no units for each parameter. In the calculation method of Cl2 and HOCl emissions, they do not consider the available chlorine parameters and Molecular weight and other indicators.
2. For Industrial Production Process, there are chemical industries producing disinfectants, which will also emit HOCl but neglected. For spatial allocation of industrial production, the paper assumed a uniform emission for them and spatially allocated the provincial emissions evenly to each point!
3. Environmental disinfection: The quantity of disinfectant utilized in each hospital is a very important parameter to estimate Cl2/HOCl emissions from hospitals. However, the paper just citied a very old data in Taizhou in 2007 and expanded to year 2018 by using the formula U2018=U2007 × C2018/C2007.
4. Biomass burning: The study used the proportion of open biomass burning of Zhou et al., (2017) to estimate emissions of HCl and pCl from biomass burning sources. However, China has made great efforts to ban open straw burning, will this method introduce overestimations?
5. Usage of pesticide: Most data are citied from the year 2016.
6. Chlorine-containing disinfectant: Table S5 gives the emission factors of Cl2 and HOCl from various disinfectant sources. Are they inconsistent with the calculations of formulas 3 and 12? If they know the emission factor data for each type of source, the emissions can be calculated directly with the activity level data.

Overall, I do think the methodologies and details of this study are somewhat rough and needs more experimental support.

Hide

RR by Anonymous Referee #1 (16 Jan 2024)

ED: Reconsider after major revisions (16 Jan 2024) by Lea Hildebrandt Ruiz

AR by Yiming Liu on behalf of the Authors (27 Mar 2024) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (01 Apr 2024) by Lea Hildebrandt Ruiz

RR by Anonymous Referee #3 (21 Jun 2024)

RR by Anonymous Referee #4 (20 Jul 2024)

Suggestions for revision or reasons for rejection

This study aims to provide a comprehensive inventory of chlorine emissions by updating the previous inventory to include data from a more recent year and expanding the range of species considered, as well as the number of anthropogenic sources. This paper provides valuable data on chlorine emissions in China. Despite the considerable effort involved, I suggest that the authors enhance the foundational support for the new additions and provide more evidence to demonstrate significant advancements in emission inventory calculation methods. Strengthening these aspects will greatly improve the reliability and impact of the study. My main suggestions for improving innovation and reducing uncertainty are as follows:

1. A significant portion of the chlorine emission sources in the study are indoors. However, the exchange of gases between indoor and outdoor environments is influenced by various factors, such as building structures, climate conditions, and building usage across different regions of China. It is recommended that the authors fully consider the impact of these factors.

2. Adding new emission sources or further subdividing the emission sources does not necessarily lead to better results. Inaccurate descriptions of the spatial and temporal distribution of sources can increase uncertainty. Given chlorine's high atmospheric reactivity, spatial and temporal distribution is crucial. For example, point sources and area sources of chlorine emissions have significantly different atmospheric chemical impacts. The study's simplistic allocation of some point source emissions to entire areas may be inappropriate; additionally, the temporal distribution of pesticide use is influenced by crop types, climate, and geographical conditions, which the study does not detail.

3. The authors should provide stronger evidence to show that this more detailed method significantly reduces uncertainty. Some of these more detailed activity amounts and emission factors have limited sources. For example, the quantity of disinfectant utilized, which is cited from only one hospital, may not be sufficiently convincing.

Overall, my view aligns with previous reviewers that the methodologies and details of this study could benefit from further refinement. I encourage the authors to pursue additional investigation and experimental support.

Hide

ED: Publish subject to minor revisions (review by editor) (24 Jul 2024) by Lea Hildebrandt Ruiz

AR by Yiming Liu on behalf of the Authors (02 Aug 2024) Author's response Author's tracked changes Manuscript

ED: Publish as is (18 Aug 2024) by Lea Hildebrandt Ruiz

AR by Yiming Liu on behalf of the Authors (24 Aug 2024) Author's response Manuscript

Journal article(s) based on this preprint

16 Oct 2024

ACEIC: a comprehensive anthropogenic chlorine emission inventory for China

Siting Li, Yiming Liu, Yuqi Zhu, Yinbao Jin, Yingying Hong, Ao Shen, Yifei Xu, Haofan Wang, Haichao Wang, Xiao Lu, Shaojia Fan, and Qi Fan

Atmos. Chem. Phys., 24, 11521–11544, https://doi.org/10.5194/acp-24-11521-2024,https://doi.org/10.5194/acp-24-11521-2024, 2024

Short summary

Siting Li, Yiming Liu, Yuqi Zhu, Yinbao Jin, Yingying Hong, Ao Shen, Yifei Xu, Haofan Wang, Haichao Wang, Xiao Lu, Shaojia Fan, and Qi Fan

Supplement

https://doi.org/10.5194/egusphere-2023-1448-supplement

Siting Li, Yiming Liu, Yuqi Zhu, Yinbao Jin, Yingying Hong, Ao Shen, Yifei Xu, Haofan Wang, Haichao Wang, Xiao Lu, Shaojia Fan, and Qi Fan

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Short summary

This study establishes an inventory of anthropogenic chlorine emissions in China in 2018 with expanded categories (HCl, Cl^-, Cl₂, HOCl) and sources (41 specific sources) with detailed spatial and temporal assignments, and emission factors based on localized survey data. This study enhances the understanding of anthropogenic chlorine emissions in the atmosphere, identifies key sources, and provides scientific support for pollution control and climate change.


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