the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Feb 2024
Measurement Report: Size-resolved secondary organic aerosol formation modulated by aerosol water uptake in wintertime haze
Abstract. This study investigated the potential effects of inorganics changes on aerosol water uptake and thus secondary organic aerosol (SOA) formation in wintertime haze, based on the size-resolved measurements of non-refractory fine particulate matter (NR-PM2.5) in Xi’an, Northwest China. The composition of inorganic aerosol showed significant changes in winter 2018–2019 compared to winter 2013–2014, shifting from a sulfate-rich to a nitrate-rich profile. In particular, the fraction of sulfate and chloride decreased but nitrate increased in the entire size range, while ammonium mainly increased at larger particle sizes. These changes thus resulted in size-dependent evolution in water uptake. Increased water uptake was observed in most cases mainly associated with enhanced contributions of both nitrate and ammonium, with the highest increase ratio reaching 5–35 % at larger particle sizes and higher relative-humidity (RH). The non-negligible influence of chloride on aerosol water uptake was also emphasized. The random forest analysis coupled with a Shapley additive explanation algorithm (SHAP) further showed enhanced relative importance of aerosol water in impacting SOA formation. Aerosol water contributed to the SOA formation in most cases in winter 2018–2019, and the SHAP value increased as aerosol water increased, especially at larger particle sizes. This implies the majority of enhanced aerosol water uptake at larger particle sizes and high RH might facilitate the efficient aqueous-phase SOA formation. This study highlights the key role of aerosol water as a medium to link inorganics and organics in their multiphase processes. As challenges to further improve China's air quality remain and SOA plays an increasing role in haze pollution, these results provide an insight into the size-resolved evolution characteristics and offer a guidance for future control.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(839 KB) - Metadata XML
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Supplement
(372 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-573', Anonymous Referee #1, 25 Mar 2024
By analyzing the size-resolved chemical composition of non-refractory fine particulate matter obtained at winter 2013-2014 and winter 2018-2019, this study investigated the potential effects of inorganics changes on aerosol water uptake and secondary organic aerosol formation. They found the increased water uptake at larger particles as the aerosol chemical profile shifted from a sulfate-rich to a nitrate-rich. Further, they reported that the enhanced aerosol water uptake at larger particle sizes resulted by the changed aerosol chemical profile, would facilitate the efficient aqueous-phase SOA formation, which provided an interesting perspective to evaluate the role of inorganics and organics in their multiphase processes. Yet, there are some issues that need to be addressed for further improving this work.
- Line 24-25, it is better to give a specific value here for quantify the “higher relative-humidify”
- Line 28-30, it is unclear what the implicit relation between SHAP value and the aerosol water.
- Line 89-91, two kinds of instruments were used for the measurement of NR-PM5 and its size-resolved chemical composition. Is there any difference for quantification of organic and inorganic components? A brief explanation should be provided here.
- Line 97-99, the experimentally determined RIEs and standard RIEs were used for different components, why?
- Line 174-175, in winter 2013-2014, chloride are obviously concentrated on the smaller particle size, while it maintained a relatively smaller and stable contribution in winter 2018-2019. Please explain it.
- Line 215. As showed in Figure 2, the mass range of NR-PM2.5 in 2018-2019 are much smaller than that in 2013-2014, it is better to explore and compare the variations in the fractions of nitrate and sulfatein the same mass range of NR-PM2.5.
- Line 300-305, I agree thatthe fraction of organics in total NR-PM2.5 changed less in winter 2018-2019 compared to winter 2013-2014. However, the fraction of water-soluble organics, which contributed more to ALWC related to total organics, maybe varied a lot.
- Line 319-325, a clear explanation for the intend implication of theSHAP value should provide first before the discussion on SOA formation.
- Line 329-332, as the particle mass concentration had been largely reduced in 2018-2019, the gas-particle partitioning of water-soluble organic compounds would be also suppressed as the aerosol surface been decreased. What about the aerosol acidity with increased nitrate fraction? And what the role of aerosol acidity on the SOA formation through multiphase reactions?
Citation: https://doi.org/10.5194/egusphere-2024-573-RC1 -
RC2: 'Comment on egusphere-2024-573', Anonymous Referee #2, 03 Apr 2024
Comments on “Measurement Report: Size-resolved secondary organic aerosol formation modulated by aerosol water uptake in wintertime haze”
This study investigated the factors influencing SOA formation at different particle sizes. Data from two observations (2013–2014, 2018–2019) in Xi’an in winter revealed that the composition of inorganic aerosols changed significantly from sulfate-rich to nitrate-rich at different particle sizes. This transition resulted in changes in aerosol water uptake. Further analysis using random forest and the Shapley additive explanation algorithm (SHAP) elucidated the relative significance of aerosol water in SOA formation, particularly at larger particle sizes. This finding implies that the enhancement of aerosol water uptake at larger particle sizes and high RH may contribute to liquid-phase SOA formation. Before this article was published, there may have been some issues that needed to be corrected as follows:
General comments
- The detailed methodology of PMF analysis as a function of particle size is not clear. Is 3D-matrix or 2D matrix PMF used? How about the time series of the size-resolved PMF factor? Detailed information on how to obtain the best solution for the size-resolved PMF shall be shown.
- Are the fractions of SOA and POA in total OA based on sizes-resolved PMF consistent with the fractions obtained with MS data only? If not, what might cause the differences?
- Section 3.2 the organic aerosols account for a large fraction of total PM masses and the fraction increases with the particle sizes get higher. Thus, the aerosol water uptake contributed by organics cannot be ignored and shall be considered here. E.g., method in Guo et al. (2015).
- The methodology for SHAP analysis is not very clear as well. The validation of the output results from the machine learning model shall be displayed.
- The meaning of Figure 6 is not easy to follow for readers who are not farmilar with SHAP model, and more explanation is needed here. For the water in Figure 6b, it seems that the water contributes negative SOA formation when the water mass concentration is low and positive SOA formation when the water concentration is high. How to explain this? The importance of water to SOA formation seems to decrease from “225-317 nm” to “447-631 nm” and then increase when the particle size increases. What might cause this?
- How to explain the temperature effect on SOA formation in Fig. 6. More explanation is needed here since temperature is the most important factors which influence the SOA formation here.
Minor comments
- Line 121: How many factors are the signals with SNR with 0.2 <SNR<3 downweighed?
- Line 142: The formula is missing a sequence number.
- The color code of Fig. 2 is not very clear, especially for the small particle size (112-631nm), please modify it so that the readers can see it more clearly.
- Line 90, Is eptof data used here or the regular PToF data? Please clarify.
References:
Guo, H., Xu, L., Bougiatioti, A., Cerully, K.M., Capps, S.L., Hite, J.R., Carlton, A.G., Lee, S.H., Bergin, M.H., Ng, N.L., Nenes, A., Weber, R.J., 2015. Fine-particle water and pH in the southeastern United States. Atmospheric Chemistry and Physics 15, 5211-5228.
Citation: https://doi.org/10.5194/egusphere-2024-573-RC2 -
AC1: 'Comment on egusphere-2024-573', Ru-Jin Huang, 07 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-573/egusphere-2024-573-AC1-supplement.pdf
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AC2: 'Comment on egusphere-2024-573', Ru-Jin Huang, 07 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-573/egusphere-2024-573-AC2-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-573', Anonymous Referee #1, 25 Mar 2024
By analyzing the size-resolved chemical composition of non-refractory fine particulate matter obtained at winter 2013-2014 and winter 2018-2019, this study investigated the potential effects of inorganics changes on aerosol water uptake and secondary organic aerosol formation. They found the increased water uptake at larger particles as the aerosol chemical profile shifted from a sulfate-rich to a nitrate-rich. Further, they reported that the enhanced aerosol water uptake at larger particle sizes resulted by the changed aerosol chemical profile, would facilitate the efficient aqueous-phase SOA formation, which provided an interesting perspective to evaluate the role of inorganics and organics in their multiphase processes. Yet, there are some issues that need to be addressed for further improving this work.
- Line 24-25, it is better to give a specific value here for quantify the “higher relative-humidify”
- Line 28-30, it is unclear what the implicit relation between SHAP value and the aerosol water.
- Line 89-91, two kinds of instruments were used for the measurement of NR-PM5 and its size-resolved chemical composition. Is there any difference for quantification of organic and inorganic components? A brief explanation should be provided here.
- Line 97-99, the experimentally determined RIEs and standard RIEs were used for different components, why?
- Line 174-175, in winter 2013-2014, chloride are obviously concentrated on the smaller particle size, while it maintained a relatively smaller and stable contribution in winter 2018-2019. Please explain it.
- Line 215. As showed in Figure 2, the mass range of NR-PM2.5 in 2018-2019 are much smaller than that in 2013-2014, it is better to explore and compare the variations in the fractions of nitrate and sulfatein the same mass range of NR-PM2.5.
- Line 300-305, I agree thatthe fraction of organics in total NR-PM2.5 changed less in winter 2018-2019 compared to winter 2013-2014. However, the fraction of water-soluble organics, which contributed more to ALWC related to total organics, maybe varied a lot.
- Line 319-325, a clear explanation for the intend implication of theSHAP value should provide first before the discussion on SOA formation.
- Line 329-332, as the particle mass concentration had been largely reduced in 2018-2019, the gas-particle partitioning of water-soluble organic compounds would be also suppressed as the aerosol surface been decreased. What about the aerosol acidity with increased nitrate fraction? And what the role of aerosol acidity on the SOA formation through multiphase reactions?
Citation: https://doi.org/10.5194/egusphere-2024-573-RC1 -
RC2: 'Comment on egusphere-2024-573', Anonymous Referee #2, 03 Apr 2024
Comments on “Measurement Report: Size-resolved secondary organic aerosol formation modulated by aerosol water uptake in wintertime haze”
This study investigated the factors influencing SOA formation at different particle sizes. Data from two observations (2013–2014, 2018–2019) in Xi’an in winter revealed that the composition of inorganic aerosols changed significantly from sulfate-rich to nitrate-rich at different particle sizes. This transition resulted in changes in aerosol water uptake. Further analysis using random forest and the Shapley additive explanation algorithm (SHAP) elucidated the relative significance of aerosol water in SOA formation, particularly at larger particle sizes. This finding implies that the enhancement of aerosol water uptake at larger particle sizes and high RH may contribute to liquid-phase SOA formation. Before this article was published, there may have been some issues that needed to be corrected as follows:
General comments
- The detailed methodology of PMF analysis as a function of particle size is not clear. Is 3D-matrix or 2D matrix PMF used? How about the time series of the size-resolved PMF factor? Detailed information on how to obtain the best solution for the size-resolved PMF shall be shown.
- Are the fractions of SOA and POA in total OA based on sizes-resolved PMF consistent with the fractions obtained with MS data only? If not, what might cause the differences?
- Section 3.2 the organic aerosols account for a large fraction of total PM masses and the fraction increases with the particle sizes get higher. Thus, the aerosol water uptake contributed by organics cannot be ignored and shall be considered here. E.g., method in Guo et al. (2015).
- The methodology for SHAP analysis is not very clear as well. The validation of the output results from the machine learning model shall be displayed.
- The meaning of Figure 6 is not easy to follow for readers who are not farmilar with SHAP model, and more explanation is needed here. For the water in Figure 6b, it seems that the water contributes negative SOA formation when the water mass concentration is low and positive SOA formation when the water concentration is high. How to explain this? The importance of water to SOA formation seems to decrease from “225-317 nm” to “447-631 nm” and then increase when the particle size increases. What might cause this?
- How to explain the temperature effect on SOA formation in Fig. 6. More explanation is needed here since temperature is the most important factors which influence the SOA formation here.
Minor comments
- Line 121: How many factors are the signals with SNR with 0.2 <SNR<3 downweighed?
- Line 142: The formula is missing a sequence number.
- The color code of Fig. 2 is not very clear, especially for the small particle size (112-631nm), please modify it so that the readers can see it more clearly.
- Line 90, Is eptof data used here or the regular PToF data? Please clarify.
References:
Guo, H., Xu, L., Bougiatioti, A., Cerully, K.M., Capps, S.L., Hite, J.R., Carlton, A.G., Lee, S.H., Bergin, M.H., Ng, N.L., Nenes, A., Weber, R.J., 2015. Fine-particle water and pH in the southeastern United States. Atmospheric Chemistry and Physics 15, 5211-5228.
Citation: https://doi.org/10.5194/egusphere-2024-573-RC2 -
AC1: 'Comment on egusphere-2024-573', Ru-Jin Huang, 07 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-573/egusphere-2024-573-AC1-supplement.pdf
-
AC2: 'Comment on egusphere-2024-573', Ru-Jin Huang, 07 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-573/egusphere-2024-573-AC2-supplement.pdf
Peer review completion
Journal article(s) based on this preprint
Data sets
Measurement Report: Size-resolved secondary organic aerosol formation modulated by aerosol water uptake in wintertime haze Jing Duan et al. https://doi.org/10.12262/IEECAS.EAPSD2024001
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Jing Duan
Ru-Jin Huang
Ying Wang
Wei Xu
Haobin Zhong
Chunshui Lin
Wei Huang
Yifang Gu
Jurgita Ovadnevaite
Darius Ceburnis
Colin O’Dowd
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(839 KB) - Metadata XML
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Supplement
(372 KB) - BibTeX
- EndNote
- Final revised paper