the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 Oct 2023
Comparison of the LEO and CPMA-SP2 techniques for black-carbon mixing-state measurements
Abstract. It is necessary to measure the mixing states of light-absorbing carbon (LAC) particles to reduce uncertainties in climate forcing due to particulate from wildfires and biomass combustion. For refractory LAC (normally called refractory black carbon; rBC), such measurements can be made using the single particle soot photometer (SP2). The SP2 measures the incandescent mass of individual particles due to heating by a 1064 nm laser. The SP2 also monitors single-particle light scattering from rBC plus internally mixed material (e.g., coatings of volatile particulate matter). rBC mixing states can be estimated from SP2 measurements by combining the scattering and incandescence signals. This is the basis of the published methods known as the (i ) scattering–incandescence lag-time, (ii ) leading-edge only (LEO), and (iii ) normalized derivative methods. More recently, the tandem centrifugal particle mass analyzer (CPMA)–SP2 method has been developed. The CPMA–SP2 method does not rely on the SP2 scattering signals and, therefore truly measures the rBC mass fraction, with no assumptions regarding particle composition or morphology. In this study, we provide the first quantitative comparison of the light-scattering and CPMA–SP2 methods for measuring mixing state. We discuss the upper and lower limits of detection (in terms of both rBC and coatings), temporal resolution, role of counting statistics, and errors associated with the measurements. We use a data set of atmospheric particles sampled at a regional background site (Kamloops, Canada; about 350 km northeast of Vancouver, British Columbia, Canada), where the majority of rBC was emitted by seasonal wildfires. In the overall comparison among measurement methods, the CPMA–SP2 method is found to have significantly better systematic uncertainties than the light-scattering methods for wildfire smoke. For example, the light-scattering methods could not quantify coatings on half of the rBC particles, because their light-scattering signals were below the SP2 detection limit. Consequently, the bias in SP2-only estimates of rBC mixing states depends on the size distribution of the rBC particles. Although more accurate, CPMA–SP2 measurements require significantly more time to acquire, whereas SP2-only light-scattering analyses (both LEO and lag-time) can provide near real-time qualitative information representing large rBC particles.
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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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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- BibTeX
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-2216', Anonymous Referee #1, 16 Nov 2023
Comment on “ Comparison of the LEO and CPMA-SP2 techniques for black-carbon mixing-state measurements”
The manuscript gave the comparison results of the measured black carbon mixing states from LEO and CPMA-SP2 techniques. The articles fall well into the scope of AMT. In general, the results are interesting and important to the related researchers. The manuscript can be accepted after some major revisions.
Major Comments:
1 The LEO detection limits results and the corresponding impacts of measured black carbon mixing states were mentioned before by Zhao, Shen et al. (2020). The new findings of this manuscript relative to that article should be detailed.
2 The Gassion fit of LEO fits of the LSD signals may still be useful even though the signals detected by the SP2 are saturated. If these particles are considered, the difference between the LEO and CPMA-SP2 methods would not be so different as shown in Figure 4.
3 Around line 360, iff the BC core were not compacted, ie the BC core is filled with some air, then the effective density of the BC core may be reconsidered as shown in (Zhang, Zhang et al. 2016, Zhang, Su et al. 2018). This effects should also be dissucssed.
Minor Comments:
1 Line 209, it should be mentioned that some lag time of the detailed information can be found in Figure 8 or some following discussion.
Zhang, Y., H. Su, N. Ma, G. Li, S. Kecorius, Z. Wang, M. Hu, T. Zhu, K. He, A. Wiedensohler, Q. Zhang and Y. Cheng (2018). "Sizing of ambient particles from a Single Particle Soot Photometer measurement to retrieve mixing state of Black Carbon at a Regional site of the North China Plain." Journal of Geophysical Research: Atmospheres 123(22): 12778-12795.
Zhang, Y., Q. Zhang, Y. Cheng, H. Su, S. Kecorius, Z. Wang, Z. Wu, M. Hu, T. Zhu, A. Wiedensohler and K. He (2016). "Measuring the morphology and density of internally mixed black carbon with SP2 and VTDMA: new insight into the absorption enhancement of black carbon in the atmosphere." Atmospheric Measurement Techniques 9(4): 1833-1843.
Zhao, G., C. Shen and C. Zhao (2020). "Technical note: Mismeasurement of the core-shell structure of black carbon-containing ambient aerosols by SP2 measurements." Atmospheric Environment 243(117885).
Citation: https://doi.org/10.5194/egusphere-2023-2216-RC1 -
AC1: 'Reply on RC1', Arash Naseri, 21 Dec 2023
Dear Reviewer,
Thank you for providing us with your valuable feedback on our manuscript titled Comparison of the
LEO and CPMA-SP2 techniques for black-carbon mixing-state measurements, submitted to Atmospheric
Measurement Techniques. We sincerely appreciate the time and effort you have dedicated to reviewing
our work, and we are grateful for the opportunity to incorporate your constructive feedback into our
revisions. After carefully considering all of your comments, we have made revisions throughout the
manuscript to address them. To clearly indicate our responses to the reviewer’s comments, we have
highlighted them in red text text, while changes made to the manuscript are highlighted in blue text.
We believe that these revisions significantly improve the quality and clarity of our manuscript. We are
thankful for your valuable input, which has helped us enhance this work. We hope that our responses
and revisions adequately address your concerns, and we eagerly await your positive consideration of our
revised manuscript. Please find our response to your comments as per attached file.
-
AC1: 'Reply on RC1', Arash Naseri, 21 Dec 2023
-
RC2: 'Comment on egusphere-2023-2216', Anonymous Referee #2, 26 Nov 2023
Naseri et al. compare several techniques to derive the mixing state from black carbon measurements obtained by the single particle soot photometer (SP2). Their results show that coupling the SP2 with a centrifugal particle mass analyzer provides the best results.
Overall the paper is well written and clearly explains the origin and application of the different methods. This manuscript presents a valuable addition to groups that seek to experimentally determine the mixing state of black carbon using similar techniques. I therefore recommend publication.
Minor comments:
“normalized derivative of the scattering signal is used in the ND approach to obtain analogous information” -> Please explain what the normalized derivative is here.
“The upper coating thickness limit of LEO (line ii), was ∼ 285 nm in our study, due to saturation of the scattering detector” -> was it not possible to utilize the low gain scattering detector? This should extend this upper limit further.
“morphological assumptions” -> please rephrase to “assumption regarding the morphology” or something like that.
Citation: https://doi.org/10.5194/egusphere-2023-2216-RC2 -
AC2: 'Reply on RC2', Arash Naseri, 21 Dec 2023
Dear Reviewer,
Thank you for providing us with your valuable feedback on our manuscript titled Comparison of the
LEO and CPMA-SP2 techniques for black-carbon mixing-state measurements, submitted to Atmospheric
Measurement Techniques. We sincerely appreciate the time and effort you have dedicated to reviewing
our work, and we are grateful for the opportunity to incorporate your constructive feedback into our
revisions. After carefully considering all of your comments, we have made revisions throughout the
manuscript to address them. To clearly indicate our responses to the reviewer’s comments, we have
highlighted them in red text text, while changes made to the manuscript are highlighted in blue text.
We believe that these revisions significantly improve the quality and clarity of our manuscript. We are
thankful for your valuable input, which has helped us enhance this work. We hope that our responses
and revisions adequately address your concerns, and we eagerly await your positive consideration of our
revised manuscript. Please find our response to your comments as per attached file.
-
AC2: 'Reply on RC2', Arash Naseri, 21 Dec 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2216', Anonymous Referee #1, 16 Nov 2023
Comment on “ Comparison of the LEO and CPMA-SP2 techniques for black-carbon mixing-state measurements”
The manuscript gave the comparison results of the measured black carbon mixing states from LEO and CPMA-SP2 techniques. The articles fall well into the scope of AMT. In general, the results are interesting and important to the related researchers. The manuscript can be accepted after some major revisions.
Major Comments:
1 The LEO detection limits results and the corresponding impacts of measured black carbon mixing states were mentioned before by Zhao, Shen et al. (2020). The new findings of this manuscript relative to that article should be detailed.
2 The Gassion fit of LEO fits of the LSD signals may still be useful even though the signals detected by the SP2 are saturated. If these particles are considered, the difference between the LEO and CPMA-SP2 methods would not be so different as shown in Figure 4.
3 Around line 360, iff the BC core were not compacted, ie the BC core is filled with some air, then the effective density of the BC core may be reconsidered as shown in (Zhang, Zhang et al. 2016, Zhang, Su et al. 2018). This effects should also be dissucssed.
Minor Comments:
1 Line 209, it should be mentioned that some lag time of the detailed information can be found in Figure 8 or some following discussion.
Zhang, Y., H. Su, N. Ma, G. Li, S. Kecorius, Z. Wang, M. Hu, T. Zhu, K. He, A. Wiedensohler, Q. Zhang and Y. Cheng (2018). "Sizing of ambient particles from a Single Particle Soot Photometer measurement to retrieve mixing state of Black Carbon at a Regional site of the North China Plain." Journal of Geophysical Research: Atmospheres 123(22): 12778-12795.
Zhang, Y., Q. Zhang, Y. Cheng, H. Su, S. Kecorius, Z. Wang, Z. Wu, M. Hu, T. Zhu, A. Wiedensohler and K. He (2016). "Measuring the morphology and density of internally mixed black carbon with SP2 and VTDMA: new insight into the absorption enhancement of black carbon in the atmosphere." Atmospheric Measurement Techniques 9(4): 1833-1843.
Zhao, G., C. Shen and C. Zhao (2020). "Technical note: Mismeasurement of the core-shell structure of black carbon-containing ambient aerosols by SP2 measurements." Atmospheric Environment 243(117885).
Citation: https://doi.org/10.5194/egusphere-2023-2216-RC1 -
AC1: 'Reply on RC1', Arash Naseri, 21 Dec 2023
Dear Reviewer,
Thank you for providing us with your valuable feedback on our manuscript titled Comparison of the
LEO and CPMA-SP2 techniques for black-carbon mixing-state measurements, submitted to Atmospheric
Measurement Techniques. We sincerely appreciate the time and effort you have dedicated to reviewing
our work, and we are grateful for the opportunity to incorporate your constructive feedback into our
revisions. After carefully considering all of your comments, we have made revisions throughout the
manuscript to address them. To clearly indicate our responses to the reviewer’s comments, we have
highlighted them in red text text, while changes made to the manuscript are highlighted in blue text.
We believe that these revisions significantly improve the quality and clarity of our manuscript. We are
thankful for your valuable input, which has helped us enhance this work. We hope that our responses
and revisions adequately address your concerns, and we eagerly await your positive consideration of our
revised manuscript. Please find our response to your comments as per attached file.
-
AC1: 'Reply on RC1', Arash Naseri, 21 Dec 2023
-
RC2: 'Comment on egusphere-2023-2216', Anonymous Referee #2, 26 Nov 2023
Naseri et al. compare several techniques to derive the mixing state from black carbon measurements obtained by the single particle soot photometer (SP2). Their results show that coupling the SP2 with a centrifugal particle mass analyzer provides the best results.
Overall the paper is well written and clearly explains the origin and application of the different methods. This manuscript presents a valuable addition to groups that seek to experimentally determine the mixing state of black carbon using similar techniques. I therefore recommend publication.
Minor comments:
“normalized derivative of the scattering signal is used in the ND approach to obtain analogous information” -> Please explain what the normalized derivative is here.
“The upper coating thickness limit of LEO (line ii), was ∼ 285 nm in our study, due to saturation of the scattering detector” -> was it not possible to utilize the low gain scattering detector? This should extend this upper limit further.
“morphological assumptions” -> please rephrase to “assumption regarding the morphology” or something like that.
Citation: https://doi.org/10.5194/egusphere-2023-2216-RC2 -
AC2: 'Reply on RC2', Arash Naseri, 21 Dec 2023
Dear Reviewer,
Thank you for providing us with your valuable feedback on our manuscript titled Comparison of the
LEO and CPMA-SP2 techniques for black-carbon mixing-state measurements, submitted to Atmospheric
Measurement Techniques. We sincerely appreciate the time and effort you have dedicated to reviewing
our work, and we are grateful for the opportunity to incorporate your constructive feedback into our
revisions. After carefully considering all of your comments, we have made revisions throughout the
manuscript to address them. To clearly indicate our responses to the reviewer’s comments, we have
highlighted them in red text text, while changes made to the manuscript are highlighted in blue text.
We believe that these revisions significantly improve the quality and clarity of our manuscript. We are
thankful for your valuable input, which has helped us enhance this work. We hope that our responses
and revisions adequately address your concerns, and we eagerly await your positive consideration of our
revised manuscript. Please find our response to your comments as per attached file.
-
AC2: 'Reply on RC2', Arash Naseri, 21 Dec 2023
Peer review completion
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Cited
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Arash Naseri
Joel Corbin
Jason Olfert
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2550 KB) - Metadata XML