the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Apr 2025
Measurement report: Investigation of Optical Properties of Different Fuels Diesel Exhaust by an Atmospheric Simulation Chamber experiment
Abstract. This study investigates the optical properties and variability of the mass absorption coefficient (MAC) of carbonaceous aerosols produced by the combustion of different fuels. Emissions were also characterized in terms of particle size distribution and concentrations of elemental (EC) and organic carbon (OC). Experiments were conducted in an atmospheric simulation chamber with a soot generator fueled with propane and a commercial diesel engine running on regular diesel and Hydrotreated Vegetable Oil (HVO). Different methods of sampling and analyzing carbonaceous aerosols were evaluated, focusing on workplace environments. The EC:TC (total carbon) ratios were found to be around 0.7 for propane, 0.15 for diesel, and 0.4 for HVO, indicating a higher proportion of OC in the diesel and HVO samples. Fresh soot particles showed monomodal log-normal distributions with peaks varying based on the fuel type and combustion process, with propane particles exhibiting a peak at larger particle sizes compared to HVO and diesel. The optical properties revealed that the MAC values varied across different fuel exhausts. Diesel combustion produced more light-absorbing particles compared to propane and HVO, with MAC values measured between 870 and 635 nm ranging from 6.2 ± 0.5 to 9.4 ± 0.4 m² g⁻¹ for commercial diesel, 5.2 ± 0.5 to 7.8 ± 1.1 m² g⁻¹ for propane, and 5.8 ± 0.2 to 8.4 ± 0.6 m² g⁻¹ for HVO.
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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
(1102 KB)
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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
(1102 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-1447', Anonymous Referee #1, 17 Apr 2025
The study presented here is a valuable contribution to the aerosol community. It provides optical properties, more specifically mass absorption cross section values, for three different soot-like aerosol samples. Two of the samples are based on the combustion of liquid fuels burned in a real diesel engine. The manuscript is well written and the data are well presented. I would suggest publishing it after addressing the following comments:
Scientific comments
- Provide information on the calibration of the various instruments, especially the PAX.
- The EC:TC ratio is quite different for the different samples. The larger amount of OC in some samples could affect the MAC amid coating. However, the authors do not address this issue. Please comment on this.
- It has been shown that MISG soot has an average diameter between 200-300 nm. The very different particle diameter compared to the other two samples will strongly affect the MAC values, making these results not comparable. In addition, the large size of MISG-generated soot particles is not representative of engine exhaust soot. Is the use of the MISG still justified?
- It would be interesting to see how the different absorption coefficient measurement techniques compare in terms of b_abs.
- In Table 4, it would be valuable to include the MAC values interpolated to 550 nm in addition to those already shown. This would make it easier for the reader to make comparisons with literature values.
- What is the wavelength in Figure 4? Please add it to the axis labels.
- I would recommend showing the absorption angstrom exponents measured by the MWAA.
- The conclusion section is weak. There is no discussion of the implications of the MAC values found in the study. Please improve.
- "Correction factors" are mentioned on page 16. Please elaborate. What corrections are referenced?Typos
- Page 11, second paragraph: MISG is misspelled.
Citation: https://doi.org/10.5194/egusphere-2025-1447-RC1 -
AC1: 'Reply on RC1', Federico Mazzei, 06 Jun 2025
Dear RC1
on behalf of all authors, I would like to thank you for your thorough and constructive comments on our manuscript. We appreciate the time and effort you have dedicated to evaluating our work, and we believe your feedback has significantly contributed to improving the quality and clarity of the paper.
Following your suggestions, we have revised the manuscript accordingly. A detailed, point-by-point response to your comments is provided in the attachment. Our replies are shown in blue.
We hope the changes made are in line with the reviewers’ feedback and expectations.
Best Regards
Federico Mazzei
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AC1: 'Reply on RC1', Federico Mazzei, 06 Jun 2025
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RC2: 'Comment on egusphere-2025-1447', Anonymous Referee #2, 28 Apr 2025
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AC2: 'Reply on RC2', Federico Mazzei, 06 Jun 2025
Dear RC2
on behalf of all authors, I would like to thank you for your thorough and constructive comments on our manuscript. We appreciate the time and effort you have dedicated to evaluating our work, and we believe your feedback has significantly contributed to improving the quality and clarity of the paper.
Following your suggestions, we have revised the manuscript accordingly. A detailed, point-by-point response to your comments is provided in the attachment. Our replies are shown in blue.
We hope the changes made are in line with the reviewers’ feedback and expectations.
Best Regards
Federico Mazzei
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AC2: 'Reply on RC2', Federico Mazzei, 06 Jun 2025
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RC3: 'Comment on egusphere-2025-1447', Anonymous Referee #3, 14 May 2025
Danelli et al. present a study investigating the EC/OC ratio, particle size distribution, and MAC of carbonaceous aerosols produced from the combustion of various fuels using an atmospheric simulation chamber. The experimental setup is well designed, and the results provide meaningful insights into the optical properties of combustion-derived aerosols. This study aligns with the scope of ACP as a measurement report. I recommend it for publication, provided the following comments are addressed:
- The current title may be misleading, as not all particles investigated are derived from diesel exhaust. I suggest revising the title to better reflect the scope of the study. For example:
“Investigation of Optical Properties of Carbonaceous Aerosols from the Combustion of Different Fuels Using an Atmospheric Simulation Chamber.” - While the study focuses on aerosol optical properties, no health-related outcomes are presented. Therefore, I suggest removing or minimizing health-related discussions in the Introduction, as they may distract from the main focus.
- For the MISG experiments, please clarify the rationale for selecting the specific “global equivalence ratio.” Was this condition intended to replicate soot production mechanisms similar to those in diesel engines? Since the EC/OC ratio is highly sensitive to combustion stoichiometry, a justification for this choice is essential to contextualize comparisons with engine-derived emissions. Additionally, please ensure the reference “Vernocchi et al., 2022” is listed in the References, as it appears to be missing.
- The measured particle size distributions are based on mobility diameters (SMPS). Did the authors consider the influence of particle morphology? For instance, the larger mobility diameters observed for soot generated by MISG are likely due to the aggregate structure typical of high-EC (soot-rich) particles. This morphology can significantly inflate the mobility diameter relative to the volume-equivalent diameter and should be discussed when interpreting the size data.
- Please include the standard deviation of the EC:TC ratio in the abstract.
Citation: https://doi.org/10.5194/egusphere-2025-1447-RC3 -
AC3: 'Reply on RC3', Federico Mazzei, 06 Jun 2025
Dear RC3
on behalf of all authors, I would like to thank you for your thorough and constructive comments on our manuscript. We appreciate the time and effort you have dedicated to evaluating our work, and we believe your feedback has significantly contributed to improving the quality and clarity of the paper.
Following your suggestions, we have revised the manuscript accordingly. A detailed, point-by-point response to your comments is provided in the attachment. Our replies are shown in blue.
We hope the changes made are in line with the reviewers’ feedback and expectations.
Best Regards
Federico Mazzei
- The current title may be misleading, as not all particles investigated are derived from diesel exhaust. I suggest revising the title to better reflect the scope of the study. For example:
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-1447', Anonymous Referee #1, 17 Apr 2025
The study presented here is a valuable contribution to the aerosol community. It provides optical properties, more specifically mass absorption cross section values, for three different soot-like aerosol samples. Two of the samples are based on the combustion of liquid fuels burned in a real diesel engine. The manuscript is well written and the data are well presented. I would suggest publishing it after addressing the following comments:
Scientific comments
- Provide information on the calibration of the various instruments, especially the PAX.
- The EC:TC ratio is quite different for the different samples. The larger amount of OC in some samples could affect the MAC amid coating. However, the authors do not address this issue. Please comment on this.
- It has been shown that MISG soot has an average diameter between 200-300 nm. The very different particle diameter compared to the other two samples will strongly affect the MAC values, making these results not comparable. In addition, the large size of MISG-generated soot particles is not representative of engine exhaust soot. Is the use of the MISG still justified?
- It would be interesting to see how the different absorption coefficient measurement techniques compare in terms of b_abs.
- In Table 4, it would be valuable to include the MAC values interpolated to 550 nm in addition to those already shown. This would make it easier for the reader to make comparisons with literature values.
- What is the wavelength in Figure 4? Please add it to the axis labels.
- I would recommend showing the absorption angstrom exponents measured by the MWAA.
- The conclusion section is weak. There is no discussion of the implications of the MAC values found in the study. Please improve.
- "Correction factors" are mentioned on page 16. Please elaborate. What corrections are referenced?Typos
- Page 11, second paragraph: MISG is misspelled.
Citation: https://doi.org/10.5194/egusphere-2025-1447-RC1 -
AC1: 'Reply on RC1', Federico Mazzei, 06 Jun 2025
Dear RC1
on behalf of all authors, I would like to thank you for your thorough and constructive comments on our manuscript. We appreciate the time and effort you have dedicated to evaluating our work, and we believe your feedback has significantly contributed to improving the quality and clarity of the paper.
Following your suggestions, we have revised the manuscript accordingly. A detailed, point-by-point response to your comments is provided in the attachment. Our replies are shown in blue.
We hope the changes made are in line with the reviewers’ feedback and expectations.
Best Regards
Federico Mazzei
-
AC1: 'Reply on RC1', Federico Mazzei, 06 Jun 2025
-
RC2: 'Comment on egusphere-2025-1447', Anonymous Referee #2, 28 Apr 2025
-
AC2: 'Reply on RC2', Federico Mazzei, 06 Jun 2025
Dear RC2
on behalf of all authors, I would like to thank you for your thorough and constructive comments on our manuscript. We appreciate the time and effort you have dedicated to evaluating our work, and we believe your feedback has significantly contributed to improving the quality and clarity of the paper.
Following your suggestions, we have revised the manuscript accordingly. A detailed, point-by-point response to your comments is provided in the attachment. Our replies are shown in blue.
We hope the changes made are in line with the reviewers’ feedback and expectations.
Best Regards
Federico Mazzei
-
AC2: 'Reply on RC2', Federico Mazzei, 06 Jun 2025
-
RC3: 'Comment on egusphere-2025-1447', Anonymous Referee #3, 14 May 2025
Danelli et al. present a study investigating the EC/OC ratio, particle size distribution, and MAC of carbonaceous aerosols produced from the combustion of various fuels using an atmospheric simulation chamber. The experimental setup is well designed, and the results provide meaningful insights into the optical properties of combustion-derived aerosols. This study aligns with the scope of ACP as a measurement report. I recommend it for publication, provided the following comments are addressed:
- The current title may be misleading, as not all particles investigated are derived from diesel exhaust. I suggest revising the title to better reflect the scope of the study. For example:
“Investigation of Optical Properties of Carbonaceous Aerosols from the Combustion of Different Fuels Using an Atmospheric Simulation Chamber.” - While the study focuses on aerosol optical properties, no health-related outcomes are presented. Therefore, I suggest removing or minimizing health-related discussions in the Introduction, as they may distract from the main focus.
- For the MISG experiments, please clarify the rationale for selecting the specific “global equivalence ratio.” Was this condition intended to replicate soot production mechanisms similar to those in diesel engines? Since the EC/OC ratio is highly sensitive to combustion stoichiometry, a justification for this choice is essential to contextualize comparisons with engine-derived emissions. Additionally, please ensure the reference “Vernocchi et al., 2022” is listed in the References, as it appears to be missing.
- The measured particle size distributions are based on mobility diameters (SMPS). Did the authors consider the influence of particle morphology? For instance, the larger mobility diameters observed for soot generated by MISG are likely due to the aggregate structure typical of high-EC (soot-rich) particles. This morphology can significantly inflate the mobility diameter relative to the volume-equivalent diameter and should be discussed when interpreting the size data.
- Please include the standard deviation of the EC:TC ratio in the abstract.
Citation: https://doi.org/10.5194/egusphere-2025-1447-RC3 -
AC3: 'Reply on RC3', Federico Mazzei, 06 Jun 2025
Dear RC3
on behalf of all authors, I would like to thank you for your thorough and constructive comments on our manuscript. We appreciate the time and effort you have dedicated to evaluating our work, and we believe your feedback has significantly contributed to improving the quality and clarity of the paper.
Following your suggestions, we have revised the manuscript accordingly. A detailed, point-by-point response to your comments is provided in the attachment. Our replies are shown in blue.
We hope the changes made are in line with the reviewers’ feedback and expectations.
Best Regards
Federico Mazzei
- The current title may be misleading, as not all particles investigated are derived from diesel exhaust. I suggest revising the title to better reflect the scope of the study. For example:
Peer review completion
Journal article(s) based on this preprint
Data sets
Dataset for "Measurement report: Investigation of Optical Properties of Different Fuels Diesel Exhaust by an Atmospheric Simulation Chamber experiment" Silvia Giulia Danelli https://data.mendeley.com/datasets/v6p5r5dmdy/1
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Cited
Silvia Giulia Danelli
Lorenzo Caponi
Marco Brunoldi
Matilde De Camillis
Dario Massabò
Federico Mazzei
Tommaso Isolabella
Annalisa Pascarella
Paolo Prati
Matteo Santostefano
Francesca Tarchino
Virginia Vernocchi
Paolo Brotto
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1102 KB) - Metadata XML