the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Feb 2025
Characterization of filter photometer artefacts in soot and dust measurements – laboratory and ambient experiments using a traceably-calibrated aerosol absorption reference
Abstract. A novel reference absorption instrument, based on photothermal interferometry – the PTAAM-2λ, and scattering measurements are used to characterize filter photometer artefacts in measurements of absorption coefficients of soot and dust-dominated aerosol samples within laboratory and ambient campaigns.
The Aethalometer AE33 and the Continuous Light Absorption Photometer (CLAP) were characterized during a laboratory campaign where different soot-like and mineral dust samples were measured. Furthermore, ambient measurements during a campaign in Granada, Spain, were used to characterize the AE33 and MAAP (Multi Angle Absorption Photometer), a pseudo-reference absorption instrument.
The laboratory campaign showed significant wavelength dependence of the multiple-scattering parameter C. The C of AE33 at 450/808 was 4.08/3.95 and 6.25/5.27 for propane soot and diesel soot, respectively. For the CLAP the C was 5.10/4.26 and 6.79/5.80 for propane and diesel soot, respectively. For mineral dust, C at 450 nm ranged between 2.74 and 3.03 for the AE33 and between 2.50 and 2.80 for the CLAP. The ambient measurements showed an overall C of 4.72 at 450 nm and of 3.90 at 808 nm for the AE33. The results for both the AE33 and the CLAP show a dependence with the particle size, with fine particles having the highest C values, and as the aerosols become larger C levels off. Both the laboratory and the ambient measurements of the AE33 showed overlapping results.
The cross-sensitivity to scattering was smaller for the CLAP than for the AE33. The values of the cross-sensitivity parameter ms at 450/808 nm were 3.0 %/1.5 % for the AE33 and 2.4/0.9 % for the CLAP at 450/808 nm.
The intercomparison of the MAAP with the PTAAM-2λ during the ambient campaign in Granada showed that the MAAP-derived absorption coefficients feature a 47 % overestimation at 637 nm and a cross-sensitivity to scattering of 2.4 %.
Competing interests: Luka Drinovec and Griša Močnik are employed by Haze Instruments d.o.o., the manufacturer of PTAAM-2l. Other authors declare no potential conflict of interest
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.- Preprint
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Status: open (until 03 Apr 2025)
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RC1: 'Comment on egusphere-2024-3995', Anonymous Referee #1, 10 Mar 2025
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This study analyzes the multiple-scattering compensation parameter (C) for AE33 and CLAP photometers and characterizes the pseudo-reference MAAP. It emphasizes the importance of correcting scattering artifacts and knowing particle sizes to accurately compensate aerosol absorption coefficients. The accuracy of PTAM-2 λ, MAAP, and AE33 is decreasing, so it is necessary to correct the key parameters discussed in the article. But the readability of the article needs to be improved, especially the abstract and introduction, which need to be able to be quickly understood by the users of the instrument. Some details are as follows:
- Abstract: The abstract is unclear about the purpose, methods, and key results. You can add content similar to Lines 40-55 to the abstract to explain why you conducted this study.
- Introduction: The introduction is not clear for readers. How do you measure the absorption of soot and dust? What are the problems with current measurement methods? PTAAM-2λ provides reference data. I think these are your key points, but the information is spread across too many paragraphs and is not direct or clear for readers.
- For example, you can use clearer and simpler sentences to introduce that you will develop a novel method to measure dust using AE33, a measurement tool designed for black carbon (BC) (Lines 17-50).
- Lines 211: Provide more details about Equation (9) in Yus-Díez et al. (2021).
- Lines 181-182: Add sentences to emphasize that PTAAM-2λ provides reference data.
- Lines 272-274: This is a powerful conclusion, but how did you obtain it? Do you mean that the change is low, as shown in Table 3?
- Lines 317-319: This is a key point that should be included in the Introduction.
Citation: https://doi.org/10.5194/egusphere-2024-3995-RC1
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