Characterization of filter photometer artifacts in soot and dust measurements – laboratory and ambient experiments using a traceably calibrated aerosol absorption reference
<p>A novel reference absorption instrument based on photothermal interferometry – the dual-wavelength photothermal aerosol absorption monitor PTAAM-2<span class="inline-formula"><i>λ</i></span> – and scattering measurements are used to characterize filter phot...
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| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/18/3073/2025/amt-18-3073-2025.pdf |
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| Summary: | <p>A novel reference absorption instrument based on photothermal interferometry – the dual-wavelength photothermal aerosol absorption monitor PTAAM-2<span class="inline-formula"><i>λ</i></span> – and scattering measurements are used to characterize filter photometer artifacts in measurements of absorption coefficients of soot- and dust-dominated aerosol samples within laboratory and ambient campaigns. We provide, for different aerosol types, reference values of the multiple-scattering parameter, quantifying the artifact introduced by the interaction between the light, the particles, and the filter.</p>
<p>The Aethalometer AE33 and the Continuous Light Absorption Photometer (CLAP) were characterized during a laboratory campaign where different soot and mineral dust samples were measured. Furthermore, ambient measurements during a campaign in Granada, Spain, were used to characterize the AE33 and MAAP (Multiangle Absorption Photometer), a pseudo-reference absorption instrument.</p>
<p>The laboratory campaign showed significant wavelength dependence of the calibration parameter, the multiple-scattering parameter <span class="inline-formula"><i>C</i></span>. The <span class="inline-formula"><i>C</i></span> of the AE33 at 450 and 808 nm was 4.08 and 3.95 and 6.25 and 5.27 for propane soot and diesel soot, respectively. For the CLAP, the <span class="inline-formula"><i>C</i></span> was 5.10 and 4.26 and 6.79 and 5.80 for propane and diesel soot, respectively. For the different mineral dust samples analyzed in the laboratory, the <span class="inline-formula"><i>C</i></span> 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 at Granada showed an overall <span class="inline-formula"><i>C</i></span> 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 <span class="inline-formula"><i>C</i></span> values and with the <span class="inline-formula"><i>C</i></span> being reduced and leveling off for larger particles. Both the laboratory and the ambient measurements of the AE33 showed overlapping results.</p>
<p>The cross-sensitivity to scattering was smaller for the CLAP than for the AE33. The values of the cross-sensitivity parameter <span class="inline-formula"><i>m</i><sub>s</sub></span> at 450 and 808 nm were 3.0 % and 1.5 % for the AE33 and 2.4 % and 0.9 % for the CLAP.</p>
<p>The intercomparison of the MAAP with the PTAAM-2<span class="inline-formula"><i>λ</i></span> during the ambient campaign in Granada showed that the MAAP overestimates the absorption coefficients for 47 % at 637 nm and features a cross-sensitivity to scattering of 2.4 %.</p> |
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| ISSN: | 1867-1381 1867-8548 |