A dual-wavelength photothermal aerosol absorption monitor. Design, calibration and performance

dc.contributor.authorDrinovec, Luka
dc.contributor.authorJagodič, Uroš
dc.contributor.authorPirker, Luka
dc.contributor.authorŠkarabot, Miha
dc.contributor.authorKurtjak, Mario
dc.contributor.authorVidović, Kristijan
dc.contributor.authorFerrero, Luca
dc.contributor.authorVisser, Bradley
dc.contributor.authorRöhrbein, Jannis
dc.contributor.authorWeingartner, Ernest
dc.contributor.authorKalbermatter, Daniel M.
dc.contributor.authorVasilatou, Konstantina
dc.contributor.authorBühlmann, Tobias
dc.contributor.authorPascale, Celine
dc.contributor.authorMüller, Thomas
dc.contributor.authorWiedensohler, Alfred
dc.contributor.authorMočnik, Griša
dc.date.accessioned2024-01-10T09:01:31Z
dc.date.available2024-01-10T09:01:31Z
dc.date.issued2022
dc.description.abstractThere exists a lack of aerosol absorption measurement techniques with low uncertainties and without artefacts. We have developed the two-wavelength Photothermal Aerosol Absorption Monitor (PTAAM-2λ), which measures the aerosol absorption coefficient at 532 and 1064 nm. Here we describe its design, calibration and mode of operation and evaluate its applicability, limits and uncertainties. The 532 nm channel was calibrated with ∼ 1 µmol mol−1 NO2, whereas the 1064 nm channel was calibrated using measured size distribution spectra of nigrosin particles and a Mie calculation. Since the aerosolized nigrosin used for calibration was dry, we determined the imaginary part of the refractive index of nigrosin from the absorbance measurements on solid thin film samples. The obtained refractive index differed considerably from the one determined using aqueous nigrosin solution. PTAAM-2λ has no scattering artefact and features very low uncertainties: 4 % and 6 % for the absorption coefficient at 532 and 1064 nm, respectively, and 9 % for the absorption Ångström exponent. The artefact-free nature of the measurement method allowed us to investigate the artefacts of filter photometers. Both the Aethalometer AE33 and CLAP suffer from cross sensitivity to scattering – this scattering artefact is most pronounced for particles smaller than 70 nm. We observed a strong dependence of the filter multiple scattering parameter on the particle size in the 100–500 nm range. The results from the winter ambient campaign in Ljubljana showed similar multiple scattering parameter values for ambient aerosols and laboratory experiments. The spectral dependence of this parameter resulted in AE33 reporting the absorption Ångström exponent for different soot samples with values biased 0.23–0.35 higher than the PTAAM-2λ measurement. Photothermal interferometry is a promising method for reference aerosol absorption measurements.
dc.identifier.doi10.5194/amt-15-3805-2022
dc.identifier.issn1867-8548
dc.identifier.urihttps://irf.fhnw.ch/handle/11654/43601
dc.identifier.urihttps://doi.org/10.26041/fhnw-7560
dc.issue12
dc.language.isoen
dc.publisherCopernicus
dc.relation.ispartofAtmospheric Measurement Techniques
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.spatialGöttingen
dc.subject.ddc620 - Ingenieurwissenschaften und Maschinenbau
dc.titleA dual-wavelength photothermal aerosol absorption monitor. Design, calibration and performance
dc.type01A - Beitrag in wissenschaftlicher Zeitschrift
dc.volume15
dspace.entity.typePublication
fhnw.InventedHereYes
fhnw.ReviewTypeAnonymous ex ante peer review of a complete publication
fhnw.affiliation.hochschuleHochschule für Technikde_CH
fhnw.affiliation.institutlnstitut für Sensorik und Elektronikde_CH
fhnw.openAccessCategoryGold
fhnw.pagination3805-3825
fhnw.publicationStatePublished
relation.isAuthorOfPublication05dd9a19-7a24-4325-805a-2d121483b168
relation.isAuthorOfPublication.latestForDiscovery05dd9a19-7a24-4325-805a-2d121483b168
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