Article Dans Une Revue Atmospheric Environment Année : 2025

Addressing the advantages and limitations of using Aethalometer data to determine the optimal Absorption Ångström Exponents (AAEs) values for eBC source apportionment

Marjan Savadkoohi
Jean-Eudes Petit
Jordi Rovira
  • Fonction : Auteur
Gang Chen
Marta Via
Minna Aurela
Martin Gysel-Beer
Martin Rigler
Asta Gregorič
Matic Ivančič
Eleni Liakakou
  • Fonction : Auteur
Iasons Stavroulas
Krista Luoma
Nikos Mihalopoulos
  • Fonction : Auteur
Tuukka Petäjä
Kaspar Daellenbach
  • Fonction : Auteur
Petr Vodička
Hilkka Timonen
  • Fonction : Auteur
Anna Tobler
Andrei Dandocsi
Stergios Vratolis
  • Fonction : Auteur
Olga Zografou
Philip Hopke
Xavier Querol
Andrés Alastuey
Marco Pandolfi
  • Fonction : Auteur

Résumé

The apportionment of equivalent black carbon (eBC) to combustion sources from liquid fuels (mainly fossil; eBCLF) and solid fuels (mainly non-fossil; eBCSF) is commonly performed using data from Aethalometer instruments (AE approach). This study evaluates the feasibility of using AE data to determine the absorption Ångström exponents (AAEs) for liquid fuels (AAELF) and solid fuels (AAESF), which are essential parameters for the AE approach. AAEs were calculated from Aethalometer data as the fit in a log-log space of the six absorption coefficients (470-950 nm) versus the corresponding wavelengths. Our results demonstrate that AAELF can be robustly determined as the 1st percentile (PC1) of AAE values from fits with R2>0.99. This R2-filtering was necessary to remove extremely low and noisy-driven AAE values commonly observed under clean atmospheric conditions (i.e., low absorption coefficients). Conversely, AAESF can be obtained from the 99th percentile (PC99) of unfiltered AAE values. To optimize the signal from solid fuel sources, winter data should be used to calculate PC99, while summer data should be used to calculate PC1 to maximize the signal from liquid fuel sources. The derived PC1 (AAELF) and PC99 (AAESF) values ranged from 0.79 to 1.08, and 1.45 to 1.84, respectively. The AAESF values were further compared with those constrained using the signal at mass-to-charge 60 (m/z 60), a marker for fresh biomass combustion, measured by aerosol chemical speciation monitor (ACSM) and aerosol mass spectrometry (AMS) instruments deployed at 16 sites. Overall, the AAESF values derived from the two methods showed strong agreement, with a coefficient of determination of 0.78. However, the uncertainties in both approaches can vary depending on site-specific sources, and in certain environments, such as at traffic-dominated sites, neither approach may be fully applicable.

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hal-04970292 , version 1 (28-02-2025)

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Marjan Savadkoohi, Mohamed Gherras, Olivier Favez, Jean-Eudes Petit, Jordi Rovira, et al.. Addressing the advantages and limitations of using Aethalometer data to determine the optimal Absorption Ångström Exponents (AAEs) values for eBC source apportionment. Atmospheric Environment, 2025, 349, pp.121121. ⟨10.1016/j.atmosenv.2025.121121⟩. ⟨hal-04970292⟩
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