A Novel Approach for the Spectral Based Source Apportionment of Carbonaceous Particulate Matter in the Atmosphere

TIBOR AJTAI, Csilla Gombi, Szabolcs Hodovány, István Magashegyi, Zoltán Bozóki, Abdul Rahman, Gábor Szabó, University of Szeged, Hungary

     Abstract Number: 348
     Working Group: Aerosol Processes and Properties in Changing Environments in the Anthropocene

Abstract
Light-absorbing carbonaceous particulate matter (LAC) has garnered increasing scientific attention due to its complex physicochemical properties and significant impacts on climate and human health. Real-time source apportionment and chemical characterization of atmospheric carbonaceous particulate matter (CPM) remain critical challenges in atmospheric research, necessitating advanced analytical approaches for accurate identification and quantification. The Absorption Ängstrom Exponent (AAE) – the slope of the absorption spectra in log-log representation – is the only real time measurable physical quantity of CPM, which has source specific and chemical composition relevancies. The first absorption based source apportionment method, so called Aethalometer model was demonstrated in the literature in 2008. However, in this model, additional and complicated low time resolution and off-line methods are used to determine the AAE of different sources resulted in limited reliability and accuracy in the estimation of CPM masses. Therefore, to address this pressing issue, an improved methodology for real-time source apportionment of CPM with high time resolution and improved reliability is deemed essential.
We proposed a simplified source apportionment model for the determination of CPM originating from different sources. The proposed method is based on the parallel measurement of size distribution and the wavelength dependent absorption responses of ambient aerosol using an experimentally verified thumb of rule relation between the total carbon (TC) and elemental carbon (EC) mass of different sources. Moreover, we also experimentally demonstrated the wavelength dependency of AAE using transmission measurement of filter accumulated aerosol for optical absorption coefficient (OAC) measurement, for the first time. The comparison of the proposed source apportionment and the Aethalometer models calculated on the same database as well as the limitation of Aethalometer model using different approximations are also demonstrated. Finally, we reveal and quantified the correlation between the measured AAE and other source specific markers of CPM.