AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Investigating the Source Dependence of Aethalometer Correction Factors Using an In-House Developed Multi-Wavelength PhotoAcoustic Spectrometer
MÁTÉ PINTÉR, Gergely Kiss-Albert, Noémi Utry, Tibor Ajtai, Gábor Szabó, Zoltán Bozóki, University of Szeged, Hungary
Abstract Number: 77 Working Group: Urban Aerosols
Abstract Atmospheric carbonaceous particulate matter (CPM) is in the spotlight of scientific interest as an air pollutant regarding its impact on climate and human health as well. Due to this, there is an intensive public debate conserving its legal regulation too. As the characteristics of CPM have large spatial and temporal variation, numerous measurement campaigns have been organized for a more thorough understanding of the large scale of parameters describing the properties of ambient aerosol. In climatic models, mayor uncertainty is attributed to light absorption by ambient CPM nowadays. This is partly due to issues of instrumentation. The commercially available and most popular instruments for the measurement of optical absorption are based on the filter method that require posterior site and aerosol composition specific calibration factors for proper data interpretation. PhotoAcoustic Spectroscopy (PA) is a generally accepted reference method for determining calibration factors.
In this study, the results of a field measurement campaign carried out during the late winter and the early spring of 2015 in Budapest, the capital of Hungary are presented. We in-situ measured size distribution (SD), total scattering coefficient (TSC), optical absorption coefficient (OAC), absorption angstrom exponent (AAE) and the thermo/optical organic, elemental and total carbon (OC, EC, TC) concentration of ambient aerosol. We also collected filter samples with 6-hour time resolution that were analyzed for levoglucosan (LG) and total carbon (TC) concentrations. Based on the diurnal variation of the measured parameters, traffic and household heating were identified as the most dominant sources of CPM. Moreover, on five measurement days, new particle formation events were observed. As OAC was parallel measured by a 7-wavelength Aethalometer and our in-house developed 4-wavelength PA Spectrometer (PAS), calibration factors (C and f) were determined for all Aethalometer wavelengths based on reference measurements. Our findings indicate that the Aethalometer C factors have both wavelength dependence and diurnal variation. Based on the latter, this study proposes that the relative strength of the emitting sources should be considered during Aethalometer data correction. Interestingly, we also observed that nucleation events require the use of individual C factors.