10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Comparison of Ambient Aerosol Sources at Rural and Suburban Background Sites in Central Europe
OTAKAR MAKEŠ, Petr Vodička, Jaroslav Schwarz, Vladimír Ždímal, Institute of Chemical Process Fundamentals of the CAS, v.v.i
Abstract Number: 838 Working Group: Source Apportionment
Abstract During July and August 2012, and subsequently in January and February 2013, six weeks long intensive measurement campaigns aimed at PM1 ambient aerosol characterization took place at measurement site at Prague - Suchdol. Subsequently similar campaigns took place in National Atmospheric Observatory Košetice at Vysočina highlands. The first campaign took place from January to March 2014 and the second campaign took place from June to August 2014. The Suchdol site, located on the NW outskirts of Prague, was selected as a representative of suburban background station. On the other hand, the Košetice site was chosen as a representative of the rural background station.
The chemical composition and mass concentration were measured by Compact Time-of-Flight Aerosol Mass Spectrometer (C-ToF AMS, Aerodyne) during all campaigns. This measurement was supported by filter sampling, SMPS and trace gases concentrations. Raw data obtained from AMS at 1 minute time resolution were trimmed and averaged over 30 minute intervals. Subsequently, the data included the matrix of concentrations of each mass (m/z, mass to charge ratio) over time and the corresponding error matrix were exported for the source apportionment analysis. Data were analyzed using SoFi software (Canonaco et al., 2013), which uses the Multi-linear engine (ME-2) (Paatero, 1999) based on the principle of positive matrix factorization (PMF). The advantage of this approach is that the user may, on the basis of partial knowledge of one or more aerosol sources, limit the number of possible solutions and thus refine the result of the model.
During the summer measurement campaign in Suchdol, the model identified five different aerosol sources. The only identified primary aerosol source was hydrocarbon-like aerosol (HOA) originating from traffic. Semi-volatile oxygenated aerosol (SVOA) was identified as a secondary source of aerosol which is already partially oxidized in the atmosphere. Another source of secondary aerosol was low-volatile oxygenated aerosol (LVOA), which can originate at a large distance from the measuring site. The remaining two identified sources were predominantly inorganic aerosols and were called as SO4+NH4 and NO3+NH4, where the second mentioned had a very pronounced daily pattern with increased concentrations at night. During the winter campaign in Suchdol, five sources of aerosol were also identified. Probably due to the low temperatures during the day, the model was not able to distinguish the SVOA source. The primary source of biomass burning aerosol (BBOA) from biomass combustion in domestic stoves was newly discovered instead. The situation at Kosetice site was considerably different because the station is not influenced by any town located in the close neighborhood, but it is influenced by the surrounding rural and forest landscape. During the summer, the model distinguished two primary sources HOA and BBOA with relatively low contributions, two secondary sources SVOA and LVOA with a pronounced daily patterns and two mostly inorganic sources SO4+NH4 and NO3+NH4. In winter, the contributions of both primary sources increased and the SVOA factor was not recognized again.
Financial support by the ACTRIS – CZ (num. LM2015037) is gratefully appreciated.