10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Source Apportionment and Variability of Submicron Organic Aerosol from Year-long Near Real-time Measurements Over an Urban Mediterranean Area
Aikaterini Bougiatioti, IASONAS STAVROULAS, Despina Paraskevopoulou, Georgios Grivas, Pavlos Zarmpas, Eleni Liakakou, Evangelos Gerasopoulos, Nikolaos Mihalopoulos, National Observatory of Athens
Abstract Number: 1423 Working Group: Carbonaceous Aerosol
Abstract Organic aerosol (OA) represents a large fraction of submicron aerosols worldwide, especially in urban areas. During the winter season, wood combustion is one of the major sources of OA in Europe (Puxbaum et al., 2007) which apart from contributing to the production of primary aerosol, is also responsible for significant secondary organic aerosol formation (Heringa et al., 2011). The economic recession in Greece during the past seven years has caused a deceleration of industrial activity and limitation of vehicular circulation (Paraskevopoulou et al., 2014). Strong correlation between economic indicators and several pollutants levels, reveal that this recession has resulted in significantly lower levels of pollutants in many large cities of Greece (Vrekoussis et al., 2013). Nevertheless, this crisis has lead residents to the “cheaper” solution of uncontrolled wood and biomass burning for domestic heating purposes, causing significant air quality deterioration. During summer all concentration levels are significantly lower and sources are more regional than local.
This study focuses on high temporal resolution chemical composition measurements performed in downtown Athens during three different winter periods and also a complete year, in order to identify the different sources of organic aerosol seasonally. It occurs that overall, organic aerosol represents half or even more of the total PM1 mass, with concentrations during all studied winters reaching up to 240 μg m-3. During the cold period 5 different factors of OA are identified, namely hydrocarbon-like OA (HOA), contributing an average of 15%, cooking OA (COA) with 9% contribution, biomass burning OA (BBOA) with 12%, a highly oxidized, low volatility OA factor (LV-OOA) with 34% and a semi-volatile OA (SV-OOA) contributing the remaining 30%. This SV-OOA has high affinity with biomass burning tracers, denoting its provenance from the fast oxidation of primary combustion sources. If the provenance of SV-OOA is combined with the primary BBOA and primary HOA from central heating systems, it is clear that almost half of the organic aerosol during wintertime in Athens originates from combustion activities.
During the warm period, 4 different factors of OA are identified, the same as before except for the primary BBOA. HOA contributes around 5.5% to the total organic fraction, COA 12%, SV-OOA around 38% and the rest 44.5% is attributed to LV-OOA. SV-OOA during summertime may be derived either from the oxidation of primary COA or from biogenic sources. Nevertheless it is clear that during the summer period the prevailing source of OA is the much oxidized OA, which has a more regional character and is linked to secondary aerosol formation.
Backtrajectory analysis, using the Potential Source Contribution Function (PSCF) method, and combination of pollutant concentrations with wind direction and speed, through Non-Parametric Wind Regression techniques were applied, in order to determine the local or regional origins of atmospheric pollution in downtown Athens throughout the year.