Insights about the Sources of Organic Aerosol from Measurements of Organic Tracer Compounds in an Eastern Mediterranean Forested Site
Agata Kołodziejczyk, Kacper Błaziak, ANGELIKI MATRALI, Christina N. Vasilakopoulou, Ksakousti Skylakou, Spyros Ν. Pandis,
University of Patras, Greece Abstract Number: 164
Working Group: Aerosol Chemistry
AbstractTerpenoids are known important precursors of secondary organic aerosol (SOA) which constitutes a significant part of particulate matter worldwide. Filter samples and fir needles were collected from a forest in a Greek mountain site for a month in July 2022, where high modeled concentrations of these biogenic compounds are expected. Analysis of essential oils derived from the needles with GC-MS and GC-FID, indicated high levels of monoterpenes (78 - 83 %) and lower levels of sesquiterpenes (5 – 10%). The filters were analyzed for organic tracers with LC-ToF-MS. Sixteen acids of biogenic and anthropogenic origin were quantified with authentic standards representing a total average concentration of 46 ± 11.6 ng m
-3. The highest average concentrations were observed for cis-pinonic (6.2 ± 1.9 ng m
-3) and terebic acid (5.8 ± 2.8 ng m
-3). Additionally, 160 other organic compounds were quantified with the use of surrogate standards with average concentrations for the campaign duration of 1107 ± 154 ng m
-3. Amongst these approximately 20 compounds were classified as organosulfates or nitroxy organosulphates based on literature with concentrations of 423 ± 106 ng m
-3. The covariance between the compounds measured was assessed to pinpoint common sources and lifetime of the analytes. Correlations were also checked between them and online AMS measurements of PM
1 chemical composition and the different sources of the organics based on Positive Matrix Factorization of its spectra. The quantified fraction of the organic aerosol (OA) ranged from 8% to 22 % (average OA 9.2 ± 2.8 μg m
-3). Part of the unidentified fraction is attributed to compounds (aldehydes, ketones etc.) which cannot be measured with negative electrospray ionization (ESI-). These results are synthesized to provide insights into the sources of OA but also its significant chemical processing under the high OH environment of the Mediterranean in the summertime.