Aged organic aerosol in the Eastern Mediterranean: the Finokalia Aerosol Measurement Experiment – 2008

Abstract

Abstract. Aged organic aerosol (OA) was measured at a remote coastal site on the island of Crete, Greece during the Finokalia Aerosol Measurement Experiment-2008 (FAME-2008, which was part of the EUCAARI intensive campaign of May 2008. The site at Finokalia is influenced by air masses from different source regions, including longrange transport of pollution from continental Europe. A quadrupole aerosol mass spectrometer (Q-AMS) was employed to measure the size-resolved chemical composition of non-refractory submicron aerosol (NR-PM 1 ), and to estimate the extent of oxidation of the organic aerosol. Factor analysis was used to gain insights into the processes and sources affecting the OA composition. The particles were internally mixed and liquid. The largest fraction of the dry NR-PM 1 sampled was ammonium sulfate and ammonium bisulfate, followed by organics and a small amount of nitrate. The variability in OA composition could be explained with two factors of oxygenated organic aerosol (OOA) with differing extents of oxidation but similar volatility. Hydrocarbon-like organic aerosol (HOA) was not detected. There was no statistically significant diurnal variation in the bulk composition of NR-PM 1 such as total sulfate or total organic aerosol concentrations. However, the OA composition exhibited statistically significant diurnal variation with more oxidized OA in the afternoon. The organic aerosol was highly oxidized, regardless of the source region. Total OA concentrations also Correspondence to: S. N. Pandis (spyros@andrew.cmu.edu) varied little with source region, suggesting that local sources had only a small effect on OA concentrations measured at Finokalia. The aerosol was transported for about one day before arriving at the site, corresponding to an OH exposure of approximately 4×10 11 molecules cm −3 s. The constant extent of oxidation suggests that atmospheric aging results in a highly oxidized OA at these OH exposures, regardless of the aerosol source.

Formation of highly oxygenated organic aerosol in the atmosphere: Insights from the Finokalia Aerosol Measurement Experiments

“…FAME-09 was in the winter (February 25-March 25, 2009) under milder oxidizing conditions. The OA measured during FAME-08 has been characterized in detail in a previous publication [Hildebrandt et al, 2010]. The OA observed during FAME-08 was highly oxygenated, resembling LV-OOA throughout the campaign, regardless of the source region.…”

“…NR-PM 1 concentrations were extremely low during this time period, presumably because the larger Saharan particles scavenge smaller particles by coagulation and low-volatility vapors by condensation. The campaign-average total dry NR-PM 1 concentration measured by the AMS was 3.2 mg m −3 , a factor of three lower than during FAME-08; average total OA was 1.4 mg m −3 , a factor of two lower than during FAME-08 [Hildebrandt et al, 2010]. The bulk composition also differed: during FAME-08 OA comprised 28% of dry NR-PM 1 and the ratio of OA to AMS-Sulfate (OA:SO 4 2− ) was approximately 0.5, during FAME-09 OA comprised 43% of dry NR-PM 1 and OA:SO 4 2− was unity.…”

“…Detailed results from FAME-08 have been published [Hildebrandt et al, 2010;Lee et al, 2010;Pikridas et al, 2010], and details on FAME-09 will be presented elsewhere. Here, we focus on the comparison of OA sampled during FAME-08 and FAME-09.…”

“…[7] Measurements were conducted at the Finokalia Station of the Environmental Chemical Processes Laboratory of the University of Crete [Hildebrandt et al, 2010] as part of the EUCAARI intensive campaigns [Kulmala et al, 2009]. Detailed results from FAME-08 have been published [Hildebrandt et al, 2010;Lee et al, 2010;Pikridas et al, 2010], and details on FAME-09 will be presented elsewhere.…”

Functionalization and fragmentation during ambient organic aerosol aging: application of the 2-D volatility basis set to field studies

“…The solar radiation was intense during the period, with daily maxima always exceeding 850 W m −2 . The non-refractory PM 1 chemical composition was measured with an Aerodyne quadrupole aerosol mass spectrometer (Q-AMS) as described in detail by Hildebrandt et al (2010a). Using the organic mass at m/z 44 as measured by the Q-AMS, they estimated O:C with the parameterization of Aiken et al (2008).…”