Chemical composition and hygroscopic properties of aerosol particles over the Aegean Sea

Abstract

Abstract. The chemical composition and water uptake characteristics of sub-micrometre atmospheric particles over the region of the Aegean Sea were measured between 25 August and 11 September 2011 within the framework of the Aegean-Game campaign. High temporal-resolution measurements of the chemical composition of the particles were conducted using an airborne compact time-of-flight aerosol mass spectrometer (cToF-AMS). These measurements were performed during two flights from the island of Crete to the island of Lemnos and back. A hygroscopic tandem differential mobility analyser (HTDMA) located on the island of Lemnos was used to measure the ability of the particles to take up water. The HTDMA measurements showed that the particles in the dominant mode were internally mixed, having hygroscopic growth factors that ranged from 1.00 to 1.59 when exposed to 85% relative humidity. When the aircraft flew near the ground station on Lemnos, the cToF-AMS measurements showed that the organic volume fraction of the particles ranged from 43 to 56%. These measurements corroborate the range of hygroscopic growth factors measured by the HTDMA during that time. Good closure between HTDMA and cToF-AMS measurements was achieved when assuming that the organic species were less hygroscopic and had an average density that corresponds to aged organic species. Using the results from the closure study, the cToF-AMS measurements were employed to determine vertical profiles of a representative aerosol hygroscopic parameter κmix. Calculated κmix values ranged from 0.19 to 0.84 during the first flight and from 0.22 to 0.80 during the second flight. Air masses of different origin as determined by back trajectory calculations can explain the spatial variation in chemical composition and κmix values of the particles observed in the region.

Profiling aerosol optical, microphysical and hygroscopic properties in ambient conditions by combining in situ and remote sensing

“…Airborne measurements performed above the Aegean Sea during the Aegean-Game (Aegean Pollution: Gaseous and Aerosol airborne MEasurements) campaign (Bezantakos et al, 2013), which was coupled with ACEMED, showed similar values for κ. Over multiple years, measurements of particle hygroscopicity at the South Aegean site of Finokalia, Crete, also exhibit very similar values (Bougiatioti et al, 2009(Bougiatioti et al, , 2011Kalkavouras et al, 2016).…”

“…Given that the hygroscopic growth data reported by Bezantakos et al (2013) correspond to RH > 80 %, this consistency between predictions and observations is a strong indication that the internal mixture assumption applies and that the AMS composition data are representative of the ambient aerosol. Moreover, the drop in predicted hygroscopicity for RH < 80 % is consistent with observed behavior for aerosol particles (e.g., Guo et al, 2015).…”

Aerosol chemistry above an extended archipelago of the eastern Mediterranean basin during strong northern winds

“…In particular, the systematic measurements of aerosols in the southern AS region (Finokalia) during late summer have shown that 30-35 % of OA comes from biomass burning in the eastern Balkans and at the European countries surrounding the Black Sea. Bossioli et al (2014) have shown that the wildfire emissions sector contributes on average ca. 50-60 % to the total PM 1 OA mass predictions in the AS region during the summer, which further supports our speculation.…”

GARRLiC and LIRIC: strengths and limitations for the characterization of dust and marine particles along with their mixtures

“…For the cases analysed herein, we consider a κ value of 0.4 to be characteristic for particles in the south-eastern Aegean Sea (Bezantakos et al, 2013). A more detailed comparison of dry in situ measurements with ambient remote sensing retrievals is outside the scope of this analysis, but it is very important when combining these different techniques (e.g.…”