Byong-Hyoek Lee

Properties of Aged Aerosols in the Eastern Mediterranean

Three month-long campaigns (FAME-07, -08, -09, -11) have been conducted at Finokalia in order to assess the water uptake, volatility and oxidation state of aged organic particulate matter (PM) along with aerosol nucleation. Finokalia is a remote coastal station located in the southeast of the Mediterranean Sea on the island of Crete, Greece. The site lacks local sources as there is no notable human activity at a range of approximately 15 km. The PM that reaches the site is heavily influenced by the surrounding source regions and the organic content highly oxidized. During the summer aerosols always contained water even under very low relative humidity (RH < 20%) possibly due to their acidity. Organic aerosol was highly and almost uniformly oxidized and the resulting mass spectra did not change throughout the summer campaign, even after it was thermally treated, indicating a high oxidation state. An organic aerosol evaporation model was used to simulate the behaviour of the thermally treated aerosol and showed that aged organic PM was two or more orders of magnitude less volatile than laboratory-generated secondary organic PM. Nucleation is controlled by the gas phase ammonia levels and the resulting PM acidity, at least during the summer, resulting in low number of particle formation events per year.

Characterization of Sesquiterpene Secondary Organic Aerosol: Thermodynamic Properties, Aging Characteristics, CCN Activity, and Droplet Growth Kinetic Analysis

Secondary Organic Aerosols (SOA) can be a considerable source of ambient organic aerosol. The generation of SOA from different hydrocarbon precursors yields different low volatile particulates that could affect aerosol hygroscopicity, CCN activity, and cloud droplet growth kinetics. In this work we investigate SOA from monoterpene and sesquiterpene ozonolysis experiments and characterize the ability of the organic component to depress surface tension, act as CCN, and affect growth kinetics. In addition, we provide experimental evidence that the aging of SOA yields hygroscopic materials.