1Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, 71003, Heraklion, Greece
2Department of Physics, University of Helsinki, P.O. Box 64, 00014, University of Helsinki, Helsinki, Finland
3School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
4Institute of Physics, University of Tartu, Ülikooli 18, 50090, Tartu, Estonia
5School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
6ICE-HT, Foundation for Research and Technology, Hellas, 26504, Patras, Greece
7Institute for Environmental Research & Sustainable Development, National Observatory of Athens (NOA), I. Metaxa & Vas. Pavlou, 15236 Palea Penteli, Greece
8National Technical University of Athens, Zografou Campus, 15780, Athens, Greece
9Energy, Environment and Water Research Center, The Cyprus Institute, Nicosia 2121, Cyprus
Received: 12 Feb 2015 – Discussion started: 15 Apr 2015
Abstract. While cloud condensation nuclei (CCN) production associated with atmospheric new particle formation (NPF) is thought to be frequent throughout the continental boundary layers, few studies on this phenomenon in marine air exist. Here, based on simultaneous measurement of particle number size distributions, CCN properties and aerosol chemical composition, we present the first direct evidence on CCN production resulting from NPF in the eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles to CCN sizes in this environment during the summertime. Sub-100 nm particles were found to be substantially less hygroscopic than larger particles during the period with active NPF and growth (the value of κ was lower by 0.2–0.4 for 60 nm particles compared with 120 nm particles), probably due to enrichment of organic material in the sub-100 nm size range. The aerosol hygroscopicity tended to be at minimum just before the noon and at maximum in the afternoon, which was very likely due to the higher sulfate-to-organic ratios and higher degree of oxidation of the organic material during the afternoon. Simultaneous with the formation of new particles during daytime, particles formed during the previous day or even earlier were growing into the size range relevant to cloud droplet activation, and the particles formed in the atmosphere were possibly mixed with long-range-transported particles.
Revised: 29 Jun 2015 – Accepted: 04 Aug 2015 – Published: 20 Aug 2015
Kalivitis, N., Kerminen, V.-M., Kouvarakis, G., Stavroulas, I., Bougiatioti, A., Nenes, A., Manninen, H. E., Petäjä, T., Kulmala, M., and Mihalopoulos, N.: Atmospheric new particle formation as a source of CCN in the eastern Mediterranean marine boundary layer, Atmos. Chem. Phys., 15, 9203-9215, doi:10.5194/acp-15-9203-2015, 2015.