Primary and Secondary Aerosol Investigation from Different Sea-Waters in the Mediterranean Sea

Wednesday, 17 December 2014: 8:00 AM
Barbara D'anna1, Nicolas Marchand2, Karine Sellegri3, Richard Sempere4, Sébastien Mas5, Christian George1, Aurèlie Meme1, Aymen Frihi1, Jorge Pey2, Allison Schwier3 and Anne Delmont4, (1)IRCELyon Institut de recherches sur la catalyse et l'environnement de Lyon, Université de Lyon, Lyon, F-69626, France; Université Lyon 1, Lyon, F-69626, France; CNRS, UMR5256, Villeurbanne, France, (2)Aix-Marseille Université, LCE FRE 3416, Marseille, France, (3)Laboratoire de Météorologie Physique Observatoire de Physique du Globe de Clermont-Ferrand, Aubiere Cedex, France, (4)Aix Marseille Université, CNRS/INSU,IRD, Mediterranean Institute of Oceanography (MIO), UM 110, 13288, Marseille, France, (5)MEDIMEER, Mediterranean Center for Marine Ecosystem Experimental Research, UMS 3301 (Université Montpellier 2, CNRS), Sète, France
The Mediterranean Sea is a special marine environment characterized by low biological activity and high anthropogenic pressure. It is often difficult to discriminate the contribution of Primary and Secondary Aerosol formed at the sea-air interface from background level of the aerosol. We therefore decided to study the sea-air exchanges in a controlled environment provided by a 2m3simulation chamber, using freshly collected sea-water samples from the SEMEX site (43°15’64 N, 05°20’01 E) near Marseille bay.

Two types of experiments were conducted for 4 weeks testing 3 different sea-waters. Primary sea-aerosol was generated by bubble-bursting method, then introduced in the simulation chamber and exposed to atmospheric oxidants (O3, OH) and light to simulated primary aerosol aging. A second set of experiments focused on secondary particle formation upon illumination and/or ozone exposure of the sea-water surface (15l of sea-water were deposited in a pyrex container located inside the simulation chamber). New particle formation was only observed for relatively high DOC level of the sea-water sample.

Particles detection and analysis was followed by a PSM (1nm size), a CPC (2.5nm size), a SMPS (granulometry), a CCN chamber for hygroscopicity studies, a TOF-AMS (Aerodyne) for chemical analysis of the sub-micrometer fraction. Off-line analysis included TEM-EDX samples for morphology and size distribution studies and a hybrid quadrupole-orbitrap mass spectrometer (Thermo Fischer) for the molecular identification of the organic fraction. VOCs were measured on-line by PTR-HR-MS.

The seawater samples were filtered at 60µm before use and were daily analyzed for chemical (colored dissolved organic matter, particulate matter and related polar compounds, transparent polysaccharides and nutrients concentration) and biological (chlorophyll a, virus, phytoplankton and zooplankton) analyses.