Resumen de Gas and particle phase chemical composition of marine emissions from Mediterranean seawaters: results from a mesocosm study
Jorge Pey Betrán, H. Langley DeWitt, Brice Temime Roussel, A. Même, Bénédicte Charrier, R. Sempere, A. Delmont, S. Mas, D. Parin, C. Rose, A. Schwier, B. R'mili, Karine Sellegri, Barbara D'Anna, N. Marchand
Marine emissions are among the largest sources of secondary organic aerosols (SOA) globally. Whereas physical processes control the primary production of marine aerosols, biological activity is responsible for most of the organic components, both aerosol and gas-phase, released from marine sources and potentially transformed into SOA when exposed to atmospheric oxidants.
As part of the Source of marine Aerosol particles in the Mediterranean atmosphere (SAM) project, a mesocosm study was conducted at the Oceanographic and Marine Station STARESO (Corsica) in May 2013. During these experiments, 3 mesocosms were deployed, filled with 2260 L of bay water and covered with a transparent Teflon dome. To observe the effect of biological activity on volatile organic compounds (VOCs) and aerosol emissions, two of the mesocosms were enriched with different levels of nitrate and phosphate respecting Redfield ratio (N:P = 16) and one was left unchanged to be used as a control. Physical and chemical properties of mesocosms and ambient atmospheres were followed during 20 days by using a high resolution real-time instruments. Aerosol size and concentration were measured by a Scanning Mobility Particle Sizer; gas-phase composition of VOCs was determined by using Proton Transfer Reaction Time-of-Flight Mass Spectrometer; and aerosol chemical composition was obtained from High Resolution Time-of-Flight Aerosol Mass Spectrometer. In parallel, numerous additional measurements were conducted to fully characterize the water within each of the enclosed mesocosms, including water temperature, pH, conductivity, chemical and biological analyses, fluorescence of chlorophyll-a, and dissolved oxygen concentration. Incident light within the mesocosms was also measured.
Preliminary results suggest new particle formation processes linked to iodine chemistry. Aerosol composition inside the mesocosms was slightly enriched in organic aerosols with respect to the outside atmosphere. Oxygenated organic compounds were the most important species in terms of mass concentration, but amine-related aerosol mass peaks varied the greatest in concentration between the mesocosms. Finally, a clear enhancement of VOCs occurred in the enriched mesocosms.
