The Mediterranean atmosphere has been found to have high concentrations of SOA, especially in summer. The origin of these elevated concentrations of SOA is unclear but past measurements suggest that they are mainly from modern (non-fossil) sources. In recent years a broad scientific effort has been undertaken to better understand the impact of air-sea exchanges on the composition of the Mediterranean boundary layer. These efforts combine mesocosms studies and intensive field campaigns in remote location in two Mediterranean islands (Corsica and Mallorca) as part of the Source of marine Aerosol particles in the Mediterranean atmosphere (SAM) and the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) projects, respectively.<br/>The mesocosm study was conducted at the Oceanographic and Marine Station STARESO (Corsica) in May 2013. During these experiments, 3 mesocosms were deployed. To observe the effect of biological activity on volatile organic compounds (VOCs) and aerosol emissions, two of the mesocosms were enriched and one was left unchanged as a control. Physical and chemical properties of mesocosms and their atmospheres were followed during 20 days: aerosol size and concentration were measured by a SMPS; gas-phase composition of VOCs was determined by using PTR-ToF-MS; and aerosol chemical composition was obtained from HR-ToF-AMS. In parallel, incident light, water temperature, pH, conductivity, chemical and biological analyses, fluorescence of chlorophyll-a, and dissolved oxygen concentration were measured in the mesocosms. Intensive field campaign was performed during summer 2013. Two high-resolution aerosol mass spectrometers (HR-ToF-AMS), co-located with other instrumentation such as a PTR-ToF-MS, an Aethalometer/MAAP, a SMPS, and HV samplers, were deployed on the islands of Corsica (on an isolated ridge 10 km from the sea) and Mallorca (seaside) to measure the chemical composition, concentration, and size of aerosol in the western Mediterranean basin. Recent improvements in the source apportionment approach based on AMS measurements made it possible to separate and identify different aerosol sources (e.g., SOA, marine aerosol)<br/>Results presented here will provide a first synthesis of this combined approach on the influence of air-sea exchange processes in terms of submicrometer particles composition, VOC abundances and new particles formation in the Mediterranean boundary layer.

Impact of air-sea exchanges on the Mediterranean marine boundary layer composition

249th National Meeting (2015)

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