Ultrafine Particle Emissions in the Mediterranean

An overview of ultrafine particles (UFP) and their sources in the Mediterranean basin is presented based on historical and new measurements in the framework of ChArMEx (the Chemistry-Aerosol Mediterranean Experiment). UFP and meteorological variables were measured from an ultralight aircraft focusing on particles in the nucleation and Aitken modes, and their potential properties as cloud condensation nuclei (CCN). Observed UFP could be assigned to different source areas and occasionally to certain types of emitters. An assessment of ship emissions contribution to the nucleation and Aitken particle modes budget over the Mediterranean is derived. Shipping along the main route from Suez to Gibraltar is a source of UFP in a similar order of magnitude or even larger than anthropogenic emissions along the shorelines and well above any natural sources. In areas far from major emission sources, the majority of UFP were identified as CCN in concentrations far above natural abundance and significantly enhanced compared to pre-climate change (~1970) conditions. This enhancement in CCN concentrations over the whole basin by anthropogenic UFP is an important input parameter for aerosol-cloud interaction models and could be a timely, well-correlated, and essential factor for the observed changes in rainfall patterns within the last decades.