Aliphatic and Aromatic Hydrocarbons in the Mediterranean Aerosol

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Abstract
The atmospheric transport of organic pollutants over long distances and their effect on the biological cycles of the sea are two major questions of concern in environmental chemistry. These processes are of particular importance in the Mediterranean Sea because of its semi-enclosed characteristics, which determine the accumulation of the pollutants entering into the system. In order to get some insight into these processes a project (PHYCEMED), was developed for the evaluation of the atmospheric budget of organic and inorganic substances in the Western Mediterranean and for the investigation of the exchange mechanisms of these materials across the air/sea interface. A high volume air sampling system including a cascade impactor was placed on board of the R/V le Suroit for collecting the acrosols along several transects parallel to the French, Spanish and North-African coasts, facing areas of different population densities and industrial activities. The cruise was realised on October 1983 and the particulate material was fractionated into the following sizes: 7.2, 3.0, 1.5, 0.96, and 0.03 μm. Quantitative and qualitative analyses of the aliphatic and the aromatic hydrocarbons present in these fractions were performed by high resolution gas chromatography and gas chromatography-mass spectrometry. Total non-aromatic hydrocarbon concentrations are in the range 30-57 ng/m3 (10-14ng/m3 for n-alkanes). The distribution of n-alkanes indicates that most of the aerosol mass is associated with small particles < 1 μm.Polycyclic aromatic hydrocarbons are identified from phenanthrene to benzo(ghi)perylene with fluoranthene and pyrene as dominant compounds. Concentrations for individual PAH vary in the range 4.1 pg/m3 for benzo(a)anthracene up to 100 pg/m3 for fluoranthene. The evaluation of different contributions such as land plant waxes or soil sources and various anthropogenic sources is discussed from n-alkanes and PAH distribution patterns.