Hydrocarbons in the Western Mediterranean Sea, 1981.

Hydrocarbons in the western Mediterranean Sea were analysed for surface microlayer and subsurface waters during April 1981. Three methods were used for determining both concentrations and markers distribution patterns: U.V. spectrofluorimetry, and original HPLC/U.V. spectrophotometry method and capillary gas liquid chromatography. No systematic relationship was found between concentrations determined by U.V. spectrofluorimetry and HPLC/U.V. spectrophotometry. Concentrations variation ranges are: 0.01-0.20 microgram 1(-1) for dissolved aromatic hydrocarbons; 0.02-0.13 microgram 1(-1) for particulate aromatic hydrocarbons; 0.02-20.57 micrograms 1(-1) for dissolved n-alkanes; 0.13-0.83 microgram 1(-1) for particulate n-alkanes. Surficial waters appear as very slightly polluted with an exception the Ligurian Sea for which highest concentrations were encountered. There is a slight enrichment of particulate hydrocarbons in the surface microlayer in the range 1-3. But, dissolved hydrocarbons can be either depleted or enriched up to 270 times in the surface microlayer, indicating the extreme efficiency of sea-air exchange processes. Aromatic fingerprints and n-alkane distribution patterns are discussed both for pollution and fractionation processes indicators at the sea-air interface.