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Aerosols, surface microlayer, and subsurface water samples have been collected during the 'Midlante' cruise of the R/V Jean Charcot (May 1974) in the northeastern tropical Atlantic, taking all possible precautions against shipboard contamination. The concentrations of n alkanes, total hydrocarbons, and fatty acids (C•2 to C32 were obtained by gas-liquid chromatography in these aerosol samples as well as for the dissolved and particulate fractions of the microlayer and subsurface waters. The aqueous phase fatty acids are of obvious planktonic origin, but an anthropogenic source cannot be definitely discounted for the aqueous phase n alkanes. On average, fatty acid lipids, n alkanes, and total hydrocarbons are all enriched in the microlayer by factors of 2-5. The three aerosol samples show a strong similarity in composition, and all differ from the corresponding aqueous samples in having lauric acid C•2 as the dominant acid instead of C•6, typical of planktonic lipids, as found for the water samples. The hydrocarbon distributions of the aerosols, which resemble petroleum-derived materials, are characteristically different from those of the subsurface and microlayer, which are similar and appear to have a marine origin. The overlying n alkane distributions of all three sample types are similar, however, being generally regular without predominance of n alkanes with n even or odd, and are also quite different from distributions characteristic of terrigenous dust containing hydrocarbons derived from higher plants. INTRODUCTION Simple lipids such as hydrocarbons and free or esterified fatty acids account for only a small part of the organic material that is present in the surface microlayer or which is transferred to and from the oceans [Hunter and Liss, 1977]. Nonetheless, owing to their chemical stability and the useful information that they can provide concerning their sources the joint study of these compounds in the marine aerosol and the microlayer may lead to useful knowledge of exchange processes at the air-sea interface. In spite of this consideration, available data are as yet rather limited. Duce et al. [1974] have measured gaseous hydrocarbons in the atmosphere, while the particulate fraction of the aerosol has been analyzed for hydrocarbons by Ketseredis et al. [1976] and Marty et al. [1978]. Only in the latter study were microlayer and bulk seawater samples collected at the same time. Simoneit [1977] and Simoneit and Eglinton [1975] have reported analyses of organic matter in aeolian dusts collected over the Atlantic.Barger and Garrett [1970, 1976] have analyzed for fatty acid lipids in marine aerosols, noting the similarity of the fatty acid distributions found with those of microlayer and subsurface seawater samples from their other studies. The authors have argued that these atmospheric lipids are of essentially marine origin. A similar conclusion was reached by Quinn and Wade [1972] in the most complete study yet made. These authors analyzed for fatty acid lipids and hydrocarbons in aerosol, microla...

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