The sea surface microlayer

Marty and Saliot (1976) gave the following values for the enrichment factor calculated for a 0.44 mm thick surface microlayer about 20 for dissolved and particulate n-alkanes for the Mediterranean Sea and between 161 and 350 for coastal samples collected along the French coast. These results are. comparable with those of Wade and Quinn (1975) who reported, for ultrasurface samples from the North Atlantic, values of the enrichment factor varying from 1.1 to 26. Analyses of sea surface samples from the Mediterranean by Morris (1974) indicated that the films collected, yielding a concentration of 40—230 mg of organic matter per m, were composed of both natural lipids in low amounts ( 5% total extract) and a complex mixture of pollutant hydrocarbons. 

Alkanes collected over a 12 months period, offshore from Louisiana and Florida, were characterised by Ledet and Laseter (1974) unexpectedly, methyl branched alkanes ranging in chain length from C15 to C3S and cycloalkanes were frequently the dominant components. Possible explanations for this enrichment may be selective removal by autoxidation, preferential oxidation of n-alkanes by bacteria, adsorption onto particles, a contribution from some crude oils particularly rich in methylalkanes or a contribution from certain plants containing large quantities of 3-methyl branched alkanes (Weete et ed., 1971). 

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Hardy, J. T., Apts, C. W., Crecelius, E. A. and Fell-ingham, G. W. (1985). The sea-surface microlayer fate and residence times of atmospheric metals. Limnol. Oceanog. 30, 93-101. 

Heussner S, Cherry RD, Heyraud M (1990) Po-210 and Pb-210 in sediment trap particles on a Mediterranean continental margin. Cont. Shelf Res 10 989-100 Heyraud M, Cherry RD (1983) Correlation of Po-210 and Pb-210 enrichments in the sea-surface microlayer with neuston biomass. Cont Shelf Res 1 283-293 Honeyman BD, Santschi PH (1989)The role of particles and colloids in the transport of radionuclides and trace metals in the oceans. In Environmental particles. Buffle J, van Leewen HP (eds) Lewis Publishers, Boca Raton, p 379-423... 

J.C. Marty, V. Zutic, R. Precali, A. Saliot, B. Cosovic, N. Smodlaka and G. Cauwet, Organic matter characterization in the Northern Adriatic Sea with special reference to the sea surface microlayer, Marine Chem. 25 (1988) 243-263. 

Blough, N. V. 1997. Photochemistry in the sea-surface microlayer. In P.S. Liss and R.A. Duce, Eds., pp. 383-424. Sea Surface and Global Change, Cambridge University Press, London. 

Wurl, O., Obbard, J.P., 2004. A review of pollutants in the sea-surface microlayer (SML) A unique habitat for marine organisms. Mar. Pollut. Bull. 48, 1016-1030. 

There are very few measurements of the DMS concentration in the sea surface microlayer. The first report (44) indicated an enrichment of 5 times relative to underlying water samples. Other reports indicate that no enrichment was observed in tne microlayer DMS concentration (23.47.511. These differences may be related to the sampling techniques used. It is possible that chemical and biological processes in tne sea surface microlayer may affect the transfer of DMS from the bulk ocean to the atmosphere. However, at present, very little is known about the processes affecting the chemistry of DMS in the microlayer. 

Implicit in this model is the assumption that molecular diffusivity and Henry s Law constant are directly and inversely proportional, respectively, to the gas flux across the atmosphere-water interface. Molecular diffusion coefficients typically range from 1 x 10-5 to 4 x 10-5 cm2 s-1 and typically increase with temperature and decreasing molecular weight (table 5.3). Other factors such as thickness of the thin layer and wind also have important effects on gas flux. For example, wind creates shear that results in a decrease in the thickness of the thin layer. The sea surface microlayer has been shown to consist of films 50-100 pm in thickness (Libes, 1992). Other work has referred to this layer as the mass boundary layer (MBL) where a similar range of film thicknesses has been... 

Henrichs, S. M., and WUliams, P. M. (1985). Dissolved and particulate amino acids and carbohydrates in the sea surface microlayer. Marine Chemistry 17(2), 141-163. 

Another form of removal of riverine humic substances from solution is indicated by enrichment of phenolic materials in the sea surface microlayer... 

Schimpf U, Garbe S, and Jahne B (2004) Investigation of the transport process across the sea-surface microlayer by infrared imagery. J Geophys Res 109 C08S13... 

Barker, D.R. and Zeitlin, H., 1972. Metal ion concentrations in the sea surface microlayer and size-separated atmospheric aerosol samples in Hawaii. J. Geophys. Res., 77 5076-5086. 

Hunter, K.A., 1977. The chemistry of the sea surface microlayer. Thesis, University of East Anglia, Norwich, 363 pp. 

Marty, J.C., Saliot, A., Buat-Menard, P., Chesselet, R. and Hunter, K.A., 1979. Relationship between the lipid compositions of marine aerosols, the sea-surface microlayer and subsurface water. J. Geophys. Res., 84 5707—5716. 

Quinn, J.G. and Wade, T.L., 1972. Lipid measurements in the marine atmosphere and the sea surface microlayer. In E.D. Goldberg (Editor), Baseline Studies of Pollutants in the Marine Environment. National Science Foundation, Washington, D.C., pp. 633— 663. 

Collection of samples of the sea surface microlayer can be performed from a rowed dinghy, at least one mile upwind of the ship. The method usually used is the metallic steel screen technique described by Garrett (1965). 

Collection of samples of the sea surface microlayer with a stainless steel screen and of subsurface layers with a glass flask extraction of the unfiltered samples with chloroform or methylene chloride TLC,... 

Liss, P.S., 1975. Chemistry of the sea surface microlayer. In J.P. Riley and G. Skirrow (Editors), Chemical Oceanography, 2. Academic Press, London, pp. 193—243. 

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