Marine surface films

Gade M (2006) On the imaging of biogenic and anthropogenic surface films on the sea by radar sensors. In Gade M, Huhnerfuss H, Korenowski GM (eds) Marine Surface Films. Springer, Heidelberg (this volume)... 

In the year 2000, the number of spills around Italy was analysed on a monthly basis. This demonstrated a relevant number of spills during the summer months on the routes to Sardinia and Corsica. This is a general trend previously identified by Gade et al. (2000). During summer the mean wind speed is lower, thus causing a higher visibility of oil pollution (and other marine surface films). 

Martin Gade, Heinrich Hiihnerfuss, Gerald Korenowski Marine Surface Films... 

Marine surface films are encountered at many places of the world s oceans, particularly in marginal seas and coastal regions. Their impact on basic processes at the air-water interface is well known since ancient times and has been a matter of scientific research ever since. There has been, however, a lack of a comprehensive compendium that provides the state-of-the-art knowledge on the chemical nature of marine surface films, with particular emphasis on their influence on air-sea interaction processes. 

N.M. Frew and R.K. Nelson, Scaling of marine microlayer film surface pressure-area isotherms using chemical attributes, J. Geophys. Res. 97 (1992) 5291-5300. 

Horrigan, S. G., Carlucci, A. F., and Williams, P. M. (1981). Light inhibition of nitrification in sea-surface films. Journal of Marine Research 39, 557-565. 

Hiihnerfuss, H. (1983). Molecular aspects of organic surface films on marine water and the modification of water waves. Chim. Ind. 65, 97-101. 

Sources of surface-active organic matter (SAOM) are varied and include primarily phytoplankton, zooplankton and their degradation products (Zutic et al. 1981, Williams et al. 1985, Henrichs and Williams 1985), but also marine bacteria (Sieburth et al. 1976, Hardy 1982, Carlucci et al. 1985, Van Vleet and Williams 1983), rivers and estuaries (both natural and anthropogenic organic matter) and atmospheric volatiles and dust (Peltzer and Gagosian 1989). Sea surface films are, therefore, complex mixtures of... 

Frew, NM, Nelson RK (1992a) Isolation of marine microlayer film surfactants for ex situ study of their surface physical and chemical properties. J Geophys Res 97 5281-5290... 

Airborne particulates typically contain increased concentrations of halogens near the ocean, in polluted areas, and in regions of volcanic activity. Fluoride concentrations are increased near aluminum and steel miUs and phosphate-fertilizer plants. Bromide concentrations were once increased near urban areas as aresult ofthe burning of gasoline additives (ethylene dibromlde, a lead scavenger), but environmental legislation has resulted in a decline of this chemical s utilization. The enrichment of iodine in marine air as compared to sea water has been attributed to concentration of the element in organic surface films. Iodine-enriched material then enters the atmosphere in the form of spray. 

The corrosion rates of metals increases sharply beyond a threshold level of relative humidity called critical relative humidity. The level of the critical humidity varies with the nature of the metal and the type of contaminant. If the atmosphere is clear and uncontaminated, corrosion is negligible at a relative humidity as high as 99%. However, in the presence of contaminants, corrosion begins to increases around 80% RH. The critical humidity requirement in the presence of contaminants, such as KCl and NaCl is considerably reduced. For example, steel can corrode even at 35% RH, in the marine environment. At a relative humidity of 55%, a surface film of 15 molecules thick is formed on mild steel, which increases to a 90 molecular layer as the relative humidity increases to 100%, causing an acceleration of the corrosion process. 

Hunter, K.A. and Liss, P.S. (1981) Organic sea surface films, in Marine Organic Chemistry, vol. 31 (eds E.K. Duursma and R. Dawson), Elsevier Oceanography Series, Chapter 9, pp. 259-298. 

Steam-turbine lubricants Lubricants in steam turbines are not exposed to such arduous conditions as those in engines. The main requirement is for high oxidation stability. However, they may be exposed to aqueous condensate or, in the case of marine installations, to sea water contamination, so they have to be able to separate from water easily and to form a rustpreventing film on ferrous surfaces, and it is usual to employ rust inhibitors. The problem of tin oxide formation on white-metal bearings is associated with the presence of electrically conducting water in lubricants and can be over-come by keeping the lubricant dry . 

Contact with steel, though less harmful, may accelerate attack on aluminium, but in some natural waters and other special cases aluminium can be protected at the expense of ferrous materials. Stainless steels may increase attack on aluminium, notably in sea-water or marine atmospheres, but the high electrical resistance of the two surface oxide films minimises bimetallic effects in less aggressive environments. Titanium appears to behave in a similar manner to steel. Aluminium-zinc alloys are used as sacrificial anodes for steel structures, usually with trace additions of tin, indium or mercury to enhance dissolution characteristics and render the operating potential more electronegative. 

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