Slicks artificial

Oil-in-water emulsion — Oil droplets dispersed in surrounding water and formed as a result of wave action or by a chemical dispersant. Oil-in-water emulsions show a tendency to coalesce and reform an oil slick when the water becomes calm, although the presence of surface-active agents in the oil or artificially added in the form of chemical dispersants increases the persistence of this type of emulsion. Natural dispersion of large quantities of oil can follow the formation of oil-in-water emulsions and weathering processes such as dissolution, oxidation, and biodegradation may be accelerated due to the large increase in the surface area of the oil relative to its volume. (See also Emulsification, Water-in-oil emulsion.)... 

Barger WR, Garrett WD, Mollo-Christensen EL, Ruggles KW (1970) Effects of an artificial sea slick upon the atmosphere and the ocean. J Appl Meteorol 9 396-400... 

The distribution of crude oil mixtures on the water surface is dominated by the viscosity of the crude oil mixture as well as on the specific environmental conditions (currents, wind and water wave directions and magnitudes). As crude oil spills will form layers that remain orders of magnitude thicker than those of monomolecular slicks, considerably higher amounts of oil material are needed to generate experimental crude oil spills. Typically some cubic metres of crude oil have to be pumped onto the sea surface, i.e., three to four orders of magnitude more than in the case of artificial sea slicks. Furthermore, caution should be applied with the application of crude oils, because the transformation of the chemical constituents is much slower than that of the components of quasi-biogenic sea slicks. Furthermore, regulations of the respective countries have to be checked. 

Several drawbacks related to the generation of crude oil spills on the sea surface have to be taken into account. While the spreading of artificial, but quasi-biogenic, sea slicks such as oleyl alcohol slicks is absolute harmless as they are part of natural processes at the sea surface, the spilling of crude... 

Fig. 5. Top left Laser-induced Raman backscatter (381 nm) and two fluorescence return signals (414, 482 nm) measured during an overflight over an oleyl alcohol slick and adjacent clean sea areas bottom left the simultaneously obtained passive microwave L-band data top right same lidar sensor, Raman backscatter (381 nm) and fluorescence return signal at 500 nm during an overflight over a Murban cmde oil spill and adjacent clean sea areas bottom right same passive microwave sensor, over an artificial oil spill in the New York Bight.

It is well known that marine slicks detected by radars and optical systems may be used to characterize areas of biological productivity or pollution. In order to retrieve parameters of marine films from radar/optical observations of slicks one needs to know the physical mechanisms responsible for the damping of short wind waves. Classical linear wave damping theory (Lucassen-Reynders and Lucassen 1969 and references therein) predicts a maximum of the relative damping coefficient in the centimetre wavelength range. Our recent field experiments with artificial slicks (Ermakov et al. 1998), however, showed that the relative damping (contrast) of short wind... 

Laboratory measurements of artificial rain impinging on slick-free and slick-covered water surfaces... 

We have presented results of our laboratory measurements with artificial rain impinging on slick-free and slick-covered water surfaces. They show that the rain-induced roughness is not appreciably affected by slicks, whereas wind waves are strongly damped. 

Fig. 3. Sequence of marine radar images in Portland Island showing (a) an artificial slick drifting with the tide, (b) an enhanced roughness line thought to indicate a zone of convergence and (c) the radar signature of an underwater dip from 40 to 60 meters water depth. Wind and sea conditions were moderate (Ui0 = 9 m s 1 from west Hs 1.5 m)...

Fig. 4. NRCS transects taken across feature (a) and (c) as seen in the third radar image of the sequence shown in Figure 3. Transect AB (solid line) across the artificial slick (a) and transect BC (dotted line) across the underwater dip (c) show a similar NRCS reduction in excess of 3 dB, with respect to the transect across clean water (dashed line)...

Trying to find experimental and theoretical confirmations of the observed effect a survey of available literature has been carried out. Experiments conducted with small artificial and natural slicks in the sea have shown that in areas covered with surface-active compounds (slicks) the high-frequency energy in a spectrum noticeably decreases, while the long waves practically are not transformed (Ermakov et al. 1985, Ermakov et al. 1986). This effect is associated with damping of short waves by the slick. 

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