Chemistry Reference
In-Depth Information
characteristics and/or their wave damping potential as inferred from wind
wave tunnel investigations. In recent experiments during the SIR C/X-
SAR campaign, it turned out that the spreading procedure, be it from fro-
zen chunks or be it with the help of spreading solvents, may give rise to
significantly different distribution patterns (the so-called „morphology“)
on the sea surface and thus to different influences on remote sensing sig-
nals.
Morphology effects reflect the phenomenon that the same film-forming
compound may be arranged and distributed at the air/water interface in the
following different manners:
x The molecules may be spread homogeneously.
x The molecules may form 'islands', so-called domains, of different
sizes between microns and several hundred microns in diameter
(Benvegnu and McConnel 1992).
x The hydrophobic alkyl chains may be arranged vertically with re-
spect to the water surface (i.e., 90°) or at a specific angle of less
than 90°. The hydrophobic alkyl chains may exhibit kinks, i.e., the
linear arrangement of the alkyl chain is disturbed by irregularities.
The head group structure may vary in dependence on the compres-
sion status. For more details on these aspects the reader is referred
to (Hühnerfuss 1986, Hühnerfuss et al. 1984, 1994).
The clear correlation between morphology effects and remote sensing
signals inspired us to perform systematic laboratory investigations on the
influence of the spreading procedure on the surface viscosity, the surface
potential and on the morphology. The latter aspect, which will be dis-
cussed further in this paper, is being studied with the help of 'Brewster
Angle Microscopy' >BAM@, while the molecular structure of the slick/ ad-
jacent water layer system is being investigated by 'Infrared Reflection-
Absorption Spectroscopy' >IRRAS@. Both methods allow
in situ
investi-
gations of the monolayer at the air water interface without disturbing the
structure and morphology of the film. Comparison with scatterometer re-
sults obtained over biogenic and man-made sea slicks during the SIR C/X-
SAR campaign will illustrate the morphology aspects and their importance
for the simulation of biogenic sea slicks.
2. Methods
In the present study, the water surface is being surveyed by two optical
methods, i.e., 'Brewster Angle Microscopy' >BAM@ and 'Infrared Reflec-
tion-Absorption Spectroscopy' >IRRAS@. A schematic sketch of the BAM
