Chemistry Reference
In-Depth Information
due, because during subsequent Archimedes 2a experiments off the Dutch
coast (Table 3) the radar signals of Schiphol airport interfered with the
DFVLR passive microwave L-band sensor thus spoiling the data set.
Conceivable explanations for the potential of lidar and passive micro-
wave L-band sensors for the discrimination between slicks and spills can
be given on the basis of the chemical structures of the respective film-
forming compounds: Crude oil always contains aromatic compounds, and
as a consequence, an increase in fluorescent signals around 500 nm can be
taken for verification. The relative amount of such aromatic compounds
may vary in dependence on the origin of the crude oil. High resolution
evaluation of lidar data may even shed light on the sort and the origin of
crude oils. The present state-of-the-art of this technique is being discussed
in this monograph by Zielinski et al. By the way of contrast, in biogenic
and nearly all anthropogenic monomolecular sea slicks the content of aro-
matic and other fluorescent compounds is negligible.
The chemical background of the different signal characteristics of a pas-
sive microwave L-band sensor in the presence of slicks and spills was dis-
cussed by Hühnerfuss and Alpers (1983). Monomolecular sea slicks in-
duce ice-like clathrate structures within the uppermost water layer thus
giving rise to a significant reduction of the relaxation time of water mole-
cules by an order of magnitude, while crude oil represents a layer of com-
pletely different dielectric constant. These two different phenomena are be-
ing reflected by a decrease in the brightness temperature in the presence of
slicks and an increase in the signal in the presence of crude oil spills.
6. References
Alpers W, Hühnerfuss H (1989) The damping of ocean waves by surface films: A
new look at an old problem. J Geophys Res 94: 6251-6265
Alpers W, Hühnerfuss H (1988) Radar signatures of oil films floating on the sea
surface and the Marangoni effect. J Geophys Res. 93: 3642-3648
Blume H-JC, Hühnerfuss H and Alpers W (1983) Variation of the microwave
brightness temperature of sea surfaces covered with mineral and monomo-
lecular oil films. IEEE Trans Geosci Remote Sensing GE-21: 295 - 300
Commission of the European Communities (1985) The Archimedes 1 Experiment
.
Gillot RH and Toselli F eds. Report
Eur 10216 EN
Davies JT, Rideal EK (1963) Interfacial Phenomena, Academic Press, New York
and London.
Gade M, Alpers W, Bao M and Hühnerfuss H (1996) Measurements of the radar
backscattering over different oceanic surface films during the SIR-C/X-SAR
campaigns. Proc
