Aquatic Pollution and Coastal Management

Unit 14 : Coastal zone management and information system

14.7.3. Study of pollutants in the marine environment
The main aim of the marine pollution studies is to measure the deterioration of marine environment over wide areas and time spans. It is necessary to set realistic limits on the fundamental issue of the international agreements on waste disposal in the sea.
The most common application of RS in marine pollutions is the detection and mapping of oil slicks, which are regarded as one of the main sources of pelagic pollution.
Ideally, remote sensing system should be able to detect unknown oil discharges as difference in spectral radiance of ocean water and land of thin layer of crude oil has already been established.
The oil film has a noticeably higher radiance in the UV, visible reflected IR bands. Intensity of reflectance in UV region is high comparable to visible and IR bands. In the visible and reflected IR region the signature of an oil film is determined by indirect method. For example the surface tension effect of an oil film, which dampens the small scale surface waves to create calm water or slicks. These slicks, produced by internal waves, typically have dark signatures in contrast to the bright signatures caused by sunlight (sunlight reflected from ripples on the sea surface) from the rougher, clean water.
Digital processing can enhance the appearance of oil slicks on satellite imagery.
Theoretically, it is found that the oil films have cool radiant temperature relative to the water temperature and thermal IR detectors are sensitive to detect such difference.
As described earlier, oil on water changes the surface tension and hence under certain sea and weather conditions can dramatically affect the surface roughness expressed by wave and ripples. Microwave Remote Sensing may be well suited for such change detection as the great benefit that lies with sensors to operate in all weather, day and night time.