Aquatic Pollution and Coastal Management

Unit 6 : Oil pollution

6.3.Fate of Spilled Oil
When liquid oil is spilled on the sea it spreads over the surface of the water to form a thin film or an “oil slick”. The rate of spreading and the thickness of the film depend on the sea temperature, nature of oil, wind and wave action, water currents and coastal configuration.

The crude oil in the sea undergoes compositional and chemical changes from the time it spilled. Light fraction evaporates, water soluble components dissolve in the water column and immiscible components become emulsified and dispersed in the water column as small droplets. In some conditions due to photo-oxidation a water in oil emulsion is produced, this may contain 70-80 % water and forms a viscid mass known as “chocolate mouse”. It forms thick pancakes on the water or sticky masses if it comes a shore.

Environmental Factors
Environmental factors determine the extent of damage done by oil spill. These factors include :

• Coastal configuration of the area.
• Tides and surface currents
• Weather