The more severe the conditions, the more rapid the spreading and breaking up of the oil. Evaporation Lighter components of the oil will evaporate to the atmosphere. The amount of evaporation and the speed at which it occurs depend upon the volatility of the oil. An oil with a large percentage of light and volatile compounds will evaporate more than one with a larger amount of heavier compounds. For example, petrol, kerosene and diesel oils, all light products, tend to evaporate almost completely in a few days whilst little evaporation will occur from a heavy fuel oil.
Evaporation can increase as the oil spreads, due to the increased surface area of the slick.
Rougher seas, high wind speeds and high temperatures also tend to increase the rate of evaporation and the proportion of an oil lost by this process. Dispersion Waves and turbulence at the sea surface can cause all or part of a slick to break up into fragments and droplets of varying sizes. These become mixed into the upper levels of the water column. Some of the smaller droplets will remain suspended in the sea water while the larger ones will tend to rise back to the surface, where they may either coalesce with other droplets to reform a slick or spread out to form a very thin film. The oil that remains suspended in the water has a greater surface area than before dispersion occurred.