Leak of (Fuel) oil

Oil leakage could have two sources:

• Oil from the cargo of an oil tanker and/or
• Oil from bunker tanks of any kind of vessel

Oil tankers

Cargo oil from a tanker could consist of various types of crude or fuel oil. The density of the oil reflects the relative proportions of its volatile and non-volatile components and thus determines the relative extents of its evaporation and natural dispersion once released. Light oils will disappear from the water surface by evaporation and natural dispersion while heavy oils will be more persistent and more likely arrive onshore somewhere downwind to extents dependent on their degree of persistence. The movement of slicks is on average 3% of the wind velocity and 100 % of the current velocity.

All ships

A collision with the after end of a ship might breach the fuel tanks, and/or flood the engine room with release of fuel oil and/or loss of propulsion whilst a collision amidships will cause damage to the ballast or cargo tanks.

Bunker oil could be diesel oil or various grades of heavy oil including Bunker C. As with cargo oils, density determines the extent of evaporation and naturally dispersion once released. Thus, diesel oil will disappear from the water surface by evaporation and natural dispersion while heavy fuel oils will be persistent and come ashore to some degree somewhere downwind.

Oil floating on the sea surface may pose a hazard to wildlife and pollute shorelines with loss of income to the tourist sector and with the need for expensive cleaning. Response measures should therefore focus on avoiding coastal pollution to the maximum extent possible, in particular when persistent substances such as heavy fuel oils are involved.