Accidental pollution: pollution which results from a sudden event, independently of human will.

Adsorption: physicochemical phenomenon in which a chemical accumulates on the surface of a solid (at its interface with air, water…) or any other liquid or gaseous fluid.

Anti-adherent: agent designed to stop a pollutant from sticking in the areas where it is applied before the pollution arrives.

Aromatic: property of a compound which contains one or more benzene rings, which give it a particular smell, an “aroma” (e.g. hydrocarbons).

Asphalt: a sticky, black, highly viscous liquid or semi-solid composed almost entirely of bitumen, used for surfacing roads and for waterproofing.


Ballast: compartment of a vessel which can be filled, or partially filled, with water to stabilise the vessel.

Barrel: unit of measurement (volume) used for petroleum and its products (around 159 litres).

Beach depletion: according to the sedimentary cycle of the shore, at the beginning of winter, the sand moves down the beach. This process is known as beach depletion.

Beach growth: according to the sedimentary cycle of the shore, before summer the sand migrates up the beach. This process is known as beach growth.

Beaching: deliberate action of landing a vessel for repairs.

Bioaccumulation: capacity of organisms to accumulate chemicals through the food chain, reaching concentrations far higher than those normally present in the environment.

Biodegradation: decomposition of certain substances (in particular hydrocarbons) by living organisms.

Biogenic hydrocarbon
: aromatic oils and essences present in many plant and animal species.

Bioremediation: involves promoting/accelerating natural break down processes by micro-organisms. Also known as biorestoration.

Bitumen: the residual fraction obtained from the fractional distillation of crude oil. It is the heaviest fraction and the one with the highest boiling point.

Black tide: see "oil spill"

Bulk: cargo which is not packaged and does not need stowed.

Bunker: compartments used to store engine fuel.

Byssus: bundle of threads secreted by certain shellfish (for example mussels) to attach themselves definitively or temporarily.


Charterer: a person who hires (charters) a vessel

Chocolate mousse: expression used to describe emulsified oil.

Chronic pollution: permanent pollution caused by human activities.

Classification society: an NGO which provides safety standards for construction and maintenance (vessels’ hulls and engines) and is responsible for the inspection of vessels to ensure the enforcement of these standards.

Containment: stopping the migration of solid or liquid, polluted substances out of a particular area using a boom.

Crude oil: a naturally occurring, unrefined, mineral liquid composed principally of hydrocarbon, which accumulates in reservoirs beneath the Earth’s surface and is used as a source of energy.


Deadweight: maximum weight (cargo + fuel + passengers) that a vessel is authorised to transport according to the ship’s papers, expressed in tons.

Deballasting: operation which involves emptying a ballast tank of its contents.

Deballasting station
: facilities where oil tankers can berth and unload their washing waters from their tanks. These waters are then treated in the deballasting station by settling.

Degassing: ventilation of tanks to eliminate hydrocarbon vapours to allow access for inspection or repair work.

Dispersant: liquid used to place oil in suspension in the water mass and promote its dispersal, in order to accelerate break down by the natural environment, at sea or in fresh water.

Dissolution: process of a solid (or gas) forming a solution in a liquid (e.g. sugar dissolving in water).

Double hull: watertight compartment surrounding the shell or part of the vessel to protect it in the event of a leak in the hull.

Drilling rig: structure consisting of a raised, flat, horizontal surface used to exploit submarine oil reservoirs.

Dry dock: basin which can be closed by gates and drained once the vessel is inside in order to carry out maintenance work or painting for example.

DWT (deadweight ton): capacity in long tons (2,240 pounds) which can be transported by a vessel (cargo and bunkers). See “deadweight”.


Ecotoxicology: science which studies the ecological consequences of pollution and chemical and radioactive contamination.

EEZ: Exclusive Economic Zone, intermediate maritime area between the territorial sea and the high sea, where the coastal State possesses sovereign rights in terms of exploration and exploitation of the sea’s and seafloor’s resources.

Effluent: waste waters or liquid waste discharged into the water during clean-up operations in pollution response.

Emulsification: dispersion of a liquid into very fine particles in another liquid, forming an extremely heterogeneous liquid.

Emulsion: mixture of two non miscible substances (i.e. which do not normally mix), such as water and oil.

Emulsion breaker: liquid used to break down emulsions in the form of pastes made of oil in water, which are recovered onshore or at sea.

Epithelium: tissue made up of juxtaposed cells arranged in one or several layers lining the inner surface of organs.

Equipment: action of equipping a vessel and supplying it with all the resources needed for navigation.

Evaporation: gradual change of state of a liquid into a gas.


Film-forming agent: substance which can form a thin layer (a film), used to reduce the adhesion of oil on hard surfaces such as rocks, riprap and concrete walls, to facilitate cleaning. It is applied before the pollutant arrives.

Final clean-up: this is the second stage of clean-up. It involves allowing sites to recover their former uses and return to normal ecological functioning.

Flag: nationality of a ship.

Flag of convenience
: registration of a ship in a country which grants its flag without assuming its responsibilities in terms of safety checks.

Flooding: saturation of a beach with water.

: clean-up technique involving the remobilisation of fresh pollution using low pressure hoses in order to channel it to a collection point.

: the part of the shore between the high and low water levels (= intertidal zone).

Fuel oil: residue from the distillation of oil, formed from a mixture of solid and liquid carbides. In appearance it is a thick, brown liquid used as combustion fuel.


Gasoline: American term for petrol.

Genotoxic: agent which increases the appearance of genetic mutations.

Gross tonnage: the volume of all the compartments located below deck onboard a vessel. It is expressed in register tons, equivalent of 100 cubic feet or 2.83 cubic metres, (old system) or in units (new convention).

Grounding: when a vessel accidentally hits the ground, causing it to need to be refloated.


High tide mark: the highest point on the foreshore reached by the high tide.

Hydrocarbon: compound containing only carbon and hydrogen, forming the main component of oil.



Initial clean-up: the first stage of clean-up operations. The aim is to remove large accumulations of pollutant and heavily polluted materials as quickly as possible in order to limit expansion of the pollution and ecological impact.

Intertidal zone: part of the shore between the furthest limits reached by the tides (= foreshore).

IOPC Funds: the International Oil Pollution Compensation Funds.


Kerosene: fuel obtained by distilling crude oil and used as fuel for jet engines in planes.


Landfarming: technique involving breaking down the pollutant by setting up a system to create bacterial action on polluted soil.

Lightering: operation which involves emptying part of the cargo of a vessel into another vessel.

Lime stabilisation: the addition of quick lime to materials polluted by oil in order to obtain more stable chemical compounds.


Oil cut: mixture of hydrocarbons defined by the interval of their boiling points or by the number of atoms of carbon in their compositions (e.g. heavy petrol: 100-180°C, C7-C10).

Oil fraction: See "oil cut"

Oil spill
: sudden, localised release of petroleum into the environment. In the case of major spillages, the quantities greatly exceed what the local environment is able to assimilate without resulting in damages.

Oil tanker: vessel designed to transport liquid hydrocarbons (crude oil or refined products) in bulk in its tanks.

Oil well: perforation through the Earth’s surface designed to extract oil.

Oleophilic: property of presenting an affinity for oils, absorbing them selectively.

Operational discharge: release at sea of waste waters containing a certain quantity of hydrocarbons. Release linked to the routine activity of a vessel.

Outcrop: an area of rock emerging at the ground surface.

Oxidation: chemical reaction in which a compound combines with one or more atoms of oxygen, with the loss of one or more electrons.


PAH: Polycyclic Aromatic Hydrocarbon = hydrocarbon formed by the fusion of a variable number of benzene rings (C6H6); the most simple PAH is naphthalene (C10H8).

Patty: a deposit of pollution roughly between 10 cm and 1 m in diameter. In the classification of pollution, it is considered smaller than a patch but larger than a tar ball.

Percolation: circulation of water through the sand, due to gravity.

: industrial chemistry of petroleum derivatives.

Petrol: a petroleum-derived, volatile mixture of flammable liquid hydrocarbons used as fuel in internal combustion engines (e.g. cars). Also known as gasoline.

Petroleum: See "crude oil"

: phenomenon of oxidation of a pollutant facilitated or provoked by sunlight.

: a large pipe or tube used to transport certain liquids over a long distance, especially liquid fuels such as hydrocarbons, natural gas etc.

Place of refuge
: area, usually a port, where a vessel in difficulty can be taken to stabilise the situation, to minimise the impact on the environment.

: a unique tool belonging to Cedre, in the form of a flume tank used to simulate the weathering of oil at sea.

Pollution reponse: all efforts made to minimise the impact of a pollution incident.

Port of refuge: see "place of refuge".

: volcanic earth, brown to grey in colour.

Ppm: Parts per million, i.e. a concentration (mg/l, g/t) of one millionth (1/1 000 000, 10-6).

Protection and Indemnity club (P&I club): insurance covering the responsibility of the shipowner.


Reference condition: initial state of the natural environment in a localised area before being polluted.

Refined product: petroleum product obtained from crude oil by refinery according to the proportions and quality required: propane, butane, petrol, kerosene, diesel, bitumen, fuel oils.

Refinery: 1) operation or series of operations through which a (homogenous or heterogeneous) mixture of substances is separated into one or more pure bodies or one or more mixtures with well defined properties. 2) Industrial plant where this process is carried out.

Remote sensing: science and technique of detection at a distance (satellite, aircraft).


Sand screener: machine which picks up a layer of sand 5 to 20 cm thick and passes it along a vibrating wire conveyor belt, acting as a screen, to recover the solid waste (tar balls).

: natural settling of particles with a higher density than water, caused by gravity.

Separator: device which separates the different components in a mixture, in this case they separate oil from water.

: deliberate separation of matters in suspension by leaving them to fall to the bottom of a recipient.

: production of the colours of the rainbow by the fractioning of light caused by thin films of silvery hydrocarbons a few microns thick.

Shipowner: the person in control of a vessel, who is responsible for its operation, maintenance and running.

Shipping lane: channel or route that ships must follow near certain coasts.

Skimming: recovery of hydrocarbons on the water surface.

Slop tank: tank into which residues are pumped and left to settle onboard oil tankers.

Sludge: fuel residue in the form of an agglomerate of solid and liquid materials with a tendency to form a deposit.

Solid waste: all types of various forms of waste, either of human or natural origin, floating at sea or deposited onshore.

Sorbent: all products designed to absorb and/or adsorb liquid spilled in the environment, in order to facilitate their recovery.

: a reserve where materials and equipment are stored for future use.

: initial phase of purification of polluted water, which involves eliminating solid waste and large particles.

Substrate: nature of surface sediments.

Surfwashing: beach clean-up technique which involves moving sediments down the beach to the area where the waves are breaking in order to expose them to wave energy.


Tainting: alteration of taste and smell of sea produce to acquire an oil-like taste when an oil spill occurs.

Tank: compartment onboard a vessel used to store cargo or ballast waters.

Tar: coal-coloured derivative of oil. By-product of the distillation of coal in the fabrication of petroleum coke. It is highly viscous or can even be solid.

Tar ball
: small ball of weathered oil

: industrial facility where oil tankers load and offload their cargo.

Tour d’Horizon: a yearly reconnaissance flight carried out within the framework of the Bonn Agreement, mainly along offshore installations, covering at least 600 nautical miles, roughly between 52 north and 63 north.

Traffic separation scheme: see "shipping lane".

: a strong, powerful boat used for towing other vessels.


Vetting: evaluation by a charterer of whether the risk presented by the use of a tanker is acceptable in terms of his standards.

: resistance of a liquid to flow.

Volatile: which easily or spontaneously changes into a gas.


Washing agent: product which helps remove oil which is stuck to rocks.

Water column: a volume of water in a real or imaginary vertical tube.

Wharf: a platform built on pilings, alongside which a vessel can berth.