An oil spill is defined as acute when it occurs suddenly and is illegal. The main sources of this pollution are accidents and incidents related to onshore industry, shipping and spills from offshore oil activities. A significant portion of oil contamination nevertheless has unknown origin, as the source of the spill is unknown and the perpetrator is thus not identified. The largest oil spill in Norway occurred in connection with the "Bravo" accident in 1977. Then around 20,000 tonnes of oil leaked into the sea. The largest spill associated with shipping occurred in 1981 when the vessel "Deivfovos" sank off Helgeland in Nordland and 1,000 tonnes of oil was spilled into the sea.
What happens to the oil?
When oil is spilled at sea, it will absorb water. How much water depends on the type of oil. Crude oil can absorb about 80% water, fuel oil/heavy oil can absorb approximately 30-50% water. The light components, which are also the most toxic, will evaporate during the initial period after the spill. The amount that evaporates depends on the oil type, temperature and wind. There are great variations between oil types. Diesel and gasoline are thin, and the visible amount on the surface disappears relatively quickly. Lighter oils contain higher amounts of toxic components. Heavy oil will remain on the surface for longer and a significantly smaller portion of this oil mixes with water.
The decay of the oil is significant for its further handling both at sea and along the coast.
Consequences of oil pollution
The same type of spill and quantity may having very different effects depending on where, when and which natural resources are present when the spill happens. In general, we can nevertheless say that the consequences for the marine environment depend greatly on the type of oil, weather conditions and the implementation of mitigation measures.
Accidental oil spills may also have economic consequences for fisheries, aquaculture and the tourism industry.
Knowledge of the long-term effects on marine organisms from oil spills is somewhat lacking, but extensive research is being conducted in the area. In recent years the NCA has also implemented a research programme in the case of acute oil spills that also measures the environmental impact over time.
Emergency preparedness against acute pollution
In the case of acute pollution, the NCA is the authority pursuant to the Pollution Control Act. The NCA must also provide advice and assistance and head an eventual government response operation.
The number of notifications of incidents of acute pollution or risk of acute pollution has been relatively stable over the past ten years. The recorded amount of oil pollution has also been stable for a long time. However, 2007 had almost double the amount due to the "Server" accident outside Bergen.
In 2011, the NCA received a total of 1403 notifications of acute pollution or threat of pollution. Of these, 382 led to actual spills, where 162 were spills at sea.
