Oil spill

An oil pollution is the contamination of the environment, particularly in the oceans, crude oil or petroleum products. With a greater pollution caused mainly in accidents ( particularly oil tankers ), is also spoken of an oil spill, especially if coasts are affected (see also list of major oil spills ). The overall entry of oil into the seas afford accidents only a modest contribution. The world's largest share of the oils come from land, partly through rivers into the sea. In normal ship operations are both legal ( see MARPOL ) and illegally initiated oils. The large proportion of the oil tanker in this case caused by the washing of tanks and ballast water uptake in cargo tanks has decreased because of changed rules and procedures. Next oil spills happen through natural oil spills, by entry of volatile hydrocarbons from the atmosphere and by the oil production at sea ( offshore ).

Behavior of oil spills in the sea

• Propagation: Oil floats except for a few heavy oils first at the water surface. Thinner oils (lighter crude oils and most petroleum products ) propagate very quickly and form a thin layer that can remove up to monomolecular thickness. Viscous oils such as heavy oil may spread more slowly and form thicker oil slicks. Also crude oil in thin layers is aging in a few hours and is increasingly tough. The spread by flow comes later than a few days to a halt.
• Evaporation: The volatile components go quickly into the atmosphere. Gasoline evaporates so within hours almost completely, crude oil depending on variety and temperature within days to one-third to one-half, with the density approximating water. An explosive atmosphere can form above the oil. For heavy oils of evaporation proportion drops to 5 % or less. The evaporation is the major contribution to aging.
• Solution: Highly volatile substances dissolve in water. This concerns in particular the low molecular weight aromatic compounds, which are substantially responsible for the toxicity of the oils.
• Drifting: From the moment of the release of the oil drifted by wind and current. The division by the sea causes the affected area is further increased.
• Dispersion: If there is enough wind, the swell thin oil broken up into drops, tough in larger clumps. While the larger remain directly on or below the surface and flow together again in the low-viscosity case, droplets remain below a certain size, stable in water and will slowly spread into deeper water layers, with time, to larger distance. Changing tidal flows act while supportive. The concentrations take in this process quickly. Along long-range trends, the volume of contaminated water spreads further. This emulsification process is called dispersion. Also it comes with increasing age to a halt.
• Emulsification: are also introduced through the sea water droplets in the low-viscosity oil to the surface. Here may be except for light refined products form a creamy water-in -oil emulsion, the water content increases to about 70 %, it is increasingly tough and then remains stable ( chocolate mousse ). It can be foamed by trapped air. In connection with oil spill, this process only as emulsification and the product is referred to as an emulsion in contrast to the dispersion.
• Sedimentation: Exceeds the dispersion together with suspended in water solids, eg whirled sediment or sediment from rivers, the oil is deposited preferentially at the solids and decreases later with these off, which can lead to the sea floor to high oil concentration. Similarly, heavy oil, and not dispersed crude oil emulsion including ultimately denser than water due to aging and decreases in different sized tar balls. These are a relatively low risk due to their low interaction with the environment and its dimensional stability.

• Biodegradation: oil is degraded at the oil / water interface of certain ubiquitous marine bacteria ( Hydrocarbonoklasten ). Dispersed oil is for these bacteria readily available because of the large surface area and is therefore rapidly degraded. Solid contaminants such as chocolate mousse, heavy oil lump or a lower layer are reduced accordingly much slower. The first bound in oil toxic substances with high biological half-life ( eg polycyclic aromatic hydrocarbons) arrive at this degradation in the marine ecosystem, particularly low molecular weight aromatics are, however, rapidly degraded. However, some use will also create additional toxic metabolites. The rate of degradation is dependent on the temperature: at 20 ° C the degradation is four times as fast as at 0 ° C. Very high molecular weight components of the oil ( asphaltenes ) in crude oil around 5% to 10 %, are not biodegradable.
• Oiling of marine animals: In a closed layer, the floating oil dampens the sea, so the smoother surfaces from the air and on satellite images are clearly visible (see right picture). As apparent resting place pull these faces on seabirds. The viscous oil glued the feathers, destroying the insulation and partly the buoyancy of the animals and is picked up by the birds while trying cleaning. This usually leads to a mass mortality of seabirds by suffocation, hypothermia, drowning and poisoning. Other animals that prefer to stay on the water surface, are at risk, particularly mammals. They shall also recognizable oil is not it as a threat. Animals in the water column, however, are relatively little risk.
• Oiling of shores: Where the floating oil to the coast, it is due to the better wetting first established there. Over time, it is particularly washed in surf -exposed coasts again from the sea. Relatively fresh deposits can be re-arranged several times with changing weather and Tidenverhältnissen. Also no longer sticky tar balls behave like other flotsam. Deposited on beaches still relatively liquid oil or corresponding emulsion stifled by the closed layer of soil organisms in the affected areas. The toxic ingredients may also in other cases the ecosystem affected severely damage, especially, despite weathering, with a long residence time of large quantities of oil. The coastal threats is particularly great because it is a geographically limited habitat that is virtually completely affected.

Measures

Combat

Most methods of combating cause a partial shift of hazards, so that the choice of means usually requires a trade-off. At sea, a non- intervention is particularly limited in soils often the most meaningful measure because here make the natural processes quickly for dispersion and degradation. Also on beaches can only lead to a worsening of the situation in certain circumstances an intervention. For larger spills, however, intervention is useful in general.

At sea

In open waters, there are various methods to contain oil spills.

Containment with booms

By oil booms that can be several meters high for sea use, the spread of an oil slick small area can be prevented. By dragging the lock with two cars thin oil slicks can be pushed together, but the speed is limited to less than 1 knot. The limitation additionally requires further measures to remove the oil from the surface.

Skimming / Skimming

On the water surface floating oil can of special ships (eg folding ships like Bottsand class or the THOR, conventionally designed ships or with outriggers as the Neuwerk or Mellum, catamarans such as the Westensee or mixed structures with catamaran bow such as the Knechtsand MPOSS ) will be included. The actual recording devices based on the principle of a weir, which is overflowed from the oil layer, or on oil adsorbent rotating rollers or brushes with strippers. From such a swamp filled the still water-containing oil is pumped and sent to separators, where the water is largely separated. For low and high oil viscosities partially different pumping systems are used. The equipment of the ships are also heated tanks. The efficiency of present systems starts at 1 meter wave height abate, from 2 meters is a use no longer useful. This means a usability until about wind force 4 Similarly, the use of speed is limited to 1 to 2 knots. The capture widths at the larger vessels up to 40 meters. In Europe, most countries consider the levy as a drug of first choice.

Chemical dispersion

The use of dispersants accelerates the natural dispersion of the oil in the water column, while preventing the adhesion of suspended solids. With next to the held on dispersed oil degradation correspondingly more pollutants from the oil of marine organisms are included. On the effectiveness of chemical dispersants, a minimum value of the swell is required in heavy seas, the use is no longer useful due to the already naturally accelerated dispersion. For example, the Netherlands has the range of applications explicitly limited to wind speeds of 3 to 7. Other operating limits are too high viscosity of the oil or emulsion formation, which prevents mixing with the dispersant. However, emulsions can be split into an additional operation through the use of demulsifiers. Also, low water depths, usually 20 meters are recognized as the boundary, which would lead to high oil concentrations in the water column, and the absence of exchange currents in some coastal areas limit the use. Because of these conditions, this method comes in the European region preferably in the Atlantic Ocean to the application. The dispersant must be accurately dosed and applied specifically to the oil slick, which requires a determination of layer thickness of the carpet. The application must be made within a few hours before the oil age or emulsified too strong. Therefore most important application means the plane is, the application of helicopters and ships, but also possible. UK stops in front of two crop dusters.

Combustion

The controlled combustion requires minimum layer thickness between 2 mm and 10 mm in fresh crude oil in heavy oil and emulsified oil, which may also contain a maximum of 30% water. Special fire-proof locks can be used. Among other pollutants reach 10 to 14 percent of the unreacted amount of oil only partly burned particles into the air. More combustion residues fall off and can jeopardize the ecosystem of the ocean floor. In Europe, inter alia, apart from the use of this method due to unfavorable geographical conditions. The method was, inter alia, for use in the case of the Exxon Valdez.

Bioremediation

As far as the natural bacterial degradation of oil spills is limited by the supply of nutrients, which may be on the high seas for phosphates and nitrates of the case, these nutrients can be added. The meaningful application of this method is very limited by the conditions. The genetic improvement in performance of hydrocarbon degrading bacteria is the subject of research, especially because certain groups of substances are degraded very slowly by the bacteria present. Because of the problematic impact assessment of a release of such modified organisms, their use is not foreseeable.

At the beach

When the oil reaches the coast, poisoned or suffocated soil organisms (such as worms) directly in the affected areas. Cleaning the beaches only allows recolonization here. Improper cleaning trials can also get oil in deeper sand layers, where it is no longer mined.

Treatment of animals

The washing of oiled birds is very controversial, because very few birds actually can be reintroduced. Birds that have been poisoned by ingestion of oil, do not have high chance of survival even after cleaning.

To protect fairy penguins on the southern coast of Australia after an oil spill, Penguin sweaters are knitted world:

" Most animals do it in such cases, on land, but are then once too weak for the complex purification procedure. Warmly wrapped up they may recover first. In addition, the knit stitch to prevent the animals to peck with the beak, the toxic compound from the plumage and swallow them. "

The Penguin sweaters have already proved following the sinking of cargo ship Rena ( New Zealand). Almost all of the 400 oil-covered penguins were released into the wild healthy again.

Prevention

The prevention of pollution of the seas is the enforcement of agreements for transportation and mining. In distress guessed tankers have quickly can be towed. This requires strong salvage ships ready to endure.

Flight monitoring of busy marine areas and the introduction of double-walled tankers belong to prevention. Double-walled tankers offer greater safety in collisions or stranding due. Furthermore ballast water in the double walled space can be taken place in the tank so that no oil residue lead to a water pollution.

The radar surveillance of the routes as well as the adequate qualification of the crew of the great, hard to maneuvering tankers play a role in the prevention of accidents.

Oil platforms have largely separate safety valves on the sea floor ( blowout preventer ), which include the production tubing in an accident the platform. This platform security serving devices can prevent an oil spill. A possible failure of these valves was the end of April 2010, and announced in the following months, as the drilling rig " Deepwater Horizon" sank in the Gulf of Mexico after an explosion and it was at first impossible to stop the gushing oil.

International agreements

• International Convention on Oil Pollution Preparedness, Response and Co -operation ( OPRC ), 1990
• Regional: North and Baltic Seas: Agreement for cooperation in dealing with pollution of the North Sea by oil and other harmful substances, 1983, precursor 1969 in response to the case of the Torrey Canyon
• Convention for the Protection of the Marine Environment of the Baltic Sea Area ( Helsinki Convention New ) 1992 1974 precursor
• About National action plans: SWEDENGER, DenGerNeth
• German -Polish administrative agreements on cooperation in marine pollution and accidents in the Pomeranian Bay