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Oil goes to the marine environment from the many sources. But, most of them are antropogenical and cause waste oil. Oil pollution is one of the form of pollution that is released from the liquid petroleum hydrocarbon because of the human activities into the environment which is generally oceans or coastal water areas. These sources causing to oil spill are; Industrial and Urban Discharges 37%, Natural Sources (oil seeps) 7%Â , Tanker Accidents 12%, Exploration and Production 11% , Other Shipping Accidents 33%. With the below graph, this situation is understood more clearly. This graph indicates how many millions of gallons of oil from the each source puts into the oceans worldwide in one year (URL 1).
Figure 1: Oil Spill Sources and their amounts ( millions of gallons per year) (URL 1)
It is clearly seen from these statistics and graph, oil spill has an huge impact on both environment and economy, since cleaning procedure which is inevitable to have clean water sources is very hard and this causes economic damage. Moreover, the ecosystem of spilled area is also destroyed. The last Mexico Gulf example shows that oil spill is one of the major and serious both environmetal and economical problem that affects both human being and the ecosystem.
In order to show importance of oil spill, its effects and possible solutions to overcome this pollution this paper is written. This paper includes firstly the general information about oil behaviour at sea and its characteristics. Then, effects of oil spills on both environment and economy including cost of cleaning techniques. Next, some the real world of oil pollution examples are given in order to present how this situation is important. After these, solutions related to oil pollution is given. Finally, in the conclusion part the summary of all these and output results are determined.
INFORMATION ABOUT MARINE SPILLS
Identification of oil spill at the sea or any shoreline of marine environment is the first indication of the oil pollution. In order to understand marine spills, fate of oil spills at the sea or marine environment is the key procedure. However, in order to find fate of spilt oil, firstly quantity and type of the oil should be known. Then, their behaviours, weathering conditions and persistence of oils at the sea are analysed. Finally in the light of these informations, fate of oil pollution is found.
Fate of Oil Spills
In the environmental studies, word of oil is used to indicate petroleum products that comprise of mostly hydrocarbons. Most crude oils are formed from propane and benzene which are known as wide spectrum, light and volatile materials or they consist of bitumens, asphaltenes, resins and waxes that are more complex and heavy compounds. Petrol and fuel oil are made up of more specific and smaller hydrocarbons. (URL 2)
Natural tendency of the oil is spreading and dispersing with the time, when it spills into the sea. This dispersion and spreading events are result of the some chemical and physical processes such as density, viscosity and pour point. And, these processes are generally called as weathering. In addition the weathering, persistence of the oil is also important when it is spilt, because dispersive character and breaking of the bonds are related to persistent of the oil. Generally, light compounds such as benzene and kerosene have tendency to evaporate and disperse very quickly. Hence, they are called as non - persistent oils. On the other hand, so many oil types do not evaporate quickly and their dispersiveness characters are very slower. Therefore, they are called as persistent oils. However, spreading process are not observed instantly. The dispersion depends on the many factors which are quantity and type of oil that is spilled, weather conditions, polluted area etc (Davidson, et. all. 2008)
In order to see fate of oil spill the weathering in other words behaviour of oil at sea and persistence of oil are scrutinized.
Some of the weathering processes such as sedimenttation/sinking, dispersion, evaporation and dissolution help to reduce negative effects of the oil. On the other hand, some of the weathering processes such as emulsions increase the viscosity of oil, and they are responsible for increasing oils persistence in the sea. Therefore, weather conditions are also important for the oil pollution. There are mainly eight processes which affect the oil spill problem. These are; spreading, evaporting, dispersion, emulsification, dissolution, oxidation, sedimentation/sinking and biodegradation. In the below figure their effects can be seen (URL 2).
Figure 2: The Main Weathering Processes Affecting Oil Spill (URL 2)
Spreading: When oil is spilled into the marine environment, it immediately starts spreading according to its viscosity. Having the less viscosity causes the more spreading in a short time. After a while, surface of the water is covered by oil. Then, after a few hours, the oil begins to break up and with the help of winds and waves (water turbulence), the oils are dispersed. The spreading rate is calculated from the temperature, wave currents, speed of winds and tidals. If these conditions become dominant, spreading and breaking up of the oil is also more rapid
Figure 3: Spreading Condition (URL 2)
Evaporation: Evaporation helps to reduce adverse effects of the oil spills, since not heavier components of the oil evaporates to the atmosphere. Of course, the evaporation ratio is related to volatility of the oil. For instance, kerosene, diesel oils and petrol are light products. Therefore, their evaporation speed is more than heavy fuel oil. Generally, if the boiling point of the oil is less than 200°C, their evaporation tendency is the first 24 hours. In addition to these, evaporation speed could increase because of the huge surfage area of the slick. Also, high wind speeds promote the evaporation rate (URL 2).
Dispersion: Water turbulence and wave speeds encourage the dispersion of oils at sea. After dispersion, suspended oil particules which remains into the water sysyem have bigger surface area than their initial situation. Because of this, dispersion supports the formation of other weathering processes such as dissolution, biodegradation and sedimentation. However, this process is also affected by viscosity of oil, wind speed etc (URL 2).
Emulsification: This term means that sea water and oil become an emulsion where water is suspended in the oil. It is the physical process that is observed because of turbulence of the water at the sea surface. After the emulsion, the viscosity of the mixture becomes much more greater than the initial oil viscosity and the color of water surface becomes brownish. Moreover, volume of the pollutants increase about three or four times, because of this mixing procedure. If the enough sunlight is obtained, maybe emulsions can separate into the their original water and oil forms (URL 2).
Figure 4: Emulsification Process (URL 2)
Dissolution: If the oil includes soluble compounds like light aromatic hydrocarbons such as benzene and toluene, these can dissolve into the water. But, these compunds can easily evaporate, and this procedure is much more quicker than dissolution. Therefore, this situation depends on the composition of the oil and its state (URL 2).
Oxidation: Oil particules give chemical reactions with the oxygen when they are breaking down. Sunlight encourages the oxidation process. Even though the strong sunlight is observed, thhis process is very slow such that the broken oil film amount is 0,1% per day (URL 2).
Sedimentation & Sinking: If the density of oil particles (refined products) are heavier than the density of fresh water, they want to sink at the bottom. However, this situation does not happen or very rarely happen into the marine environment, since the dencity of sea water is greater than the fresh water's density. Therefore, the particles do not sink at the bottom very easily. Most of the case, adhesion of organic particles into the oil causes the sinking (URL 2).
Figure 5: Sedimentation & Sinking Process (URL 2)
Biodegradation: There are too many microorganisms in the sea which can utilize compounds of oil to the water and carbon dioxide. But stil, some compounds of the oil may not be utilized because of their resistancy. One of the major factors that increases efficiency of the procedure is nutrient level of the water. In addition to this, dissolved oxygen amount and the temperature is also important. Dissolved oxygen is used by microorganisms. After creation of oil droplets, surface area of the oil increases. This increment will also increase the available surface area which is used for biodegradation of oil particules (URL 2).
From these processes spreading, evaporation, dispersion and dissolution are significant at the early stages of the oil spill event, oxidation, sedimentation and biodegradation processes are important when the later steps of oil spill event. All these helps us for determination of fate of oil spill. However, it is not an easy task, since all these eight processes are occuring more or less at the same time. Therefore, they have matrix effects for the oil spill problem.
Persistence of Oil
Persistence of oil concept is essential for both understanding the concept of oil spill problem and also helps to solve this problem, since the character of the oil, the clean - up techniques are developed.
Persistent oils include high - boiling materials that do not disperse immediately. That means they become a threat to the ecosystem when they are spilled to environment. On the other hand, non - persistent oils have usually volatile bodies and when they are spilled to the environment, they can easily leave the system because of evaporation. However, if the amount of non - persistent oils is too much, then they also become a threat to the ecosystem, because cleaning methods for these are very limited. But still, in the oil spill problem, most of the case the point is persistent oils. According to International Oil Pollution Compensation Funds (IOPC Funds), the definetion of the non - persistent oil is defined like this; the 50 % hydrocarbon fraction of the oil is distilled at a temperature of 340Â°C (645Â°F), when they are tested according to the American Society for Testing and Materials (ASTM) Method D86/78 (The National Research Council, 2003).
Effects of Oil Pollution
Oil pollution has a huge adverse effects both on environment and economy. Each oil spill has different impacts to the environment. Some impacts depend on the;
Oil spilled type,
Physical characteristic of spilled area,
Existing species in the area (sensitivity of area),
Time of the spilling,
Weathering conditions of the sea and season.
(Australian Maritime Safety Authority, 2010)
Different type of oil spills also causes to the economic losses, since each oil spill problem may have unique solution. That induce the exrta cost. To understand the situation more clearly the environmental impacts and economical impacts are illustrated different sections.
The environmental effects are changing with respect to oil spill range. oil spill does not cause vanishing, but causes some temporary effects. U.S. Environmental Protection Agency (EPA) explains these adverse impacts. According to EPA, "Most biological communities are susceptible to the effects of oil spills. Plant communities on land, marsh grasses in estuaries, and kelp beds in the ocean; microscopic plants and animals; and larger animals, such as fish, amphibians and reptiles, birds and mammals, are subject to contact, smothering, toxicity, and the chronic long-term effects that may result from the physical and chemical properties of the spilled oil."( URL 4)
Figure 6: Oil Spill (URL 3)
Oil spill causes a harm in a two ways. These are toxic contamination; oil particules which reach to the central nervous system of animals can damage their lungs. Also, oil spill decrease eating ability of animals since foods are also affected by this pollution and that damages the cell of animals. Most of the time, animals have long - term problems. Other is physical contact which means physical harm of oil spill. Most of the furs of animals are also affected. Below some examples are written to show effects of oil spill to the natural environment. (Zhu, et. All. 1999)
Seabirds: Seabirds are major species that are directly affected by the oil pollution. Oil patricules penetrate into fur of seabirds and this causes dead of seabirds, since their body can not handle with such a diverse oil. Especially at the cold places the 2 or 3 cm2 can kill the seabirds. After oil enters their furs, flying is not possible for seabirds. Moreover, birds can not float on the surface of water after spilling. Most of the case, because of toxicity of oil, even though cleaning is applied for these species and the place, seabirds can not survive. One direct example is from the Exxon Valdez oil spill around Alaska in 1989, according to researches more than 300.000 birds killed.(Zhu, et. all. 1999).
Marine Mammals: Marine mammals are whales, dolphins, sea lions, walruses, polar bears, sea otters, river otters, beavers, seals porpoises, and manatees can be affected from the oil pollution. These marine mammals are very precious animals and their furs are very important for them. When the oil spills, it directly penatrate these mammals furs like seabirds case. Therefore, they can die from overheating if the season is summer or spring, or their internal organs and their eyes, skins are also damaged. Some other sea species which are also affected from oil pollution are; sea turtles, fish, shellfish etc (Zhu, et. all. 1999).
Shallow Coastal Waters: Generally dilution capacity of the shallow coastal waters is enough to hold oil concentration below the dangerous levels. However, if the oil consists of toxic and on - volatile compounds, the dispersion is created and with the help of wind speed so many marine species kill. In addition these, fish eggs and larvaes also kill, since planktons which are temporary home of these and live in the water also die from pollution.(Zhu, et. all. 1999).
Shorelines: Shorelines are durable to the oil pollution more than others, because they have a tendency to eliminate oil spills. But, this is mostly related to the weather conditions, in other words wind speeds, temperatures, railfalls etc. With the help of this resistancy, most of the organism which lives in the shoreline can withstand the impact of oil spill. However, if the toxic is too much to handle for these species, the productivity of shoreline decreases (Zhu, et. all. 1999).
Economic impacts of oil spills are not too much talked as environmental impacts. But economical impacts are directly related to environmental effects. Oil spills adversly affect to the economics of the countries, since once the coastal areas are polluted with the oil, both tourism activities such as diving, swimming, bathing, fishering etc vanish, people who earn money from these areas loose theri jobs and in order to clean the marine environment a lot of money is spent. Hence, this situation affects both government and public health. (URL 5)
Fishermen have so much economic loss because of oil pollution both at the spill period and cleaning procedure, since while the cleaning of water body is cleaning, stil fishermen do not fish. In addition to these, loss of oil also economic problem of the government. However, all these are related to the environmental problems of ois spill, since if the oil pollution will not be done, economic loss will also eliminated. (URL 5)
Solutions to Oil Pollution Problem
There are some solutions related to oil spill problem. One of them is natural recovery, another is engineering operations. In the natural recovery case, it is necessary several years or decades to remove all negative effects of oil pollution from the marine ecosystem. Because of the uniqueness of the situations, some areas is recovered weeks, some are recovered 10 or 20 years periods. If the oil sinks to the bottom of the sea, then the recovery continue very long time. Natural recovery is also related to climate conditions. Researches shows that in the hotter climate regions, recovery of ecosystem is faster than the cold climate areas. However, the rate of natural recovery of the marine ecosystem is generally depends on the composition of the oil (URL 6).
There are two natural reproductivity strategies which are used by water species. First one has important recovery effect, in contrast second case is less common strategy. The limitless eggs and larvaes which are located into the planktons help reproduction of species. By the currents, they flourish to the new places. In the reality very little amount of individuals survive from this situation. However, this is the most common strategy. The less common one is observed to the long - lived species which do not reach its maturity for a long time. Researches are shown that these type of species face to face with less adaptation problems. Therefore, their populations recovery take a long time compared to the others. But, all these depend on the population of ecosystem and their durable tendency to the toxicity, wind and sun conditions (URL 6).
Engineering techniques are also used to overcome the oil spill problem. These are skimming which includes booms, usage of dispersants, and usage of biological microorganism. (Proffitt, et. all. 2007)
Skimming: Skimming which is used to clean up oils is very popular method. The system is like this; by using skimming equipments that has very fine filtering system in it water is drawn. Before skimming procedure, booms which are generally tubes produced from neoprene or other solid materials are used. Then, the oil is skimmed from the water surface. (Proffitt, et. all. 2007)
Dispersants: These are the chemicals which break the bonds between water and oil particules, so they are separated eachother. Oil particules become smaller than previous case. (Proffitt, et. all. 2007)
Biological Helpers: In this method microorganism are used. These microorganisms generally fertilizing species help to break bonds of oil compounds. These species including phoshorous and nitrogen encourage the bacteria in the water. Therefore, the dispersion procedure is completed in a natural way. (Proffitt, et. all. 2007)
After the oil removal of oil pollutants which is called recovery, restoration of the environment comes. One of the example of restoration is after oil contamination is reduced, the area is replanted. With this method, erosion problem of the area is decreased and ecosystem is also encouraged. However, when restoration is doing, it is necessary to think about the animals also. For instance, in order to increase population of animals, predator control method is used. Hence, reproductivity of the species is also provided.
Figure 7: Before (left) & After (right) Replanting of Salt Marsh (URL 7)
3.1 Oil Pollution Response
Oil spill response plays key role to solve and overcome the oil pollution. Most of the oil spill problem should be solved based on the watershed, since the spilled oil is not related to political boundaries but natural drainage.
The last Mexico Gulf situation can be given as an example of this situation, because this pollution affects both U.S.A and Mecixo. In addition to this, clean energy politics is now more considerable thing. Reaction of the public about oil spills more and more increasing. This situation is helping to shift politics to the more clean energy. On the other hand, because of the spilled oils, the fuel oil and gasoline costs are increasing. Therefore, for the oil pollution case, both public, companies and governments are responsible for this situation.
The Real World of Oil Pollution Examples
There are too many oil spill accidents that gives enormous adverse effects to the environment. In order to understand these adverse effects some examples are given below table:
Table 1: Tanker Accidents and Their Impacts (URL 8)
off Tobago, West Indies
700 nautical. miles off Angola
Castillo de Bellver
off Saldanha Bay, South Africa
off Brittany, France
700 nautical. miles off Nova Scotia, Canada
Scilly Isles, UK
Gulf of Oman
Navarino Bay, Greece
La Coruna, Spain
300 nautical. miles off Honolulu
Shetland Islands, UK
120 nautical. miles off Atlantic coast of Morocco
Off the Spanish coast
La Coruna, Spain
Milford Haven, UK
off Maputo, Mozambique
Prince William Sound, Alaska, USA
This above table includes the only ship accidents. However when the world's biggest or worst oil spills are searched, these below table is formed.
Table 2: World's biggest Oil Spills and Their Amouts (URL 8)
Name of Event
Amount of Oil Spill (MG)
Gulf War, Kuwait
Deepwater Horizon, Gulf of Mexico
Ixtoc I, Mexico
Atlantic Empress/Aegean Captain, Trinidad and Tobago
Fergana Valley/Mingbulak, Russia
Nowruz Oil Field, Persian Gulf
Castillo de Bellver, South Africa
The Amoco Cadiz
ABT Summer, Angola
The MT Haven, Italy