Oil Pollution
What is it?
Oils refer to hydrocarbon based materials that vary widely depending on where they come from and what industrial processing they have undergone. There are many different types of oil that are distinctly different with regards to their composition. This is their individual combination of chemicals, heavy metals and sulfur among other substances. This also results in oils having a wide range of characteristic due to their compositional differences, meaning they have differing impacts on the way they affect our oceans when spilt.
Some oils naturally occur in the marine environment at a level that has no detectable impact on the function or health of a marine ecosystem. They are naturally released from seeps and fractures in the ground or sediment.
Where does it come from?
Oils are a primary source of energy worldwide and oil products are being produced and consumed at a vastly increasing rate. This has caused increasing rates of oil spills which have many environmental impacts. Oil spills occur on a daily basis and happen for a variety of reasons. Marine oil spills define the release of oil from accidents involving tankers, offshore platforms, pipelines, refineries, drilling rigs, storage facilities as well as recreational boats and marinas. These normally occur as a result of human error or carelessness, equipment failure or malfunction, illegal dumping or natural disasters such as hurricanes, cyclones and storms.
What happens to it?
Most oils spilt in the ocean float on its surface, they spread rapidly to form what is called an oil slick. Oil then continues to spread from slick to sheen, a very thin layer seen often with a rainbow of colours. Once within the marine environment, oil is subject to weathering. The term oil weathering refers to the biological, physical and chemical breakdown of the oil material. How the weathering processes affect the oil is dependent on the characteristics and composition of oil as well as the extent and type of weather it is subjected to.
Chemical weathering:
This defines remediation processes where aircraft or boats spread chemicals to disperse the oil slicks on the sea surface, into the water column. This helps prevent oil slicks from being transported on the surface to coastal mangroves, wetlands, beaches or tidal flats where they can directly endanger environmentally and economically important coastal areas.
Biological weathering:
This refers to the biological breakdown of oil into water soluble compounds by microorganisms or microbes. There are a wide variety of these organisms and they tend to be species specific to certain compositions of oil. The rate of biodegradation is dependent on the type of oil, the levels of nutrients and oxygen in the water and the temperature of the water.
Physical weathering:
This covers natural environmental processes such as weather, wind, sunlight and waves. How the physical weathering affects the spill depends on the characteristics and composition of the oil that has been split:
Evaporation: Volatile and lighter oils evaporate, the rate of which increases with higher temperatures and sunlight.
Oxidation: Some oils are photosensitive and under sunlight (solar radiation) become oxidised which is a form of breakdown.
Density differences and stratification: Density differences between oils and seawater occur with breakdown processes such as oxidation and allow a process called stratification to occur. Where an oil moves through the water column is dependent on its density and this changes during its breakdown, resulting in different layers of seawater and oil. This is stratification. There are also a few types of oil that are very dense and sink, these are usually found in seafloor sediments and their contamination there is found to be particularly persistent.
Natural dispersion: Oil dispersion can also occur through wind, waves and turbulence however this process occurs much slower without chemical dispersants that accelerate it.
Emulsification: This is another common physical weathering process that occurs due to turbulent mixing of water and oil. Wind, waves and currents acting upon the oil spill on the sea surface causes sea water droplets to become suspended in the oil. The mixing of these two liquids causes the volume of the pollutant to increase between 3-4 time the original amount and produce what is called an emulsion.
Dissolution: Water soluble compounds in an oil may dissolve in surrounding water. This again is dependent on the composition of the oil and its breakdown state. Dissolution most frequently occurs when the oil has been dispersed in the water column.
Where have they happened in the UK?
The most notable spills in British waters are known to be:
The Torrey Canyon in 1967: 120,000 tonnes of crude oil were spilt when the oil tanker shipwrecked off the western coast of Cornwall.
The Rosebay in 1990: 1,100 tonnes of crude oil were spilt after an oil tanker collision off the south coast of Devon.
The Braer in 1993: 85,000 tonnes of crude oil were spilt when the oil tanker ran aground during a storm in the Shetland Islands.
The Sea Empress in 1996: 72,000 tonnes of crude oil were spilt when the tanker became grounded on mid channel rocks in the Milford Estuary, Pembrokeshire.
The Shell oil leak in 2011: 220-880 tonnes of crude oil were spilt from a leak in the flowline on the Shell oil platform, 113 miles off the coast of Aberdeen.
How are oil spills dealt with?
Responding to an oil spill covers a number of different targets:
1) To stop any flow of oil
2) To protect the environment, especially ecologically sensitive areas
3) To remove and disperse the oil spill as fast and effectively as possible.
There are a number of different methods and resources that can be implemented to respond to an oil spill. The combination of those used is dependent on the geographical location, the amount and type of oil spilt as well as the accessible local resources.
Booms: Equipment known as booms are used to contain and reduce the spread of an oil slick on the sea surface. These are physical floating barriers that can also be used to help prevent oil from reaching sensitive coastal locations.
Skimmer boats: These remove oil from the waters, they skim or scoop oil from the water’s surface however their effectiveness is dependent on the thickness of the slick. Collected oil is then able to be disposed of properly.
In situ burning: This is a less frequently used method that involves burning freshly spilled oil on the sea surface to prevent it from entering the marine environment.
Chemical dispersants: These are used to break down oil on the sea surface and disperse it into the water column. Dispersants do not reduce the amount of oil spilled, they merely cause its movement from one area (the sea surface) to another (the water column). This helps prevent oil spills from reaching environmentally sensitive coastal habitats however, the dispersion of oil into the water column has ecological consequences on the plants and animals there.
Manual clean-up crews: For oil spills that reach the coastal environment, manual labouring clean-up crews are deployed to help tackle the shoreline pollution along with additional machinery equipment.
How is it harmful?
The ecological implications of oil spilt at sea is dependent upon:
1) Spill location
2) Proximity to environmentally sensitive areas such as fish nurseries or bird foraging sites
3) Amount and type of oil spilt
4) The extent of physical forces that act on the spilled oil such as the weather and waves
Answering the question of how much harm an oil spill causes is therefore very dynamic. Overall, the impact of major spills is always enormously harmful to animals, habitats and ecosystems. Ecological effects have been recorded in terms of mortality of organisms and destruction or degradation of surrounding habitat.
Seafloor plants and animals: Mass kills, known as scientifically as mass mortality can occur to seafloor dwelling animals if the oil reaches them in sufficient quantity. Marine animals have distinct differences in sensitivity and those that are more resilient will dominate ecosystems after oil spill mortalities. Fluxes in ecosystem dynamics have consequential effects on a wide variety of plants and animals due to changes to the food web. Animals not directly implicated by the oil spill may be indirectly implicated through food web changes.
Fish: Oil spills pose significant threat to fish eggs and larvae. This is because the eggs and larvae are small in size, with underdeveloped or no membranes and detoxification systems to mitigate the toxic effects of oil. The spills have been found to cause deformities and reduce an organisms ability to feed and grow, the result of which leaves affected individuals more prone to predation and starvation. Adult fish have been found to suffer from change to heart and respiration rates which impairs both growth and reproduction. These effects have a consequential impact of fish stocks. This is of ecological importance in terms of food web and ecosystem dynamics as well as economic importance to the fishing industry.
Air breathing marine animals: Oil destroys the insulation capacity of many marine mammals fur such as sea otters and seals. It also destroys the waterproofing of seabird feathers. Without waterproofing or insulation, many of these animals die from hypothermia in cold water. Sea turtles have been found to become trapped in oil. Whales, porpoises and dolphins who surface to breathe have been documented to inhale oil from spills which affects their lung function, immune and reproductive system. Seabirds who clean their feathers to attempt to remove oil are also affected by oil poisoning.
Other Problems
Oil spills have far reaching implications. The wide variety of oil compositions and following breakdown compositions from weathering, as well as the persistence of oil in the environment has the capacity to do extreme amounts of damage. Even processes that are designed to help clear up the oil spill have ecological implications. Chemical dispersants released by airplanes and boats onto oil spills have toxic effects on local marine life.
Chemical dispersants were used in unprecedented quantities to combat the Deep Water Horizon spill in 2011. This spill was classed as one of the biggest marine oil spills in history, and an estimated 200 million gallons of crude oil were spilt in a marine oil rig industrial disaster in the Gulf of Mexico. 16,000 miles of coastline were affected and an estimated area of 68000 square miles of the ocean. After the
Deep Water Horizon disaster, the chemical dispersants used were found to cause toxin release from the oil. The chemical dispersant in combination with the spilt oil was deemed to be more ecological harmful than the oil itself.
How does it affect humans?
Health: It is believed that public health could well be compromised by marine oil spills. With oil and dispersant chemicals being found to accumulate up the trophic levels of the marine food web and with humans at the top as predators and fish eaters it is possible that contaminated fish consumption may have significant detrimental consequences on public health. Furthermore, chemical dispersants have been proven to pose significant health risks to humans. Clean-up workers responsible for working with the chemicals have reported suffering from numerous health problems directly resulting from the dispersants.
Economy: With a high proportion of the world’s population living by and having dependence on the ocean for income, resources and food, the impacts of oil spills are of significant concern socioeconomically. Damage to the environment from oil impacts tourism, industrial and localised fisheries. To some extent this economic damage can be measured by the total amount of liability and compensational funds regulated by legislation: For example in the case of Deep Water Horizon the disaster cost BP $65 billion.
Putting a value to environmental damage however is impossible.
Can it be stopped?
Major oil spills within the ocean have reduced in frequency since the 1900s, this is most likely due to advances and improvements in technology. However, as demonstrated by the Deepwater Horizon disaster in 2011, environmental destruction by oil pollution events is still a great threat to our oceans. Equally, the unmonitored and widely unknown amounts that recreational boats and marinas contribute to ocean oil pollution is of great concern.
Within the UK the sale of recreational boats, the use of the boats and their maintenance is unregulated. Unlike with road vehicles in the UK, for recreational boats there is no law to enforce servicing to ensure their safety, which would include their environmental safety. Furthermore, individuals need no qualifications or specific knowledge to purchase a boat or use it.
As a result, regulating and stopping marine oil input from recreational boats is completely impossible.
What has been done?
Although there is no law to ensure the environmental safety of recreational boats, the UK has a few laws that exist to prosecute individuals or businesses who pollute ocean with oil if they are in breach of certain conditions. In the case of serious oil pollution events, national law requires the people or business responsible to limit the harm and be liable for the pollution clean up.
While this may instigate more large scale businesses and commercial vessel sectors to ensure provisions are put in place to prevent large scale oil spills from occurring for which they could be held accountable, this doesn’t directly do anything to prevent accidental oil spills from occurring. There is also nothing to enforce monitoring, prevention and accountability of small oil spills relating to recreational boat use.