Meghan Hodges
Oil pollution is one of the most disastrous forms of environmental damage, with both short- and long-term effects on local ecosystems. The largest source of oil pollution is land-based runoff, which is responsible for 11% of oil pollution in the oceans. This occurs when rain or snowmelt picks up oil from roads and deposits the contaminated water into rivers that eventually flow into the ocean. Natural seeps from seafloor rocks are another major source, contributing 40-50% of all oil released into the oceans. While these natural seeps are considered less problematic, human activity is still a leading cause of oil pollution. Oil spills, which can be caused by human error, natural disasters, technical failures, or deliberate releases, are responsible for roughly 8% of overall oil pollution.
| Characteristics | Values |
|---|---|
| Largest source of oil pollution | Land-based runoff |
| Second-largest source of oil pollution | Natural seeps from seafloor rocks |
| Oil spills caused by human error | 30-50% |
| Oil spills caused by equipment failure or malfunction | 20-40% |
| Largest oil spill in European waters | Amoco Cadiz disaster off Brittany, France, in 1978 (223,000 metric tons of crude oil and ship fuel) |
| Largest oil spill in U.S. waters | Deepwater Horizon oil spill in 2010 |
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What You'll Learn
Natural seeps from seafloor rocks
Natural seeps have been occurring for thousands, if not hundreds of thousands, of years. The waters off Southern California, for instance, are home to hundreds of these seeps, contributing about five million gallons of oil to the ocean each year. Slicks from larger seeps can be seen from satellites and have been observed travelling as far as 100 miles down the coast. Santa Barbara, California, is another location where many natural seeps are found, with 20 to 25 tons of oil leaking from the seafloor each day.
The impact of natural seeps is less problematic than man-made spills as ecosystems have adapted to these regular releases. For instance, ocean bacteria have evolved to digest oil molecules, and some unique species of animals are able to use the hydrocarbons and other chemicals released at seeps as a source of metabolic energy. Furthermore, the oil from natural seeps is often biodegraded by microbial action deep beneath the seafloor.
However, natural seeps still impact the marine environment. Oil can be toxic to sea life such as fish, sea stars, shrimp, and seabirds, with the effects largely concentrated in the immediate area around a seep. In addition, it is difficult to distinguish between spilled oil and seep oil in areas with many natural seeps, making clean-up operations more challenging.
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Land-based runoff
The report highlights that while land-based runoff is the top source of oil pollution in the sea, there is a lack of precise data to quantify this source. Estimates suggest that there are at least 1.2 million tonnes per year of petroleum hydrocarbon in North America from land-based sources. However, more comprehensive research is needed to differentiate petroleum sources from other forms of oil.
The "Oil in the Sea: IV" report also ranks the other sources of oil pollution in the ocean. Natural seeps, which occur when oil escapes through fractures or faults in the seafloor, are the second-largest source. Oil spills, while often highly concentrated, are the third-largest contributor. Other sources include discharge from oil and gas operations, such as offshore production or commercial vessels.
To address land-based runoff, individuals can play a crucial role in reducing this type of pollution. The report suggests that people can help by using less fossil fuel, driving less, improving fuel efficiency, transitioning to electric vehicles, and maintaining their cars properly. These collective actions can significantly reduce the amount of oil that enters the ocean from land-based sources.
It is worth noting that oil spills, while not the largest contributor, can have severe environmental and economic consequences. Oil spills harm marine life, damage coastal areas, and impact industries such as fishing and tourism. Therefore, addressing both land-based runoff and oil spills is essential for protecting our oceans and the ecosystems they support.
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Operational releases from vessels
Oil spills are a major source of oil pollution, with thousands of minor and several major spills reported each year. While natural seeps from seafloor rocks are the largest source of oil spills, operational releases from vessels are a significant contributor, estimated to account for 21% of oil releases from vessels. These releases can occur through operational discharges of oily tank washings, which leave behind a hydrocarbon residue. The adoption of the load-on-top (LOT) process in the 1970s significantly reduced this type of pollution, decreasing it from 1.1 million tonnes/year in 1973 to 0.25 million tonnes in 1989.
To address operational releases from vessels, regulations such as the Oil Pollution Act of 1990 have been implemented, leading to a significant drop in the number of oil spills. Additionally, techniques like floating booms, skimming, and the use of sorbents are employed to contain and remove oil during cleanup operations.
While progress has been made in reducing operational releases from vessels, it is important to continuously improve prevention efforts and regulation policies. This includes exploring innovative methods for cleaning up oil spills and promoting environmental stewardship to protect ocean habitats. By combining stringent regulations, effective cleanup technologies, and increased awareness, we can work towards minimising the impact of operational releases from vessels on our precious marine ecosystems.
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Human error and equipment failure
Oil spills are a major source of oil pollution, threatening ocean ecosystems and causing environmental and economic damage. While natural seeps from seafloor rocks are the largest source of oil spills, human activity is a leading cause of this pollution.
Human error can result from operational or unpreparedness issues. For example, recreational boats can spill oil due to human error, although these spills are typically small and challenging to track due to underreporting. Larger vessels, such as oil tankers, can also experience human error-related spills, as seen in the Torrey Canyon and Amoco Cadiz disasters in European waters and the Exxon Valdez spill in Alaska. These incidents led to stricter shipping regulations and improved responses to ecological emergencies.
Equipment failure or malfunction is another significant contributor to oil spills. This can include the failure or rupture of oil pipelines, rigs, wells, and offshore platforms. One of the most infamous oil spills, the Deepwater Horizon incident in the Gulf of Mexico, resulted from equipment failure during offshore oil production.
To prevent and mitigate the impact of oil spills due to human error and equipment failure, it is essential to identify vulnerable points in oil transportation infrastructure and implement effective prevention efforts and regulation policies. Additionally, in the event of a spill, prompt response and specialised cleaning procedures are necessary to minimise the spread and environmental damage.
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Offshore oil operations
Offshore drilling operations have been responsible for some of the largest oil spills in history. In 1969, a blowout on an offshore platform off the coast of Santa Barbara, California, spilled over four million gallons of oil. More recently, in 2010, the Deepwater Horizon oil spill in the Gulf of Mexico released approximately 134 million gallons of oil into the ocean over eighty-seven days. This was caused by an explosion on a floating oil rig, which resulted in oil flowing directly into the deep ocean. The Deepwater Horizon spill is considered an international pollution incident, with oil spreading across the ocean for three months before it was capped.
The continuous discharges of PW from offshore oil and gas operations are the largest source of crude oil contamination in the sea. In addition to the natural pollutants in the oil, potentially hazardous production chemicals are also discharged. These include substances such as phenols, alkylphenols, and naphthenic acids, which can have endocrine-disrupting effects on aquatic organisms. Other substances of concern are BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), which are expected to evaporate quickly but can still have severe effects such as carcinogenicity and DNA damage.
Accidental discharges (spills) of oil from offshore operations can also occur due to failures in processes, equipment, or human error. These spills can range from small drips to large-scale ongoing pollution incidents. The timing and location of a spill are critical factors in its impact; a relatively small spill during the spawning season can have a more significant effect than a much larger spill at a different time. While stringent shipping and environmental regulations have reduced the number of major oil spills, thousands of minor spills and several major ones are still reported each year.
The pollution caused by offshore oil operations can have severe environmental and economic consequences. Oil spills can harm marine life, such as birds and mammals, by reducing the insulating ability of their feathers and fur. They can also make seafood unsafe to eat and disrupt economic activities such as fishing and tourism. The clean-up and restoration of oil spills can be expensive and time-consuming, requiring specialist equipment and contractors. In the United States, the Oil Pollution Act of 1990 established that those responsible for oil spills can be held accountable for the costs of cleanup and restoration.
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Frequently asked questions
Natural seeps from seafloor rocks are the largest source of oil spills, contributing to around 40-50% of all oil released into the oceans.
Other sources of oil pollution include oil spills, runoff from land, operational discharges from vessels, improper disposal of drilling muds, shipping and traffic accidents, tank washing, depot leakage, and failure or rupture in oil pipelines.
Oil spills are responsible for roughly 8% of overall oil pollution. The number of oil spills has decreased in recent years due to stricter legislation like the Oil Pollution Act of 1990.
Oil pollution is one of the most disastrous damages to the environment, causing both short-term and long-term harm to local ecosystems. Oil spills can kill sea creatures, make seafood unsafe to eat, and ruin beaches.
