Gulf still polluted 10 years after Deepwater Horizon

Four hoses from four ships pour seawater onto the burning Deepwater Horizon platform

Scientists complete a Gulf-wide survey of oil pollution among fish populations for the first time since the huge oil spill

On 20 April 2010, while drilling at sea 250 miles southeast of Houston, a blowout caused an explosion on the Deepwater Horizon oil rig that killed 11 crewmen and ignited a fireball visible from 40 miles away. The fire was inextinguishable and, two days later, on 22 April, the Horizon sank, leaving the well gushing at the seabed and causing the largest oil spill to ever occur in US waters

A massive new study – comprising samples from 2,500 fish representing 91 species spread across 359 locations in the Gulf of Mexico – suggests contamination from oil pollution, 10 years after Deepwater Horizon oil spill, remains widespread.

Researcher Erin Pulster, marine scientist at the University of South Florida, is pictured identifying fish specimens alongside research partners from the National Autonomous University of Mexico
Marine scientists at the University of South Florida identifying fish specimens alongside research partners from the National Autonomous University of Mexico
Image: USF

“This is the largest comprehensive fish survey ever conducted in a large marine ecosystem” says study author Erin L. Pulster, marine scientist and postdoctoral researcher at the University of South Florida.

“Given the extensive oil and gas extraction activities in the Gulf of Mexico for the last eight decades, it is unclear why this has not been conducted prior to the Deepwater Horizon oil spill.”

Scientists measured higher concentrations of PAH toxins in fish near places with greater oil and gas activity.

Polycyclic aromatic hydrocarbons, or PAHs, are one of the most toxic chemical components found in crude oil. The toxins, which have been linked to heart disease and cancers in humans, get trapped in the bile of fish. Researchers also found PAH hotspots among fish populations near coastal cities like Tampa Bay, which suggests urban runoff can exacerbate oil pollution problems.

An oil platform
The pollution they found is not only leftover from the Deepwater Horizon spill, but all around the oil and gas rigs running today, which is in turn only part of a wider picture every day human pollution

“The continued degradation of the Gulf of Mexico ecosystem is demonstrated by the chronic, widespread oil pollution,” Pulster said.

Anthropogenic sources include the Deepwater Horizon oil spill, leaking infrastructure, riverine discharge, marine vessel traffic and the resuspension of contaminated sediments

Erin L. Pulster, marine scientist and postdoctoral researcher at the University of South Florida

Despite the alarming results, scientists suggest the evidence of PAH contamination is more concerning for the health of Gulf ecosystems and fish populations than the health and safety of consumers of Gulf seafood.

Previous studies have revealed 50 to 80 percent population declines in deep water fish populations near the Deepwater Horizon blowout site.

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10 ways to clean up an oil spill…

1. Oil Booms

The use of oil booms is a very simple and popular method of controlling oil spills. Equipment called containment booms acts like a fence to prevent the oil from further spreading or floating away.

2. Skimmers

Once the oil has been confined by using oil booms, skimmers or oil scoops can be deployed onto boats to remove the contaminants from the water surface. Skimmers are machines specially designed to suck up the oil from the water surface like a vacuum cleaner.

3. Sorbents

Sorbents are materials that soak up liquids by either absorption (pulling in through pores) or adsorption (forming a layer on the surface). Both these properties make the process of clean-up much easier. Materials commonly used as oil sorbents are hay, peat moss, straw or vermiculite.

4. Burning In-situ

In this method, the oil floating on the surface is ignited to burn it off. This in-situ burning of oil can effectively remove up to 98% of an oil spill, which is more than most of the other methods. The toxic fumes released from the burning can cause significant damage to the environment as well as marine life.

5. Dispersants

When the spilled oil cannot be contained by using booms, the only option left is to accelerate the disintegration of oil. Dispersal agents, such as Corexit 9500, are chemicals that are sprayed upon the spill with the help of aircraft and boats, which aid the natural breakdown of oil components.

They allow the oil to chemically bond with water by increasing the surface area of each molecule. This ensures that the slick does not travel over the surface of the water, and is easier to degrade by microbes. The toxicity of dispersants can affect marine organisms, especially the non-mobile ones such as corals and seagrass.

Workers cleaning oil from a rocky shoreline with Hot Water and High-Pressure Washing

6. Hot Water and High-Pressure Washing

This procedure is mainly used in situations where the oil is inaccessible to methods of mechanical removal such as using booms and skimmers. It is used to dislodge the trapped and weathered oil from locations which are generally inaccessible to machinery.

Water heaters are used to heat up water to around 170°C, which is then sprayed by hand with high-pressure wands or nozzles. The oil is thus flushed to the water surface, which can be collected with skimmers or sorbents.

7. Manual Labour

As the name suggests, the method requires hand-held tools and manual labour to clean up the contaminants. It involves the use of manual means like hands, rakes, shovels etc. to clean the surface oil and oily debris and place them in special containers to be removed from the shoreline.

8. Bioremediation

Bioremediation refers to the use of specific microorganisms to remove any toxic or harmful substances. There are various classes of bacteria, fungi, archaea and algae that degrade petroleum products by metabolizing and breaking them into simpler and non-toxic molecules (mostly fatty acids and carbon dioxide). This process is generally not used when the spill has happened in the deep seas and is gradually put into action once the oil starts to approach the shoreline.

9. Chemical Stabilisation

Right after an oil spill, the immediate concern is to prevent the oil from spreading and contaminating the adjacent areas. While mechanical methods like using oil booms effectively contain the oil, they have certain limitations to their use.

Quite recently, experts have been using compounds like ‘Elastol’, the compound gelatinizes or solidifies the oil on the water surface and thus keeps it from spreading or escaping. The gelatin is easy to retrieve, and this makes the process highly efficient.

10. Natural Recovery

The simplest method of dealing with the oil spill cleanup operation is to make use of the vagaries of nature like the sun, the wind, the weather, tides, or naturally occurring microbes. It is used in certain cases when the shoreline is too remote or inaccessible, or the environmental impact of cleaning up a spill could potentially far outweigh the benefits.

The treatments follow a general rule: (All distances measured from the shoreline)

  • 200 nautical miles and beyond – No treatment is used, unless the case is very severe.
  • Between 20 and 200 nautical miles, booms and skimmers may be used.
  • Between 20 and 10 nautical miles, dispersants are used.
  • For areas very close to the shoreline, biological agents are used.

These are only general rules and can be altered based on the type of oil that has been spilt and the prevailing weather conditions. No two oil spill cases are the same, so each one is evaluated individually based on its own merit.


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