Environmental Management (0680) | Impact of oil pollution

🌊 Environmental Management (0680) Study Notes: Impact of Oil Pollution

Introduction: The Cost of Energy

Hey future environmental managers!

Oil (petroleum) is a massive source of energy for the world, but transporting and extracting it carries serious risks. This chapter looks at how oil spills devastate marine environments and what we do to prevent and clean them up. Understanding this balance between energy demand and environmental safety is crucial for your exam!

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1. Causes of Oil Pollution in Marine and Coastal Ecosystems (Syllabus 2.5)

Oil pollution doesn't just happen because someone dropped a barrel. It occurs when large volumes of crude oil or refined petroleum products escape into the ocean. The syllabus focuses on three main causes:

1.1 Off-shore Oil Extraction

What it is: Drilling for oil miles out at sea, often from large platforms.

How spills happen:

• Accidents during the drilling process (e.g., blowouts).

• Equipment failure or natural disasters (like hurricanes) damaging the platform or wellhead.

Did you know? The 2010 Deepwater Horizon spill in the Gulf of Mexico, caused by a rig blowout, is one of the largest accidental oil spills in history.

1.2 Pipelines

What it is: Large networks of pipes used to transport crude oil from the extraction site (off-shore platform) to land refineries.

How spills happen:

• Corrosion or cracking of old pipes.

• Damage from anchors, fishing equipment, or geological shifts on the seabed.

1.3 Shipping (Oil Tankers)

What it is: The main way oil is moved globally, using massive oil tankers.

How spills happen:

• Collisions between ships.

• Grounding (the ship hits the sea floor or a reef, tearing the hull).

• Structural failure in bad weather.

Key Takeaway: While spectacular tanker crashes grab headlines, routine maintenance leaks, and pipeline failures also contribute significantly to chronic, low-level oil pollution.

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2. Impacts of Oil Pollution on Ecosystems (Syllabus 2.5)

Oil is less dense than water, so it floats, creating a slick on the surface. This slick is highly visible, toxic, and disrupts almost every part of the marine ecosystem.

2.1 Impact on Birds

Birds, especially diving seabirds, are extremely vulnerable.

• Loss of Insulation: Oil coats their feathers, causing the tiny barbs that keep the feathers waterproof and insulating to separate. This means the birds lose body heat quickly, leading to hypothermia (fatal chilling).

• Immobility: The heavy, sticky oil makes it impossible for them to fly or swim effectively to catch food.

• Poisoning: When birds try to clean their feathers (preening), they ingest the toxic oil, which damages their internal organs and leads to death.

2.2 Impact on Marine Mammals

This includes animals like sea otters, seals, and whales.

• Hypothermia: Mammals like sea otters rely on air trapped in their dense fur for insulation. Oil coats the fur, replacing the air and causing them to lose insulation and die from cold.

• Inhalation/Ingestion: Whales and dolphins can inhale toxic oil vapors or ingest oil when feeding near the surface, causing respiratory and digestive damage.

2.3 Impact on Coral Reefs

Coral reefs are highly sensitive and take decades to recover.

• Smothering and Toxicity: Oil, especially when dispersed by waves or chemicals (see Section 4), can sink below the surface and smother the delicate coral polyps.

• Blocked Sunlight: The surface slick reduces the amount of light reaching the zooxanthellae (algae) that live inside the coral, which are essential for the coral’s food supply (photosynthesis).

2.4 Impact on Beaches (Coastal Ecosystems)

Beaches are the end destination for most oil slicks, particularly in tidal areas.

• Habitat Destruction: The oil soaks into the sand, gravel, and rock crevices, killing smaller organisms (crabs, worms, shellfish) that form the base of the coastal food web.

• Long-Term Damage: Cleanup is difficult; oil can remain trapped under sand or rocks for many years, releasing toxins slowly and preventing habitat recovery.

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3. Strategies for Reducing Oil Spills (Prevention) (Syllabus 2.6)

The best environmental strategy is to prevent the pollution in the first place. These strategies aim to reduce the likelihood of oil leaving the source.

3.1 International Legislation: MARPOL

MARPOL stands for the International Convention for the Prevention of Pollution from Ships.

• It is a global treaty setting rules to prevent pollution by ships (including accidental and operational pollution).

• It controls things like the disposal of oil and garbage, and crucially, mandates the construction standards for tankers.

Don't worry about remembering the full name—just remember MARPOL is the key international law that forces ships to be safer and cleaner.

3.2 Double-Hulled Oil Tankers

Before the 1990s, most tankers had a single steel layer (hull) separating the oil from the ocean. If this hull was pierced, a spill was guaranteed.

The solution: Double-hulled oil tankers.

• They have an inner and an outer layer of steel, separated by empty space or ballast water.

• If the outer hull is pierced (e.g., in a minor collision or scrape), the inner hull remains intact, preventing the oil from leaking.

Analogy: Think of a double-hulled tanker like a protective bubble wrap layer around the oil cargo. It significantly reduces the risk of massive spills from accidents.

Key Takeaway: MARPOL enforced the global adoption of double-hulled tankers.

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4. Strategies for Minimising the Impact (Cleanup) (Syllabus 2.6)

Once a spill has occurred, management teams focus on minimising the environmental damage. This involves cleaning up or breaking down the oil before it reaches sensitive coastlines.

4.1 Containment: Oil Booms

What they are: Floating physical barriers (like giant inflatable fences) used to surround and contain a floating oil slick.

Process:

1. Booms are rapidly deployed around the spill area.

2. The contained oil is prevented from spreading or drifting toward sensitive coastal areas (e.g., mangroves, fishing grounds).

Limitations: Booms are only highly effective in calm waters. They can fail in strong currents, high winds, or rough seas, allowing the oil to escape over or under the barrier.

4.2 Removal: Skimmers

What they are: Specialised vessels or equipment designed to physically scoop, vacuum, or skim the oil off the surface of the water once it has been contained by booms.

Process:

1. Oil is concentrated using booms.

2. Skimmers then mechanically remove the oil, which can often be recovered and recycled or disposed of safely.

Advantage: This technique removes the pollutant completely from the ecosystem.

4.3 Chemical Dispersion: Detergent Sprays (Dispersants)

What they are: Chemicals, similar to strong household detergents, sprayed onto the oil slick from planes or ships.

Process (Step-by-step):

1. The dispersant is sprayed onto the oil slick.

2. The chemical breaks the large slick into thousands of tiny droplets.

3. These small droplets sink or mix into the water column, where they are more easily broken down by natural processes (bacteria).

Common Mistake to Avoid: Detergents do not remove the oil; they just spread it out and hide it!

Disadvantage: The dispersants themselves can sometimes be toxic to marine life, especially organisms living at depth (like juvenile fish or deep-sea coral). Their use is controversial and often restricted.

Remember that managing environmental disasters, like oil spills, requires a balanced approach: strong international laws to reduce frequency, combined with effective, rapid technologies to deal with the spills that inevitably occur!