(F) 18 - Oil spills Flashcards
Consequences of moving a lot of fuel (by sea, rail, and pipelines)
Pipeline
- most of Canada’s oil is transported by pipeline
- 99% of Canada’s oil is exported to the USA
Sea
- most tanker traffic is to the USA
- rest is to overseas markets
- major ports on Canadian west and east coast
Things go wrong…resulting in an oilspill!
- pipelines can rupture or malfunction
- accidents can happen via trains due to faulty tank pressure or faulty train brakes
- accidents can happen at sea
4 major pipelines (connected to many local ones)
– Trans Mountain (Edmonton to BC)
– Keystone (Hardisty, AB to USA)
– Express (Hardisty, AB to USA)
– Enbridge (Edmonton to USA)
Petroleum vs. Oil vs. Bitumen (dilbit)
Petroleum: broad category that includes both crude oil and petroleum products. The terms oil and petroleum are often used interchangeably
Crude oil: liquid mixture of hundreds of different petrochemicals (hydrocarbons), later refined to make products such as gasoline, heating oil, etc.
Diluted bitumen (dilbit): bitumen (crude oil + sand) diluted with lighter petroleum (usually naphtha) to make it less viscous
Terrestrial vs. Marine oil spill impacts
Terrestrial
- Most common, usually involving a ruptured pipeline
- Over 1000 incidents in Canada in the past decade alone
- Impacts localized area
Marine
- Less frequent, but more petroleum released
- One single spill can release as much as an entire year of terrestrial spills
- Damages disperse, oil transported across vast distance with ocean currents
5 Natural weathering processes that oil undergoes on water and land
- Evaporation
- Spreading
- Dissolution
- Residual materials
- Degradation
Evaporation
Evaporation of fumes and vapors reduces volume of spillage, can eliminate up to 100% of gasoline, 50% of crude oil, and 10% of denser bunker fuel
Spreading
The movement of an oil slick over water or land. Slow on land (soil highly absorbent), quicker on water (due to water currents and wind)
Dissolution
Pollution of the water beneath an oil slick, lighter hydrocarbons become dissolved in water
Residual materials
Heavier hydrocarbons (lighter ones either evaporate or dissolve) form a gelatinous emulsion (water-in-oil) known as mousse, can wash up onto shorelines or sink
- overtime mousse loses water and forms tar balls that persist in the environment for a long time
Degradation
The slow decomposition of petroleum by either microbes (biodegradation) or photo-oxidation by UV radiation
Fate of spilled petroleum on land
- Localized impacts, unless a very large spill
- Soils high in organic matter can absorb petroleum
- Will tend to accumulate in low spots on the landscape
*Extensive damages can occur though if petroleum reaches water
Toxicity of oil on organisms, on soils, to food webs, and to coastal areas
Food Web Impacts
- top predators directly impacted; disappearance impacts trophic cascade resulting in proliferation of midlevel predator
- local level of fish proliferate but ingest hydrocarbons which bioaccumulate
Risk of Suffocation for Aquatic Organisms
- surface waters are supersaturated with O2 due to atmospheric exchange
- oil slicks form a barrier btw air and epilimnion, preventing atmospheric exchange
- dissolved O2 decreased = epilimnetic organisms can suffocate
Soil Impacts
- biggest concern: petroleum will seep into groundwater
- BTEX may kill soil microorganisms, arthropods, also higher organisms; can potentially disrupt food webs
Increased Coastal Erosion
- oil can be especially toxic to march and coastal grasses
- kill the grasses, reduce the protection from wind and water, erosion increases
Biochemical vs. Physical Toxicity of Oil
Biochemical toxicity of oil
- direct ingestion by an organism
- think of shellfish that can’t move
Physical toxicity of oil
- even if they don’t directly ingest the oil, by trying to clean themselves they will
- affects ability of birds to fly and insulate their body (can lead to hyperthermia
- more time spent grooming = less eating, lower attention to predators
What makes petroleum toxic?
- It contains many volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylene (BTEX)
- VOCs are carcinogens, can cause neurological and reproductive damage, and are irritants
Acute toxicity aka why oil spills need to be cleaned up asap
- Some hydrocarbons can destroy cellular membranes, killing tissues
- The process of cleaning up oil spill can also kill organisms
- Toxicity of oil varies on its source and level of processing
Ex: Canadian Crude Oil: classified as sweet vs sour
- Sweet: lighter, better for making gasoline, lower in sulfur
- Sour: higher in sulfur (more processing required), more harmful, impact on skin is similar to sweet
6 ways we clean oil spills
- Mechanical recovery (containment booms, skimmers, sorbents)
- In-situ burning
- Chemical recovery (dispersants, gelling agents/solidifers)
- Bioremediation (microorganisms)
- Electrical resistance (terrestrial spills)
- Cleaning wildlife
Mechanical recovery (containment booms, skimmers, sorbents)
Physical containment, collection of spilled oil
- Containment booms: can be used in water or soil
- Skimmers and Sorbents: absorb the oil then can be thrown away
In-situ burning
Controlled burning of spilled oil to remove it
- if done properly, can remove large amounts of oil
- but… it causes air pollution
- only works in low wind areas and best for lighter petroleum
- will produce residues that most often sink and persists
Chemical recovery (dispersants, gelling agents/solidifiers)
Use of dispersants or gelling agents to either break the oil down into smaller droplets, or to congeal it together
Dispersants
- mixture of surfactants
- used in choppy waters, when other methods are ineffective
- ex. COREXIT; may be more acutely toxic than the oil…after having used them abundantly, discovered they can bioaccumulate and can lead to death in organisms (including humans). Used because the problem of the spill disappears very fast.
Gelling Agents (Solidifiers)
- physically bonds with oil, forming a rubbery solid
- low toxicity, low flammability
- may be able to recycle the solidified oil
- problem: expensive, and need large volume
Bioremediation (microorganisms)
Use of fertilizers and nutrients to increase microorganism growth, which in turn break down (biodegrade) the oil
- microorganisms breakdown and degrade petroleum
- can seed organisms into spills, or fertilize spills to increase their populations
Electrical resistance (terrestrial spills)
Used to clean terrestrial spills
- easier to just remove the affected soil from the site
- but if it can’t be removed, bioremediation can be used = use of electrical resistance heating (installing electrodes)
- electrodes release a current that breaks down the oil; soil is heated by the current, electrifying it so the hydrocarbons evaporate
- cannot be done everywhere, especially not in water
Cleaning wildlife
Dawn is used
2 Examples of major oil spills
- Deepwater Horizon (2010)
- Exxon-Valdez (1989)
Deepwater Horizon (2010)
- know why its important and what we learned
What happened:
- Piping failure and buildup of natural gas
- Natural gas filled up the drill column and eventually exploded
- Blowout Preventer (BOP) malfunctioned and manual override was not enacted fast enough to prevent blowout
- Leak happened deep underwater, detecting and stopping it took 89 days meanwhile, the oil spread to shorelines
Problems at the site:
- previous equipment malfunction
- faulty concrete
- lied on safety records
- ignored signs of problem
- ignored workers concerns
The Cleanup
- oil skimmed, oil burned, oil dispersed using COREXIT
- the reason we knew what to do was due to the Exxon-Valdez Oil Spill
The Gulf of Mexico is healing…slowly
- recovery by animals is slowed due to bioaccumulation (and biomagnification) of toxic COREXIT
- oil itself also linked to birth defects and deaths of marine organisms
- most oil weathered by now, so fisheries closures have been lifted
- still studying the impacts
Exxon-Valdez (1989)
- know why its important and what we learned
What happened:
- oil tanker struck a big reef in Alaska and oil spilt; by the time we realized what happened it had spread… a lot
- wildlife wasn’t helped
- fisheries impacted
- all juveniles died (the area was a spawning place) = population decrease
- still seeing impacts via biomagnification and still find residual material today
Learning from the Exxon-Valdez Oil Spill
- weathered oil will persist, has been observed on Alaskan Coast 16+ yrs after the spill
- chronic oil exposure will impact wildlife:
1) chronic ingestion from grooming
2) reduced reproduction, increased mortality in fish, mammals, birds
3) bioaccumulation will occur
- indirect effects:
1) food web disruptions from trophic cascades
2) reduced biogenic habitat (created by impacted species)
3) loss of keystone species (ex. sea otters)
4) disruption of social species (ex. orcas)
