A beach after an oil spill
An oil spill
is the release of a liquid petroleum hydrocarbon
into the environment due to human
activity, and is a form of pollution
term often refers to marine
spills, where oil is released into the ocean
or coastal waters
. The oil may be a
variety of materials, including crude oil
refined petroleum products (such as gasoline
or diesel fuel
or by-products, ships
' bunkers, oily refuse or
oil mixed in waste
. Spills take months or even
years to clean up.
Oil is also released into the environment from natural geologic seeps
on the sea floor
. Most human-made oil pollution comes
from land-based activity, but public attention and regulation has
tended to focus most sharply on seagoing oil tankers.
The oil penetrates and opens up the structure of the plumage
of birds, reducing its insulating ability,
and so making the birds more vulnerable to temperature fluctuations
and much less buoyant
in the water. It also
impairs birds' flight abilities, making it difficult or impossible
to forage and escape from predators. As they attempt to preen
, birds typically ingest oil that covers their
feathers, causing kidney
function, and digestive tract
irritation. This and the
limited foraging ability quickly causes dehydration
imbalances. Hormonal balance alteration
including changes in luteinizing
can also result in some birds exposed to petroleum.
Most birds affected by an oil spill die unless there is human
exposed to oil spills
are affected in similar ways as seabirds. Oil coats the fur of
, reducing its insulation abilities and
leading to body temperature
fluctuations and hypothermia
of the oil causes dehydration and impaired digestions.
Because oil floats on top of water, less light penetrates into the
water, limiting the photosynthesis
marine plants and phytoplankton
as well as decreasing the fauna populations, affects the food chain
in the ecosystem.
Methods of cleaning
A US Navy oil spill response team
drills with a "Harbour Buster high-speed oil containment
A sheen is usually dispersed (but not cleaned up) with detergents
which makes oil settle to the bottom. Oils that are denser than
water, such as Polychlorinated
(PCBs), can be more difficult to clean as they make
the seabed toxic.
Methods for cleaning up include:
- Bioremediation: use of microorganisms or biological agents to break down or remove
- Bioremediation Accelerator: Oleophilic, hydrophobic chemical,
containing no bacteria, which chemically and physically bonds to
both soluble and insoluble hydrocarbons. The bioremedation
accelerator acts as a herding agent in water and on the surface,
floating molecules to the surface of the water, including solubles
such as phenols and BTEX, forming gel-like agglomerations.
Non-detectable levels of hydrocarbons can be obtained in produced
water and manageable water columns. By overspraying sheen with
bioremediation accelerator, sheen is eliminated within minutes.
Whether applied on land or on water, the nutrient-rich emulsion,
creates a bloom of local, indigenous, pre-existing,
hydrocarbon-consuming bacteria. Those specific bacteria break down
the hydrocarbons into water and carbon dioxide, with EPA tests
showing 98% of alkanes biodegraded in 28 days; and aromatics being
biodegraded 200 times faster than in nature.
- Controlled burning can effectively
reduce the amount of oil in water, if done properly. But it can
only be done in low wind, and can cause
- Dispersants act as detergents, clustering around oil globules and
allowing them to be carried away in the water. This improves the
surface aesthetically, and mobilizes the oil. Smaller oil droplets,
scattered by currents, may cause less harm and may degrade more
easily. But the dispersed oil droplets infiltrate into deeper water
and can lethally contaminate coral. Recent
research indicates that some dispersants are toxic to corals.
- Watch and wait: in some cases, nautural attentuation of oil may
be most appropriate, due to the invasive nature of facilitated
methods of remediation, particularly in ecologically sensitive
- Dredging: for oils dispersed with
detergents and other oils denser than water.
- Skimming: Requires calm
Equipment used includes:
- Booms: large floating barriers that round up oil and lift the
oil off the water
- Skimmers: skim the oil
- Sorbents: large absorbents that absorb oil
- Chemical and biological agents: helps to break down the
- Vacuums: remove oil from beaches and water surface
- Shovels and other road equipments:
typically used to clean up oil on beaches
- Secondary containment - methods to prevent releases of oil or
hydrocarbons into environment.
Spill Prevention Containment and Countermeasures (SPCC) program by
- Double hulling - build double hulls
into vessels, which reduces the risk and severity of a spill in
case of a collision or grounding. Existing single-hull vessels can
also be rebuilt to have a double hull.
Environmental Sensitivity Index (ESI) Mapping
NOAA's Office of Response and Restoration
Environmental Sensitivity Index (ESI) maps are used to identify
sensitive shoreline resources prior to an oil spill event in order
to set priorities for protection and plan cleanup strategies. By
planning spill response ahead of time, the impact on the
environment can be minimized or prevented. Environmental
sensitivity index maps are basically comprised of information
within the following three categories: shoreline type, and
biological and human-use resources.
type is classified by rank
depending on how easy the oil would be to cleanup, how long the oil
would persist, and how sensitive the shoreline is . The floating
oil slicks put the shoreline at particular risk when they
eventually come ashore, covering the substrate
with oil. The differing
substrates between shoreline types vary in their response to
oiling, and influence the type of cleanup that will be required to
effectively decontaminate the shoreline. In 1995, the National Oceanic
and Atmospheric Administration
extended ESI maps to lakes,
rivers, and estuary shoreline types . The exposure the shoreline
has to wave energy and tides, substrate type, and slope of the
shoreline are also taken into account – in addition to biological
productivity and sensitivity. The productivity of the shoreline
habitat is also taken into account when determining ESI ranking .
and marshes tend to have higher
ESI rankings due to the potentially long-lasting and damaging
effects of both the oil contamination and cleanup actions.
Impermeable and exposed surfaces with high wave action are ranked
lower due to the reflecting waves keeping oil from coming onshore,
and the speed at which natural processes will remove the oil.
Habitats of plants and animals that may be at risk from oil spills
are referred to as “elements” and are divided by functional group.
Further classification divides each element into species groups
with similar life histories and behaviors relative to their
vulnerability to oil spills. There are eight element groups: Birds,
Reptiles and Amphibians, Fish, Invertebrates, Habitats and Plants,
Wetlands, and Marine Mammals and Terrestrial Mammals. Element
groups are further divided into sub-groups, for example, the
‘marine mammals’ element group is divided into dolphins
, manatees, pinnipeds
(seals, sea lions & walruses),
. Issues taken into
consideration when ranking biological resources include the
observance of a large number of individuals in a small area,
whether special life stages occur ashore (nesting or molting), and
whether there are species present that are threatened, endangered
Human use resources are divided into four major classifications;
importance or cultural
resource site, high-use recreational areas or shoreline access
points, important protected management areas, or resource origins.
Some examples include airports, diving sites, popular beach sites,
marinas, natural reserves or marine sanctuaries.
Estimating the volume of a spill
By observing the thickness of the film of oil and its appearance on
the surface of the water, it is possible to estimate the quantity
of oil spilled. If the surface area of the spill is also known, the
total volume of the oil can be calculated.
Oil spill model systems are used by industry and government to
assist in planning and emergency decision making. Of critical
importance for the skill of the oil spill model prediction is the
adequate description of the wind and current fields. There is a
worldwide oil spill modelling (WOSM) program.
|First trace of color
|Bright bands of color
|Colors begin to dull
|Colors are much darker
Largest oil spills
Oil spills of over 100,000 tonnes or 30 million US
gallons, ordered by tonnes
|Spill / Tanker
||*Tonnes of crude oil
|Gulf War oil
||January 21, 1991
|Ixtoc I oil
||Gulf of Mexico
||June 3, 1979–March 23, 1980
|Atlantic Empress / Aegean Captain
||Trinidad and Tobago
||July 19, 1979
||March 2, 1992
|Nowruz oil field
|Castillo de Bellver
||Saldanha Bay, South
||August 6, 1983
||March 16, 1978
|Amoco Haven tanker
||Mediterranean Sea near Genoa, Italy
||Gulf of Oman
||December 19, 1972
||Scilly Isles, UK
||March 18, 1967
||A Coruña, Spain
||May 12, 1976
||Gulf of Alaska
||March 24, 1989
One tonne of crude oil is roughly equal to 308 US gallons, or 7.33 barrels.
Shown for comparison
- C. Michael Hogan (2008) Magellanic Penguin, GlobalTwitcher.com,
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Transactions of the Royal Society of London. B 297(1087):
- Untold Seabird Mortality due to Marine Oil Pollution,
Elements Online Environmental Magazine.
- Oil Spills
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Science News vol. 172, p. 67.
- NOAA (2002). Environmental Sensitivity Index Guidelines,
version 3.0. NOAA Technical Memorandum NOS OR&R 11. Seattle:
Hazardous Response and Assessment Division, National Oceanic and
Atmospheric Administration, 129p.
- Gundlach, E.R. and M.O. Hayes (1978). Vulnerability of Coastal
Environments to Oil Spill Impacts. Marine Technology Society. 12
- NOAA (2008). Introduction to Environmental Sensitivity Index
maps. NOAA Technical Manual. Seattle: Hazardous Response and
Assessment Division, National Oceanic and Atmospheric
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International Maritime Organization/ International Petroleum
Industry Environmental Conservation Association Report Series,
Volume 1. 22p.
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Oil Spill Program, Technical Seminar. Ottawa, Ontario: Environment
Retrieved 2008-03-10. (PDF) Oil Spill Case Histories 1967 – 1991,
Report No. HMRAD 92-11. Seattle: National Oceanic and Atmospheric
Administration. September 1992. p. 80.
- The World Almanac and Book of Facts, 2004
- Oil Spill Case Histories 1967-1991, NOAA/Hazardous
Materials and Response Division, Seattle WA, 1992
- Nelson-Smith, Oil Pollution and Marine Ecology, Elek
Scientific, London, 1972; Plenum, New York, 1973