BP Deepwater Horizon Disaster (Photo: Gerald Herbert / Associated Press)
OIL POLLUTION
Nearly half of the estimated 1 million tons of oil that makes its way into marine environments each year comes not from tanker spills but from land-based sources such as factories, farms, and cities.
On April 20, 2010, an explosion at the BP Deepwater Horizon oil rig released approximately 200 million gallons of crude oil into the Gulf of Mexico. It was the biggest oil spill ever in U.S. waters and remains one of the worst environmental disasters in world history.
Major oil rig explosions make headlines, but in reality, this kind of spectacular disaster accounts for only a small percentage of global marine oil pollution. Of the estimated one million tonnes of oil entering the marine environment annually, oil tanker disasters account for around 10 per cent of global marine oil pollution. However, oil spills are especially serious because of the heavy concentration of oil in one region. Because oil spills are localized, they can severely contaminate beaches and sediment, and cause serious harm to marine wildlife. Oil spills can suffocate fish, get caught in the feathers of birds and mammals and block light from photosynthetic plants in the water.
Around 35 per cent of sea oil pollution comes from regular shipping operations; this includes oil released during incidents involving all other types of vessel, as well as oil from illegal tank cleaning. The largest share, amounting to 45 per cent, comes from land-based sources such as factories, farms, and cities. Oil is used to fuel vehicles and heat buildings, as well as lubricate machinery and bicycles, and make plastic, medicine, ink, fertilizer, paint, varnish and electricity.
Oil surrounds the feet of local resident as he patrols for affected wildlife (David McNew:Getty Images)
It is estimated that a city of five million people will, through pavement runoff, discharge the same amount of oil into waters as a large oil tanker spill would.
There are a number of domestic, municipal and industrial sources of oil pollution. Any oil that is spilled in industrial or domestic operations can be washed down storm drains; this includes spills in fuel depots, oil leaks in vehicles and lawnmowers, and non-accidental pouring of paint or oil down storm drains. Runoff carries a great deal of oil into water sources, especially from asphalt. It is estimated that a city of five million people will, through pavement runoff, discharge the same amount of oil into waters as a large oil tanker spill would.
A pelican covered in oil flies over an oil slick at Refugio State Beach in Goleta, CA on May 20 2015 (Lucy Nicholson / Reuters)
For seabirds, oil can sink their natural buoyancy and literally drag them into a watery grave. And the birds that try to clean themselves ingest a sticky poison that ravages their livers, lungs, and intestines.
Effects of Oil Pollution
There are a number of processes that can occur when oil spills, depending on the water source and the type and amount of spilled oil. Oil pollution can damage ecosystems, including plants and animals, and contaminate water for drinking and other purposes.
- The most common effect is the spreading of the oil over the surface of the water. Most oil is less dense than water, so when oil spills, it spreads across the water surface. However, oil can settle to the bottom of the water, which is dependent of the density of the oil and the type of water.
- The oil can move with currents, tides and wind. This can be a significant problem in rivers with currents carrying the oil a great distance from its origin. In oceans, tides can carry the oil to beaches and intertidal zones.
- Some oil will evaporate. Up to 50 percent of the volume of most oil spills can evaporate. Light fuels, such as gasoline, will almost entirely evaporate within one or two days.
- The feathers and fur of birds and marine animals can become coated in oil; when birds are coated in oil, they have difficulty flying and most will
- Fish can be suffocated by the thick sludge of oil on the water surface, and bottom-dwelling fish can develop liver disease, as well as reproductive and growth problems.
- Plants that grow in or near the water can be harmed by oil pollution. An oil spill can block the sunlight that plants need for photosynthesis, which kills plants growing in the water.