ENVIRONMENT

The biggest oil tanker spill in more than 25 years has released huge amounts of an unusual type of petroleum to the Western Pacific. (Nature)

Learn more about oil spills and their impact on the environment with our collection of activities, maps, and other resources.

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Discussion Ideas

• On January 6, the oil tanker Sanchi collided with a cargo ship in the waters off Shanghai, China. All 32 crew members of the Sanchi perished, and tanker spilled about 111,300 metric tons of a type of petroleum, or oil, into the surrounding ocean. What is petroleum? Skim through our great reference resource for some help.
  • Petroleum is a liquid or mostly liquid fossil fuel. Like all fossil fuels, petroleum is formed as the remains of ancient marine plants and animals are buried and subjected to intense heat and pressure over millions of years. Today, petroleum is found in vast underground reservoirs where ancient seas were located. Petroleum reservoirs can be found beneath land or the ocean floor. Their crude oil is extracted with giant drilling machines.
  • The list of countries with the most oil reserves is dominated by OPEC, the Organization of Petroleum Exporting Countries. OPEC member nations sit on more than 80% of the world’s proven oil reserves.
    • But, as Investopedia reminds us, “having the oil does not always translate into selling the oil. The countries that have the highest oil reserves (which means they have found proven sources of oil in the ground) are not always the ones that have the highest oil production (which means they are able to “harvest” the oil from the ground and sell it).” The top oil-producing countries are Russia, Saudi Arabia, and the United States.
    • The petroleum product carried by the Sanchi came from the largest natural gas field in the world, the South Pars or North Dome field in the Persian Gulf. Ownership of the field is shared by OPEC members Iran and Qatar. The Sanchi was an Iranian vessel.

• The Sanchi spilled a petroleum product known as natural gas condensate. “The infamous spills of the past—such as the Deepwater Horizon disaster in the Gulf of Mexico in 2010, or the Exxon Valdez tanker rupture in Alaska’s Prince William Sound in 1989—involved heavier crude oil.” How does crude oil differ from natural gas condensate?
  • Crude oil is a thick, sticky substance made of differing chemical compounds. Light oils can contain up to 97% hydrocarbons, while heavier oils and bitumens might contain only 50% hydrocarbons and larger quantities of other elements (such as nitrogen or sulfur).
  • Natural gas condensate is a type of ultra-light crude oil. It is less dense and tar-like than heavy crude, has a lighter (nearly transparent) color, and usually has a higher percentage of hydrocarbons.

• How does natural gas condensate behave differently from crude oil in an ocean spill?
  • Scientists don’t know for sure, although “[u]nlike heavy crude, condensate doesn’t accumulate in shimmering slicks on the water’s surface, which makes it difficult to monitor and contain. Neither does it sink to the ocean floor, as do some of the heavier constituents in crude over time. Rather, it burns off, evaporates or dissolves into the surface water, where some of its chemical components can linger for weeks or months.”

• What are some concerns that scientists have about the Sanchi spill?
  • No one knows how much of the condensate dissolved into the water. “’The part I’m most worried about is the dissolved fraction,’ says one expert. Toxic chemicals in the condensate could harm plankton, fish larvae and invertebrate larvae at fairly low concentrations at the sea surface. Fish could suffer reproductive impairments so long as chemicals persist in the water, and birds and marine mammals might experience acute chemical exposure.”
  • Scientists aren’t sure where the pollution could travel, or how to contain it. “Groups in both China and the United Kingdom have run ocean-circulation models to predict the oil’s journey, and the models agree that much of the pollution is likely to end up in a powerful current known as the Kuroshio, which flows past southeastern Japan and out to the North Pacific.”
    • Some models indicate the Sanchi’s natural gas condensate may interact not only with ecosystems of the western Pacific, but Japan’s rich sardine and anchovy fisheries, and whale migration routes as well. Other models indicate the toxins will dissipate by the time they reach the Kuroshio.
  • The Sanchi also carried a smaller amount of a heavier type of oil, hydrofluoroolefin or HFO. HFO, also known as “bunker oil”, characteristically sinks to the bottom of the ocean, where its toxins can impact benthic ecosystems.

TEACHERS TOOLKIT

Nature: Unique oil spill in East China Sea frustrates scientists

Nat Geo: Oil Spills

Nat Geo: What is petroleum?