The spill from sunken tanker Sanchi has more than trebled in size in the past couple of days, according to local authorities, based on the observations of three coastguard vessels. Three oil slicks were spotted with a total surface area of 332 sq km, compared to 101 sq km reported on January 16th. Three The condensate carried by the Sanchi does not form a traditional surface slick when spilled, but remains highly toxic to marine life, and is much harder to separate from water. However, it does dissipate more quickly than does bunker fuel.
People are now also looking to environmental impact of Sanchi sinking, with fears that the thousands of tons of condensate on board could threaten fisheries and marine life in East China Sea.
However with many details of the wreck still unknown, scientists have mainly said that it was too early to predict the effects with any certainty.
While Sanchi’s cargo load was condensate, a volatile type of oil similar to gasoline that is used to make jet fuel and other products, and which is highly toxic to marine life but also prone to fast dissipation, the Sanchi was also carrying a far smaller load of bunker fuel: less toxic than condensate but much more persistent in the environment.
At the moment no-one knows how much of the condensate burned up in the fire or evaporated in the eight days between the collision and the sinking. Nor do they yet know how much is now leaking from the sunken vessel into surrounding waters. China’s State Oceanic Administration said satellite images showed four discrete oil slicks, with a total area of 101 km2 near the wreck site on January 17th. On January 18th, however, the reported spill area had shrunk to 21 km2 in three slicks.
Condensate, which is buoyant and highly soluble in water, contains a mixture of hydrocarbons, including aromatics like benzene and toluene, along with straight-chain, branched, and cyclic alkanes, Christopher Reddy of Woods Hole Oceanographic Institution said. Condensate’s properties make it difficult to contain and clean up because it cannot be skimmed and many sorbents will not retain such light material.
In the short term, the condensate could dissolve in the water column and create a plume that could damage or kill marine organisms, especially those in their early life stages, said Deborah P. French-McCay, an oil spill expert at environmental and energy consulting firm RPS Group.
Greenpeace East Asia has claimed that the spill area is a spawning ground for bluefin leatherjacket and swordtip squid and a wintering ground for seafood species including hairtail, yellow croaker, chub mackerel, and blue crab. Marine mammals also use it as a migratory pathway. However, the impact of the condensate would most likely be short-lived because it can rise through the water column and evaporate at the surface or be dispersed and diluted by ocean mixing, especially in windy conditions
The bunker fuel is less acutely toxic than condensate, but it is heavier, more The tanker may have been carrying only 1,000 metric tons of bunker fuel and the bunker fuel may not come to the surface; if temperatures are below about 10 °C on the seafloor—although fuel on the seafloor could still affect marine life.
Ekaterina Popova and her colleagues at the U.K. National Oceanography Centre used a sophisticated ocean model to predict the transport of particles representing oil at the surface from where the ship sank by averaging surface current fields in the region over the past 15 Januaries. They predict that oil on the surface would likely be drawn into the strong Kuroshio current and could reach the coastline of Japan within a month. On that timescale, any condensate at the surface would likely evaporate, disperse, or be degraded, Helton says. However, bunker oil would be more likely to persist and be transported to the coast, which “could be really bad” for fisheries and wildlife, French-McCay says. In contrast to the model results, an official for Japan’s Environment Ministry said on January 16th that the spill was not expected to reach Japan’s shores.