Sanchi oil tanker sinking is the 'worst situation' for marine ecology say scientists
An oil tanker burning in the East China Sea for more than a week has finally sunk, Chinese media say.
The Sanchi and a cargo ship collided 260km (160 miles) off Shanghai on 6 January, with the tanker then drifting south-east towards Japan.
Iranian officials now say all 32 crew members - 30 Iranians and two Bangladeshis - on the tanker are dead.
The tanker was carrying 136,000 tonnes of condensate, an incredibly toxic form of ultra-light crude.
China Central Television said that the Sanchi had gone down after "suddenly igniting" around noon (04:00 GMT).
The sinking of the oil tanker the Sanchi on Sunday, which had burned for more than a week in the East China Sea, is the worst possible outcome, say experts who are concerned the submerged oil could have a severe impact on marine life.
The Sanchi broke apart after a fierce explosion and sank at around 4:45 pm on Sunday, said the China's Ministry of Transport in a statement on Sunday afternoon.
"The ship sinking is the worst situation," Ma Jun, director of the Institute of Public and Environmental Affairs told the Global Times on Sunday.
"The condensate oil, a kind of ultra-light oil on Sanchi, is different than other types of crude oil and is poisonous to marine life," he warned.
Unlike crude, condensate does not form a traditional surface slick when spilt. Instead, it generates a toxic underwater plume of hydrocarbons invisible from the sea surface.
Whales, porpoises, seabirds, fish, and plankton in contact with these hydrocarbons in the East China Sea will either die quickly or develop "sub-lethal injuries" such as physiological impairment, reproductive failure and chronic diseases.
The region is also a crucial spawning site for many large fish species, whose eggs and larvae have "undoubtedly been exposed" to the toxic compounds, he said.
"Just because there is no traditional surface slick does not mean there is minimal impact. While the toxic phase of the spill may only last a few months, the injury to populations could persist much longer," he said.
He slammed governments for failing to gather environmental data more quickly.
"As no one has been conducting a scientific assessment of (the environmental impact), the governments and ship owners are likely to claim, erroneously, there was limited damage."
The ministry said that the ship began to list and apparently broke apart after an explosion that sent flames as high as 1,000 meters.
It would have been better for the oil to have burned than to sink with the ship, Lin Boqiang, director of the China Center for Energy Economics Research at Xiamen University, told the Global Times on Sunday.
"The condensate oil will probably leak from the broken ship as it sinks and any marine life that encounters it could be killed," said Lin. "Therefore, it is important to assess how much oil leaked into the sea to determine how serious the marine ecology might be impacted."
Ma said the ship sank not far from Zhoushan, East China's Zhejiang Province and constant monitoring will be necessary to track any oil slick that might move close to shore.
Scientists worry the accident will affect the well-known Zhoushan fisheries.
Ma said it is important to evaluate how much of the ship's cargo had burned off during the long-fought fire and Sunday's explosion to determine how much was left on the ship when it went down.
Four Chinese rescuers recovered the bodies of two sailors and the voyage data recorder on Saturday, the Legal Mirror reported on Sunday.
The Sanchi, which was carrying 136,000 tons of light crude oil from Iran, collided with the CF Crystal, a Hong Kong-registered bulk freighter, about 160 nautical miles east of the Yangtze estuary on January 6. The tanker had a crew of 32, including 30 Iranians and two from Bangladesh, the Xinhua News Agency reported.
The Panama-flagged Sanchi was bringing the condensate from Iran to South Korea when the collision with the Hong Kong-registered freighter CF Crystal, carrying grain from the US, happened in the East China Sea. The crewmen of the Crystal were all rescued.
The cause of the collision is still not known.
After the collision the Sanchi drifted at about 2.2km/h (1.4mph), south-eastwards towards the Japanese island of Amami Oshima.
Condensate is very different from the black crude that is often seen in oil spills.
It is highly toxic, low in density and considerably more explosive than regular crude.
Condensate creates products such as jet fuel, petrol, diesel and heating fuel.
"Oil spills from the ship are still burning" at the scene, China's transport ministry said Monday.
An oil spill 18.5-kilometres long and up to 7.4-kilometres wide surrounded the site as of Monday afternoon, according to the official People's Daily newspaper.
Dramatic photos showed a huge column of black smoke rising from bright red flames.
Alaska-based oil spill consultant Richard Steiner called the accident "the single largest environmental release of petroleum condensate in history".
"Given the poor condition of the hull of the ship after a week of explosions and fire, it is my assumption that none of the cargo holds or fuel compartments remain intact, and thus all of the condensate and fuel has been released," Steiner told AFP.
Even if only 20 per cent of the vessel's cargo was released into the sea, it would still be an amount about equivalent to Alaska's disastrous 1989 Exxon Valdez crude oil spill, he said.
"I don't know of any condensate spill into a marine environment larger than 1,000 tonnes, and most that we know of have been less than one tonne," he said.
The Sanchi was carrying 136,000 tonnes of condensate.