Impact of oil spills could be indefinite

Oil spilled from a ship 30 years ago off the Massachusetts coast still remains in the sediments, according to research, raising fears that impacts could be indefinite.

On 16 September 1969, a barge, The Florida, spilled between 650,000 and 700,000 litres of No. 2 fuel oil – the same as diesel fuel – in Buzzards Bay near West Falmouth. Using the novel technique of two dimensional gas chromatography, scientists at the Woods Hole Oceanographic Institution (WHOI) have found that there has been very little decomposition of oil buried in the sediments of the Buzzards Bay salt marsh.

“Even after all these years, concentrations of some compounds are similar to those observed immediately after the spill and reflect the persistent nature of No. 2 fuel oil in coastal salt marsh sediments,” said Christopher Reddy, lead author of the study.

A 36cm core revealed no evidence of petroleum residues in the top six centimetres, nor in the lower eight centimetres. However, the central 22cm contained petroleum hydrocarbons in similar concentrations to those observed shortly after the spill.

Located near to WHOI, the site has become one of the best studied spills, despite being only a fraction of more well known events such as the 40 million litre Exxon Valdez spill. There are no other spills that have been studied for longer than 10 years, Reddy told edie.

One theory as to the preservation of the oil is that bacteria normally associated with its decompostion have been unable to feed. They may be missing sulphate, said Reddy, noting that future research will include adding nutrients – such as sulphate – to assist the bacteria. The scientists will also try to establish how much of the original spilled fuel still remains in the bay, and its toxicological effects on local species. Animals burrowing into the sediments can be exposed to high levels of compounds in the oil, points out Reddy.

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