Oban-based sci­en­tists as­sist cri­sis re­sponse

The Oban Times - - News -

CON­FIR­MA­TION that diesel has be­gun leak­ing from the stranded Transocean Win­ner plat­form, which ran aground on the Isle of Lewis last Mon­day, has sparked con­cern over the likely des­ti­na­tion and en­vi­ron­men­tal im­pact of the oil spill, writes Dr Keri Wal­lace, of the Scot­tish As­so­ci­a­tion for Marine Science (SAMS).

Sci­en­tists from SAMS are pro­vid­ing on­go­ing ex­pert in­put into the re­sponse process for the cri­sis.

At the time of writ­ing, the ex­act quan­tity of diesel oil leaked off Lewis was still un­known but the make-up of the sub­stance be­ing re­leased, al­ready tells us quite a lot.

Marine diesel is usu­ally bro­ken up into tiny droplets by wind and wave ac­tion, and moved away from the spill-site by ocean cur­rents within a day or less. For this rea­son there is sel­dom any oil to phys­i­cally re­cover from the wa­ter’s sur­face. The tiny oil droplets dis­persed through­out the body of wa­ter don’t just dis­ap­pear. They tend to stick to small par­ti­cles float­ing in the sea­wa­ter, be­fore even­tu­ally sink­ing and set­tling- out on the seabed.

Im­ages of thick black oil slicks are not usu­ally as­so­ci­ated with spills of marine diesel such as this. In­stead diesel oil is not sticky or vis­cous, and at the coast is washed off the shore- line quickly by waves and ti­dal cur­rents. Where the fuel does pen­e­trate into coastal soils or sands it is nat­u­rally de­graded by mi­crobes in one to two months.

Diesel is com­monly re­garded as one of the most toxic types of fuel oil, ca­pa­ble of killing most marine life that comes into di­rect con­tact with it. In open wa­ter how­ever, diesel spills are usu­ally dis­persed so quickly that few fish and birds are af­fected. This is par­tic­u­larly the case in ex­posed coastal lo­ca­tions such as those found around the West­ern Isles.

It is the lo­ca­tion and unique cir­cum­stances of each diesel leak that de­ter­mine which spe­cific en­vi­ron­men­tal im­pacts are most likely. For ex­am­ple, con­se­quences can be se­ri­ous where diesel is trapped and con­cen­trated in coastal ar­eas or where pre­vail­ing con­di­tions trans­port the fuel into nest­ing bird colonies, fish farms or ar­eas of con­ser­va­tion im­por­tance. For this rea­son it is im­por­tant for emer­gency oil spill re­spon­ders to un­der­stand ex­actly how dis­persed diesel spills will be moved by cur­rents and ti­dal flows around the site.

Oceanog­ra­phers at SAMS have ex­per­tise in oil spill tra­jec­tory mod­el­ling and are cur­rently pro­vid­ing ocean fore­casts to Marine Scot­land Science, the cen­tral co- or­di­na­tors of the cri­sis re­sponse.

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