LOS ANGELES — A key ingredient of the chemical dispersants released last summer at BP’s spewing wellhead persisted in the Gulf of Mexico’s deep waters for two months and was carried by currents nearly 200 miles, according to a study released Wednesday.
The research, by scientists from California universities and the Woods Hole Oceanographic Institution in Massachusetts, sheds light on the fate of the 771,000 gallons of dispersants, which had never before been released at such depths, but does not address their effect on deep sea life or whether they worked as intended.
BP applied 2 million gallons of dispersant to break down the oil in its four-month spill and keep it from reaching sensitive shore environments. More than half that amount was sprayed on the gulf surface, but 771,000 gallons were pumped into clouds of oil and gas that billowed nearly a mile below.
Dispersants have a history of use on shallow spills, but deep sea application was untested, leading to controversy over the federal decision to allow it.
Analyzing water collected on three research cruises last summer, the scientists measured a surfactant contained in the formulation of the Corexit dispersant applied at the sea floor. The compound did not readily degrade and remained in fine clouds of oil and gas at depths of 3,000 to 3,600 feet.
The ingredient, dioctyl sodium sulfosuccinate, was detected 190 miles from the wellhead and two months after BP stopped applying dispersants.
Researchers said the quantities were far below levels shown to be toxic in lab tests.
“We would be hard-pressed to state that, given the present state of knowledge, what we found is toxic,” said Elizabeth Kujawinski, an associate scientist at Woods Hole.
