A tar ball from the BP oil spill washed ashore on a beach in Alabama. NOAA
More than nine years after the Deepwater Horizon spill, oil can still be found buried deep in the sand along hundreds of miles of the Gulf Coast. Now, scientists have discovered that these clumps of oil and sand could take at least 30 years to decompose, according to recent research published in the journal Scientific Reports.
The research, led by ecologists at Florida State University, conducted a three-year study of oil buried in the white sands of Pensacola Beach in northwest Florida. Previous studies had found that small droplets of oil decay within a year of washing ashore, broken down by sand-dwelling microbes. But larger, golf ball-sized clumps of oil — the most common size found along Gulf Coast beaches — take roughly three decades to decompose entirely, the new study found. Larger clumps would take even longer, the scientists said.
Layers of oil found buried more than 2 feet deep on a beach in Pensacola, Florida. Credit: Markus Huettel
“After the Deepwater Horizon spill, we found sediment-oil agglomerates at Pensacola Beach that were the size of an office printer, and even larger,” Markus Huettel, a marine ecologist at Florida State University, said in a statement. “After burial, these would persist in the beach much longer than our golf ball-size agglomerates.”
Huettel and his colleagues found that if not located on a beach — with its unique microbes, sediment transfer, and water and air circulation — similar-sized oil clumps would take more than three times longer to break down.
“The beach, breathing in tidal rhythm, can be compared to a large organism that aerobically ‘digests’ the organic matter — including oil — by inhaling oxygen and exhaling carbon dioxide,” Huettel said. “The apparent cleanness of the sand that we all enjoy when going to the beach is a reflection of the effective beach biocatalytic decomposition process that removes degradable material in a relatively short time.”
