Oil Spills Raise Ocean’s Arsenic Level, Create ‘Toxic Time Bomb’

Oil floats on the surface of the Gulf of Mexico
A sheen of oil floats on the surface of the Gulf of Mexico near Gulf Shores, Alabama. Photographer: Kari Goodnough/Bloomberg

Oil spills like the one in the Gulf of Mexico interfere with the ocean’s natural filtration system, allowing arsenic levels to build up and threaten the long-term health of marine plants and animals, researchers found.

Minerals on the ocean floor attract arsenic found in seawater, latching onto the poison and burying it under layers of sand, silt and sediment, according to a new study released today by scientists from Imperial College London. The study was published today in the journal Water Research.

Arsenic is also found in oil. Leaks from underground reservoirs, spills and wastewater from rigs all increase levels of the chemical in the ocean and threaten the marine ecosystem as well as the food chain, the researchers said.

“The real danger lies in arsenic’s ability to accumulate, which means that each subsequent spill raises the levels of this pollutant in seawater,” said Mark Sephton, a professor at Imperial’s department of earth science and engineering. “Our study is a timely reminder that oil spills could create a toxic ticking time bomb, which could threaten the fabric of the marine ecosystem in the future.”

Oil creates a barrier between positively charged sediment in seawater and negatively charged arsenic, and weakens the magnetic attraction between them, researchers found. The result is a one-two punch with more arsenic in the water and a clogged filtration system that traditionally keeps the poison in check, they said.

There is no way to know how much arsenic is currently being pumped into the Gulf of Mexico from the oil spill at BP Plc’s Macondo well, Sephton said. It started leaking after an April 20 explosion on the Deepwater Horizon killed 11 crew members and sank the rig.

Additional arsenic from the oil and the damaged filtration system will concentrate in the marine ecosystem, creating ever more dangerous levels of the poison the further it moves up the food chain, the researchers said.

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