Oil spills raise toxic arsenic levels in ocean

Oil spills can raise levels of toxic arsenic in the ocean, creating an additional long-term threat to the marine ecosystem, according to new research.

Arsenic is a poisonous chemical element found in minerals and it is present in oil. High levels of arsenic in seawater can enable the toxin to enter the food chain.

Wimolporn Wainipee, postgraduate and lead author of the study from the Department of Earth Science and Engineering at Imperial College London (ICL), said: “We carried out our study before the leak in the Gulf of Mexico occurred, but it gives us a big insight into a potential new environmental danger in the region.

“Thousands of gallons of oil are leaked into the world’s oceans every year from big spills, offshore drilling and routine maintenance of rigs,” he said.

In the current study, the ICL team discovered that oil spills can partially block the ocean’s natural filtration system and prevent this from cleaning arsenic out of the seawater.

Arsenic occurs naturally in the ocean, but sediments on the sea floor filter it out of seawater, which keeps the levels of naturally occurring arsenic low.

However, arsenic is also flushed into the ocean in wastewater from oil rigs and from accidental oil spills and leakages from underground oil reservoirs.

Researchers discovered that oil spills and leakages clog up sediments on the ocean floor with oil, which prevents the sediments from bonding with arsenic and burying it safely underground with subsequent layers of sediment.

The scientists say this shutdown of the natural filtration system causes arsenic levels in seawater to rise, which means that it can enter the marine ecosystem, where it becomes more concentrated and poisonous.

Mark Sephton, professor in earth science and engineering at ICL, said: “We can’t accurately measure how much arsenic is in the Gulf at the moment because the spill is ongoing.”

“However, the real danger lies in arsenic’s ability to accumulate, which means that each subsequent spill raises the levels of this pollutant in seawater.”

“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,” said Sephton, according to an ICL release.

These findings were published in Water Research.