New Method Predicts Oil Spill Toxicity

The Deepwater Horizon oil spill in 2010 had dramatic, immediate impacts on the surrounding Gulf of Mexico ecosystems. As five million barrels of oil spilled, slicks spread across the Gulf’s surface, coating local beaches and harming organisms from miniscule microbes to huge sea turtles. Though the Gulf of Mexico appears much healthier today, oil still persists in the ecosystem.

Bigelow Laboratory Senior Research Scientist Christoph Aeppli has developed a new technique to improve the understanding of how the toxicity of oil changes when it is exposed to the environment. When oil from a spill hits the shore, it mixes with sand and sinks, forming what Aeppli calls “sand patties.” When these eventually wash ashore, they release a continuous supply of weathered oil, which affects local beaches.

“Oil spill science has been using the same analytical methods for the last 30 years, which don’t capture changes that occur within days after a spill,” Aeppli said. “We are trying to develop tools and methods to account for the changes that happen during weathering.”

Weathering is a process that occurs when oil is exposed to sunlight and microbes after a spill, causing the oil to degrade and form new compounds. Aeppli discovered that oxygenated hydrocarbons can persist for years in the environment, posing a risk to public health.

Aeppli found that sunlight shining on the surface slick was the primary force oxygenating the oil released in the Deepwater Horizon spill, and that this occurred in the first weeks after the spill. The new compounds formed persisted for the next seven years that he observed, and Aeppli believes they will remain in the Gulf of Mexico for decades.

“People always say that microbial processes are the main pathway changing the oil composition, but this shows that oxidation by sunlight is really important,” he said.

Aeppli developed a computational approach to translate oil’s chemical composition to its potential toxic effects. This technique predicts toxicity based on molecular properties of oxygenated hydrocarbons, and it will allow managers to forecast the risk of an oil spill that hasn’t yet occurred.

“This new technique will allow us to predict the toxicity of oil after it has spent time in the ocean,” Aeppli said.

With this model in hand, Aeppli is trying to facilitate conversations between oil industry representatives and researchers.

“We have an advisory group of oil spill experts from private companies and the government, and we are getting feedback from stakeholders,” he said. “We don’t want to stop after publishing a paper, but instead are taking the extra steps to help implement this tool.”