Following Coastal Oil Spills, the Clean-up Crew is Microscopic

Xiaolong Geng, a postdoctoral researcher at NJIT's Center for Natural Resources Development and Protection, models beach restoration.

In the wake of an offshore oil spill, there is little difficulty in spotting – and discarding – the sticky black tar balls that wash up on the beach. The conundrum for clean-up crews is how to remove the smaller, more diffuse particles that embed between tiny grains of sand, disrupting the coastal ecosystem in less obvious ways.

Excavating the entire beach and depositing it in a landfill is not an option, say two NJIT engineers who have spent the last four years developing less intrusive ways to restore polluted coastlines. They have recently created a model, published in the May issue of the journal Water Resources Research,  that predicts how quickly naturally occurring bacteria biodegrade, or break down, oil on tidal beaches.

“It’s not always feasible or advisable to physically remove all of the oil that has washed up on the beach, and so it’s vital to understand the conditions that facilitate biodegradation by microorganisms,” said Xiaolong Geng, the paper’s principal author and a postdoctoral researcher at NJIT’s Center for Natural Resources Development and Protection (NRDP).

“We have already simulated bacteria eating oil in various sediment types and now we’re applying that model to the complicated dynamics of the coast, where tides, the mixing of seawater and groundwater within the sand, temperature and salinity are some of the variable factors,” Geng added, noting that bacteria consume hydrocarbons in the oil as a source of energy and carbon for functioning and growth.

One of the NRDP’s next steps will be to determine if it’s possible to speed up beach remediation by fueling the growth of oil-eating bacteria populations along polluted stretches of coastline with injections of nutrients such as nitrogen and oxygen into the sediment.

Michel Boufadel, director of NJIT's Center for Natural Resources Development and Protection, recently traveled to Santa Barbara, the site of a recent offshore spill, to advise on the ongoing clean-up.

“We’ve seen in the lab that adding oxygen and nutrients makes bacteria eat faster,” Geng said.

 Research on offshore spill cleanups has historically focused on the oil’s interaction with the ocean and sea-dwelling species, while relatively less attention has been paid to understanding the engineering required to restore tidal beaches.

“Coastal zones are highly productive both from economic and ecologic points of view. Half of the Earth’s population lives within 200 miles of a coast and that proportion is expected to increase over time,” said Michel Boufadel, the NRDP’s director and the paper’s co-author, along with researchers from the environmental engineering firm Langan Engineering.

Since its establishment in 2012, the NRDP has received several major grants from the federal government, as well as international institutions and agencies, to investigate oil behaviors in the environment. Boufadel provided technical analyses and remedial strategies in response to the two largest oil spills in U.S. history, the Deepwater Horizon and Exxon Valdez spills.

He traveled to the site of another recent spill – an estimated 100,000 gallons of crude oil from an underground pipeline off the coast of Santa Barbara, Calif. – to advise on the ongoing clean-up.

Tracey Regan