DURHAM, N.C. – A 91 study identifying high levels of radioactivity, salts and metals in shale gas wastewater has been named the best science paper of 2013 by the editors of the journal Environmental Science & Technology (ES&T).

The study, conducted by scientists at Duke’s Nicholas School of the Environment, was selected from among more than 1,700 peer-reviewed papers published in ES&T last year.

The study revealed that the treatment of wastewater from oil and gas operations at a site in western Pennsylvania failed to remove some contaminants, such as chloride and bromide, before the wastewater was discharged into an adjacent creek.  This contamination could pose risks to downstream communities because bromide can react with chlorine—used to disinfect river water before it’s used as drinking water — to yield highly toxic byproducts.

Tests also showed that river sediment at the disposal site contained 200 times the level of radioactivity as sediment samples collected just upstream of the treatment facility. 

“The level of contamination we found in the river sediments exceeds federal thresholds for safe disposal of radioactive waste,” says Avner Vengosh, professor of geochemistry and water quality. “It could bio-accumulate in the tissue of fish in downstream waters and pose potential environmental risks for thousands of years to come.”

“Even if we stop the contamination today, the accumulation of radioactivity in these sediments poses health risks for our lifetimes,” he says.  “This is a long-term legacy of radioactivity.”

Chemical analyses of the wastewater suggested that it was originating mainly from Marcellus shale gas drilling operations, and less from conventional oil and natural gas wells, says Nathanial R. Warner, a 2013 PhD graduate of Duke who is now a postdoctoral researcher at Dartmouth College.

“Marcellus shale gas brine has a unique isotopic and chemical fingerprint that we can identify using techniques developed in our lab,” he explains.

Similar contamination may be happening at other locations where untreated shale gas wastewater is being discharged or spilled into streams and rivers, Vengosh says. Shale gas from the Marcellus Formation is utilized in part of Pennsylvania, West virginia and Ohio.

Robert B. Jackson, professor of environmental science, and Cidney A. Christie, a 2013 Master of Environmental Management graduate of the Nicholas School, co-authored the paper, which was published Oct. 2.  Funding came from the Nicholas School and the Park Foundation.

You can read the study’s full findings at http://pubs.acs.org/doi/full/10.1021/es402165b.