Fracking, or the process of drilling into the earth to release gas and oil, has made the USA a net exporter of gas. But the controversial technique also produces radioactive waste, with researchers now illuminating how this waste is created.
Oil and natural gas production in the USA have increased dramatically over the past decade due to fracking.
The wastewater that is produced during the widely used method contains toxins like barium and radioactive radium, which releases a cascade of other elements, such as radon, upon decay.
Now, researchers have for the first time shown how this fracking waste becomes radioactive.
“The stuff that comes out when you frack is extremely salty and full of nasties,” commented Mukul Sharma, a professor at Dartmouth College and head of the new research project. “The question is how did the waste become radioactive?”
During fracking, millions of gallons of water combined with sand and a mixture of chemicals are pumped deep underground at high pressure, explained a statement. The pressurized water breaks apart the shale and forces out natural gas and oil.
While the sand prevents the fractures from resealing, a large proportion of the so-called “slick water” that is injected into the ground returns to the surface as highly toxic waste.
In seeking to discover how radium is released at fracking sites, the research team combined sequential and serial extraction experiments to leach radium isotopes from shale drill core samples.
They showed that the increasing salinity in water produced during fracking draws radium from the fractured rock, while also confirming that as wastewater travels through the fracture network and returns to the fracking drill hole, it becomes progressively enriched in salts.
The highly saline composition of the wastewater is responsible for extracting radium from the shale and for bringing it to the surface.
“Radium is sitting on mineral and organic surfaces within the fracking site waiting to be dislodged. When water with the right salinity comes by, it takes it on the radioactivity and transports it,” explained Sharma.
Photo credit: WildEarth Guardians/ CC BY-NC-ND 2.0