In the study, funded by the Nicholas School and Duke's Center on Global Change, the researchers analyzed samples collected from nearly 70 private wells in five counties in northeastern Pennsylvania and New York -- the vicinity of the controversial Marcellus Shale region.
The scientists found methane in 85% of the samples but samples taken from wells located close to active hydraulic fracturing sites exhibited much higher levels -- an average of 17 times higher.
The scientists were able to differentiate between thermogenic methane and biogenic methane. The former comes from very deep underground and is captured in gas wells during fracking, while the latter is produced at shallower depths and is not associated with hydraulic fracturing. The researchers determined that the methane found in the water samples collected from sites within a kilometer of fracking activity was of the thermogenic variety and exhibited a chemical signature matching that of the gas chemistry profiles of shale gas wells in the area.
"At least some of the homeowners who claim that their wells were contaminated by shale-gas extraction appear to be right," says Robert B. Jackson, Nicholas Professor of Global Environmental Change and director of Duke's Center on Global Change.
On a more positive note, the study found no evidence of contamination from fracking fluids.