New York – A new Columbia University study has found heightened concentrations of some common substances in drinking water near sites where hydraulic fracturing has taken place.
The substances are not at dangerous levels and their sources are unclear, but the researchers say the findings suggest underground disturbances that could be harbingers of eventual water-quality problems, according to a news release from the Earth Institute at the Columbia University.
The study may be the first of its kind to spot such broad trends, the release said. The researchers, from Columbia University’s Lamont-Doherty Earth Observatory and other institutions, found that both distance and topography play a role. In lowland drinking wells within one kilometre (about six-tenths of a mile) of a drill site, they found higher levels of dissolved calcium, chlorine, sulfates and iron. In lowland wells more than a kilometre away, they found higher levels of methane, sodium and manganese compared with equally distant wells on higher ground. Upland wells within a kilometre of a drill site showed no specific trends.
Lead author Beizhan Yan, a Lamont-Doherty geochemist, said, “The finding suggests increased mixing of different ground water sources.” This could be due to several possibilities, he said. For one, the sudden, powerful pulses introduced by fracking might act like a pump, expanding and contracting subterranean spaces, and squeezing the contents around. This stress could propagate up to the surface and initiate mixing of groundwater, either from the sides or below, he said. The observations might also be due to leaky well casings at shallow depths, or spills of fracking fluids on the surface trickling down, he said.
Study coauthor Steven Chillrud, also a geochemist at Lamont-Doherty, said, “We don’t really know what the mechanism is, but this shows there’s an impact related to distance. It’s an intriguing signal that really needs to be followed up on.”
The team took about 60 water samples from private wells, but decided these were too few to spot any trends, so they also looked at some 1,850 samples taken by other researchers in industry and academia, which they reanalyzed.
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