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Sid Perkins
A study of methane in drinking water near shale gas operations
will provide ammunition for protesters.Richard B. Levine/NewscomA
controversial method of extracting natural gas from shale rock
formations significantly increases methane concentrations in
drinking
water taken from wells nearby, suggests the latest study by US
environmental scientists. The findings come just as a moratorium on
the practice in one US stateis due to expire, and are likely to
stoke the public debate.
Injecting large quantities of water and other fluids to fracture
deep rock formations to liberate the methane within a practice
called hydraulic fracturing, orfracking has become economically
viable only in the past decade or so. In that short time, it has
gained popularity with natural-gas producers: in one county
inPennsylvania alone, approvals for fracking permits increased
27-fold between 2007 and 2009.
According to the US Energy Information Administration, in 2009,
63 billion cubic
metres of gas were produced from deep shale formations. That had
doubled by 2010, and by 2035 fracking is projected to account for
some 47% of US gas production.
Contamination concernHowever, many homeowners in areas where
fracking is common say the practice hastainted their drinking
water, either with methane or with the waste water that is produced
by the process. Research published in the Proceedings of the
NationalAcademy of Sciences1 today will give them further
ammunition.
Robert Jackson, a biogeochemist at Duke University in Durham,
North Carolina, and his colleagues measured the methane
concentrations in 60 drinking-water wellsin northeastern
Pennsylvania and nearby areas of New York state. Dissolved
metha
ne concentrations in water from the 34 wells located more than 1
kilometre fromfracking operations averaged about 1.1 milligrams of
dissolved methane per litre. But in water taken from 26 wells
within 1 km of one or more fracking operations, methane
concentrations averaged 19.2 mg l1. Isotopic analyses of the carbon
inthat methane shows that the gas has the same signature as that
being recoveredfrom deep underground by fracking operations.
Although methane concentrations in drinking water aren't
regulated, says Jackson, the gas readily comes out of solution and
is an asphyxiation and explosion hazard. The US Department of the
Interior recommends mitigating methane levels in water if
concentrations reach 1028 mg l1.
"We don't know the precise mechanism of how the gas is getting
into the wells,"says Jackson. The team suspects that the gas is
leaking from the pipes that bring methane to the surface, or is
escaping the deep layers of fractured rock either through fissures
generated during the fracking process or through abandoned water or
gas wells.
Fracking under scrutinyThis study is the first to look at the
extent of water contamination from fracking in a comprehensive,
objective way, says Robert Howarth, a biogeochemist at Cornell
University in Ithaca, New York. "Data clearly show that water wells
within1 kilometre of active gas wells have a high probability of
being contaminated with methane," he notes. This contamination, he
contends, shows the need to reassess the use of the technology.
ADVERTISEMENTLate last year, David Paterson, then-governor of
New York state, instituted a te
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mporary moratorium on fracking operations that drill wells
horizontally and inject more than 300,000 litres of fluid. Once the
ban expires on 30 June, the state's environmental conservation
department will release the results of a study onthe risks of
fracking to air and water quality.
With the public debate set to ramp up in New York state and
elsewhere in the coming months, the report by Jackson and his team
"couldn't come at a more timely m
oment", says William Schlesinger, a biogeochemist at the Cary
Institute of Ecosystem Studies in Millbrook, New York. "It's a nice
piece of work, and it's too visible to overlook."
References1.Osborn, S. G., Vengosh, A., Warner, N. R. &
Jackson, R. B. Proceedings of theNational Academy of Sciences USA
advance online publication (2011).
http://waterfilterhealth.info
