[報導] CSI 1108 相關科學報導
上兩週AXN的本店 11x08, (就是跟"永不妥協"很像的環保議題那集)
正好剛看到 Fracking 技術的後續相關報導;
不過現實中的地點是在賓州和紐約州,
內文中也提及真的有居民"點燃了自家的水".
可惜的是,雖然 2010年時就有相關的報告和警訊,
不過目前美國政府的處理速度和規範的範圍仍遠不及被污染的區域.
以下為原文轉錄,提供給有興趣的版友參考.
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Hydraulic Fracturing for Natural Gas Pollutes Water Wells
By David Biello | May 9, 2011
Drilling for natural gas is booming in Pennsylvania—thanks to
fracturing shale rock with a water and chemical cocktail paired with
the ability to drill in any direction. Despite homeowner complaints,
however, research on how such hydraulic fracturing, or fracking,
is impacting local water wells has not kept pace. Now a new study
that sampled water from 60 such wells has found evidence for natural
gas–contamination in those within a kilometer of a new natural gas well.
"Methane concentrations in drinking water were much higher if the
homeowner was near an active gas well," explains environmental scientist
Robert Jackson of Duke University, who led the study published online
May 9 in Proceedings of the National Academy of Sciences. "We wanted to
try and separate fact from emotion."
The researchers discovered methane in 51 of the 60 wells tested—that
is not out of the ordinary. A small amount of methane from both deep and
biological sources is present in most of the aquifers in this region of
Pennsylvania and New York State. By measuring the ratio of radioactive
carbon present in the methane contamination, however, the researchers
determined that in drinking water wells near active natural gas wells,
the methane was old and therefore fossil natural gas from the Marcellus
Shale, rather than more freshly produced methane. This marks the first
time that drinking water contamination has been definitively linked to
fracking.
In fact, concentrations were 17 times higher in those drinking water
wells within one kilometer of an active natural gas well than those
farther away. Also, average methane concentrations of 19 milligrams
of methane per liter in those wells were well above the
10-milligram-per-liter recommendation set by the U.S. Department of
the Interior for action to reduce concentrations.
Above 28-milligram-per-liter concentrations, such wells must be properly
ventilated to reduce the risk of explosion.
One well tested had methane concentrations of 64 milligrams per liter.
"I saw a homeowner light his water on fire," Jackson notes. "The
biggest risk is flammability and explosion."
Few studies have been done to date on the health risks of chronic
exposure to methane and other gaseous hydrocarbons. (The researchers
also found ethane, propane and butane in some of the drinking water wells.)
At the same time, the researchers found no evidence that either
the chemicals in fracking fluids or the natural contamination in deep
waters were polluting relatively shallow water wells in the vicinity
of the deep natural gas wells. That suggests that leaking wells are
likely the source of such methane contamination, rather than any
migration upward from the deep. "It's easier to envision a gas well
casing that's leaking, especially with the high pressures, than it is to
envision the mass movement of gas or liquids 5,000 feet upwards," Jackson
notes. "I don't know that it's impossible but I think it's unlikely."
Because of such concerns the U.S. Department of Energy has convened
a special task force to improve the safety and environmental impacts of
such fracking for natural gas, including how best to dispose of the
voluminous wastewater as well as ensuring proper sealing of wells to
prevent such groundwater contamination.
"America's vast natural gas resources can generate many new jobs
and provide significant environmental benefits," noted Secretary of
Energy Steven Chu in a prepared statement announcing the panel, "but
we need to ensure that we harness these resources safely." In fact,
the panel is charged with providing "recommendations as to actions
that can be taken to improve the safety and environmental performance
of shale gas extraction processes and other steps to ensure protection
of public health and safety," according to Chu's memo laying out its
mission, which must deliver "immediate steps to be taken to improve
the safety and environmental performance of fracking" within 90 days
of its first meeting.
Fracking is specifically exempted from much federal regulation, such
as the Safe Drinking Water Act of 1974. Local regulatory requirements
may not help: for instance, although the researchers discovered methane
contamination at homes within 1,000 meters of active natural gas wells,
the Pennsylvania Department of Environmental Protection only holds drilling
companies responsible for drinking water within 305 meters. "That's a
ninefold increase in area," Jackson notes. "Who pays for [testing]?
Should gas companies be required to do it?"
And it remains to be seen whether natural gas delivers environmental
benefits—such as reduced emissions of carbon dioxide when burned—giv
that it in itself is a potent greenhouse gas if it escapes during
drilling or pipeline operations, so-called fugitive emissions. "We are
interested in getting pre- and post-drilling samples," Jackson says
of his future research, although he has been threatened with subpoena.
"We'd like to get data for fugitive methane emissions as well. This
summer we're going to try and detect methane in the air."
文章來源:
http://www.scientificamerican.com/article.cfm?id=
fracking-for-natural-gas-pollutes-water-wells&WT.mc_id=SA_WR_20110511
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