Leaks from carbon dioxide injected deep underground to help fight climate change could bubble up into drinking water aquifers near the surface, driving up levels of contaminants in the water tenfold or more in some places, according to a study by Duke University scientists.
Based on a
year-long analysis of core samples from four drinking-water aquifers, "We
found the potential for contamination is real, but there are ways to avoid or
reduce the risk," says Robert Jackson, Nicholas Professor of Global
Environmental Change and professor of biology at Duke.
criteria that we identified in the study can help identify locations around the
country that should be monitored or avoided," he says. "By no means
would all sites be susceptible to problems of water quality."
appears in the online edition of the journal Environmental Science &
carbon dioxide deep below Earth's surface, a process known as geosequestration,
is part of a suite of new carbon capture and storage (CCS) technologies being
developed by governments and industries worldwide to reduce the amount of
greenhouse gas emissions entering Earth's atmosphere. The still-evolving
technologies are designed to capture and compress CO2, emissions at their
source – typically power plants and other industrial facilities – and transport
the CO2 to locations where it can be injected far below the Earth's surface for
long-term storage. The U.S. Department of Energy, working with industry and
academia, has begun the planning for at least seven regional CCS projects.
fear of drinking water contamination from CO2 leaks is one of several sticking
points about CCS, and has contributed to local opposition to it," says
Jackson, who directs Duke's Center on Global Change. "We examined the idea
that if CO2 leaked out slowly from deep formations, where might it negatively
impact freshwater aquifers near the surface, and why."
his postdoctoral fellow Mark Little collected core samples from four freshwater
aquifers around the nation that overlie potential CCS sites, and incubated the
samples in their lab at Duke for a year, with CO2 bubbling through them.
year's exposure to the CO2, analysis of the samples showed that "there are
a number of potential sites where CO2 leaks drive contaminants up tenfold or
more, in some cases to levels above the maximum contaminant loads set by the
EPA for potable water," Jackson
says. Three key factors – solid-phase metal mobility, carbonate buffering
capacity and electron exchanges in the overlying freshwater aquifer – were
found to influence the risk of drinking water contamination from underground
study also identified four markers that scientists can use to test for early
warnings of potential carbon dioxide leaks. "Along with changes in
carbonate concentration and acidity of the water, concentrations of manganese,
iron and calcium could all be used as geochemical markers of a leak, as their
concentration increase within two weeks of exposure to CO2," Jackson says.
Leaking Underground CO2 Storage Could Contaminate Drinking Water
November 29, 2010