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Duke Researchers: Watch out for CO2 Contamination

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 the researchers found “the potential for contamination is real, but there are ways to avoid or reduce the risk,” said Robert B. Jackson, Nicholas Professor of Global Environmental Change and professor of biology at Duke.

“Geologic criteria that we identified in the study can help identify locations around the country that should be monitored or avoided,” he said. “By no means would all sites be susceptible to problems of water quality.”

The study appears in the online edition of the journal Environmental Science & Technology.

Duke researchers collected core samples from four freshwater aquifers around the nation that overlie potential CCS sites and incubated the samples in their university lab for a year, with CO2 bubbling through them.

After a year’s exposure to the CO2, analysis showed 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 said. 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 carbon leaks.

The 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 said.

The study was funded by the Department of Energy’s National Energy Technology Laboratory and Duke’s Center on Global Change.