Carbon sequestration - much touted as a cure-all for unsustainable levels of polluting emissions - could increase contaminants in drinking water ten-fold, a new study has found.
Leaks from carbon dioxide injected deep underground could bubble up into drinking water aquifers, say Duke University scientists, who spent a year analyzing 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 Professor Robert B Jackson.
"Geologic criteria that we identified in the study can help identify locations around the country that should be monitored or avoided. By no means would all sites be susceptible to problems of water quality."
The US Department of Energy is currently planning at least seven regional carbon capture and storage (CCS) projects.
Jackson's team collected core samples from four freshwater aquifers that overlie potential US CCS sites and incubated them in their lab for a year, with CO2 bubbling through them.
Analysis of the samples then showed that there were 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.
Three key factors – solid-phase metal mobility, carbonate buffering capacity and electron exchanges in the overlying freshwater aquifer – were found to influence the risk.
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 increases within two weeks of exposure to CO2," Jackson says.