Duke scientists develop coal ash tracers

Duke University researchers said Tuesday they have developed a new tool to tell when water is contaminated by coal ash and not by other sources.

Regulators will be able to "trace the coal ash effluents to their source," Avner Vengosh, a Duke professor of geochemistry and water quality, said in a statement.

The research is timely for North Carolina, where contaminated groundwater has been found at all 14 of Duke Energy's coal-fired power plants and seepage reported from ash pond dams. What hasn't been clear is whether the contamination came from ash or natural sources.

Duke, under the legislature's orders, is drilling hundreds of new wells at its plants to detect the extent, flow and sources of contaminated groundwater.

Chemical variations have previously been used to identify ash contaminants. The forensic tracers Duke University developed are based on the distinctive characteristics of two elements found in ash, boron and strontium.

The isotopes in boron that come from coal ash always differ from naturally-occurring boron, said Laura Ruhl, a former Duke graduate student now teaching at the University of Arkansas at Little Rock. Strontium is less distinct, she said, but using the two elements together provides "definitive evidence" whether contamination is from ash.

Vengosh and Ruhl published their findings this week in the peer-reviewed journal Environmental Science & Technology. Co-authors included Gary Dwyer and Heileen Hsu-Kim of Duke and James Hower of the University of Kentucky.