Bill Chameides, dean of Duke University's Nicholas School of the Environment and a member of the National Academy of Sciences, blogs regularly at theGreenGrok.com.
Remember that huge spill of coal ash at the Tennessee Valley Authority's Kingston coal-fired power plant on December 22nd? New measurements by Duke University scientists confirm not only the presence of toxic metals like arsenic but also dangerous levels of radioactivity. (See press release.)
How Fossil Fuels Work
Fossil fuels work because they contain hydrocarbons: compounds made of hydrogen and carbon atoms. Burning hydrocarbons produces water (H2O), carbon dioxide (CO2), and heat - heat that can be used to drive a turbine to make electricity or to power an engine.
Natural gas is almost entirely composed of a hydrocarbon (CH4) and is the cleanest burning of the fossil fuels. Coal on the other hand is composed of lots of stuff besides hydrocarbons, including sulfur, nitrogen, and metals, some of them radioactive - it's the dirtiest of the fossil fuels. In addition to CO2, coal combustion produces air pollutants such as sulfur oxides, nitrogen oxides, and particulate matter, and it leaves behind solid waste called coal ash. The ash can be as much as 10 to 15 percent of the original weight of the coal and contains all the stuff in coal that does not go up in the smoke stack: lots of carbon as well as a wide variety of metal oxides (more on this here [pdf]). To this mix is added the compounds removed from the power-plant gaseous effluent to meet air quality standards; these include sulfur-, nitrogen-, and now mercury-containing compounds.
It is estimated that coal-fired power plants in the United States produce about 125 million tons of ash per year (find more information here). I had naively assumed that the ash was put to use in some way, for example as a substrate for building materials. But according to an industry trade group survey [pdf], only somewhere between 15 to 40 percent of the ash produced annually over the past four decades was put to use.
This means that most of the coal ash is simply dumped into a holding pond or landfill and allowed to accumulate. The Environmental Protection Agency estimated that in 1999 some 600 coal ash holding ponds and landfills were in operation at U.S. coal-fired power plants. A more recent New York Times article reported there are some 1,300 coal ash dump sites in the United States -- "most of them unregulated and unmonitored." More than 60 of these sites have had documented water contamination due to leakage from these ponds (see detailed information here).
Duke Researchers Find that River Is Clean but Radioactive Materials Are Disturbing
It is an understatement to say that before December 22 of last year, most of us did not give a lot of thought to all that coal ash accumulating in our backyards. But that has now changed. (It turns out that coal waste is the second largest waste stream in the United States, right after trash.) My colleagues at Duke's Nicholas School of the Environment, Dr. Avner Vengosh and his graduate student Laura Ruhl, decided to go to Kingston Tennessee to take some samples of the ash and analyze its contents.
Not surprisingly, they found high levels of arsenic in a partially dammed tributary of the Emory River. Arsenic and other toxic metals (such as lead and mercury) had been found in earlier water samples collected and analyzed by scientists from Appalachian State University. The encouraging news is that Vengosh and Ruhl found that the river water itself is clean; only trace levels of arsenic were detected in the water flowing beyond the dammed tributary, suggesting that "in less than three weeks since the spill, river flow has diluted the arsenic content." This indicates that the threat to drinking water quality may be minimal.
However, in addition to the high concentrations of toxic metals like arsenic, my Duke colleagues found elevated amounts of two radioactive forms of radium: radium-226 and radium-228. Radioactive radium, found naturally in the Earth's crustal material including coal, is produced from the radioactive decay of uranium. But just because it occurs naturally, does not mean it is benign. EPA classifies radium as cancer-causing to humans (see details here [pdf]).
So, the coal sludge is polluted with arsenic and radioactivity, but the river water looks to be clean. So no big deal, right? Maybe not. As the sludge dries out, the ash picked up by the wind as dust (scientists refer to this as particulate matter) will be carried into the atmosphere. Once there, this dust can be inhaled by people, where it can be deposited on the linings of their lungs giving them unwelcome doses of radioactivity and toxic metals. For this reason, Vengosh believes that "preventing the formation of airborne particulate matter from the ash ... seems essential for reducing possible health impacts."
Something for the folks in Roane County to think very carefully about, but I wonder if the concern raised by Vengosh and Ruhl's measurements go well beyond the Kingston plant to all the coal-fired power plants and their coal ash dumping sites throughout the United States. Is dangerous particulate matter being liberated from them regularly? And if so, what risks might they pose to the people living near these plants?
"Analysis Shows Exposure to Ash from TVA Spill Could Have 'Severe Health Implications" - www.nicholas.duke.edu/news/ns-vengosh.01.28.09.html
Photo Gallery of Kingston Plant Ash Spill - www.tva.gov/emergency/photo_gallery/pages/123002.htm