Coal-ash spills highlight ongoing risk to ecosystems Received March 13, 2009
NASA
Although regular monitoring of matic worst-case scenarios, Two recent large-scale spills of ground- and surface-water sources whereas in many cases what we’re coal-combustion waste have around coal-ash dumping sites is really seeing is a continual problem thrown a spotlight on an old probsorely lacking, EPA, some state that isn’t necessarily brought to the lem: how to handle the enormous agencies, and environmental advoforefront.” Hopkins was a member quantity of solid waste produced cacy organizations have docuby coal, our main source of mented contamination at electricity. Both spills hapvarious sites. Direct epidepened at power plants run miological evidence of disby the Tennessee Valley eases associated with such Authority (TVA). The first, contamination is sparse. which was considered to be But local communities reone of the worst spills of its main concerned about the kind, occurred on Decemelevated levels of arsenic, a ber 22, 2008, in Kingston, known carcinogen; seleTenn., 40 miles south of nium; and other trace eleKnoxville. A holding pond ments in their drinking water. for coal ash collapsed, releasing billions of gallons of Toxic outcomes on coal-ash sludge onto ecosystems nearby farmland and into Coal ash and its potential the waters of the Emory impacts have interested sciand Tennessee rivers. Less entists for decades. Consider than one month later, the the case of Belews Lake in second spill happened at Stokes County, N.C. The lake TVA’s Widows Creek Fossil is an artificial reservoir iniPlant in Stevenson, Ala., tially built in 1970 to provide because of a break in a cooling water for the largest pipe that removes water of Duke Energy Corp.’s coalfrom a holding pond for fired power plants. The plant gypsum (another byprodbecame operative in 1974, uct of coal combustion). and a year later, fish populaFor decades, researchers, tions in the lake began to environmental advocates, decline. Researchers moniThe spill from space: an aerial view of the TVA power plant’s local communities, and toring the lake and its biota holding ponds in Kingston, Tenn., showing the site before even the U.S. EPA have (top) and after (bottom) the spill. The dark blue is water, and found the cause to be water been concerned about the the light blue is water contaminated with coal-ash sludge. entering the lake from a flyongoing risks posed by the ash pond, which contained of a 2006 National Research Coununregulated management of coal exceedingly high levels of selenium cil committee that evaluated the ash. The waste contains elevated (150-200 micrograms per liter). The use of coal ash to fill abandoned levels of toxic metals and other eleelement, which is used by organisms mines. Although the committee did ments like arsenic, selenium, and as a micronutrient at low concentranot look at waste ponds like the manganese that leach into groundtions, becomes toxic in higher doses. ones operated by TVA, the report water under certain conditions or “Selenium was accumulating in emphasized the scientific evidence are accidentally released into the female [fish] tissues,” says Hopkins. for the accumulation of metals in environment. The female fish passed on the selethe tissues of organisms living Instances like the TVA spills nium to their offspring, where the around the impoundments, the bring the subject of coal-combuselement caused developmental absubsequent health impacts on ecotion waste to the attention of the normalities. The end result? By 1978, systems, and potential humanpublic, says William Hopkins, a 16 out of the 20 fish species in health consequences due to Belews Lake had been wiped out. wildlife ecotoxicologist at Virginia ground- and surface-water Beginning in 1986, Duke Energy Polytechnic Institute and State Unicontamination. improved its handling of fly ash versity. “But those are really dra10.1021/es9006977
2009 American Chemical Society
Published on Web 03/25/2009
May 1, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3003
such that contaminated water from the ponds no longer entered Belews Lake, thus causing selenium levels to decline. Still, a 1997 paper by U.S. Forest Service researcher Dennis Lemly showed that the hazard levels from residual selenium in the lake dropped from 1986 to 1997 yet remained “moderate”, illustrating the persistent hazards of such contamination. But the example of Belews Lake “represents just one extreme,” emphasizes Hopkins. In most cases, the impacts are more subtle, he notes. The impoundments themselves pose an ecological hazard, he says. “Any time you build some sort of pond, which is essentially what these [impoundments] are, you’re going to attract some wildlife.” The animals use the ponds for reproductive purposes, feeding, and overwintering. “When they do that, they accumulate trace elements in their tissues, and we’ve documented a variety of behavioral, physiological, and developmental abnormalities due to that accumulation,” he adds. Hopkins’s own research illustrates how salamanders and frogs that breed in these ponds also have high levels of selenium, which is maternally transferred, disrupts embryonic development, and threatens amphibian populations. Although the impacts of selenium on ecosystems have been relatively easy to document, other cases are less well understood. The waste products from burning coal contain between 10 and 20 trace elements, including metals like arsenic, mercury, and lead. The individual levels of these elements vary depending on the type of coal and how it is handled in the power plant. “For the most part, pointing out what caused what is going to be hard, because it’s a complex mixture of trace elements,” Hopkins points out.
increased the amount of waste generated by coal-fired power plants. Nearly 130 million tons of coal ash are produced every year in the U.S. Recycling and beneficial uses of coal ash in buildings, road bases, and agriculture have risen and now account for 43% of total waste generated, according to the American Coal Ash Association, an industry-funded group. Still, about one-third of the total ends up in ponds like the ones in Kingston, where the ash is mixed with water and then allowed to settle to the bottom of the ponds. Later, the water from the top is removed and released into nearby lakes and rivers. Recognizing the need to understand the leaching behavior of elements in coal ash, EPA’s Science Advisory Board recommended that the agency revise its leach tests. The existing tests use simple conditions, such as a fixed pH and liquid-to-solid ratio. But to assess the potential for leaching, one has to understand how the elements behave under different conditions, says Susan Thorneloe of EPA’s National Risk Management Research Laboratory. “Leaching can occur over many decades, and we want to simulate in a lab what might occur so that we can identify those materials where there is a potential concern,” says Thorneloe. She expects the leach tests to be ready for use in the summer of 2010. The results will allow regulators to know how the different elements found in coal-combustion waste behave in different environments at different waste sites. For example, some of the initial results show that there is a range of pH values under which arsenic can leach into groundwater, whereas the previous single-pH tests had suggested a low risk of leaching for this element, notes Thorneloe. But EPA’s efforts are not enough for many. On March 4, a letter signed by more than 109 organiza-
Increasing burden of waste Our growing dependence on coal as a cheap source of electricity has
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tions, including the Natural Resources Defense Council (NRDC), a nonprofit environmental group, urged lawmakers to end the wet dumping of coal ash. This follows on the heels of another report jointly released in early January by several groups, including the Environmental Integrity Project, a nonprofit group that is staffed by former EPA attorneys to ensure better environmental regulations. The new report used EPA data to identify 100 other wet coal-ash impoundments around the country that could be as toxic as the first TVA pond. The report found that 74% of these ponds are unlined, a method that EPA has identified as the most hazardous way to store such waste. In the meantime, researchers, community activists, and environmental advocates alike are pushing for federal regulations on coal ash. “The challenges that [we face] in terms of waste management are only going to increase,” notes Hopkins. “I think we need to be proactive and address some of these concerns rather than pretend that these don’t exist.” Patrice Simms, a senior project attorney at NRDC, agrees. “As coal plants become better and better controlled for their air emissions, more and more of [these] materials will end up in the solid waste materials,” he notes. “If it [coal-combustion waste] deserves to be regulated as an air pollutant, it certainly deserves to be regulated as a solid waste.” Some of that message has already reached lawmakers in Washington, D.C. On January 7, two days before the Widows Creek accident, the Senate Environment and Public Works Committee held a hearing on the Kingston spill, and Rep. Nick Rahall (D-WV) has since introduced legislation that would require federal standards for coalash ponds. —RHITU CHATTERJEE
