A
new Duke University-led study has revealed the presence of radioactive
contaminants in coal ash from all three major U.S. coal-producing
basins.
The study found that levels of
radioactivity in the ash were up to five times higher than in normal
soil, and up to 10 times higher than in the parent coal itself because
of the way combustion concentrates radioactivity.
The finding raises concerns about the
environmental and human health risks posed by coal ash, which is
currently unregulated and is stored in coal-fired power plants’ holding
ponds and landfills nationwide.
“Until now, metals and contaminants such
as selenium and arsenic have been the major known contaminants of
concern in coal ash,” said Avner Vengosh, professor of geochemistry and
water quality at Duke’s Nicholas School of the Environment. “This study
raises the possibility we should also be looking for radioactive
elements, such as radium isotopes and lead-210, and including them in
our monitoring efforts.”
Radium isotopes and lead-210 occur
naturally in coal as chemical by-products of its uranium and thorium
content. Vengosh’s research team revealed that when the coal is burned,
the radium isotopes become concentrated in the coal ash residues, and
the lead-210 becomes chemically volatile and reattaches itself to tiny
particles of fly ash. This causes additional enrichment of radioactivity
in the fly ash.
“Radioactive radium and lead-210 ends up
concentrated in these tiny particles of fly ash, which though
individually small, collectively comprise the largest volume of coal ash
waste going into holding ponds and landfills,” said Nancy Lauer, a
Ph.D. student in Vengosh’s lab who was lead author of the study.
Vengosh, Lauer and their colleagues
published their peer-reviewed paper Sept. 2 in the journal Environmental
Science & Technology.
The study comes as the U.S. Environmental
Protection Agency’s first-ever regulations on coal ash disposal are set
to go into effect in October.
Currently, coal ash disposal sites are
not monitored for radioactivity, Vengosh noted, “so we don’t know how
much of these contaminants are released to the environment, and how they
might affect human health in areas where coal ash ponds and landfills
are leaking. Our study opens the door for future evaluation of this
potential risk.”
Smokestack scrubbers installed at U.S.
power plants keep these contaminants from escaping into the air when the
coal is burned, he stressed. But if the contaminated coal ash is
spilled, or if effluents leak from ponds or landfills, it may pose a
hazard.
“Because of the tiny size of the fly ash
particles, they are much more likely to be suspended in air if they are
disposed in a dry form. People breathing this air may face increased
risks, particularly since tiny particles tend to be more enriched in
radioactivity,” Lauer said.
Vengosh said this study is the first
systematic study to compare radioactivity in coal and coal ash from the
Illinois, Appalachian and Powder River basins. The researchers collected
multiple samples of coal and coal ash from all three coal-producing
basins and then measured the radioactive elements in each sample.
Their
tests showed that coal and coal ash from different basins exhibited
different levels of radioactivity — the Illinois basin had the most,
followed by the Appalachian and then the Powder River, which is in
Wyoming and Montana. The tests also showed that the ratio of radium to
uranium in the parent coal was consistent with the ratio found in its
residual coal ash.
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