American Chemical Society podcast: Small dams create greenhouse gas 'hot spots'

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American Chemical Society
American Chemical Society podcast: Small dams create greenhouse gas 'hot spots' The latest episode in the American Chemical Society's (ACS') award-winning Global Challenges/Chemistry Solutions podcast series questions the "green" reputation of small hydroelectric dams.

Based on a report by Andreas Maeck, Ph.D., in the ACS journal Environmental Science & Technology, the new podcast is available without charge at iTunes and from http://www.acs.org/globalchallenges.

Maeck explains that the large reservoirs of water behind the world's 50,000 large dams are a known source of methane. Like carbon dioxide, methane is one of the greenhouse gases, which trap heat near Earth's surface and contribute to global warming. Methane, however, has a warming effect 25 times more powerful than carbon dioxide. The methane comes from organic matter in the sediments that accumulate behind dams. That knowledge led to questions about hydroelectric power's image as a green and nonpolluting energy source. Maeck's team decided to take a look at methane releases from the water impoundments behind smaller dams that store water less than 50 feet deep.

They describe analysis of methane release from water impounded behind six small dams on a European river. "Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7 percent," said the report. It noted that such emissions are likely to increase due to a boom in dam construction fostered by the quest for new energy sources and water shortages.

### Global Challenges/Chemistry Solutions is a series of podcasts describing some of the 21st century's most daunting problems, and how cutting-edge research in chemistry matters in the quest for solutions. Global Challenges is the centerpiece in an alliance on sustainability between ACS and the Royal Society of Chemistry. Global Challenges is a sweeping panorama of global challenges that includes dilemmas such as providing a hungry and thirsty world with ample supplies of safe food and clean water, developing alternatives to petroleum to fuel society, preserving the environment and ensuring a sustainable future for our children and improving human health.

For more entertaining, informative science videos and podcasts from the ACS Office of Public Affairs, view Prized Science, Spellbound, Science Elements and Global Challenges/Chemistry Solutions.

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 163,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

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