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American Chemical Society's Weekly PressPac -- May 21, 2008


Melting glaciers may release DDT and contaminate Antarctic environment
Environmental Science & Technology

In an unexpected consequence of climate change, scientists are raising the possibility that glacial melting is releasing large amounts of the banned pesticide DDT, which is contaminating the environment in Antarctica. The study is scheduled for the June 1 issue of ACS bi-weekly journal Environmental Science & Technology.

In the study, Heidi N. Geisz and colleagues estimate that up to 2.0-8.8 pounds of DDT are released into coastal waters annually along the Western Antarctic Ice Sheet from glacial meltwater. The researchers point out that DDT reaches Antarctica by long-range atmospheric transport in snow, and then gets concentrated in the food chain. DDT has been banned in the northern hemisphere and has been regulated worldwide since the 1970s. Geisz found, however, that DDT levels in the Adelie penguin have been unchanged since the 1970s, despite an 80 percent reduction in global use.

Global warming may explain that contradiction, they say. As the annual winter temperature on the Antarctic Peninsula has increased by about 10 degrees Fahrenheit in the last 30 years, glaciers have retreated. The possibility that glacial meltwater has contaminated Antarctic organisms with DDT, the study says, has compelling consequences if global warming should continue and intensify. JS

Melting Glaciers: A Probable Source of DDT to the Antarctic Marine Ecosystem


Heidi N. Geisz
College of William and Mary
Gloucester Point, Va. 23062
Phone: (804) 684-7474
Fax: (804) 684-7786


Light-driven "molecular brakes" provide stopping power for nanomachines
Organic Letters

Researchers in Taiwan report development of a new type of "molecular brake" that could provide on-demand stopping power for futuristic nanomachines. The brake, thousands of times smaller than the width of a human hair, is powered by light and is the first capable of working at room temperature, the researchers say. Their study is scheduled for the June 5 issue of ACS' Organic Letters, a bi-weekly journal.

In the new study, Jye-Shane Yang and colleagues point out that the ability to control specific motions of small molecules or larger molecular structures is essential for the development of nanomachines. Some of these machines may find use in delivering drugs or performing surgery deep inside the human body. Although scientists have already built molecular motors, wheels, and gears for powering nanomachines, the development of a practical braking system remains a challenge, the researchers say.

Yangs group assembled a prototype molecular brake that resembles a tiny four-bladed wheel and contains light-sensitive molecules. The paddle-like structure spins freely when a nanomachine is in motion. In laboratory studies, the scientists showed that exposing the structure to light changes its shape so that "blades" stop spinning, putting on the brakes. The braking power can be turned off by altering the wavelength of light exposure, they add. MTS

"A Pentiptycene-Derived Light-Driven Molecular Brake"


Jye-Shane Yang, Ph.D., Professor
National Taiwan University
Taipei, Taiwan 10617
Phone: 886-2-33661649
Fax: 886-2-23636359


Next-generation explosives: More power and safety without the pollution
Chemistry of Materials

Scientists in Germany are reporting development of a new generation of explosives that is more powerful than TNT and other existing explosives, less apt to detonate accidentally, and produce fewer toxic byproducts. Their study of these more environmentally friendly explosives is scheduled for the June 24 issue of ACS Chemistry of Materials, a bi-weekly journal.

In the new study, Thomas M. Klaptke and Carles Mir Sabate point out that conventional explosives such as TNT, RDX and HMX, widely-used in military weapons, are rich in carbon and tend to produce toxic gases upon ignition. In addition to polluting the environment, these materials are also highly sensitive to physical shock, such as hard impacts and electric sparks, making their handling extremely dangerous. Greener, safer explosives are needed, the researchers say.

To meet this need, Klaptke and Sabate turned to a recently explored class of materials called tetrazoles, which derive most of their explosive energy from nitrogen instead of carbon. They identified two promising tetrazoles: HBT and G2ZT. The researchers developed tiny bombs out of these materials and detonated them in the laboratory. The materials showed less sensitivity to shock than conventional explosives and produced fewer toxic products when burned, the researchers say. MTS

Bistetrazoles: Nitrogen-Rich, High-Performing, Insensitive Energetic Compounds


Thomas M. Klaptke, Ph.D.
University of Munich
Munich, Germany
Phone: 49 89 2180 77491 (or secretary, 49 89 2180 77494)
Fax: 49-89-2180-77492


Rice in your gas tank: Boosting biofuel production from rice straw
Energy & Fuels

Researchers in China are reporting a discovery that could turn rice straw into an inexpensive new renewable source of biofuel. Their new study, scheduled for the July 16 issue of ACS' bimonthly journal Energy & Fuels, describes a way to boost production of biofuel from rice straw by almost 65 percent.

In the new study, Xiujin Li and colleagues point out that China is the world's largest rice producer, a crop that leaves behind about 230 million tons of rice straw each year. Rice straw is the stem and leaves left behind after harvesting the grains. Scientists, however, have not tapped rice straw for production of biogas because bacteria cannot easily break down its cellulose due to the complex physical and chemical structures of lignocellulosic biomass.

The researchers treated rice straw with sodium hydroxide before allowing bacteria to ferment it into a biogas. That so-called pretreatment increased biogas production by making more cellulose and other compositions in straw available for digestion by the bacteria. Three prototype facilities have been built in China using this technology. MTS

"Physiochemical Characterization of Rice Straw Pretreated with Sodium Hydroxide in the Solid State for Enhancing Biogas Production"


Xiujin Li, Ph.D.
Beijing University of Chemical Technology
Beijing, People's Republic of China 100029
Phone: 86 10 64434743


Electronic waste disposal: A growing challenge
Chemical & Engineering News

Millions of tons of unwanted computers, cell phones and other electronic waste (E-waste) are filling the worlds recycling bins each year. But the lack of standardized recycling methods and E-wastes potentially toxic health effects have sparked a growing debate over how to deal with this tsunami of cast-off technology, according to an article [] scheduled for the May 26 issue of Chemical & Engineering News, ACS weekly newsmagazine.

C&EN Senior Editor Jeff Johnson points out that barely 15 percent of the estimated two million tons of E-waste produced each year in the United States is recycled or reused. Leftovers are often shipped to poorer countries like Africa, India, or China, where workers face health dangers as they attempt to remove lesser valued, more toxic parts, the article notes.

But change may be around the corner. Environmental advocates, community groups, Congress, and some in the electronics industry are seeking alternatives to these informal recycling efforts, including the manufacture of greener electronic parts and equipment, tougher regulations on the disposal and shipping of E-waste, and take back programs that encourage manufacturers to collect the E-waste that they produce, according to the article.

A Tsunami of Electronic Waste

This story will be available on May 26 at

Michael Bernstein
ACS News Service
Phone: 202-872-6042
Fax: 202-872-4370

Journalists Resources

Press releases, chat room sessions, and more from ACS 235th National Meeting

Its never too late to explore a treasure trove of news sources, background material and story ideas available from the ACS latest National Meeting, which was held in New Orleans from April 6-10, 2008. Reporters can view press releases, search an archive with abstracts of more than 9,000 scientific presentations and hundreds of non-technical summaries of those presentations, and access other resources at: or

The ACS Office of Communications also offers recorded video versions of its national meeting chat room briefings and accompanying chat transcripts by going to To use this site, you must first register with by going to Its free and only takes a minute or two to sign up. To view the archived chat room sessions, proceed by clicking the Login button at the top right of the Ustream window and then selecting Past Clips. Please note that Ustream requires the latest version of Adobe Flash, which can be downloaded without charge here. [].

ChemMatters Matters for Journalists

This quarterly ACS magazine for high school chemistry students, teachers, and others explains the chemistry that underpins everyday life in a lively, understandable fashion. ChemMatters is available at You can also receive the most recent issues by contacting the editor, Pat Pages, at: 202-872-6164 or

ACS Press Releases

General science press releases on a variety of chemistry-related topics.

General Chemistry Glossary

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Contact: Michael Woods
American Chemical Society

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