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Frontiers
Pow! Bam! Zap! Pollution Fighters Crowd the Horizon
January 1998
They stand ready to zap, vaporize, or otherwise
transmogrify "bad" chemicals into "good" ones. A bunch of hardy cartoon
heroes? No, they're the next generation of NSF-funded pollution fighters.
Take plasma generators. At the University of Illinois in Urbana Champaign,
engineer Mark Kushner and others are developing tools to make diesel fuel's
noxious chemicals harmless. The device will pass the post combustion fumes
through a plasma, an ionized gas with free electrons.
Unlike conventional combustion, which relies on heat of atoms and molecules
to break molecular bonds and initiate a chemical reaction, plasma chemistry
is a kind of cold combustion. Applying an electrical field excites the
charged electrons without directly affecting the plasma's neutral atoms.
Because the electric field moves the lightweight electrons ("think of
ping pong balls," says Kushner), and not the heavier atoms ("think bowling
balls"), the gas doesn't get very hot while the energetic electrons break
bonds more selectively than their atomic cousins. As a result, scientists
have more control of the reaction.
The idea, still being optimized on the computer drawing board, is to
design a plasma generator, about as big as a muffler, in which electrons
collide with the nitrous oxides (a contributor to acid rain) in the exhaust
and convert them to harmless nitrogen and oxygen molecules. One of the
remaining problems, says Kushner, is power efficiency. Computer models
are helping to address this and other issues.
Another group of pollutants targeted for change is toxic metals. Soils
filled with toxic metals have to be carted away and stored as hazardous
waste. But at the University of Georgia in Athens, geneticist Richard
Meagher and his team have genetically engineered a variety of plants that
soak up mercury through their roots and convert the metal to the less
toxic elemental mercury, used in tooth fillings. The trick is performed
by a bacterial gene that produces an enzyme --MerA-- hungry for toxic
mercury. So far Meagher's group has placed the bacterial gene into mustard
plants, tobacco, canola and even yellow poplar trees. "And they all thrive
on mercury", he says.
The researchers aren't sure yet whether the converted mercury transpires
up to the leaves, where it vaporizes, or simply diffuses through the roots, "but
in any case, we don't find mercury in the plant itself." With the help
of their vast root system, transgenic plants could theoretically clean
up hundreds of acres of mercury contaminated land at a percent of what
it would cost using conventional methods.
Meagher hopes that this approach--called phytoremediation--will prove
helpful in water as well as in soil. He's found another verison of the
bacterial enzyme --MerB-- that munches methyl mercury, the kind that shows
up in fish from polluted waters and can cause severe neurological damage.
Meagher's team has also begun experimenting with MerA to see if they can "each" it
through test tube evolution to soak up other toxic metals as well, including
copper, cadmium, and nickel.
Other NSF-sponsored pollution fighters crowd the horizon, from compressed
carbon dioxide as a safer alternative to harmful organic solvents to a
new Engineering Research Center whose goal is to find a cleaner way to
manufacture microchips.
Who knows? Today's fantasy may be tomorrow's superhero.
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