Super Trees

Wed Oct 14 00:59:36 EST 1998

Noreastah (noreastah at wrote:
: >Hybrid poplar trees suck up heavy metals and solvents
: >Eds: Hold for release at 5 p.m. EDT.
: >AP Science Writer
: >Cleaning up polluted industrial sites may not require billion-dollar
: >government programs. Instead, scientists suggest, plant a poplar tree.
: >Laboratory-designed hybrids of the fast-growing poplar tree have been
: found
: >to act like 100-foot straws that suck contamination from soil and
: >groundwater.
: >In a process known as phytoremediation, the tree either safely stores
: the
: >chemicals in its tissues or metabolizes them into apparently less
: volatile
: >compounds. Then the tree releases these byproducts through its leaves
: as
: >vapor into the atmosphere.
: >This natural cleanup takes several years to complete. But tests show
: the
: >method is inexpensive and might work at least as well as high-tech soil

: >roasting and groundwater filtering, while keeping the site green and
: >attractive.
: >Researchers say phytoremediation eventually may transform the way
: industry
: >and government agencies treat long-term pollution problems, which are
: >estimated to top $200 billion nationwide.
: >Still unknown, however, is whether the chemical byproducts generated by
: the
: >poplars really are less harmful, or if diluting them in the atmosphere
: only
: >creates another hazard.
: >''We may soon be using trees to heal the hurt inflicted on the Earth,''

: >said David E. Salt, an environmental chemist at Northern Arizona
: University
: >in Flagstaff. ''But would we simply be exchanging soil pollution for
: air
: >pollution?''
: >In one study, published in the October issue of the journal Nature
: >Biotechnology, researchers at the University of Georgia took a gene
: from a
: >strain of bacteria that enables it tolerate high levels of ionic
: mercury, a
: >highly toxic version of the heavy metal.
: >They modified the merA gene and inserted it into the genetic code of
: the
: >yellow poplar. Laboratory tests showed the genetically engineered
: poplar
: >had a tenfold increase in mercury resistance and also its ability to
: >transport it through its roots and tissues, reduce it to a less
: volatile
: >form and release it into the air. The genetic hybrid has not yet been
: >planted in field tests.
: >The yellow poplar, also known as the tulip poplar, is one of the
: largest
: >and most commercially valuable hardwood trees. It grows primarily east
: of
: >the Mississippi River.
: >Environmental scientists favor it for phytoremediation for the same
: reasons
: >that make the tree popular with commercial foresters, plywood
: manufacturers
: >and neighborhood landscapers.
: >It grows up to 15 feet per year and absorbs 25 gallons of water a day.
: Its
: >broad green leaves measure 6 inches square, providing plenty of leaf
: >surface to release processed contaminants. It has an extensive root
: system.
: >And it's resistant to everything from gypsy moths to toxic wastes.
: >In a study published in the October issue of the Journal of
: Environmental
: >Engineering, scientists at the University of Missouri-Rolla and the
: >University of Iowa report that more conventional poplar trees
: effectively
: >reduce high soil levels of atrazine, a farm fertilizer.
: >Other remediation technologies strip the soil of vital nutrients and
: >microorganisms, so nothing can grow on the site even if it has been
: >decontaminated, they said.
: >''Phytoremediation simultaneously restores soil health and revegeates
: >during the cleansing process,'' said co-author Joel G. Burken of the
: >University of Missouri-Rolla.
: >One of the nation's largest phytoremediation experiments is being
: conducted
: >in Oregon. In 1984, a tanker truck skidded on icy Interstate 5 near
: Central
: >Point, spilling hundreds of gallons of the solvent TCE.
: >Conventional cleanup efforts spanning 13 years failed to remove the
: >solvent, a suspected carcinogen, from the surrounding soil and
: groundwater.
: >In 1997, University of Washington scientists planted 800 hybrid
: poplars.
: >The results will not be available for several years. But in laboratory
: >simulations, the Washington team said, poplars reduced TCE
: concentrations
: >by 97 percent.
: >
: >
: >
: >

: --
: ---

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