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Erosion-control efforts could benefit from microscopic hitchhikers
that are helping scientists track down the source of dust particles that
blow into cities. A new approach for analyzing dust-carried microorganisms
was devised by ARS researchers. It's the first technique able to distinguish
dust blown off dirt roads from dust that started as eroded soil from farms.
In the technique, scientists analyze fatty acid profiles of different microbes
in windblown dust. Fatty acids are chemicals that help form a cell's structure.
Each group of microbes has a unique profile--just as every person has a
unique set of genes. Microbial communities that live in organic cropland
soils, for example, differ from microorganisms that thrive in the compacted
soil that makes up an unpaved road. First, the scientists establish profiles
from microorganisms collected in pollution-monitoring air filters. They
compare these with a library of profiles from soil samples across Washington
state. Similarities between a filter sample and a library sample suggest
the dust's area of origin. Farmers and air quality authorities can use the
results to gauge success of erosion control practices. That's because, over
time, reducing erosion will alter the makeup of the dust's microbial profiles.
(Patent Application 08/548,852)
Land Management and Water Conservation Research Unit, Pullman, WA
Ann Kennedy, (509) 335-1552
Encapsulating herbicides in cornstarch "packaging" delivers
them to the right spot in the soil--reducing the chance they'll be lost
in the air. When herbicides that are not encapsulated are sprayed on
crop fields, they're exposed to wind, rain and warm temperatures that facilitate
herbicide loss into the air as a vapor. These airborne herbicides can land
in waterways at least 150 miles away. Scientists used mobile chambers to
measure vapor losses for the first 35 days after atrazine and alachlor were
applied to plowed and unplowed cornfields. Rain in the first week after
application helped reduce overall herbicide loss in the atmosphere. But,
in the unplowed fields, losses of alachlor wrapped in cornstarch capsules
dropped from nine to four percent--meaning more herbicide stayed in the
soil to fight weeds. Atrazine losses dropped from four to almost two percent
when that chemical was spread in capsules on unplowed fields. Even the non-encapsulated
pesticides had lower losses on unplowed fields, because plant stubble on
the surface helped bury and shelter the herbicides from air and higher temperatures.
On plowed fields, packaging the herbicides in corn starch did not lower
the 14-percent alachlor vapor losses, but cut atrazine losses from four
to almost two percent.
Hydrology Laboratory, Beltsville,
MD
Timothy J. Gish, (301) 504-7490
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Last Modified: 02/11/2002
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