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SMOG AFFECTING
RURAL AREAS
AUBURN, Ala.__-- It's that time of year when lawnmowers are buzzing
and vacationers are burning up the highways. That increased use of
gasoline and other fuels, combined with hot weather, can elevate
levels of smog, also known as groundlevel ozone (O3), in
urban areas, causing human health threats. Researchers at Auburn
University have found that rural areas also suffer from groundlevel
ozone pollution.
According to Russ Muntifering, a professor of animal and dairy
science at Auburn, groundlevel ozone is monitored in urban areas by
the Environmental Protection Agency (EPA) to protect human health.
Muntifering has been heading a study to evaluate O3's
influence on rural areas and agronomic production and is finding
that the ill effects of O3 may be affecting plant and
livestock production.
Muntifering is participating in a multidisciplinary study to
evaluate the impact of elevated groundlevel ozone levels on select
warm-season forages. According to Muntifering, O3's
detrimental effects on plants are well documented in pine forests
and on urban trees. His study is examining the secondary effects of
O3 on other plants that are vital to the food chain, and
may ultimately affect our food supply.
Muntifering explained that groundlevel ozone (tropospheric ozone) is
found in the atmosphere close to the Earth's surface and is not to
be confused with stratospheric ozone, which is the ozone layer near
the Earth's outer atmosphere that is being depleted by other types
of pollution. Groundlevel ozone is produced photochemically through
an interaction between sunlight and such pollutants as vehicular
(lawnmowers, cars, etc.) and industrial emissions. Because of this,
O3 levels tend to be highest during the summer months
when many people are traveling in cars on vacation and mowing lawns,
and when the sun is heating up the atmosphere.
These emissions mix with volatile organic compounds produced mostly
in the Southeast by trees. When all these elements are heated by the
sun, they form O3. O3 can aggravate myriad
human health problems, including respiratory and allergy problems.
Though it would be nice if the tropospheric ozone could be sent
upward in the atmosphere to plug holes in the stratospheric layer,
Muntifering noted that this is not possible. "The simplistic
attitude might be, if we are producing it down here, why not send it
up there and plug the hole, but the two columns simply do not
equilibrate with each other," said Muntifering.
While the bulk of O3 is produced in major metropolitan
areas (Atlanta, Ga., and Birmingham, Ala., are major sources in the
Southeast), it is not confined to these areas and plumes of O3
drift into rural areas. The only way to control production of O3
is to control emissions, which the EPA does through National Ambient
Air Quality Standards that are constantly monitored in large
metropolitan areas. If O3 reaches certain levels in these
areas, the EPA begins to regulate emissions. In the Southeast, there
are numerous locations currently considered O3 problem
areas. About 10 percent of the South's forest and cropland are
located in or near these danger zones.
The EPA also is becoming increasingly concerned about the effect of
O3 on the entire ecosystem. "EPA is saying," said
Muntifering, "does it not now make sense to think beyond just human
health and think about ecosystem stress as a basis for a secondary
set of standards for air quality?" Though no such standards have
been established, research such as Muntifering's may help establish
those standards. "What more relevant plant system to study," asked
Muntifering, "than agriculture, the system that undergirds our
sources of food and fiber?"
"We know O3 is injurious to plants," said Muntifering. He
noted that signs of O3 injury can be seen readily on
trees and ornamental plants in large cities. Those signs are
typically leaf injury and accelerated plant senescence.
To learn more about what type of O3 injury may be
occurring to other plants, Muntifering has joined forces with AU
agronomist Mary Miller-Goodman and AU forestry researcher Art
Chappelka to evaluate the effects of elevated O3 on two
warm-season forage crops -- bahiagrass and serica lespedeza.
Bahiagrass and serica lespedeza were used for this study because
both are popular summer forages of Alabama that are eaten by
livestock and wildlife, are used for erosion control on roadsides
and are commonly planted near forested areas or as a ground cover in
orchards.
For the study, the researchers are using specially designed
open-topped chambers, similar to ones used for carbon dioxide (CO2)
studies, in which the plants can be placed and exposed to varying
levels of O3. Bahiagrass and serica lespedeza seeds were
planted in pots and these pots were placed in the chambers. Various
treatments of O3 were applied to these plants, and
researchers have been analyzing the development (rate of growth,
quality of root system, amount of plant matter produced, etc.) of
the plants.
Muntifering, who is a ruminant nutritionist, is exploring the
digestibility and palatability of these grasses.
"A universal response of plants to stress is production of plant
stress compounds known as polyphenolics, which include such
substances as tannins and lignins," said Muntifering. Forages that
have high tannin levels can be bitter tasting; thus they are less
attractive to livestock and wildlife. Increased tannins and lignins
may affect an animal's ability to digest the proteins in the plant.
If continued funding is obtained for the research, the scientists
also hope to explore the effect of O3 on tall fescue, a
cool-season forage common to the Southeast that also can be infested
with a fungal endophyte, which causes health problems in livestock.
-30-
Katie Smith
6/4/98
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