06/04/1998

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-

News from:

Office of Ag Communications & Marketing

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
Contact Katie Jackson, 334-844-5886 or smithcl@auburn.edu

06/04/98