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Professor's research on aerial spraying
helps farmers hit target
December 14, 1998

It's a familiar sight in agricultural areas. A small propeller plane spraying pesticide over a farmer's field. From the ground it looks like only the foliage has been touched. But that's only what the naked eye perceives, explains David R. Miller, a leading researcher in the behavior of aerosols in the atmosphere.

Spotlight on Research

What's not apparent is the drift of the pesticide away from its target caused by air turbulence. "The air is a chemical soup; what stays in it can't be detected by the eye," says the professor of natural resources management and engineering.

In fact, in studies done on the incidence of pesticide drift away from crops and forests, researchers can account for only about 75 percent of what is sprayed.

"Most people think about drift going into the next field, but some goes far beyond that," says Miller, who joined UConn in 1971 and shares his appointment with the University's cooperative extension system.

Between one and five percent of most pesticide sprayed in the world ends up in the air as atmospheric pollutants, he says..

Miller uses a simple looking laser-radar device, a LIDAR (Light Detection and Ranging System), to monitor pesticide drift as it is occurs. The LIDAR is not available commercially. Miller built it - one of the few in the world used to track pesticides - with cooperation from government agencies..

The portable system, which includes an occular instrument that resembles a large telescope, is usually placed on a platform overlooking an orchard or field.

Miller's research on the atmospheric drift of aerial pesticide spray has resulted in a safer environment and recommendations for changes in pest-control operations.

The United States Department of Agriculture's forest service has recommended guidelines for aerial spraying, which Miller and two forest service colleagues developed.

"We tried to come up with reasonable guidelines for atmospheric conditions so they (the sprayers) can hit what they're aiming for," says Miller, a 1998 UConn Alumni Association.

research award winner.

Air speed, direction, turbulence, temperature and humidity affect the path and evaporation rate of droplets released from an airplane. The characteristics of air just above the tree tops and inside tree canopies usually change very rapidly in the morning and more slowly in the afternoon.

Neither scientists like Miller nor the government can control air turbulence. The way pesticides are released into the atmosphere through aerial spraying can be improved, however.

The sprayers can control the droplet size, the setting of the nozzle, the duration sprayed and the time the spraying occurs. "There's an enormous difference between night and day spraying," explains Miller. He notes atmospheric conditions during night-time spraying encourages small droplets of pesticide to drift.

Most federal and state agencies are first taking a voluntary approach to persuade sprayers to control pesticide drift. But if voluntary guidelines don't work, officials may make them mandatory. "The problem," says Miller, "with regulating sprayers is that the atmosphere is constantly changing."

His research on the behavior of aerial spraying has attracted the attention of the U.S. Army and the Environmental Protection Agency. "They all have reasons for wanting to know how the atmosphere works," says Miller.

Miller's findings could be applicable to the army's defense against chemical weapons, he says.

His research interests further include forest meterology, where his findings have led to practical procedures for forest protection and managment. He has also been involved with the experimental monitoring and numerical modeling of watersheds.

Working in collaboration with other faculty, he monitored how much nitrogen - a nutrient affecting water quality - entered Long Island Sound from the atmosphere and other sources. Data from the five-year study that ended in 1994 shows nearly eight percent of the nitrogen in the Sound fell directly from the sky.

This information has been useful to the state Department of Environmental Protection. Now it can better evaluate how much nitrogen sewage treatment plants dispersed into the Sound.

Miller, who began his career in forestry, is also working with the DEP to monitor mercury concentrations around Connecticut. Mercury occurs naturally in the environment, e.g., from volcanic emissions or from soil.

Man-caused mercury emissions can occur as the result of trash burning or the incineration of medical hazardous waste. Unlike lead, mercury is absorbed by the soil, and then is re-emitted into the air.

Mercury as a gas in the atmosphere, where it enjoys extraordinary longevity, is not harmful to humans. But when the element enters the food chain, it becomes methyl-mercury, a mineral- chemical compound that is harmful to humans. In fish products, the dangerous compound resides in the meat of the animal, not the fat one throws away.

Miller is using some mathematical models to study how mercury travels and transforms itself in the air. "We don't have a clue what goes on once it goes into the soil," he says.

The real solutions to these problems are years down the road, explains Miller, who also wears the hat of state climatologist. "All of this is after the fact. We're working toward real-time solutions."

Miller's research is funded by a variety of public sources - none of it by industry. "Little long-term or basic research gets done by companies," he says. "If people in universities don't do it, then it doesn't get done."

Molly Colie