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Program analyzes Georgia rainfall

By Sharon Omahen
University of Georgia

Jerry Walker thinks Georgia does a great job controlling emissions. And he should know. Twenty-five years ago he set up a monitoring site that analyzes chemicals in the state's rainfall that contribute to acidic rain.

Now an emeritus professor with the University of Georgia, Walker set up the first long-term wet-deposition monitoring site in Georgia in 1978. The site was at a UGA College of Agricultural and Environmental Sciences farm in Pike County.

Now one of six in Georgia, the site is part of a 250-site network run by the National Atmospheric Deposition Program. Many sources fund the NADP, including state agricultural experiment stations, universities, industries and federal agencies.

Analyzing the nation's rain

The sites collect rain and snow samples across the nation. Scientists analyze them weekly for their chemical makeup. The lower a substance's pH, the more acidic it is.

"By measuring and analyzing the rain, we can determine its long-term effects on agricultural crops, forest and the environment," Walker said. "The monitoring system allows us to track the chemistry of storms and evaluate potential impacts of new sources of emissions."

John Melin, an engineering program specialist, has collected the rain samples at the UGA site from the beginning. Every Tuesday morning, Melin and site operators across the nation collect, weigh and measure the pH of samples from their sites. Then they mail a subsample to the national office in Champaign, Ill., for further analysis.

"Acid rain was a big concern in the 1970s," Walker said. "But you have to realize that normal rain has a pH level of 5.6, so it's always a little on the acidic side. That's because the carbon dioxide in the air creates carbonic acid, which dissolves into the rain."

Levels vary from state to state

Pure water has a pH of 7.0. In 2000, the most acidic rain in the United States had a pH of 4.3, according to the U.S. Environmental Protection Agency.

In 2001, southwestern Ohio's pH was 4.4. The Pike County, Ga., site's pH was 4.8, Walker said. "It's really hard to compare pH levels, as they vary. It could be 4.3 in Pennsylvania and 5.5 in California."

Acid rain is worse in the Northeast and Midwest than in Georgia, he said.

"That's because of the emission of gases from the power plants ... burning coal for fuel," he said. "This creates a lot of sulfur dioxide, which leads to sulfuric acid in the rain."

Scientists have confirmed that sulfur dioxide and nitrogen oxides are the main causes of acid rain. The EPA reports that two-thirds of all sulfur dioxide and one-fourth of all nitrogen oxides in the United States come from electric power generation.

In Georgia, an estimated 26.7 percent of the sulfur emitted by utility units is returned through precipitation, Walker said.

Plants benefit from the sulfur

"Scientists have long recognized the importance of this element to plant growth," he said. "In some locations, sulfur is added to deficient soils."

Walker said he's pleased with his 25 years of monitoring precipitation in Georgia. "Our state panned out a lot better than I thought it would in the beginning," he said.

"But that's because we've made changes," he said. "We've added controls to our smoke stacks and decreased our auto emissions. Georgia's a lot better off than some other states. So it's not all doomsday like you often hear."

The goal of the national program is to pinpoint problems and record long-range trends.

"The program's data shows that, in general, things are better now than they were when the monitoring program was first started," Walker said.

To view the program's findings, visit the NADP Web site (

(Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

Measuring and analyzing collected rain
Measuring and analyzing collected rain

John Melin collects rain, sleet and snow samples for submission to the National Atmospheric Deposition Program. Melin is shown measuring and analyzing a sample.

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John Melin collects rain, sleet and snow samples for submission to the National Atmospheric Deposition Program. Melin is shown measuring and analyzing a sample. Download Image
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