By Carol Lea Spence
Photography by Matt Barton
Deep in the back hills of UK’s Robinson Forest flows Cole's Fork, a headwater system for a 6,000-acre watershed. Getting there is its own adventure, jostled in a tin can of a Jeep over deeply rutted trails that skirt drop-offs of several hundred feet—a place that might be more easily reached on muleback.
UK forestry professor Chris Barton steers and talks at the same time, a real talent given the terrain. “The streams at Robinson Forest are considered some of the highest quality water in the state. Cole’s Fork is considered an exceptional water resource for Kentucky.”
Wading into the middle of Cole’s Fork to take measurements, we also wade into the middle of this story, one that goes up—into the atmosphere—and down—into the earth. And it’s a story that goes back a long way with an ending yet to be written.
It was the 1980s, and acid rain was on everyone’s lips, literally and figuratively. Though scientists had been aware of the problem since 1872 and had studied it seriously since the 1950s, the situation had become severe enough by the 1980s to warrant serious measures. In 1989, President George H.W. Bush put forward additions to the Clean Air Act that would address a burgeoning crisis.
Acid rain is the catchall phrase for any precipitation that reacts with sulfur dioxide and nitrogen oxides in the atmosphere and becomes acidified. It can result in acidified streams and soils, aluminum changing from a solid to a liquid (never a good thing), and vegetation death. While natural forces can, in part, cause acid rain, industry has contributed the most to the equation. According to the U.S. Environmental Protection Agency, burning coal to generate electricity caused 69 percent of sulfur dioxide and 20 percent of nitric oxides in the air.
Who, Us? Worry?
Alarm bells rang when acidification began killing forests in the Northeast and in northern Europe. These are heavily industrialized areas with slightly acidic granite-based soils without buffering potential, so the acid inputs acidified the soil even further. Water traveling through the soil entered the watershed and acidified streams.
Kentucky, too, was plagued by acid rain—approximately 92 percent of the state’s electricity is generated by coal-fired power plants—but the soils are known to have a higher buffering capacity.
“Here in Kentucky, we have soils that have a higher pH. When you have acids that come in contact with those soils, there’s enough alkaline material to neutralize the effects of that acidity,” Barton said.
Though extensive research had been conducted in the ’70s and ’80s in New England, little research had taken place in Kentucky during that time. The U.S. Forest Service in the mid-1990s, hoping to get a current picture of the situation and to pick up on any trends, funded Tasios Karathanasis, UK Plant and Soil Sciences professor, to conduct a pilot project at two sites in the Daniel Boone National Forest.
“The main concern we had here in Kentucky was that we have a lot of coal-powered plants, and we knew they had increased emissions,” Karathanasis said. “At the time they were trying to follow the new regulations and reduce emissions, but we did not have any data on how that was working.”
Barton was a graduate student then, working under Karathanasis for his master’s and doctoral degrees. Though the project didn’t have anything to do with his thesis or dissertation, it provided an excuse to get out into the woods, which he loved; he took it on.
They dug pits in Wolfe and McCreary counties on ridge top sites with sandy soils that are normally more acidic than surrounding areas. Cutting shelves into the sides of the pits at 1-foot and 2-foot depths, they placed pan lysimeters on each shelf—a system that would collect the rainwater percolating through the soil. About once a month from 1994 through 1999, Barton traveled to the sites and drew water from the lysimeters for analysis.
Periodically poor quality rainwater would break through the soil, resulting in significant spikes in nitrate and sulfate levels.
“We hypothesized that if this continued over time, it could affect the soil chemistry,” Barton said. “Perhaps with continued inputs, we might start to see some of these effects they were recording in more northern environments.”
The good news was that National Atmospheric Deposition Program analyses of rainwater quality from the early ’90s to the present showed a reduction in sulfates of about 55 percent and nearly 40 percent in nitrates in that part of Eastern Kentucky. The regulations were working.
“The interesting thing about that is the amount of coal burned in Kentucky for electric power generation almost doubled during that time,” Barton said. “Basically, the energy industry in Kentucky was in compliance with the Clean Air Act. They achieved the reduction in the air pollutants. You had this environmental quality act that was implemented, and it actually worked from the air perspective.”
An Exceptional Water Source
Members of the Forestry Department have taken a weekly water sample from Cole’s Fork since the early 1970s, measuring temperature, conductivity, dissolved solids, dissolved oxygen, pH, and oxidation reduction potential—a measure of the water's ability to neutralize contaminants.
Similar to what is being found in atmospheric levels, there has been about a 50 percent reduction in the amount of sulfates in the Cole’s Fork stream system. The geology in this watershed is predominantly sandstone, shale, and coal. Like the landscape where Barton’s soil pits are located, it’s not a geology that readily buffers acids.
“We’ve noticed that the pH really hasn’t changed that much over the years. If acid rain were affecting this forest, we would start to see those pH levels go down,” Barton said.
They have also not seen indications that aluminum in the soils has become mobile, which happens at pH levels below 5. When aluminum changes from a solid to a solution, trees take it up. This proves fatal. In the streams, many fish species are susceptible to the metal, too. In Cole’s Fork, pH levels have remained around 6 and no aluminum has been detected in the water.
“So this system, for the most part, at the watershed level, appears to be in relatively good shape with regards to acidifying trends from acid deposition,” Barton said.
"The Daniel Boone National Forest is known for its richness and diversity of species. That's a
direct reflection of the soil." —Claudia Cotton
Claudia Cotton, forest soil scientist for the Daniel Boone, manages more than 700,000 acres of national forest. A UK forestry alumna and Barton’s former student, she was aware of his 1990s soil study. When funds became available in 2011 from a settlement between Duke Energy and the EPA, she and Barton jumped on the opportunity to revisit the original sites to see if what Karathanasis and he had predicted had actually happened.
The Wolfe County site is lush and greenly still in high summer. Wild blueberries bushes are scattered on the hillside and tall, straight-backed trees form a high canopy over the research area. The only indication that scientific work has happened here are capped plastic pipes inconspicuously sticking out of the ground. The area is leaf littered and branch-strewn like the rest of the woods—on purpose to avoid attention.
Given that rainwater and stream samples had improved, it’s not too much to think that soil chemistry also would improve or at least stay the same. Instead, soil samples taken from the sites in 1993 and then again in late 2011 showed that the soil pH has dropped from a slightly acidic pH in the mid 4s to 5s, to a very acidic 3.8 to 3.6. There is also a precipitous decline in the amount of calcium from the early ’90s to today. Calcium helps buffer acid inputs.
Claudia Cotton and Tyler Sanderson demonstrate how they collect water from pan lysimeters buried
at a ridgetop in the Daniel Boone National Forest.
“The results were actually a little bit alarming at first. You would have thought with an improvement or a decrease in the acid inputs, you wouldn’t see that. We’re still trying to figure out what happened,” Barton said. “Maybe it was the fact that the acid inputs long ago are still having an effect on those forest soils. Or maybe all it takes is one big peak to drive that system in the wrong direction. Most of the soil scientists who have looked at our data are actually kind of shocked.”
On the other hand, there were mixed results when the team analyzed the soil solution, the water percolating through the soil into the lysimeter trays. One site followed the pattern they’d seen in the rainwater, a 60 percent reduction in sulfates. The other site didn’t change at all. There were also mixed results with the soil solution pH.
“It makes this type of study very difficult to comprehend, because you don’t know exactly what’s going on and you can’t go out and sample every rain event the way we have it set up,” Barton said.
At the Core
A Virginia pine resists a bit, letting out a hollow tock, tock, tock as Tyler Sanderson twists a corer into its trunk. It won’t hurt the tree, but it helped Sanderson, who at the time was working on his master’s degree in forestry, record the effects acidification might be having on the vegetation at the Wolfe County site. The tree relinquishes the core with a drawn-out sound like a forest floorboard creaking, and reveals an 8-inch long, quarter-inch diameter of finely ringed wood.
As Cotton explained, “The vigor and the resiliency of the forest directly reflect the health and composition of the soil.”
Tyler Sanderson cores a Virginia pine as part of his study on the effects of acid rain on vegetation.
No one has really quantified the effect of acid rain on forest productivity or tree growth, which is what Sanderson set out to do.
He cored about 20 trees from the Wolfe and McCreary sites and studied their growth rings to see if they slowed down or increased dramatically at times, potentially due to the change in the soil chemistry.
Barton believes the vegetation part of the study will be a “great addition” to the work, and “definitely the most difficult to interpret.” Trees don’t naturally grow uniformly, so any changes could be because of weather, or the age of the tree, or changes in the atmosphere or soil.
Knowing there was a decline in sulfur dioxide in the atmosphere, the scientists thought they might be able to detect that in the wood with increased growth. They didn’t, but they also didn’t see a major decline in growth over the years, so as far as they can tell, the trees have not been affected by the acid deposition.
“We don’t see anything alarming that would suggest that these trees are going to crash in the near future,” Barton said.
Determined to Unearth
More work has to be done before a clearer picture emerges from the data.
“If we were looking at precipitation quality, we might think everything is completely rosy, but when we look at it from an ecosystem level, there are a lot of things going on that are promising and others that aren’t,” Barton said.
Back in the lab, Sanderson determined tree growth with the help of a computer that measures the
width of each ring. Sanderson was able to use the College of Engineering's Environmental Research
and Training Laboratories to analyze the concentration of elements in the samples.
Figuring out why the soil chemistry continues to decline will be important to understanding how to reverse those effects or prevent additional impacts to the system. The next step for Barton and Cotton is to find more sites in Eastern Kentucky with documented information on ridge top soils, resample those sites, and determine if what they’re seeing is localized or a regional phenomenon.
Despite the unanswered questions, Barton is encouraged by much of the data he’s collected.
“(These federal regulations) have been extraordinarily effective in meeting the goals of the Clean Air Act,” he said. “Had they not enacted those regulations, perhaps this cycle would be a little bit further along, and maybe we would be seeing some decline or some loss in productivity.”
Karanthanasis summed it up.
“We are making progress.”