RESEARCHERS in Pennsylvania are finding they can fight the effects of acid rain once it enters small streams. But the systems will not solve the acid rain problem, and they are expensive, says Dean Arnold, head of the Acidic Stream and Lake Treatment Research Program at Pennsylvania State University.
Still, for a state that has the worst acid-rain problem in the United States, these systems can help a few streams until the nation's new clean-air legislation kicks into gear.
It is raining when program technician Jim Boyer pulls up to Wolf Run, a small mountain stream in northern Centre County. To the side of the stream, Penn State researchers have installed a Swedish Boxholm doser - one of five technologies they are trying out.
The doser is a silo-like contraption that dispenses dissolved limestone powder into the stream, neutralizing its acid.
Of the five technologies that the Penn State project is monitoring, the Swedish doser has worked the best, says Joe Gallagher, the program's senior research technician.``We have had no problems except keeping up with the lime.''
Upstream of the doser, Wolf Run has an average pH between 5.0 and 5.5. After treatment, the water has a pH of 6.5 or better, which means it is 10 times less acidic, even a few miles later at the end of the stream. While the stream's brook trout can survive in acidic water of 5.0 pH, they thrive at 6.5 pH. Mr. Gallagher says his counts show that fish populations have responded to the treatment, which began a year ago. A local sportsman's club maintains the facility.
It might cost $30,000 to $40,000 to install such a system, Gallagher estimates, which would use from $2,000 to $3,000 a year in lime. The real problem is that it costs at least that much money to truck the lime to the site. So with maintenance, a group could expect to spend some $5,000 to $10,000 a year on preserving a small stream from acidification, he says. It is far too expensive to try to treat rivers, he adds.
Some streams are more vulnerable to acidification than others, depending on the bedrock and soils in the area. Because many Pennsylvania watersheds are not limestone based, their natural buffering capacity against acidity is low. And since the state's average rainfall has a pH of 4.1 - the lowest of any state in the nation - the acidification problem in Pennsylvania is particularly worrisome, says Jim Lynch, professor of forest hydrology at Penn State.
While not all of the state's lakes and streams suffer from acid rain, acidification in specific areas is proceeding rapidly. For example: of 167 lakes surveyed in the Pocono Mountains of northeast Pennsylvania, nearly one third could become acidic in the next 10 years, says Patricia Bradt, principal research scientist for the Environmental Studies Center at Lehigh University.
Scientists and environmentalists don't agree how rapidly the nation's new clean-air bill will change things. Dr. Lynch, for one, expects a marked change fairly soon. But Deborah Sheiman of the Natural Resources Defense Council is less optimistic about the new legislation.``It's not enough for the most sensitive areas,'' she says.
That outlook suggests that temporary means - for those groups that can afford it - may be the only solution for some time. Penn State has had varying success with its four other experimental systems, including:
A diversion well that takes acidified stream water, mixes it with 3/4-inch limestone gravel in an 8-foot underground tank, then releases the treated water back into the stream. The drawbacks: Someone has to add new limestone every few days and check the pipe intake for clogs.
Dispensing boxes that are set directly in the stream and filled with time-released limestone and clay briquettes. But at 18 cents a briquette, the system is expensive.
A turbine-powered doser like the Swedish doser, but needing to be filled more often, and has problems discharging its very fine lime powder. It was also impeded by a beaver that clogged the water intake with branches.
A water-powered doser, which has the most potential for treating a range of streams, has suffered continual mechanical breakdowns.