Acid Rain, Trout, and the Clean Air Act (Clean Virginia, Part 6)

Jul 2, 2015

University of Virginia Professor Jim Galloway outside his office.
Credit Kara Lofton

In 1979, researchers at the University of Virginia launched the Shenandoah Watershed Study. Among other things, the study tracked the impact of the Clean Air Act on watersheds -- and wildlife such as trout -- across much of western and central Virginia. WMRA’s Kara Lofton reports.

In the 1950s and 1960s, cheap energy came mostly from coal-fired power plants. The plants effectively produced lots of energy at low financial cost to citizens, but it had other costs to the public in the form of the unregulated release of heavy metals and acidic pollutants into the atmosphere.

So in 1963, in response to growing national concern about air pollution, Congress passed the Clean Air Act, which authorized research into techniques for monitoring and controlling air pollution. It was the first attempt at air quality regulation. But it wasn’t enough. Soon even the rain became toxic to the very ecosystems it was supposed to sustain. Several amendments to that original act have been passed since.

Jim Galloway is a professor of environmental studies at the University of Virginia.

JIM GALLOWAY: Rain is acidic due to human action because of sulfuric acid and nitric acid. Both of these are primarily from coal-fired power plants – to some degree natural gas fired power plants.

The problem with acid rain is that ecosystems, in particular watersheds, have a very delicate balance of parts, which includes maintaining a balanced chemical pH. When acidic rain falls into watersheds, it very quickly disrupts every system in the watershed from trout to algae to nutrients.

So in 1979, Galloway and a few other young faculty from the University of Virginia pioneered the Shenandoah Watershed Study in order to track how watersheds respond to both natural and human-originated environmental changes. As luck would have it, that was just two years after a major amendment to the Clean Air Act that established National Emission Standards for Hazardous Air Pollutants, including those that contribute to acid rain.

GALLOWAY: We were extremely fortunate, although we didn’t know it at the time, that when we started in 1979, that over the course of the study, the emissions of sulfur dioxide to the atmosphere and nitrogen oxides, which contribute to sulfuric acid and nitric acid, greatly decreased due to the Clean Air Act and its amendments. And so over the course of time we’ve seen a steady decrease in the acidity of precipitation.

The decrease is due, in part, to new technology that regulates the amount and kind of pollution that is allowed to enter the atmosphere. The most advanced of the technology can remove up to 98% of sulfur dioxide and other acidic gas emissions that cause acid rain.

This is particularly important in Virginia because the type of soil here actually absorbs sulfur and releases it in the same slow way that a poorly sealed sink will eventually drain itself.

GALLOWAY: It takes a very long time for chemical recovery to occur because the soils store the acid sulfate in the soil structure and it is only released slowly over time.

And chemical recovery must occur before biological recovery can start, he said.

Back in the late 1970s when they first started the study, Galloway’s team began to track remote streams in Shenandoah National Park with traditionally lively populations of brook trout. Galloway said brook trout are important because they are very sensitive to changes in their natural environment.

GALLOWAY: People like trout as living species, people like trout to eat…there is a public engagement with the science we are doing by this focus on trout and so what we found is that as streams acidify, the biological populations become less diverse: fewer fish, fewer plants, fewer microorganisms. In some cases the acidity of the stream has increased so much that there are no fish in the streams.

But that may soon change.

GALLOWAY: In the last ten to 15 years, as the acidity of precipitation has decreased due to the decreased emissions of sulfur dioxide and nitrogen oxides, we have seen a lessening of acidity in the streams themselves.

He said while the trout populations are still lower than they should be, models suggest that as the streams continue to become less acidic over the next couple decades, the fish should come back. As they do, the ecosystem should stabilize, the soil will let go of the sulfur and it’s possible that the term “acid rain,” will just become part of history.

In the end, the efficacy of the law can be seen in places such as Galloway’s Virginia mountain streams, where equilibrium has returned and the brook trout, that sensitive “canary in the coalmine” type creature, can recover and even thrive.