From the sweeping Alpine Garden of Mount Washington to the narrow heights of Franconia Ridge, the White Mountains of New Hampshire are home to some of the East Coast's most beautiful alpine ecosystems. These complex communities of plants and animals — living in exposed environs above treeline — are hardy enough to withstand punishing extremes of weather, yet they are fragile enough to be easily disturbed by human impacts. AMC researchers are investigating one such impact — acid rain — in an effort to help protect the alpine zone.
Research at lower altitudes has demonstrated that acid pollution damages ecosystems in a variety of ways. It can directly alter plant physiology (for example, by reducing plants' tolerance to the cold) and can also negatively affect the chemistry of soils that support plant growth. In addition, increased acidity of streams and lakes can harm or even kill fish and other aquatic life.
While the deleterious effects of acid rain at lower elevations are clear, the effects of acid pollution on alpine ecosystems are not well known. AMC researchers have been monitoring acid deposition in the alpine areas of the White Mountains for the past two decades to learn more about the impacts of acid rain there.
What Exactly Is Acid Rain?
Acid rain encompasses more than what we normally think of as rain; it also includes acidic clouds and snow, as well as other ways that acid is deposited from the atmosphere to the earth. Acid rain results from the burning of fossil fuels such as coal and oil. Smoke stacks and tail pipes emit sulfur dioxide and nitrous oxides into the atmosphere, where they mix with atmospheric moisture to form sulfuric and nitric acids. This pollution can be transported hundreds of miles on air currents and return to the Earth's surface as acid rain.
At Lakes of the Clouds Hut, AMC studies began in 1984. At an elevation of about 5,000 feet, clouds are a near-constant presence at this site. The AMC's research here bears out the importance of cloud vapor — which envelops the environment and condenses to water when it comes in contact with plant surfaces — as a source of acid pollution.
Acidity is measured using the pH scale, which runs from 0 to 14. A pH value of 7 is considered neutral, while numbers below 7 indicate greater acidity. Clean rain water has a pH of 5.6 (slightly acidic) due to naturally present carbon dioxide dissolving in water and forming dilute carbonic acid.
Acidity on High
The AMC has found that at the Lakes site since 1984, the mean summertime (June to mid-September) pH of cloud water ranges from 3.6 to 4.1, while the pH of rain water ranges from 4.0 to 4.4. The lowest pH value the AMC has recorded for cloud water is 2.6 (approximately the same acidity as lemon juice), while the lowest rain water pH was 3.1 (approximately the acidity of vinegar). Chemical analyses of Lakes of the Clouds rain and cloud water showed that about two-thirds of the acidic input was due to sulfuric acid (primarily from power plants, especially coal-burning plants) and about one-third from nitric acids (primarily from automobiles).
Cloud water, which is generally more acidic than rain water, appears to be a significant source of acid to ecosystems at higher elevations, especially given that mountaintops are immersed in clouds about 50 percent of the time. Recent research from Whiteface Mountain in New York's Adirondack State Park suggests that clouds can contribute up to 85 percent of the total input of sulfur and acid to high-elevation ecosystems.
What Can We Do?
Faced with the evidence that acid pollution from our activities at ground level reaches even into the alpine zone, what can we do about it?
In the political arena, the Clean Air Act amendments of 1990 have helped to reduce sulfur dioxide in the past decade, but unfortunately long-term damage has already occurred. To make matters worse, nitrous-oxide emissions from cars have not been regulated as stringently as other pollutants, and so their levels only recently started to decline. In order to protect sensitive ecosystems such as the alpine zone from acid pollution, deeper cuts in emissions of sulfur and nitrogen pollutants are still needed. Unfortunately, the Bush administration has moved toward weakening current clean-air rules and expanding loopholes for industry in the current Clean Air Act. You can speak up for stronger air policies through our Conservation Action Network.
On the research side, the AMC plans to assess the effects of long-term acid pollution on alpine plants and soil in the White Mountains. This will require investigating current soil conditions and the relationship between plant-distribution patterns and acid deposits, as well as overall ecosystem health. The AMC hopes that this research will help shape sensible air-quality policy and protect the beautiful, fragile places of the alpine zone.
