Lakes in New England and the Adirondack Mountains are recovering from the effects of acid rain faster now than in the 1980s and 1990s, according to a study led by a former University of Maine researcher.
Acid rain—which contains higher than normal amounts of nitric and sulfuric acid and is harmful to lakes, streams, fish, plants, and trees—occurs when sulfur dioxide and nitrogen oxide in the atmosphere mix with water and oxygen.
In the United States, about two-thirds of sulfur dioxide and one-quarter of nitrogen oxide come from burning fossil fuels, including coal, the U.S. Environmental Protection Agency says.
The concentration of sulfate in rain and snow fell by 40 percent in the 2000s, and the concentration of sulfate in lakes in the Northeast declined at a faster rate from 2002 to 2010 than during the 1980s or 1990s, says the Kristin Strock, former PhD student at UMaine, now assistant professor. professor at Dickinson College in Pennsylvania.
Also, during the 2000s, the concentration of nitrates in rain and snow fell by more than 50 percent, and their concentration in lakes also decreased, Strock found.
The Clean Air Act enacted in the US in 1970 has been amended several times, including amendments implemented in 1994 that regulated emissions, especially from coal-fired power plants. The Interstate Clean Air Rule issued in 2005 by the EPA sought to reduce sulfur dioxide and nitrogen oxides by 70 percent. Total U.S. emissions of sulfur and nitrogen fell by 51 and 43 percent, respectively, between 2000 and 2010, Strock says, which was twice the rate of decline for both in the 1990s.
Strock and the research team analyzed data collected since 1991 at 31 sites in Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and southern New York, and at 43 sites in New York's Adirondack Mountains.
The research team included Sarah Nelson, assistant research professor with the Senator George J. Mitchell Center and associate research assistant professor of Watershed Biogeochemistry at the UMaine School of Forest Resources. Jasmine Saros, associate director of the Climate Change Institute at UMaine and professor in the UMaine School of Biology and Ecology. Jeffrey Kahl, then director of environmental and energy strategies at James Sewall. and William McDowell of the Department of Natural Resources and Environment at the University of New Hampshire.
“More than two decades of data collection in this study is part of the EPA-LTM network, which also includes over 30 years of research and monitoring in 16 remote lakes in Maine and over 25 years in the Bear Brook Watershed in Maine” , Nelson says.
“This long-term monitoring data allows us to observe patterns such as climate-related changes, as well as evaluate the effectiveness of environmental regulations such as the Clean Air Act. The new findings reported here underscore the importance of such long-term monitoring, the which can often be difficult to maintain funding'.
While the results reveal a recent acceleration of recovery, the researchers say continued observation is necessary because of the variability of the results. In New England, Strock says the variability may be due to the effect of human development, including road salt, on lakes.
Several other factors can affect watersheds and interact with acid rain, the researchers say, including calcium depletion in forest soils, long-term increases in carbon dioxide in the atmosphere, long-term changes in air temperature, and changes in in frequency and intensity. extreme wet and dry seasons.
More information:
“Decade Trends Reveal Recent Acceleration in Acidification Recovery Rate in Northeastern US” Kristin E. Strock, et al. Surround. Sci. Technol., 2014, 48 (9), pp. 4681–4689. DOI: 10.1021/es404772n