Drop in acid rain altering Appalachian stream waterDecember 12, 2006Appalachian hardwood forests may be getting a respite from acid rain but data from a long-term ecological study of stream chemistry suggests that the drop in acid rain may be changing biological activity in the ecosystem and hiking dissolved carbon dioxide in forest streams. "These are unexpected results," says David DeWalle, professor of forest hydrology at Penn State. "Rising amounts of carbon dioxide in streams and soil could have implications for the forest ecosystem, and the carbon balance in general." DeWalle and his colleagues have been monitoring stream water chemistry in the Appalachians since 1990. They are studying the effect of reduced sulfur emissions - required under the Clean Air Act - on the water quality of five streams in Pennsylvania.
"These streams are as pristine as you can get, and we have been sampling them nearly every month over the past 15 years," he says. Some expected changes in stream chemistry are already showing. Water quality in the streams is gradually improving from the reduced sulfur emissions, and researchers are also seeing less nitrogen from the atmosphere and in the streams. "This reduction in nitrogen deposition is yet to be seen in many parts of New England," DeWalle says. "We are probably seeing it earlier than others because we are pretty close to the sources of these emissions." There have also been some unexpected changes. DeWalle and his Penn State colleagues Bryan Swistock, extension specialist, and Anthony Buda and Sarah MacDougall, graduate students, say they are recording rising amounts of dissolved carbon dioxide in all five streams. DeWalle, whose work is funded by the U.S. Environmental Protection Agency, thinks that by reducing pollutants emitted to the atmosphere, we are creating a different set of conditions for organisms in the soil. The rising dissolved carbon dioxide in the streams, he suggests, might be traced to increased respiration by these organisms. He explains that organic matter broken down by these organisms generates byproducts such as carbon dioxide, water and residual dissolved organic matter. The increased respiration, he adds, may be gradually increasing soil carbon dioxide and reducing the amount of residual organic matter. As the organisms break down more of the organic matter, there is less of it leaving as dissolved organic matter in stream water. "There have been some experiments where they added nitrogen to the soil and saw a reduction in soil respiration. We have of course, reduced the nitrogen, and indicators of stream chemistry suggest that this may have caused the opposite reaction and stepped up the respiration," says DeWalle. Though the stream chemistry data suggests increased respiration in the soil, researchers caution that the hypothesis needs to be tested with experiments that mimic reduced amounts of nitrogen in the atmosphere. Penn State researchers are already seeing increasing amounts of silica and sodium in streams which may be from the weathering of minerals and sandstone bedrock, caused presumably by the increased carbonic acid in soil and groundwater. "If you have higher carbon dioxide in the soil, you get more carbonic acid in the groundwater, which increases the weathering of minerals. You would not normally expect weathering rates to increase with reduced acid rain," DeWalle told attendees at the American Geophysical Union conference today (Dec. 12) in San Francisco. Appalachian forests play a crucial role in maintaining a healthy ecosystem, and support thousands of jobs through the hardwood industry. "This area is a region bigger than Pennsylvania, where we see declines in both sulfur and nitrogen emissions. Although that is a positive thing, it is having an influence, it appears, on the forest ecosystem. Higher amounts of carbon dioxide in the soil means more of it ultimately may be emitted back to the atmosphere as a greenhouse gas," adds the Penn State researcher. Penn State | |||||||||||||||||||||
|
Related Acid Rain Current Events and Acid Rain News Articles Strange molecule in the sky cleans acid rain, scientists discover Researchers have discovered an unusual molecule that is essential to the atmosphere's ability to break down pollutants, especially the compounds that cause acid rain. Tunguska catastrophe: Evidence of acid rain supports meteorite theory The Tunguska event is regarded as one of the biggest natural disasters of modern times. On 30 June 1908 one or more explosions took place in the area close to the Tunguska River north of Lake Baikal. The explosion(s) flattened around 80 million trees over an area of more than 2000 square kilometres. Database shows effects of acid rain on microorganisms in Adirondack Lakes Prior to the federal Clean Air Act, unhindered industrial emissions were released into the air throughout the Midwestern and Eastern United States for decades. Many of those harmful chemicals came right back down to earth in the form of acid rain, a chemical concoction that includes nitric and sulfuric acid. Ancient mineral shows early Earth climate tough on continents A new analysis of ancient minerals called zircons suggests that a harsh climate may have scoured and possibly even destroyed the surface of the Earth's earliest continents. Seismic images show dinosaur-killing meteor made bigger splash The most detailed three-dimensional seismic images yet of the Chicxulub crater, a mostly submerged and buried impact crater on the Mexico coast, may modify a theory explaining the extinction of 70 percent of life on Earth 65 million years ago. Nitrous oxide from ocean microbes A large amount of the greenhouse gas nitrous oxide is produced by bacteria in the oxygen poor parts of the ocean using nitrites, Dr Mark Trimmer told journalists at a Science Media Centre press briefing today. Pitt professor says harmful byproducts of fossil fuels could be higher in urban areas Nitrogen oxides, the noxious byproduct of burning fossil fuels that can return to Earth in rain and snow as harmful nitrate, could taint urban water supplies and roadside waterways more than scientists and regulators realize. Recovery from acid rain 'much slower than expected' Acid rain was one of the world's worst pollution problems of the 1970s and 1980s, affecting large areas of upland Britain, as well as Europe and North America. Acid Rain Has a Disproportionate Impact on Coastal Waters The release of sulfur and nitrogen into the atmosphere by power plants and agricultural activities plays a minor role in making the ocean more acidic on a global scale, but the impact is greatly amplified in the shallower waters of the coastal ocean, according to new research by atmospheric and marine chemists. University of Oregon researcher finds that on water's surface, nitric acid is not so tough Nitric acid is a notoriously strong and chemically destructive compound found in water on earth and in our atmosphere. However, a team of researchers have found that its punch is much weaker when it sits on the top of a water surface. More Acid Rain Current Events and Acid Rain News Articles |
|||||||||||||||||||||
|
|||||||||||||||||||||
|
|||||||||||||||||||||