Effects of Atmospheric Acid Reduction on Water Chemistry of Three Virginia Trout Streams

Kevin Pyszka


Acid deposition from fossil fuel combustion has adversely affected streams in North America for more than four decades by emitting SOx and NOx gases into the atmosphere. Free radical reactions occur to form sulfuric and nitric acid. That is released into the streams. The pH and ANC (acid neutralizing capacity) decrease, which leads to fauna and flora mortality. The U. S. Congress passed the Clean Air Act to reduce power plant emissions in 1990. SOx and NOx gases have decreased by 82 % and 76%, respectively between 1996 and 2015. We have intensively collected water chemistry data on three acid sensitive streams in the George Washington National Forest: Little Stony Creek, Mill Creek, and Mountain Run monthly since 1987. The purpose of this project is to ascertain if the reductions in acid deposition are being realized with a positive response within the streams. Little Stony, Mill Creek, and Mountain Run have shown a 25.6, 25.6, and 42.8% reduction in sulfate concentration, respectively.  Resulting in an ANC increase of 19% (8.1 µeq/L to 13.6 µeq/L), 9.0% (-11.1µeq/L to -8.5 µeq/L), and 24.8% (-27.2 µeq/L to -20.4 µeq/L) for Little Stony, Mill Creek, and Mountain Run, respectively.  All three streams show a positive response to the reductions in atmospheric acid but have not yet returned to pre-industrial age values.


Atmospheric Acid, Water Chemistry, Limestone Treatment

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