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Decreased atmospheric sulfur deposition across the southeastern U.S.: when will watersheds release stored sulfate?

Rice, Karen C.; Scanlon, Todd M.; Lynch, Jason A.; Cosby, Bernard J.. 2014 Decreased atmospheric sulfur deposition across the southeastern U.S.: when will watersheds release stored sulfate? Environmental Science & Technology, 48 (17). 10071-10078. https://doi.org/10.1021/es501579s

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Abstract/Summary

Emissions of sulfur dioxide (SO2) to the atmosphere lead to atmospheric deposition of sulfate (SO42–), which is the dominant strong acid anion causing acidification of surface waters and soils in the eastern United States. Since passage of the Clean Air Act and its Amendments, atmospheric deposition of SO2 in this region has declined by over 80%, but few corresponding decreases in streamwater SO42– concentrations have been observed in unglaciated watersheds. We calculated SO42– mass balances for 27 forested, unglaciated watersheds from Pennsylvania to Georgia, by using total atmospheric deposition (wet plus dry) as input. Many of these watersheds still retain SO42–, unlike their counterparts in the northeastern U.S. and southern Canada. Our analysis showed that many of these watersheds should convert from retaining to releasing SO42– over the next two decades. The specific years when the watersheds crossover from retaining to releasing SO42– correspond to a general geographical pattern of later net watershed release from north to south. The single most important variable that explained the crossover year was the runoff ratio, defined as the ratio of annual mean stream discharge to precipitation. Percent clay content and mean soil depth were secondary factors in predicting crossover year. The conversion of watersheds from net SO42– retention to release anticipates more widespread reductions in streamwater SO42– concentrations in this region.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1021/es501579s
CEH Sections/Science Areas: Emmett
ISSN: 0013-936X
NORA Subject Terms: Hydrology
Agriculture and Soil Science
Date made live: 20 Jan 2015 14:46 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/509336

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