Watershed Sulfur Biogeochemistry: Shift from Atmospheric Deposition Dominance to Climatic Regulation

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• 作者：Myron J. Mitchell ; Gene E. Likens
• 刊名：Environmental Science & Technology
• 出版年：2011
• 出版时间：June 15, 2011
• 年：2011
• 卷：45
• 期：12
• 页码：5267-5271
• 全文大小：819K
• 年卷期：v.45,no.12(June 15, 2011)
• ISSN：1520-5851

文摘

North American atmospheric S emissions peaked in the early 1970s followed by a dramatic decrease that resulted in marked declines in sulfate (SO₄^2-) concentrations in precipitation and many surface waters. These changes in S biogeochemistry have important implications with respect to the mobilization of toxic (Alⁿ⁺, H⁺) and nutrient (Ca²⁺, Mg²⁺, K⁺) cations and the acidification of watersheds. We used the continuous long-term record for watersheds 1, 3, 5, and 6 (37鈥?4 years from 1965 through 2008) of SO₄^2- concentrations and fluxes at Hubbard Brook Experimental Forest in New Hampshire (U.S.) for evaluating S budgets. Analysis revealed that the annual discrepancies in the watershed S budgets (SO₄^2- flux in drainage waters minus total atmospheric S deposition) have become significantly (p < 0.001) more negative, indicating the increasing importance of the release of S from internal sources with time. Watershed wetness, as a function of log₁₀ annual water flux, was highly significant (p < 0.001) and explained 57% (n = 157) of the annual variation for the combined results from watersheds 1, 3, 5, and 6. The biogeochemical control of annual SO₄^2- export in streamwater of forested watersheds has shifted from atmospheric S deposition to climatic factors by affecting soil moisture.