IngentaConnect Input-Output Budgets of Major Ions for a Forested Watershed in We...

Authors: Castro M.S.¹; Morgan II R.P.²

Source: Water, Air, and Soil Pollution, Volume 119, Numbers 1-4, April 2000 , pp. 121-137(17)

Publisher: Springer

Abstract:

We measured concentrations and fluxes of major ions in wet deposition, throughfall and stream water in a forested watershed on the Allegheny Plateau of western Maryland to investigate canopy-atmosphere interactions and to calculate input–output budgets. Wet deposition was dominated by H^+, SO_4^2-, NO_3^- and NH_4^+ ions. Hydrogen and SO_4^2-accounted for 70 and 58% of the total cation and anion equivalents, respectively. Annual wet deposition rates of SO_4^2- (0.56 keq ha^-1 yr^-1), NO_3M^- (0.31 keq ha^-1 yr ^-1) and NH_4^+ (0.17 keq ha^-1 yr ^-1) were at the high end of the range in wet deposition rates reported for other sites in the eastern United States. On an annual basis, the forest canopy consumed 20% of the free acidity in incident precipitation, had no net effect on Na^+ and NH_4^+deposition, and was a net source of K^+, Ca^2+, Mg^2+, SO_4^2- and NO_3^-; 1.5 to 22 times greater than the wet deposition rates. On an annual basis, the watershed of the unnamed tributary to Herrington Creek (HCWS) retained essentially all of the throughfall H^+ and NH_4^+ inputs, 35% of the throughfall K^+input and 62% of the throughfall NO_3^-input. In contrast, HCWS was a net source of SO_4^2-, Cl^-, Ca^2+, Mg^2+ and Na^+; export rates were 2 to 5 times greater than throughfall inputs. Sulfate was the dominant anion associated with cation leaching, accounting for 78%of the total anion export of 1.8 keq ha^-1 yr ^-1 in 1996–1997.

Keywords: nitrogen; wet deposition

Language: English

Document Type: Regular paper

Affiliations: 1: Appalachian Laboratory, University of Maryland Center for Environmental Science, 301 Braddock Road, Frostburg, Maryland 21532, U.S.A. (author for correspondence, e-mail: castro@al.umces.edu) 2: Appalachian Laboratory, University of Maryland Center for Environmental Science, 301 Braddock Road, Frostburg, Maryland 21532, U.S.A.

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Input–Output Budgets of Major Ions for a Forested Watershed in Western Maryland