Sulfur isotope dynamics in two Central European watersheds affected by high atmospheric deposition of SO{sub x}
Sulfur fluxes and {delta}{sup 34}S values were determined in two acidified small watersheds located near the Czech-German border, Central Europe. Sulfur of sulfate aerosol in the broader region was isotopically heavier than sulfur of airborne SO{sub 2}. The annual atmospheric S deposition to the Jezeri watershed decreased markedly in 1993, 1994, and 1995, reflecting reductions in industrial S emissions. Sulfur export from Jezeri via surface discharge was twice atmospheric inputs, and increased over the same three-year period. The {delta}{sup 34}S value of Jezeri streamflow as intermediate between the average atmospheric deposition and soil S, suggesting that the excess sulfate in runoff comes from release of S from the soil. Bedrock is not a plausible source of the excess S, because its S concentration is very low and because its {delta}{sup 34}S value is too high to be consistent with the {delta}{sup 34}S of runoff. A sulfur isotope mixing model indicated that release of soil S accounted for 64 {+-} 33% of sulfate S in Jezeri discharge. Approximately 40% of total sulfate S in the discharge were organically cycled. At Nacetin, the same sequence of {delta}{sup 34}S was observed. The seasonality found in atmospheric input was preserved in shallow soil water, but not in deeper soil water. {delta}{sup 34}S values of deeper soil water were intermediate between those of atmospheric input and Nacetin soils, again suggesting that remobilization of soil S accounts for a significant fraction of the S in soil water at Nacetin. The inventories of soil S at both of these sites are legacies of more intense atmospheric pollution during previous decades, and are large enough to supply significant sulfur fluxes to runoff for several more decades. The ongoing release of this stored soil S may significantly delay the recovery of water quality under declining atmospheric S deposition. Analysis of possible scenarios that would result in different S isotope composition of rainfall, runoff and soil suggested that biologic S isotope fractionation must be involved.
- Research Organization:
- Czech Geological Survey (CZ)
- OSTI ID:
- 20017437
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 64, Issue 3; Other Information: PBD: Feb 2000; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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