A simple routine method for assessing the SO42− remobilization potential of forest soils for sulfate-sulfur from atmospheric deposition | Ein einfaches Routineverfahren zur Beurteilung des Remobilisierungspotentials von Waldböden für Sulfat-Schwefel aus atmosphärischen Einträgen
1999
Prietzel, Jörg | Kölling, Christian
A simple method to assess the SO₄²⁻ remobilization potential of forest soils for accumulated sulfatesulfur from atmospheric deposition is presented. On the basis of three parallel batch extractions, (i) the total potential of sulfate mobilization equal to the pool of inorganic sulfate (PTOT: extraction with 0.5 M NH₄F), (ii) the maximum potential of sulfate mobilization under conditions of a strong decrease of the sulfate concentration in the seepage water to pre-industrial values (PMAX: extraction with deionized water at a solution:soil ratio of 50:1), and (iii) the present potential of sulfate mobilization at current sulfate concentrations in the seepage water (PREAL: extraction with deionized water at a solution:soil ratio of 5:1) can easily be assessed for any soil. The method was tested with 25 horizons of different Southern German forest soils. On average, the maximum potential of SO₄²⁻) mobilization of the studied soils was only 60% of PTOT; indicating an irreversible retention of the remaining S pool under site conditions. Based on the maximum SO₄²⁻ mobilization potential PMAX and the ratio PREAL/PMAX, an evaluation scheme characterizing the intensity and type of SO₄²⁻ mobilization from forest soils is presented. For most profiles, the amounts of extractable SO₄²⁻ ranged between 5 and >100 kmolec ha⁻¹ m⁻¹ soil depth, indicating a long-lasting future SO₄²⁻ loading of forest soil seepage water by remobilization of soil-accumulated SO₄²⁻. A significant portion of the soil SO₄²⁻ pool will not be mobilized unless SO₄²⁻ concentrations in the seepage water decrease considerably.
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