Ein einfaches Routineverfahren zur Beurteilung des Remobilisierungspotentials von Waldboden fur Sulfat-Schwefel aus atmospharischen Eintragen

A simple method to assess the SO₄^2- remobilization potential of forest soils for accumulated sulfate-sulfur 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 SO₄^2- 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 SO₄^2- mobilization potential PMAX and the ratio PREAL/PMAX, an evaluation scheme characterizing the intensity and type of SO₄^2- mobilization from forest soils is presented. For most profiles, the amounts of extractable SO₄^2- ranged between 5 and >100 kmole(c) ha^-1 m^-1 soil depth, indicating a long-lasting future SO₄^2- loading of forest soil see-page water by remobilization of soil-accumulated SO₄^2-. A significant portion of the soil SO₄^2- pool will not be mobilized unless SO₄^2- concentrations in the seepage water decrease considerably.