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This article in SSSAJ

  1. Vol. 51 No. 2, p. 446-452
     
    Received: Oct 7, 1986
    Published: Mar, 1987


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doi:10.2136/sssaj1987.03615995005100020035x

Dynamics of Sulfate Retention by Acid Forest Soils in an Acidic Deposition Environment1

  1. P. K. Khanna2,
  2. J. Prenzel3,
  3. K. J. Meiwes3,
  4. B. Ulrich4 and
  5. E. Matzner3

Abstract

Abstract

The process of input and output of SO4 in spruce and beech forest ecosystems at Solling, West Germany, are dynamic in nature, showing both short term, seasonal cycles and long-term changes. During the observation period (1969–1982), the atmospheric inputs of SO4 were higher for winter than summer periods and for the spruce stand than the beech stand. The respective mean values in kg SO4-S ha−1 for spruce and beech stands were 53.5 and 28.7 for winter periods and 34.0 and 22.0 for summer periods. Leaching losses of SO4 reflected the amount of drainage water and were usually high during winter (e.g., the mean SO4 values for spruce were 15.8 (summer) and 81.6 (winter) kg S ha−1). Leaching losses of SO4 increased significantly after 1975 to 1976 following an acidification phase in these soils. Along with SO4, the concentrations of Al in percolates increased significantly from values <0.35 mmol of Al prior to 1976 to about 0.60 mmol Al as median values after 1976 on spruce site. Retention or loss of SO4 by these highly acidic soils is explained on the basis of the formation and dissolution of aluminium hydroxy sulfate minerals (e.g., jurbanites; AlOHSO4). AlOHSO4 may exist as an intermediate product in these soils buffering proton concentration, which is ultimately dissolved at low pH values to produce Al and SO4 in soil percolates. The ion-activity product values (IAP) of AlOHSO4 in the soil percolates and the equilibrium soil solutions varied with time (lower and lesser variable values of about 17 on spruce and about 18 on beech after 1976), vegetation (beech vs. spruce) and soil depths (higher values for organic soil horizons than mineral horizons). The relationship between IAP values and the solubility product values has been described in terms of SO4 input to, and SO4 status of these soils.

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