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This article in SSSAJ

  1. Vol. 58 No. 5, p. 1546-1555
     
    Received: Nov 15, 1993


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doi:10.2136/sssaj1994.03615995005800050039x

Sulfate Adsorption in Forest Soils of the Great Lakes Region

  1. Neil W. MacDonald ,
  2. John A. Witter,
  3. Andrew J. Burton and
  4. Daniel D. Richter
  1. School of Natural Resources and Environment, Univ. of Michigan, Ann Arbor, MI 48109-1115
    Dep. of Forestry, Michigan State Univ., E. Lansing, MI 48824-1222
    School of the Environment, Duke Univ., Durham, NC 27706-0328

Abstract

Abstract

Sulfate adsorption by forest soils modifies the impact of pollutant deposition on cation leaching processes. We examined relationships among SO2−4 adsorption, soil properties, and seasonal variation in soil solution chemistry at 13 sites representing deciduous forest ecosystems common in the Great Lakes region. Objectives of the study were to test the validity of previously proposed SO2−4 adsorption indices, to examine within- and among-site variability in SO2−4 adsorption potential, and to investigate the effects of seasonal changes in soil solution chemistry on SO42- retention. Mineral soils were sampled by horizon at all sites, and soil solutions were sampled at lower E and lower B horizon boundaries at 10 sites. Proposed indices overpredicted sulfate adsorption in certain SO2−4 releasing subsurface horizons, seriously limiting the applicability of the published regression equations. We developed improved regression equations using the sum of initial extractable SO2−4 and additional SO2−4 adsorbed under laboratory conditions as the dependent variable. Sulfate retention indices predicted by the improved equations were independent of existing levels of extractable SO2−4 and past history of atmospheric SO2−4 deposition. Examination of within- and among-site variability in SO2−4 adsorption potentials suggested that soils need to be grouped tightly on a taxonomic basis for modelling purposes. Seasonal variation in soil solution SO2−4 concentration and fluxes was consistent with an annual cycle of SO2−4 retention and release. Although seasonal patterns in SO2−4 concentrations and fluxes appeared to be controlled by hydrologic and S-cycling processes, the magnitude of SO2−4 fluxes was primarily related to atmospheric SO2−4 deposition rates.

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