Sulfate adsorption-desorption in a Swedish forest soil

The Forest Roof project at Lake Gardsjon located on the Swedish Southwest c oast near Gothenburg was established to assess the response of the ecosyste m following a major reduction in loading of sulfur acidic deposition. The o bjective of the study was to describe the adsorption-desorption processes o f sulfate in Haplorthod soils at the Gardsjon site. A sequential batch tech nique was used to sequentially leach the upper three mineral horizons with forest floor leachate containing different concentrations of sulfate. Resul ts showed that adsorption-desorption processes were highly irreversible and hysterestic in nature. Moreover, the soil solution SO42-, pH and DOC were interrelated. These findings suggest that improvements in the prediction ca pability of models for acidified surface waters, lakes and soils are needed . Therefore, existing sulfate models with fully reversible Langmuir or Freu ndlich approaches need to account for additional ir-reversible reactions.