Sulfate Dynamics and Base Cation Release in a High Elevation Appalachian Forest Soil
Two soils from the Fernow Experimental Forest near Parsons, West Virginia were characterized and evaluated in terms of their susceptibility to enhanced soil acidification via acidic atmospheric inputs. After initial physical, chemical, and mineralogical characterization, the soils were analyzed for their ability to adsorb and retain sulfate (SO42-) through a series of batch adsorption and desorption experiments. Reconstructed soil profiles were then subjected to water leaching as the preliminary step to a base release study in which each soil will be placed under simulated acid rain and evaluated for base cation release and subsequent changes in soil chemistry.
Experiments with SO42- adsorption and desorption divide the soils into two categories: (i) shallow surface horizons with high organic matter and little Fe oxide content which had little ability to adsorb additional SO42- and low capacity to retain SO42-; and (ii) deeper subsurface soils with low organic matter and high Fe oxide content which could adsorb SO42- at solution concentrations above 0.5 mmol/L. All soil horizons desorbed SO42- and had no ability for additional adsorption at solution concentrations below 0.5 mmol/L, which implies that the site may be saturated with respect to natural conditions. Initial mass (IM) and Langmiur modeling were used to illustrate SO42- dynamics and make correlations with soil physical, chemical, and mineralogical properties. Fe oxides and Al-saturated organic matter were shown to be the preferential sites for SO42- adsorption but may be already saturated or very near saturation.
Preliminary results from the base release study indicate that the two soils are dominated by different chemical processes and hence release ions into soil solution at different rates. Ion release is shown to be a function of both reactions on the exchange complex and the dissolution of mineral components.
Advisor:W. Lee Daniels; James Burger; Dr. Lucian Zelazny
School:Virginia Polytechnic Institute and State University
School Location:USA - Virginia
Source Type:Master's Thesis
Keywords:crop and soil environmental sciences
Date of Publication:05/22/1998