Aluminum and Organic Matter Mobilization from Forest Soil Infiltrated with Acidified Calcium Sulfate Solutions
- Duane F. Berry ,
- Lucian W. Zelazny and
- Hubert L. Walker
Investigations of acid rain effects on forest soils have generally overlooked Ca, a major component of precipitation. This study was conducted to determine the effects of Ca on the mobilization of Al and organic matter in a Cecil soil (clayey, kaolinitic, thermic Typic Kanhapludult). Acidic solutions (pH 4.2) containing ambient or near-ambient precipitation concentrations of Ca, K, and SO4 were used to infiltrate columns containing Oa, EB, or Oa/EB bihorizon soil material. Leachate was analyzed for dissolved organic carbon (DOC), Al, Ca, K, and H ions. A net release of protons was observed when the Oa surface horizon was infiltrated with 0.05 mol m−3 CaSO4 or 0.25 mol m−3 CaSO4 or K2SO4 leaching solutions, but not 0.05 mol m−3 K2SO4 solution. Infiltration of Oa horizon soil with Ca solutions resulted in release of more protons than with K solutions of comparable ionic strength. Calcium leaching solutions were also more effective than K solutions (7.7% and 28% for 0.05 and 0.25 mol m−3 solutions, respectively) in mobilizing Al from Oa/EB bihorizon soils. These differences were not found in EB horizon soils treated with the same leaching solutions. Our results suggest that CaSO4 leaching solutions, at concentration levels consistent with those in precipitation, displaced protons from the Oa horizon, which subsequently infiltrated the underlying EB horizon causing increased solubilization of Al. While some Al was undoubtedly associated with organic matter, overall, movements of Al and organic matter in Oa/EB bihorizon soil columns were found to be independent of one another.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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