Pore water geochemistry near the sediment-water interface of a zoned, freshwater wetland in the southeastern United States |
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Authors: | R J Donahoe Chongxuan Liu |
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Institution: | (1) Department of Geology, The University of Alabama, Box 870338, Tuscaloosa, AL 35487, USA, US;(2) Department of Geography and Environmental Engineering, Johns Hopkins University, 313 Ames Hall, Baltimore, MD 21218, USA, TP |
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Abstract: | Sediment and its associated pore water were collected from a zoned, freshwater, riparian wetland, located in the Talladega
National Forest, northeastern Hale County, Alabama, to study the porewater chemistry and its spatial changes within and between
the wetland ecological zones. Obvious changes in pH, Eh and element concentrations were observed between the different wetland
ecological zones. Major cations (Ca, Mg, and Na) and trace elements (B, Ba, Sr, and Mn) have very good spatial correlation
with Fe and Mn distributions, both in the pore water and the sediment, suggesting that adsorption on, and desorption from,
iron and manganese oxyhydroxides are important processes controlling the distributions of these elements in the wetland sediment.
However, an equilibrium adsorption model is not able to explain the distribution of trace elements between the pore water
and sediment. A redox kinetic model gives similar vertical profiles for iron and the correlated elements as those measured
in the field and thus suggests that the relative rates of ferrous iron oxidation and the reductive dissolution of ferric iron
in the sediment are important variables determining the distributions of these elements in the wetland pore waters.
Received: 31 October 1996 · Accepted: 27 May 1997 |
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Keywords: | Sediment Pore water Iron Geochemistry Redox |
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