Phosphorus Sorption by Sediments in a Southeastern Coastal Plain In-Stream Wetland
2006
Novak, J. M. | Watts, D. W.
A close relationship has been reported between sediment organic C (SedOC) content and its P sorption capacity (Pₘₐₓ) and total P (TP) concentration. Phosphorus sorbed to organically complexed cations is a proposed explanation for this relationship. The objectives of this study were (i) to determine relationships between in-stream wetland SedOC content and both the sediment's Pₘₐₓ and TP concentrations, and (ii) to ascertain the role of both organically complexed and oxalate-extractable cations on the sediment Pₘₐₓ and TP values. The sediment's oxalate-extractable Fe (Feₒₓ) and Al (Alₒₓ) contents were determined using acidified ammonium oxalate, while sodium pyrophosphate was used to extract organically complexed cations (Alₚᵣyₒ, Caₚyᵣₒ, Feₚyᵣₒ, Mgₚyᵣₒ, and Mnₚyᵣₒ). Both the sediment's Pₘₐₓ and TP contents were strongly correlated with its SedOC concentration (r ² > 0.90, P < 0.001). Only the Alₒₓ contents were significantly correlated with TP and Pₘₐₓ, suggesting that amorphous Al forms have an important role in P sorption. All five pyrophosphate-extracted cations were significantly correlated with SedOC contents. Regression analyses showed that the Alₚyᵣₒ accounted for 88% of the variation in sediment Pₘₐₓ values, whereas a combination of Alₚyᵣₒ and Caₚyᵣₒ accounted for 98% of the variation in sediment TP concentrations. Additionally, Al and Ca chelated by SedOC compounds also have an important role in P binding and indicate that a linkage exists between the wetlands SedOC and Pₘₐₓ content and its ability to accumulate TP. This study identified that two different mechanisms have significant roles in regulating P sorption by sediments in a southeastern Coastal Plain in-stream wetland.
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