Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2006
Publication Date: 10/27/2006
Citation: Novak, J.M., Watts, D.W. 2006. Phosphorus sorption by sediments in a southeastern Coastal Plain in-stream wetland. Journal of Environmental Quality. 35:1975-1982.
Interpretive Summary: Wetland sediments often have a significant role in the binding, storage, and release of dissolved phosphorus (DP) in southeastern coastal ecosystems. It is important to understand pathways of DP binding within wetlands to minimize water quality deterioration in downstream aquatic ecosystems. Several sediment samples from a wetland were collected, and we determined which sediment’s chemical properties strongly influence their P binding capability. We found that the organic carbon concentration of the sediment has a strong influence on its ability to bind DP. Additionally, DP binding was also influenced by certain trace metals associated with the sediment’s organic carbon compounds. Certain characteristics of the wetlands sediments have a significant effect in the DP binding process; thereby, influencing the DP storage capability of coastal wetlands.
Technical Abstract: A close relationship has been reported between sediment organic carbon (sed. OC) content and its phosphorus sorption capacity (Pmax) and total phosphorus (TP) concentration. Phosphorus (P) sorbed to organically-complexed cations is a proposed explanation for this relationship, however; few studies have verified this P binding pathway. The objectives of this study were: 1) to determine relationships between in-stream wetland sediment organic carbon (sed. OC) content and both the sediments Pmax and TP concentrations, and 2) to ascertain the role of both organically complexed and oxalate extractable cations on the sediment Pmax and TP values. Sediments Pmax values were determined using standard P sorption isotherms. Sediments oxalate extractable Fe (Feox) and Al (Alox) contents were determined using acidified ammonium oxalate, while sodium pyrophosphate was used to extract organically complexed cations (Al, Ca, Fe, Mg, and Mnpyro). Both the sediments Pmax and TP contents were strongly correlated with its sed. OC concentration (r2 = 0.90 and P <0.001). Only the Alox contents were significantly correlated with TP and Pmax (r2 and P between 0.87 and 0.52 and 0.008 and <0.001, respectively) while Feox concentrations were not. All five pyrophosphate-extracted cations were significantly correlated with sed. OC contents. Regression analyses showed that the Alpyro accounted for 86% of the variation in sediment Pmax values, whereas a combination of Alpyro•Capyro accounted for 98% of the variation in sediment TP concentrations. This study revealed that organically chelated cations play an important role in P binding and indicates a linkage exists between the wetlands sed. OC and Pmax content and its ability to accumulate TP.