A Comparison of Fluvial Sediment Phosphorus (P) Chemistry in Relation to Location and Potential to Influence Stream P Concentrations |
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| Authors: | R W McDowell A N Sharpley |
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| Institution: | (1) AgResearch Ltd, Invermay Agricultural Research Centre, Private Bag 50034, Mosgiel, New Zealand;(2) USDA-ARS, Pasture Systems and Watershed Management Research Unit, Curtin Road, University Park, PA 16802-3702, USA |
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| Abstract: | Fluvial sediments are subject to cyclic submersion during changes in stream flow, which can affect their phosphorus (P) sorptive capacity. As fluvial sediments play a major role in determining P concentrations in stream flow, we compared the P chemistry of exposed stream bank and submerged bed sediments from an agricultural catchment in central Pennsylvania, USA. Total P concentration was greater in bank (417 mg kg-1) than bed sediments (281 mg kg-1), but because bed sediments contained more sand-sized material, they could release more P and support a higher solution P concentration (0.043 mg l-1) than bank sediments (0.020 mg l-1). Phosphorus release was a function of Mehlich-3 soluble Fe in stream sediments (r > 0.65), reflecting redox processes in the fluvial system. In contrast, P sorption maxima of bank and bed sediments were related to Mehlich-3 soluble Al (r > 0.78) and organic matter concentration (r > 0.79). Overall, our research suggested that erosion of bank sediments should contribute less P and may be a sink for P in the stream system compared with resuspension of bed sediment. However, bank sediments may have the potential to be a large source of P in downstream reservoirs or lakes, where increased microbial activity and reducing conditions may solubilise sediment-bound P. |
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| Keywords: | stream fluvial sediment phosphorus kinetics risk |
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