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Title: Internal phosphorus loading in Lake Pepin (Minnesota-Wisconsin)
Authors: Metropolitan Council of the Twin Cities Area
Water Operations Technical Support Program (U.S.)
James, William F., Aquatic biologist
Barko, John W.
Eakin, Harry L.
Keywords: Anoxia
Porewater phosphorus
Water quality
Sediment phosphorus fractions
Lake Pepin
Publisher: Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: This study examined rates of internal phosphorus (P) loading from sediments in Lake Pepin, a natural impoundment located on the upper Mississippi River. Laboratory determinations of rates of P release from the sediment, measured using intact sediment core systems, were very high, with mean values ranging from 3.8 to 15 mg m⁻² day⁻¹ under oxic and anoxic conditions, respectively. Independently determined Fickean diffusional fluxes (mean of 4.9 mg m⁻² day⁻¹), measured in situ under oxic conditions using sediment peepers, were not statistically different from those rates determined in the laboratory under similar temperature, pH, and oxygen conditions. The dominant inorganic P fractions in the sediments were NaOH-extractable P followed closely by HCl-extractable P. Under both oxic and anoxic conditions, significant correlations existed between rates of P release and the NH4Cl- and NaOH-extractable P fractions, suggesting that loosely bound and iron- and aluminum-bound sediment P contributed to P release from the sediments in this lake. Correlations between total sediment P and extractable sediment P fractions indicated that loosely bound and iron- and aluminum-bound P increased, while calcium-bound P decreased, with increasing total P content of the sediment. Results suggest that internal P loading from the sediments under oxic as well as anoxic conditions can play a very important role in the P economy of this system.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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