Origin and diagenesis of polyphosphate in lake sediments: A 31PߚNMR study

Polyphosphate (polyߚP) was detected with the use of 31P nuclear magnetic resonance (NMR) spectroscopy in sediments from a large variety of lakes with different trophic state and morphometry. In the top 0.5 cm of sediment, polyߚP was 1.5 to 11.4% of total P. Nonreactive phosphorus (NRP) in the NaOH fraction (often classified as organically bound phosphate) was up to 46%inorganic polyߚP. In some surface sediments, the polyߚP content equalled the ironߚfixed phosphorus determined by chemical phosphorus fractionation. Sediments were probably supplied with polyߚP by sedimentation because there were substantial amounts of polyߚP in plankton and settling seston. As demonstrated with sediments of Lake Petersdorf, benthic organisms can also contribute to the formation of polyߚP (up to 0.11 mg P [g dry weight]ߚ1) under favorable aerobic conditions. PolyߚP is more rapidly transformed into single orthophosphate during diagenesis than other inorganic and organic P species. The transformation of organic P compounds and polyߚP can contribute significantly to the release of P during diagenesis and should be considered along with the reductive dissolution of P sorbed to iron oxihydroxides.