Origin and diagenesis of polyphosphate in lake sediments: A 31P-NMR study

Abstract

Polyphosphate (poly-P) 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, poly-P 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 poly-P. In some surface sediments, the poly-P content equalled the iron-fixed phosphorus determined by chemical phosphorus fractionation. Sediments were probably supplied with poly-P by sedimentation because there were substantial amounts of poly-P in plankton and settling seston. As demonstrated with sediments of Lake Petersdorf, benthic organisms can also contribute to the formation of poly-P (up to 0.11 mg P [g dry weight] -1) under favorable aerobic conditions. Poly-P is more rapidly transformed into single orthophosphate during diagenesis than other inorganic and organic P species. The transformation of organic P compounds and poly-P 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.