Investigation into organic phosphorus species in sediments of Baiyangdian Lake in China measured by fractionation and 31P NMR

Organic phosphorus (OP) species in sediments of the Baiyangdian Lake in China was investigated via fractionation and phosphorus-31 nuclear magnetic resonance (P-31 NMR) spectroscopy. Results of chemical fractionation showed that different OP fractions ranked in the order: humic acid-P > HCl-OP > fulvic acid-P a parts per thousand aEuro parts per thousand NaHCO3-OP > residual OP. Labile OP and moderately labile OP, which can be degraded for phytoplankton uptake, contributed to 58.7-68.5% of total extracted OP, indicative of the potential P release from sediments in the lake. P-31 NMR spectroscopy results suggested the rank order of P species present in the NaOH-EDTA extractant of the sediments: orthophosphate > monoester-P > DNA-P > pyrophosphate-P. Phytate, polyphosphates, and phosphonates, which appeared in sediments of some deeper lakes, were not detected in the shallow lake. Significant correlations were identified between total P (TP) in water column and sediment TP, monoester-P and DNA-P, positively indicating that sediment P species, especially OP components, should probably contribute to the contents of P in water column and further to the lake eutrophication.