Fractions and transformation of organic phosphorus in sediments from a eutrophic lake in China

Several organic phosphorus compounds (Po) in sediment from a representative eutrophic lake were surveyed using a sequential fractionation procedure, which included microbial biomass phosphorus (Biomass-P), fulvic acid phosphorus (FA-P), humic acid phosphorus (HU-P), and residual phosphorus (Res-P). In addition, several organic compounds including orthophosphate monoesters, orthophosphate diesters, and pyrophosphate were simultaneously measured using ³¹P nuclear magnetic resonance (³¹P NMR). Results showed that Po contributed over 50% of total phosphorus (TP), and the average concentration of Po species generally decreased from Res-P > FA-P > HU-P > Biomass-P. Additionally, the relative proportions of phosphorus compounds in the sediment followed the decreasing order of orthophosphate monoesters > orthophosphate diesters > pyrophosphate. In general, Po was the dominant phosphorus species. Residual P was not a single species but comprised of a group of species, and tended to be stable. Although orthophosphate monoesters had the highest concentrations and ratios in Po, orthophosphate diesters displayed a more distinct remineralization trend. Principal component analysis (PCA) coupled with correlation analysis suggested that a greater amount of orthophosphate diesters resided in Res-P, than HU-P or FA-P.