Characteristics of Phosphorus Compounds and Their Effects in Sediments of an Eutrophic Chaohu Lake, China

Surface sediments and sediment cores in a shallow eutrophic lake, Chaohu Lake, were analyzed by 31P‐NMR to reveal the phosphorus (P) species and their effects on upper water quality. Total P (TP) in the NaOH‐EDTA extracts was dominated by inorganic phosphate (Pi), with higher levels being observed in the heavily eutrophic western lake (79.1 ± 1.7%) than in the eastern lake (68.1 ± 2.4%). These findings were opposite to those for organic phosphorus (Po). Pi (ortho‐phosphate and pyrophosphate) and Po (phosphonates, ortho‐phosphate monoesters and phospholipids, DNA) were detected in the NaOH‐EDTA extracts of the sediments by 31P‐NMR. The majority of Po consisted of ortho‐phosphate monoesters (80.2 ± 2.7%). For sediment cores, the contents of phospholipids and DNA declined more rapidly than that of ortho‐phosphate monoesters and pyrophosphate as sediment depth increased, with these compounds primarily occurring in the top 10 cm of sediment. The positive relationship between Po in sediment and TP in the water showed that Po compounds in the sediment would be released to the water. These compounds of Po will be mineralized to Pi and potentially bioavailable for recycling to surface water, supporting further growth of aquatic organisms and leading to algal blooms.