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 P-31-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 (P-i), 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 (P-o). P-i (ortho-phosphate and pyrophosphate) and P-o (phosphonates, ortho-phosphate monoesters and phospholipids, DNA) were detected in the NaOH-EDTA extracts of the sediments by P-31-NMR. The majority of P-o 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 P-o in sediment and TP in the water showed that P-o compounds in the sediment would be released to the water. These compounds of P-o will be mineralized to P-i and potentially bioavailable for recycling to surface water, supporting further growth of aquatic organisms and leading to algal blooms.