Migration And Transformation Of Different Phosphorus Forms In Typical Eutrophic Lake Sediments

Eutrophication of freshwater lakes caused by excessive input of phosphorus?P?is a serious water environment problem worldwide.Organic phosphorus with different structural composition has different bioavailability and release risk.Therefore,it is important to control the release of endogenous phosphorus in freshwater lake sediments by analyzing the mechanism of migration and transformation of different forms of phosphorus,characterizing the composition and circulation mechanism of inorganic phosphorus and organic phosphorus in lakes,and analyzing bioavailability characteristics.In this study,Taihu Lake,a typical freshwater shallow lake in the east of china,was used as an example.The chemical behavior of phosphorus in lake sediments was characterized in many ways through chemical fractionation extraction,oxygen culture,³¹P-NMR and other techniques.The study focued on the source identification and migration transformation mechanism of iron-bound phosphorus and organic phosphorus in sediments in Zhushan Bay in Taihu Lake.The study found that:?1?The total phosphorus content in eutrophic lake sediments decreased with depth.Phosphorus has the characteristics of surface enrichment,iron-bound phosphorus and organic phosphorus is closely related to the release of endogenous phosphorus in lake.?2?The depth of oxygen penetration in the sediment depends on the oxygen supply.The potential release of phosphorus under anaerobic conditions increases.The redissolution of solid-phase iron-bound phosphorus is the most important source of unstable phosphorus;the reduction and precipitation mechanism of iron-bound phosphorus under different oxidation states shows that iron-bound phosphorus can act as an intermediate between organic phosphorus and calcium-bound phosphorus,and it leads to the permanent burial of autogenous calcium-bound phosphorus.?3?The main components of organophosphorus are the stable organophosphorus components HA-Po and Res-Po,orthophosphate monoester is the main component of HA-Po,the rapid and unstable hydrolysis of orthophosphate diester further promotes the accumulation of orthophosphate monoester in the sediment;the partially hydrolyzed FA-Po in HA-Po is an important source of unstable inorganic phosphorus in Zhushan Bay;the main source of phosphorus-containing organic matter in lake sediments is endogenous algae residues,and eutrophic lakes with higher algal biomass have occurred faster enzymatic hydrolysis,mineralization and metabolic process;APA plays an important role in promoting the hydrolysis of phosphate monoesters to active phosphates.The rapid sedimentation-remineralization mechanism and APA play an important role in maintaining eutrophication in eutrophic lakes.