The Connection Of Fractionation, Migration And Transformation Of Phosphorus In Sediments Of Chaohu Lake And Occurrence Of Water Bloom

Lake eutrophication is one of the most important water environmental problems in our country.Eutrophic lake sediments as a lake nutrient stores, outside source to gradually brought under control conditions, can release nutrients to the water, so for a long period of time to maintain water eutrophication. Therefore, the deep discussion about Fractionation, migration and transformation of phosphorus in lake sediments will be of great significance for the defense and control of eutrophication.In my thesis, based on the site monthly surveys and the summer enclosure,and systematically studied the different phosphorus sediments, the space and time distribution and law of interchange in the mud interface, and the interaction between transformation of phosphorus in sediment and water bloom.Major work and conclusions are as follows:The concentrations of the total P (TP) in the surface sediment from western lake were obviously higher than eastern lake. The proportion of active P was accounted for 44%~81% of TP. NaOH-P as main existent of active P accounted for 47%~60% of TP in the western lake, which plays an important role in phosphorus release to overlying water. The study of vertical distribution of phosphorus in sediments indicate that the quantity of NaOH-P and BD-P decrease as the increasing depth, which shows that human activities' pollutional load to P in sediment of Chaohu Lake have a increasing trend. The quantity of DTP,DIP and DOP in inerstitial water inwestern lake were higher than eastern lake.Phosphorus concentration grads in water - sediment interface provide a condition for sediment spread to water-body. Different P speciations in the interstitial water were significantly correlated with TP,BD-P and NaOH-P in the sediment。By a comparison of the before and the peak of the water bloom . It was found that: the percent of NH4Cl-P and BD-P decrease when the large-scale cyanobacteria booms outbreak, particularly, the release of BD-P is obvious; the release of NaOH-P mainly occurred before the large-scale cyanobacteria booms . The large-scale outbreak of cyanobacteria booms and decomposition of dead algae will change the biochemical environment of the water-sediment interface, when the release of BD-P is particularly important.The seasonal variation of phosphorus speciations in the sediments and the pore water were studied by collecting the surface sediments in different seasones from Lake Chaohu: the DTP and DIP of pore water significantly decrease in summer and upturn in autumn. Compared with the overlying water it was found that pore water phosphorus' tendency to spread towards overlying water is biggish in spring and autumn. Org-P, BD-P and NaOH-P were closely correlated with the water bloom. Org-P was declining from spring to winter in western lake. In western lake, BD-P was reduced gradually from spring to winter, but in eastern lake, it was improved in autumn. In western lake, NaOH-P was the lowest in summer, it wouid rise gradually in autumn, but in eastern lake, it was stable in the four seasons .Through the analysis of sediment physical and chemical properties, focusing on the distribution feature of APA , APA is closely related with phosphorus transformation, finally,the sediment TN and LOI was found significantly associated. There is a higher level of APA West Lake District, while Chaohu 's APA has a decreasing trend with depth.Experiment shows that: water bloom will promote the sediment releasing phosphorus to overlying water bodies, at the same time promote the TP and APA of overlying water to increase, and the higher the nutrition level in sediment,the greater of the increaseing-degree for TP and the APA, on the contrary, the PH and DO of overlying water will be more lower. When sediments in the same nature, the higher level of nutrition for the overlying water, the more easily to release for NH4Cl-P and Org-P ; the lower level of nutrition, the more easily to release for BD-P. Submerged plant Hydrilla verticillata can reduce the amount of chlorophyll, improve the levels of PH and DO in water bodies,absorb phosphate in water, inhibit APA in water. At the same time the existence of Hydrilla verticillata can reduce the amount of TP, BD-P, NaOH-P, Org-P and HCl-P in sediment .