Release And Bioavailability Of Internal Phosphorus In Shallow Lakes

This dissertation aimed to explore the relationship between internal phosphorus and artificial eutrophication of shallow lakes. A case study on the transformation of phosphorus forms, the pattern and risk of phosphorus release, and the bioavailability of phosphorus in the lake sediments was carried out in three shallow lakes in the middle and lower reaches of the Yangtze River.Firstly, the occurrence and spatial distribution of phosphorus forms in the sediments of Taihu Lake, Chaohu Lake and Longganhu Lake were investigated by using two methods—SMT and EDTA for phosphorus fractionation. It was shown that both iron/aluminum bound phosphorus and organic phosphorus in the sediments have important anthropogenic sources. They were significantly correlated with amorphous iron/aluminum oxides and organic matter contents in the sediments, which may contribute to the spatial variation of the concentrations of phosphorus forms. Anthropogenic inputs also contribute partially to the distribution of calcium bound phosphorus concentrations. The elevation of pH values of the overlying water would cause the release of iron/aluminum bound phosphorus and accumulation of calcium bound phosphorus in the sediments. There was large difference in organic phosphorus species in lake sediments with different trophic status. The transformation of acid extractable organic phosphorus was one of important processes in the lake eutrophication.Second, chemical speciation of phosphates in the pore water was simulated by...