Phosphorus Speciation and Distribution in Sediments and the Relationship with Total Phosphorus in the Overlying Water

To study phosphorus (P) speciation and distribution in lake water and sediments, and the relationship with total P (TP) in the overlying water, the concentration of different forms of P in lake water and sediments was determined. Samples were collected from Xuanwu and Dong Lakes. The results indicated that the concentration of P in sediments was largely influenced by human processes, vegetation, hydraulic conditions, and geographic settings. The inorganic P (IP) content was much higher than the organic P (OP) content, while NaOH-extractable P (NaOH-P) was the main inorganic P fraction, accounting for 40–50% of IP. The HCl-extractable P (HCl-P: calcium (Ca) bound P) content was low but stable, because Ca bound P was not easily adsorbed. The TP content of lake water and sediments were positively correlated, as was NaOH-P and apatite P (AP), while there was no obvious correlation between the TP content of lake water and OP and HCl-P. This suggests that labile P accounted for most of the exchange capacity of P at the water-sediment interface. The results indicated that the content of P in lake-bottom sediments was closely related to the concentration in lake water, providing a theoretical basis for the treatment of eutrophic water bodies with regard to the internal P loading.