[Effect of disturbance intensity on phosphorus release and its transformation in the sediment from Taihu Lake].

Lab-scale experiments were conducted to investigate the effect of sediment disturbance under different intensity conditions on phosphorus (P) release and sedimentary P transformation. The sediments came from Taihu Lake. The results show that the concentrations of total P (TP), particulate P (PP) and dissolved total P (DTP) in the overlying water under high intensity conditions (equal to the force of 12 m x s(-1) wave velocity on the bottom sediment in Taihu Lake) were higher than those under low intensity conditions (equal to the force of 8 m x s(-1)). The concentrations of TP and PP were up to 0.950 mg x L(-1), 0.384 mg x L(-1) and 0.882 mg x L(-1), 0.328 mg x L(-1) for both intensities after 1 h and then the levels kept unchanged almost till the end of the experiments. However, the DTP decreased gradually. It is attributed to the adsorption by suspended sediments and quick uptake by microorganisms. Under both intensities conditions, the Tot-P of the suspended particulate matter (SPM) due to disturbance increased by 10 mg x kg(-1) (mean during 0-12 h) and 60 mg x kg(-1) (mean during 0-12 h). The changes of Fe/Al-P during the experiment (0-12 h) verified the transformation trend between sedimentary P forms in the SPM under high intensity. Because the net increase (85.7 mg x kg(-1), mean during 0-12 h) was higher than the measured value (10 mg x kg(-1), mean during 0-12 h) and the theoretically calculated value (27 mg x kg(-1), mean during 0-12 h). It suggests that other sedimentary P forms were transformed into Fe/Al-P. Correspondingly, the decrease of NH4Cl-P and HCl-P can verify this. It suggested that sediment disturbance might induce the indirect transformation between sedimentary P forms by the assistance of overlying water.