Phosphorus release characteristics of different trophic lake sediments under simulative disturbing conditions

The effect of simulative disturbing on phosphorus (P) release characteristics and the differences of the P buffering capacity of different trophic lake sediments were investigated. The magnitudes of the dissolved total phosphorus (DTP), soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) released from the studied sediments increased with the increasing of disturbing intensity. The equilibrium time of the DTP release from the heavily polluted sediments was approximately 16 h, and that from the slightly polluted sediments was 8 h. This may be related to the difference of P forms in the different trophic sediments. About 30% of the DTP released from Wuli Lake and Yue Lake was from DOP, about 60% and 50%, respectively, was from Gonghu Lake and East Taihu Lake. DOP was the important fraction of DTP released. The effect of disturbing on P release was related to both disturbing intensity and sediment pollution level. After the disturbing stop, the DTP, SRP and DOP concentrations in the overlying water of the different sediments decreased rapidly within 3, 10 and 3 h, respectively, then gradually reached equilibrium at different time for the sediments with different pollution level. The different trophic lake sediments had different P buffering capacity, P buffering capacity of the slightly polluted sediments was lower at the initial lower SRP concentrations and was higher at the initial higher than that of the heavily polluted sediments.