Abstract:

Continuously submerged and intermittently submerged sediments collected from Shendinghe River estuary of Danjiangkou reservoir,were employed to conduct the dynamic water level(WL) regulation experiments with 3 rates of change of water level (0 cm.d^-1,3 cm.d^-1 and 6 cm.d^-1).The whole experiments lasted three WL regulating cycles (nearly four months) and each single cycle included four WL dynamic phases:decline,stable,ascend and re-stable.The results show that:WL regulation promotes OM loss of sediment and results in the increase of pH value.When compared with the data without WL regulated control,3 cm.d^-1 and 6 cm.d^-1 WL regulations lead to the increase of 185.56%-204.92%(continuously submerged sediments) and185.28%-228.76%(intermittently submerged sediments) in concentrations of amorphous iron oxides,respectively.Furthermore,after WL regulation, concentrations of exchangeable phosphorus (Ex-P),aluminum bounded phosphorus (Al-P),iron bounded phosphorus (Fe-P),calcium bounded phosphorus (Ca-P) and total phosphorus (TP) increase in intermittently submerged and continuously submerged sediments,whereas OM loss,occluded phosphorus (O-P) activation and transformation,greatly contribute to the decline of organic phosphorus (Org-P) and O-P in sediment.With respect to the activation of Org-P and O-P under WL regulation,both of the two phosphorus fractions should be categorized into bio-available phosphorus components.

Key words: phosphorus, sediment, water level regulation, physical and chemical properties, activation