Phosphorus transport and speciation in the Changjiang (Yangtze River) system

Dissolved and particulate samples were collected from the Changjiang (Yangtze River) in April and September 2006 to determine the sources and distribution of P species in the river system. Concentrations of DIP, DOP and TP varied obviously throughout the basin, and displayed short-term variability and seasonal change. The predominant species of DTP was PO43-. The concentrations of P are related to water discharge, suspended particulate matter and anthropogenic influences. Based on the study data, the nutrient and the sediment retention capacity of the Three Gorges Reservoir (TGR) were quantified. The P species structure has a significant change throughout the TGR. A mass balance analysis revealed that the reservoir was temporarily acting as a DOP source. Some long-term data for PO43- concentration at the Datong station are presented. The PO43- level has increased in the last three decades because of the increased use of chemical fertilizer.