Sediment phosphorus fraction and release potential in the major inflow rivers of Chaohu Lake, Eastern China

Surface sediment samples from nine inflow rivers of Chaohu Lake in Eastern China were analyzed by the sequential extraction procedure and the zero equilibrium phosphorus concentration (EPC0) was determined to evaluate the behavior of phosphorous at the water-sediment interface. The results reveal that substantial amounts of P had accumulated in river sediments from agricultural runoff and domestic sewage. For most of the sample sites, the total P content was higher in sediments from urban rivers than in those from rural rivers. On average, the reactive inorganic P consisted of slightly more than 60% of the total P, with Fe-P being the dominant P form. Compared with rural sediments, the Al-P contents were significantly higher in urban sediments, while the Res-P contents were significantly lower. The differences can be attributed to the differential discharge of P from watersheds with contrasting land uses and to the dramatic changes in the ambient conditions of urban rivers. A higher soluble reactive phosphorus (SRP) value of the overlying water relative to the EPC0 value in the mouth of the urban rivers of Chaohu Lake indicates that bottom sediments still play a role in adsorbing phosphorus from the water column before it reaches Chaohu Lake.