Fractionation of Phosphorus in Sediments of Eutrophic Lake and River

Fractionation of phosphorus was carried out ; organic P, calcium P, aluminum P, iron P and residual P were determined in sediments of Lake Inbanuma, a eutrophic lake, and the Shinkawa River, an organic polluted river entering the lake. Large differences between the lake and the river were observed in both the concentration and percentage of fractionated P in the surface sediments. The enrichment in aluminum P and iron P observed in the river surface sediments seemed to result from domestic sewage entering the river. Changes of fractionated P in the surface sediments with the water flow from the river to the lake corresponded to those in the overlying water. From these correspondences the sedimentation process of P and the possibility of P release from the sediment into the overlying water were considered. Vertical profiles of fractionated P indicated a recent marked increase of P loading which is attributed to domestic sewage entering the river.