[Phosphorus forms and its distribution characteristics in sediments and soils of water-level-fluctuating zone of the backwater reach from input river of Three Gorges Reservoir].

The contents of different phosphorus forms in surface sediments and the soils of water-level-fluctuating zone of the backwater reach from input river of Three Gorges Reservoirwere measured, using thestandard measurement and test (SMT) procedure of phosphorus forms in freshwater sediments. Correlation coefficients between phosphorus forms and sample geochemical characteristics, such as organic matter and major components were analyzed. The results indicated that the TP content in surface sediments varied from 483.4-848.4 mg/kg, and the average content was 569.0 mg/kg. The TP content in surface sediments placed in the mid-lower level, comparing with the TP content in surface sediment from the shallow lakes in the middle and lower reaches of Yangtze River. The TP content in soils of water-level-fluctuating zone varied from 488.9-1487.7 mg/kg, and the average content was 813.3 mg/kg. The average content of TP in soils of water-level-fluctuating zone whole exceeded the surface sediment, indicating of the influence of human's activity on phosphorus contents in soils of water-level-fluctuating zone. Distribution characteristics of phosphorus forms were different between the sediment and soils of water-level-fluctuating zone: (1) The ratio of IP/TP in the surface sediments (average value 55.7%) was higher than that in soils of water-level-fluctuating zone (average value 49.4%); (2) The domination phosphorus forms of IP in surface sediments was Ca-P (average ratio 83.5%), and the ratio of (Fe/Al-P)/IP was only 15%. The average ratio of Ca-P/IP in the soils of water-level-fluctuating zone was 73.9%, whereas the ratio of Fe/Al-P in IP raised to 22%; (3) The average content of active phosphorus (OP + Fe/Al-P) in surface sediment was 261.8 mg/kg, the average ratio of active phosphorus in TP was 49%, whereas the average content of active phosphorus (OP + Fe/Al-P) in soils of water-level-fluctuating zone was 405.7 mg/kg, the average ratio was 54%. The active phosphorus in soils of water-level-fluctuating zone would become potential pollution sources of water under correct environmental conditions,therefore, the potential impact of phosphorus on water eutrophication in soils of water-level-fluctuating zone couldn't be neglected.