The Distribution Characteristics of Soil TP and IP forms at the Xiangxi River Riparian Zone in the Three Gorges Reservoir

The soil samples along the Xiangxi River bank in the Three Gorges Reservoir were collected at exposed period. The total phosphorus and inorganic phosphorus contents in soil were determined, and their distribution characteristics were analyzed. The results show that the average content of TP is 1.0735g.kg(-1) (145-175m) and 1.225g.kg(-1) (175-185m) respectively. The downstream and upstream has the maximum and minimum values respectively. Ca-P and O-P are the major IP forms of Xiangxi River riparian zone. The midstream and upstream (145-175m) has the maximum and minimum content of Al-P and Fe-P respectively, while the downstream (175-185m) has maximum content of Al-P and Fe-P respectively. The downstream (145-185m) has minimum content, while the upstream and midstream has the maximum content of WS-P and O-P respectively. The upstream and downstream (145-185m) has the maximum and minimum content of Ca-P respectively. The bio-available phosphorus content decreased gradually and bio-unavailable phosphorus content increased gradually from downstream to upstream.