Abstract:

Soil nitrogen and phosphorus in water fluctuation zone are one of the potential sources and the nutrients for the upper layer water column.Nitrogen and phosphorus concentration among five representative tributary in Three Gorges Reservoir Area were analyzed before the impoundment of Three Gorges Reservoir to a water level of 172 m at the end of 2008.It was found that mean of soil total nitrogen in study area was 1317±0484 mg/g with variation range of 0459~2735 mg/g，while that of phosphorus was 0676±0282 mg/g with a range of 0314~2799 mg/g.Soil total nitrogen from different type of landuse showed significant difference.Soil nitrogen in agriculture farmland and fruit gardens was remarkably higher than those in riverbank and flood plains.Difference of soil nitrogen was also observed among different tributaries，the soil nitrogen in Zhuyi Basin and Daning Basin was obviously higher than in the other basins.However，the soil phosphorus among various types of landuse in the study area as well as different basins showed no significant difference.Compared with some shallow lakes in the downstream plain of the Yangtze basin，soil total nitrogen and total phosphorus were high relatively，and had a potential risk of releasing to the upper layer water column.Fengle town and Yanglu town in Xiaojiang River and Hujiaba town in Zhuyi River were the highest risk to release nitrogen and phosphorus in study areas.