Concentration of nutrients in the soil in water-level-fluctuating zone of Three Gorges Reservoir

Contents of nutrients in the surface soil in the water-level-fluctuating zone of Three Gorges Reservoir was investigated. Soil samples were collected at 57 sampling stations from Wushan County to Chongqing City in April 2010. The average organic matter concentration was 10.636±4.401 mg g-1 with a range of 1.097–19.947 mg g-1, total nitrogen was 0.865±0.423 mg g-1 with a range of 0.127–1.903 mg g-1, and total phosphorus was 0.595±0.222 with a range of 0.205–1.365. Variability of organic matter and total nitrogen concentrations between sampling sites was high, whereas total phosphorus concentration was little diversified. Results of TOC/TN analysis showed that organic matter in surface soils was mainly derived from sedimentation of biomass. Nitrogen and phosphorus in soils of the water-level-fluctuating zone could become potential pollution sources. Therefore, more attention should be paid to the potential impact of nitrogen and phosphorus in soils of this zone on reservoir eutrophication. Single standard index of total nitrogen ranged from 0.72 to 2.12 and was generally above 1, indicating relatively serious nitrogen pollution. However, total phosphorus concentration was relatively low, with standard index values ranging from 0.83 to 1.40, indicating that the phosphorus pollution is not very serious.