Monitoring and comprehensive assessment of total nitrogen in Danjiangkou Reservoir.

Concentrations of total nitrogen (TN) in Hanjiang reservoir of Dangjiangkou Reservoir were monitored and comprehensive analyzed based on the optimized sampling points. The obtained TN concentrations in recent years were maintained at a certain level,without obvious decrease trend. TN concentration in 2008 was higher than the maximum permissible values of Environmental Quality Standard for Surface Water of GB3838-2002,which had a relatively high level in those of environmental monitoring network of surface water in Hubei Province,with TN as the highest content in wet period and at the end of reservoir while the lowest value in level period and at the largest bay. Outside contamination from rivers might be the most significant source of TN in the Reservoir of Han River,probably because of the upstream soil erosion,agricultural non-point source pollution as well as industrial and domestic effluents. Consequently,further pollution control of Danjiangkou Reservoir should be strengthened,including environmental monitoring of sediment in the Reservoir.