[Spatio-temporal variation of nitrogen, phosphorus in different period in Three Gorges Reservoir after its impoundment].

It is very important to investigate the change of nutrient in Three Gorges Reservoir for analyzing the influence after normal storage and proposing reasonable management methods. The water quality parameters were determined monthly from March in 2008 to February in 2009. Six horizontal monitoring sites and one vertical site were set in Three Gorges Reservoir. The period was separated into two different periods with taking account of the water level after the Three Gorges Reservoir storaged water, which were October-February and March-September respectively. Then, the spatial-temporal variation characteristics of nutrient and environmental features in different periods were studied with the water quality data. The results showed that there were no significant differences of water quality parameters except DO in different periods. There were also no significant differences of the vertical distribution of hydrology, water quality indexes among the three observed levels. The concentration of DO in high water level (8.29 mg/L)was higher than that in low water level (7.49 mg/L) and the mean of saturation degree of DO was 83.5%. Total nitrogen (TN), NH4+ -N, total phosphorus (TP) values were 1.42-2.23 mg/L, 0.15-0.36 mg/L, 0.08-0.14 mg/L respectively, and plane of nutrition in high water level was higher than that in low water level. The main factor influenced the concentrations of TN, NH4+ -N and TP were rainfall runoff process. Significantly positive correlation was observed by correlation analysis between nutrients fluxes and the flux at the section Cun Tan. The fluxes of TN, NH4+ -N, TP were 368.4, 97.2, 29.5 thousands tons respectively, and the non-point pollution accounts for more than 55.5%.