Abstract: Study on the variation characteristics and flux of total nitrogen(TN) and total phosphorous (TP) in soil in the water-level-fluctuation zone of Danjiangkou reservoir is of practical significance for clarifying the pollution output characteristics and protecting the water quality of the reservoir. In this paper, Danjiangkou reservoir was divided into Hanku reservoir and Danku reservoir. The variation characteristics of TN and TP in soil in the typical water-level fluctuation zone of Danjiangkou reservoir in different periods from September 2020 to September 2021 were monitored and analyzed. In addition, the TN and TP fluxes were estimated by using the break-even model. Results reveal that during the flooding period from September 2020 to December 2020, the content of TN and TP in different water-level-fluctuating areas of Danjiangkou reservoir changed significantly. To be specific, the content of TN and TP in the farmland and garden fields of Hanku reservoir increased notably, while TN and TP were lost in other areas. During the water-level-falling dry period from March 2021 to June 2021, the content of TN and TP in different water-level-fluctuation zones of Danjiangkou reservoir showed an increasing trend on the whole. From September 2020 to September 2021, the content of TN and TP in different water-level-fluctuation zones of Danjiangkou reservoir displayed a decreasing trend. During flooding period, the water-level-fluctuation zone of Danjiangkou reservoir acted as the release source of nitrogen and phosphorus, with TN flux reaching 834.66 t and TP flux 10 422.12 t. During water-level falling dry period, the water-level-fluctuation zone of Danjiangkou reservoir acted as the sink of nitrogen and phosphorus, with TN flux of -8 623.69 t and TP flux -10 032.94 t. From September 2020 to September 2021, the water-level-fluctuation zone of Danjiangkou reservoir acted as the release source of nitrogen and phosphorus on the whole, with TN flux amounting to 20 122.22 t and TP flux 1 509.52 t. The pollutant release risk of water-level-fluctuation zone of Danjiangkou reservoir should not be ignored as it poses a threat to the water quality of the reservoir.

Key words: water-level-fluctuating zone, TN, TP, flux, Danjiangkou reservoir