开展丹江口水库消落带土壤总氮(TN)和总磷(TP)变化特征与通量研究,对明晰消落带污染输出特征、保护水库水质安全有着重要的实践作用。将丹江口水库划分为汉库和丹库两个区域,以不同区域内典型消落带为研究对象,监测分析了2020年9月—2021年9月不同时期不同区域消落带土壤TN和TP的变化特征,并通过收支平衡法构建模型,估算了丹江口水库消落带在不同时期的TN和TP通量。结果表明,2020年9—12月淹水期内,丹江口水库不同区域消落带TN、TP含量变化显著,汉库耕地和园地的TN、TP含量显著上升,其余区域消落带土壤均存在TN、TP流失现象。2021年3—6月落干期内,丹江口水库不同区域消落带TN、TP含量总体上呈现上升积累趋势。2020年9月—2021年9月,丹江口水库不同区域消落带TN、TP含量整体呈下降趋势。丹江口水库消落带在淹水期表现为氮和磷的释放源,TN通量834.66 t,TP通量10 422.12 t;在落干期表现为氮和磷的吸收汇,TN通量-8 623.69 t,TP通量-10 032.94 t。2020年9月—2021年9月,丹江口水库消落带总体上表现为氮和磷的释放源,TN通量20 122.22 t,TP通量1 509.52 t。丹江口水库消落带污染物释放对水库水质安全的风险不容忽视。

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.