LIU Jing ^1,2 , ZHANG Xinyu ³ , WEI Huaibin ⁴

(1. College of Water Resources, North China University of Water Resources and Electric Power, Zhengzhou 450046, China;

2. School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom;

3. School of Water Conservancy, North China University of Water Resources and Electric Power, Zhengzhou 450046, China;

4. School of Management and Economics, North China University of Water Resources and Electric Power, Zhengzhou 450046, China)

Abstract: To reveal the " source / sink" characteristics of nutrients in the hyporheic zone of sluice-controlled river, this study took Huaidian sluice channel of Shaying River in Huaihe River Basin as the research object, and carried out an in-situ sediment collection experiment under the background of water storage regulation in mid-January, 2021. By analyzing the distribution and diffusion flux of nitrogen and phosphorus nutrients at the sediment-water interface, the " source / sink " role of nutrients in the hyporheic zone was identified, and the endogenous risk of sluice-controlled rivers was ascertained. The results show that: 1) the concentrations of NH+4-N and TP in interstitial water are 6. 5 and 1. 1 times of those in overlying water, respectively, which indicates that the reis asign if icant concentration gradient of nutrients at the sediment-water interface, which easily leads to the migration of NH+4- N and TP in the hyporheic zone to overlying water; 2) According to the comprehensive pollution index evaluation, the water quality of overlying water and interstitial water is in a state of heavy pollution or serious pollution, and the pollution degree under the sluice is significantly greater than that above the sluice, which indicates that the regulation of water storage has a negative impact on the waters down stream the sluice; 3) The exchange fluxes of NH+4-N, NO -3-N and TP at the sediment-water inter face are 0.39-10.07,-3.45--2.04 and -0. 03 - 0. 17 mg / ( m 2 ·d) respectively, indicating that the sediment is the " source" of NH+ 4-N,“sink” of NO-3-N,and both “ source and sink” of TP; 4) Spatially, S2 ( at the stilling basin downstream the sluice) and S4 ( at the nutrient deposition section downstream the sluice) are the main enrichment places of nitrogen and phosphorus, among which S2 mainly exists in the form of ammonia nitrogen, with the largest contribution ratio to water quality ( up to 59. 03%) and the high estintrogen to phosphorusr atio( 13. 25) , which is suitable for the explosive growth of algae; 5) The release of endogenous NH+4-N in S2 ist he key to the endogenous prevention and control of Huaidian sluice River under the background of water storage regulation. Reducing the input of exogenous pollutants and optimizing the regulation of sluices are crucial to improving the water environment of sluice-controlled rivers.

Key words: sluice-controlled river; hyporheic zone; sediment-water interface; nutrients diffusion flux