Abstract: The aim of this research is to explore the risk and law of endogenous static release of nitrogen and phosphorus of Shengzhong Lake in winter. In the winter of 2018, water samples and sediment samples were collected from 15 sampling sites in Shengzhong Lake. The conventional physical and chemical indexes of water body and the nitrogen and phosphorus content in sediment interstitial water were determined. Meanwhile, the endogenous static release of nitrogen and phosphorus in sediments were simulated in laboratory. Results unveil that i) the total nitrogen content in the sediment interstitial water of Shengzhong Lake ranges from 1.846 mg/L to 5.293 mg/L. Ammonia nitrogen is the dominant form of total nitrogen, reaching 0.437-3.603 mg/L, followed by nitrate nitrogen, at 0.545-1.452 mg/L. Various forms of nitrogen and phosphorus differ remarkably in spatial distribution. ii) The content of total phosphorus in interstitial water is ranged from 0.194 mg/L to 0.561 mg/L, of which the content of dissolved orthophosphate stands between 0.029 mg/L and 0.417 mg/L. iii) Endogenous static release of nitrogen and phosphorus was observed in the Shengzhong Lake in winter. The risk of phosphorus release is greater and its release regularity is more obvious; whereas nitrogen mainly releases in the form of nitrate nitrogen, and ammonia nitrogen barely releases. The risk of endogenous release of nitrogen and phosphorus in the central area of the lake is lower than that in other areas. The research findings offer scientific basis for the implementation of management policies and sustainable utilization of water resources in the Shengzhong Lake.

Key words: sediment, interstitial water, nitrogen, phosphorus, static release, Shengzhong Lake