Experiment on Sediment Ammonia Nitrogen Release of Chaohu Lake in Varying Hydrodynamic Disturbance

Abstract

Shallow water has low depth, and hydrodynamic conditions may change with the effect of wind and waves, resulting in sediment suspension and pollutant release. To investigate the influence of sediment incipient motion on ammonia nitrogen (NH3-N) release in shallow lakes under hydrodynamic disturbance, we monitored ammonia nitrogen concentration in the overlying water of sediments in Chaohu Lake under static, weak, and strong disturbance conditions and analyzed the ammonia nitrogen release rate based on the these concentrations. In static condition, the sediment particles on the surface moved individually (individual movement), and the ammonia nitrogen release rate was 9.59 mg/m2/day. When the disturbance was weak and a small proportion of sediment particles started to move (small movement), the ammonia nitrogen release rate increased to 34.21 mg/m2/day. When the disturbance was further strengthened, and most of the sediment particles moved (general movement), the ammonia nitrogen release rate was 77.04 mg/m2/day. Distribution showed that the release rate varied the most in the western area followed by the eastern area, and the central area had the lowest release rate. The daily release of ammonia nitrogen in Chaohu Lake ranged from 8742.3 kg to 61,008.59 kg. In this experiment, we combined sediment movement and pollutant release, which provides a new reference for the study of pollutant release in shallow lakes and for ammonia nitrogen management in other shallow lakes.