Effects of hydrodynamics processes on phosphorus fluxes from sediment in large, shallow Taihu Lake

The turnover of phosphorus (P) in lake sediments, a major cause of eutrophication and subsequent deterioration of water quality, is in need of deep understanding. In this study, effects of resuspension on P release were studied in cylindrical microcosms with Y-shape apparatus. The results indicated that there was a positive correlation between flux of suspended substance across sediment-water interface (Fss) and the wind speed, and an increasing FSS during each wind process followed by a steady state. The maximal FSS under light, moderate, and strong wind conditions were 299.9±41.1, 573.4±61.7, and 2093.8±215.7 g/m2, respectively. However, flux of P across sediment-water interface (FP) did not follow a similar pattern as Fss responding to wind intensity, which increased and reached the maximum in initial 120 min for light wind, then decreased gradually, with maximal flux of 9.4±1.9 mg/m2. A rapid increase of FP at the first 30 min was observed under moderate wind, with maximal flux of 11.2±0.6 mg/m2. Surprisingly, strong wind caused less FP than under light and moderate wind conditions with maximal flux of 3.5±0.9 mg/m2. Fss in water column declined obviously during the sedimentation process after winds, but FP varied with wind regime. No obvious difference was detected on FP after 8 h sedimentation process, compared with the initial value, which means little redundant P left in the water column after winds.