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 (F-ss) 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/m(2), respectively. However, flux of P across sediment-water interface (F-p) 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/m(2). A rapid increase of Fp at the first 30 min was observed under moderate wind, with maximal flux of 11.2 +/- 0.6 mg/m(2). Surprisingly, strong wind caused less Fp than under light and moderate wind conditions with maximal flux of 3.5 +/- 0.9 mg/m(2). 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.