Characterization of the phosphate adsorption and morphology of sediment particles under simulative disturbing conditions

Abstract

The behavior of nutrient release and adsorption from sediments was influenced by hydrodynamic disturbance significantly. The resuspension/sedimentation processes of sediment particles and phosphate adsorption in Taihu Lake were investigated under different disturbing intensity by utilizing simulative conditions. The effect of morphological characteristics of suspended particles on phosphate adsorption was also studied. In order to elucidate the characteristics of particles suspended by disturbance, the size and structure of particles during different time were monitored on-line by using photometric dispersion and particles image analysis. The method of fractal geometry to explore the morphology characteristics of particles was also used. The results showed that sediments suspended obviously and the phosphate concentration of overlying water decreased rapidly when strong disturbance was applied. Moreover, two different disturbing conditions, one was static condition without wind and the other was weak disturbing intensity with slow wind velocity, following heavy disturbance were compared, and it turned out that the turbidity and phosphate concentration were lower in the latter because the size and the structure of suspended particles were more favorable in the latter disturbing condition. The flocculation index of suspended particles was 0.25 and characteristic length was 30 μm under 100 rpm disturbance; comparatively, when heavy disturbance increased to 120 rpm, the flocculation index grew up to 0.60 and the characteristic length was greater than 60 μm. The fractal dimensions of suspended particles were between 1.65 and 1.92.