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| 1 | Effects of sediment physical properties on the phosphorus release in aquatic environment显示文摘Particle size, porosity, and the initial phosphorus concentration in sediments are the main factors affecting phosphorus release flux through the sediment-water interface. Sediments can be physically divided to muddy and sandy matters, and the adsorption-desorption capacity of sediment with phosphorus depends on particle size. According to phosphorus adsorption-desorption experiments, phosphorus sorption capacity of the sediment decreases with the increase of particle dimension. But among the size-similar particles, sediment with a bigger particle size has the larger initial phosphorus release rate. In terms of muddy and sandy sediments, there are inversely proportional relationships between the release rate and the flux. Due to the contact of surface sediment and the overlying water, the release flux from the sediment is either from direct desorption of surface sediment layer or from the diffusion of pore water in the sediment layer, which is mainly determined by sediment particle size and porosity. Generally, static phosphorus release process may include two stages: the first is the initial release. As for coarse particles, phosphorus is desorbed from surface sediment. And for fine particles, phosphorus concentration in water often decreases, mainly from pore water by the molecular diffusion. During the second stage, pore water flows faster in coarse sediment, and phosphorus is easy to desorb from the surface of the particles as diffusion dominates. For the smaller liquid-solid ratio of fine particles and the larger amount of phosphorus adsorption, the release flux from pore water due to diffusion is very small with longer sorption duration. | ZHU HongWei WANG DaoZeng CHENG PengDa FAN JingYu ZHONG BaoChang | 2015 | Science China(Physics,Mechanics & Astronomy)2015，58，2： | 8 |
| 2 | The mechanisms of contaminants release due to incipient motion at sediment-water interface显示文摘Sediments in many rivers and lakes are subjected to resuspension due to a combination of hydrodynamics.However,the roles of contaminant-contained dissolved and particulate sediments during the resuspension release are rarely studied.This study focuses on the release quantity of contaminants in both water phase and solid phase.Conservative tracer(NaCl)and reactive tracer(Phosphorus)were respectively added to cohesive fine-grained sediments and non-cohesive coarse-grained sediments.A range of typical shear stress was conducted to characterize the time-depended release of contaminants in a laboratory flume.When the sediment started to move,the concentration of contaminant in the overlying water increased with the bed shear stress,but the dissolved contaminants responded faster than the particulate ones.The observed contaminant release process can be divided into three main stages:the initial two hours fast mixing:the release contribution of pore water could reach up to 75%;the middle 4–6 h adsorption:the partitioning coefficient of contaminant between water phase and solid phase decreased over the time,and the adsorption of contaminates from resuspended sediment dominated the negative release;the last equilibrium stage:the desorption and adsorption reached equilibrium,and the reactive contaminant made an impact on the water quality in the solid phase.The existing formulas to evaluate the release flux are far from practice meaning as the sediment contaminants undergo a very complex release process. | ZHU HongWei CHENG PengDa ZHONG BaoChang WANG DaoZeng | 2014 | Science China(Physics,Mechanics & Astronomy)2014，57，8： | 4 |
| 3 | Transport mechanisms of contaminants released from fine sediment in rivers显示文摘Contaminants released from sediment into rivers are one of the main problems to study in environmental hydrodynamics. For contaminants released into the overlying water under different hydrodynamic conditions, the mechanical mechanisms involved can be roughly divided into convective diffusion, molecular diffusion, and adsorption/desorption. Because of the obvious environmental influence of fine sediment( D90 = 0.06 mm), non-cohesive fine sediment, and cohesive fine sediment are researched in this paper, and phosphorus is chosen for a typical adsorption of a contaminant. Through theoretical analysis of the contaminant release process, according to different hydraulic conditions, the contaminant release coupling mathematical model can be established by the N–S equation, the Darcy equation,the solute transport equation, and the adsorption/desorption equation. Then, the experiments are completed in an open water flume. The simulation results and experimental results show that convective diffusion dominates the contaminant release both in non-cohesive and cohesive fine sediment after their suspension, and that they contribute more than 90 % of the total release. Molecular diffusion and desorption have more of a contribution for contaminant release from unsuspended sediment. In unsuspension sediment, convective diffusion is about 10–50 times larger than molecular diffusion during the initial stages under high velocity; it is close to molecular diffusion in the later stages. Convective diffusion is about 6 times larger than molecular diffusion during theinitial stages under low velocity, it is about a quarter of molecular diffusion in later stages, and has a similar level with desorption/adsorption. In unsuspended sediment, a seepage boundary layer exists below the water–sediment interface,and various release mechanisms in that layer mostly dominate the contaminant release process. In non-cohesive fine sediment, the depth of that layer increases linearly with shear stress. In cohesive fine sediment, the range seepage boundary is different from that in non-cohesive sediment, and that phenomenon is more obvious under a lower shear stress. | Pengda Cheng Hongwei Zhu Baochang Zhong Daozeng Wang | 2015 | Acta Mechanica Sinica2015，31，6： | 3 |
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