The mechanisms of contaminants release due to incipient motion at sediment-water interface

Zhu, Hongli; Cheng, Pengda; Zhong, BaoChang; Wang, Dao-zeng

doi:10.1007/s11433-013-5255-6

Cited by 9 publications

(7 citation statements)

References 7 publications

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“…The main difficulty lies in sediment desorption-adsorption behaviors and are influenced by many factors, such as contaminant characteristics, particle properties, sediment transport, and flow turbulence. As mentioned above, the time scale of desorption is far more than the sediment movement and is very sensitive to the experimental conditions [15]. Vertical pollutants distributions are closely related to suspended sediment.…”

Section: Introductionmentioning

confidence: 99%

Empirical model for estimating vertical concentration profiles of re-suspended, sediment-associated contaminants

Zhu

Cheng²,

et al. 2017

Acta Mech. Sin.

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Vertical distribution processes of sediment contaminants in water were studied by flume experiments. Experimental results show that settling velocity of sediment particles and turbulence characteristics are the major hydrodynamic factors impacting distribution of pollutants, especially near the bottom where particle diameter is similar in size to vortex structure. Sediment distribution was uniform along the distance, while contaminant distribution slightly lagged behind the sediment. The smaller the initial sediment concentration was, the more time it took to achieve a uniform concentration distribution for suspended sediment. A contaminants transportation equation was established depending on mass conservation equations. Two mathematical estimation models of pollutant distribution in the overlying water considering adsorption and desorption were devised based on vertical distribution of suspended sediment: equilibrium partition model and dynamic micro-diffusion model. The ratio of time scale between the sediment movement and sorption can be used as the index of the models. When this ratio was large, the equilibrium assumption was reasonable, but when it was small, it might require dynamic micro-diffusion model.

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Section: Introductionmentioning

confidence: 99%

Empirical model for estimating vertical concentration profiles of re-suspended, sediment-associated contaminants

Zhu

Cheng²,

et al. 2017

Acta Mech. Sin.

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“…在磷溶液充分浸泡下的厚度为H 的底泥沉积物中, 溶解态磷向上覆水体的扩散方程可以写为 [8]   混作用机理的贡献比 R i 定义为 [5] , 用分配系数 p K 表征上覆水体中吸附性污染物在固液相之间的分配关系, 即 [5,8] solid , (2) 泥沙污染物起动再悬浮释放的累积通量. 单位沉积物中污染物质量是颗粒态和溶解态的量之和 q (mg)的表达式为 [7,8]…”

Section: 结果与分析unclassified

“…一方面, 水体中悬浮泥沙的运动、输移直接影响着污染物在固-液两相间的分配关系和时空分布; 另一方面, 污染物随泥沙沉积到底床中, 沉积底泥成为潜在的重要污染"源"或"汇", 在一定的水动力扰动和环境条件下会发生"源"、 "汇"机制的转换 [5][6][7] . 水体中污染物和泥沙颗粒之间的相互作用使得泥沙成为污染物在河流、湖泊水体中扩散、迁移和转化的主要载体, 从而影响水生态环境, 泥沙对环境的这种作用称为泥沙的环境效应 [8] .…”

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“…受水动力影响, 含沙水体经常与底床发生泥沙交换, 当有明显的再悬浮和沉降发生时, 部分泥沙颗粒就会进入或者脱离水层 [23] . 底泥颗粒起动再悬浮时, 污染物通过再悬浮泥沙颗粒的吸附解吸作用和孔隙水的掺混作用影响上覆水质 [5][6][7] . 存在于底泥沉积物中的吸附性污染物随着泥沙的再悬浮被释放到水体中, 在起动阶段已经有一些污染物参与了释放过程, 但泥沙释放污染物释放的过程不会消失, 会随着再悬浮泥沙作进一步的释放, 此时水体中悬浮泥沙是吸附性污染物发生解吸吸附的主要载体 [24] .…”

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Physical processes and influencing factors of contaminants release due to resuspended sediments in water environment

Zhu¹,

Wang²,

Fan³

et al. 2015

Sci. Sin.-Phys. Mech. Astron.

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“…Laboratory experiments such as oscillating grids [9], annular tanks and open water channels have been conducted to study the contaminated sediment release regularly under conditions of flowing water [10,11]. By using the annular tank test, the law of sediment suspension and release were simulated by different disturbance forces [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Transport mechanisms of contaminants released from fine sediment in rivers

et al. 2015

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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 (D 90 = 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 the initial 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.

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The mechanisms of contaminants release due to incipient motion at sediment-water interface

Cited by 9 publications

References 7 publications

Empirical model for estimating vertical concentration profiles of re-suspended, sediment-associated contaminants

Empirical model for estimating vertical concentration profiles of re-suspended, sediment-associated contaminants

Physical processes and influencing factors of contaminants release due to resuspended sediments in water environment

Transport mechanisms of contaminants released from fine sediment in rivers

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