The mechanism of erosion of a riverbank is not easy to analyze and each sediment particle is under influence of number of forces. Among all these forces, force of cohesion between the particles plays a very dominant a...The mechanism of erosion of a riverbank is not easy to analyze and each sediment particle is under influence of number of forces. Among all these forces, force of cohesion between the particles plays a very dominant and significant role, and, till date, not much progress has been made to analyze this force in a deterministic manner. A particle is bound to its neighboring particles under this force of cohesion. In this paper, the analysis of forces acting on a particle on a riverbank has been made with a model called the Truncated Pyramid Model. A particle requires a certain velocity to escape from the riverbank and determination of the escape velocity can pave the way for finding out other parameters like entrainment rate, erosion coefficient and so on. Calculation and estimation of riverbank erosion rate is an important aspect of river basin management. In this paper it has been shown that the escape velocity is dependent on certain micro-level parameters like inter-particle distance and volume of the water bridge between two adjacent particles. Also, for saline water the particle requires less velocity to escape compared to the pure-water scenario. The findings of the present paper exactly fall in line with the results of another paper where the researchers showed that cohesive force between the particles decreases as water turns from pure to impure.展开更多
Researchers are paying more and more attention to the adsorption and transport of heavy metals in soil. In this study, laboratory experiments were performed to investigate the characteristics of adsorption and transpo...Researchers are paying more and more attention to the adsorption and transport of heavy metals in soil. In this study, laboratory experiments were performed to investigate the characteristics of adsorption and transport of mercury in soils of different locations in the western suburb of Beijing. To characterize the adsorption mechanism of mercury in soil, adsorption isotherms were determined through a batch experiment. Soil column experiments were performed in saturated soil under steady-state flow at a specific water head. The breakthrough curves (BTC) for the tracer (bromine) and mercury were obtained after continuous input. Moreover, two solute transport models [convection-dispersion equation model (CDE) and two-site non-equilibrium model (TSN)] were used to simulate heavy metal movement in soil on a laboratory column scale. According to the simulating results, we explored which model is more adapted to simulate the movement of heavy metals in saturated soil in the western suburb of Beijing.展开更多
文摘The mechanism of erosion of a riverbank is not easy to analyze and each sediment particle is under influence of number of forces. Among all these forces, force of cohesion between the particles plays a very dominant and significant role, and, till date, not much progress has been made to analyze this force in a deterministic manner. A particle is bound to its neighboring particles under this force of cohesion. In this paper, the analysis of forces acting on a particle on a riverbank has been made with a model called the Truncated Pyramid Model. A particle requires a certain velocity to escape from the riverbank and determination of the escape velocity can pave the way for finding out other parameters like entrainment rate, erosion coefficient and so on. Calculation and estimation of riverbank erosion rate is an important aspect of river basin management. In this paper it has been shown that the escape velocity is dependent on certain micro-level parameters like inter-particle distance and volume of the water bridge between two adjacent particles. Also, for saline water the particle requires less velocity to escape compared to the pure-water scenario. The findings of the present paper exactly fall in line with the results of another paper where the researchers showed that cohesive force between the particles decreases as water turns from pure to impure.
基金This study is granted by the Foundation for the Social Service of Minis-try of Science and Technology (2001DIA10021). And also is granted byChina Ministry of Science and Technology under the program of"Ecologi-cal and Environmental Monitoring, Forcasting and Management System inMining Area"(No. 2004DIB3J110) and"Development and Experimentof Ecological and Environmental Monitoring and Forcasting Technology forMining Area"(No. 2005BA901A03).
文摘Researchers are paying more and more attention to the adsorption and transport of heavy metals in soil. In this study, laboratory experiments were performed to investigate the characteristics of adsorption and transport of mercury in soils of different locations in the western suburb of Beijing. To characterize the adsorption mechanism of mercury in soil, adsorption isotherms were determined through a batch experiment. Soil column experiments were performed in saturated soil under steady-state flow at a specific water head. The breakthrough curves (BTC) for the tracer (bromine) and mercury were obtained after continuous input. Moreover, two solute transport models [convection-dispersion equation model (CDE) and two-site non-equilibrium model (TSN)] were used to simulate heavy metal movement in soil on a laboratory column scale. According to the simulating results, we explored which model is more adapted to simulate the movement of heavy metals in saturated soil in the western suburb of Beijing.