Lateral transportation of soil heavy metals in rainfall events could significantly increase the scope of pollution. Therefore, it is necessary to develop a model with high accuracy to simulate the migration quantity o...Lateral transportation of soil heavy metals in rainfall events could significantly increase the scope of pollution. Therefore, it is necessary to develop a model with high accuracy to simulate the migration quantity of heavy metals. A model for heavy metal migration simulation was developed based on the SWAT(Soil and Water Assessment Tool) model. This model took into consideration the influence of soil p H value, soil particle size, runoff volume, sediment amount,concentration of water-soluble heavy metals dissolved in runoff and insoluble absorbed to the soil particles. This model was reasonable in Huanjiang watershed, Guangxi Zhuang Autonomous Region, south China, covering an area of 273 km~2. The optimal drainage area threshold was determined by analyzing the effects of watershed subdivision on the simulation results to ensure the simulation accuracy. The main conclusions of this paper were:(1) watershed subdivision could affect simulation migration quantity of heavy metals;(2) the quantity of heavy metals transported by sediment accounted for 97%–99% of the total migration quantity in the study watershed. Therefore, sediment played the most important role in heavy metal migration;(3) the optimal drainage area threshold percentage to ensure high simulation accuracy was determined to be 2.01% of the total watershed;(4) with the optimal threshold percentage, this model could simulate the migration quantity of As, Pb and Cd accurately at the total watershed and subwatershed level. The results of this paper were useful for identifying the key regions with heavy metal migration.展开更多
In this paper, the one-dimensional(1D) particle-in-cell(PIC) simulation is used to study the modulation instability of ion acoustic waves in electron–ion plasmas. The ion acoustic wave is described by using a nonline...In this paper, the one-dimensional(1D) particle-in-cell(PIC) simulation is used to study the modulation instability of ion acoustic waves in electron–ion plasmas. The ion acoustic wave is described by using a nonlinear Schr¨odinger equation(NLSE) derived from the reductive perturbation method. Form our numerical simulations, we are able to demonstrate that,after the modulation, the amplitude increases steadily over time. Furthermore, by comparing the numerical results with traditional analytical solutions, we acquire the application scope for the reductive perturbation method to obtain the NLSE.We also find this method can also be extended to other fields such as fluid dynamics, nonlinear optics, solid state physics,and the Bose–Einstein condensate to validate the application scope of the results from the traditional perturbation method.展开更多
基金supported by the Hi-Tech Research and Development Program(863)of China(No.2014AA06A513)the Beijing Postdoctoral Research Foundation+2 种基金the Project of Heavy Metal Risk Warning and Phytoremediation in Mining Concentrated Area(No.GJHZ201308)the Special Fund for Environment Protection Research in the Public Interest(No.201409044)the Study on Heavy Metal Accumulation Risk and Early Warning in Typical Ore Concentration Area(No.201111020-4).
文摘Lateral transportation of soil heavy metals in rainfall events could significantly increase the scope of pollution. Therefore, it is necessary to develop a model with high accuracy to simulate the migration quantity of heavy metals. A model for heavy metal migration simulation was developed based on the SWAT(Soil and Water Assessment Tool) model. This model took into consideration the influence of soil p H value, soil particle size, runoff volume, sediment amount,concentration of water-soluble heavy metals dissolved in runoff and insoluble absorbed to the soil particles. This model was reasonable in Huanjiang watershed, Guangxi Zhuang Autonomous Region, south China, covering an area of 273 km~2. The optimal drainage area threshold was determined by analyzing the effects of watershed subdivision on the simulation results to ensure the simulation accuracy. The main conclusions of this paper were:(1) watershed subdivision could affect simulation migration quantity of heavy metals;(2) the quantity of heavy metals transported by sediment accounted for 97%–99% of the total migration quantity in the study watershed. Therefore, sediment played the most important role in heavy metal migration;(3) the optimal drainage area threshold percentage to ensure high simulation accuracy was determined to be 2.01% of the total watershed;(4) with the optimal threshold percentage, this model could simulate the migration quantity of As, Pb and Cd accurately at the total watershed and subwatershed level. The results of this paper were useful for identifying the key regions with heavy metal migration.
基金the National Natural Science Foundation of China(Grant No.11675014).
文摘In this paper, the one-dimensional(1D) particle-in-cell(PIC) simulation is used to study the modulation instability of ion acoustic waves in electron–ion plasmas. The ion acoustic wave is described by using a nonlinear Schr¨odinger equation(NLSE) derived from the reductive perturbation method. Form our numerical simulations, we are able to demonstrate that,after the modulation, the amplitude increases steadily over time. Furthermore, by comparing the numerical results with traditional analytical solutions, we acquire the application scope for the reductive perturbation method to obtain the NLSE.We also find this method can also be extended to other fields such as fluid dynamics, nonlinear optics, solid state physics,and the Bose–Einstein condensate to validate the application scope of the results from the traditional perturbation method.
