| Abstrakt: |
Engineered surface barriers are expected to be used to cover sites containing buried waste radionuclides after site closure. Understanding the transport of contaminants in the soil below a surface barrier is of importance in order to protect the underlying groundwater. The travel velocity of these contaminants is dependent on numerous factors, such as the thickness, properties, the pre‐barrier hydrologic condition of the vadose zone, and the initial depths and properties of the contaminants. Although solute transport can be modeled with numerical modeling using site‐specific data, by nature a numerical method does not reveal the relationship between inputs and outputs. This work develops algebraic expressions of the velocities of convective solute transport in the vadose zone below a surface barrier, time lag, solute safe depth, zero‐protection depth of a surface barrier, and solute travel time to the groundwater. This development shows that solute convection in the soil with a surface barrier consists of up to three stages: constant high velocity, decreasing velocity, and constant low velocity. Solute transport based on the algebraic expressions was verified against numerical simulations. The algebraic expressions may be used to assess the expected impacts of a surface barrier to the convective transport of contaminants in the vadose zone. Core Ideas: Convective solute transport below a surface barrier consists of three stages.Algebraic expressions are developed to quantify the impacts of a surface barrier on solute convection.The impacts are reflected by the time lag, solute safe depth, zero‐protection depth, and travel velocity.The algebraic expressions are verified against numerical simulations. Plain Language Summary: Engineered surface barriers are like gigantic umbrellas above a waste site to intercept precipitation so the rainfall will not enter the buried hazardous materials. Often the movement of contaminants in the soil needs to be calculated using supercomputers. This article develops some simple mathematical formulas for quick calculation. A few formulas are established to determine how fast a contaminant moves, at what depth a contaminant will be safe, at what depth a surface barrier has no impact to contaminant movement, and how long it takes for a contaminant to move to the groundwater. The formulas were verified against results from a supercomputer. These formulas are useful to assess the impact of a surface barrier on the movement of the buried hazardous materials. [ABSTRACT FROM AUTHOR] |
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