Reactive Transport Numerical Modeling of Typical Heavy Metal Pollutants in Three-Dimensional Fracture Networks

The geologic discontinuities present in natural fractured rock governs groundwater flow and solute transport process. Due to the complexity of real-world fracture network, discrete fracture network (DFN) is often be described and generated based on specific probability distributions determined by different parameters (shape, location, size, density, orientation, etc.). Due to DFN's highly heterogeneous and an isotropic features, it's a challenge to simulate groundwater flow and solute transport processes using traditional numerical solution based on the experience achieved in porous media. In this paper, a 3-D DFN model is built for field-scale study, and mapped to an equivalent porous medium (EPM) model, which further couples groundwater flow model with the multi-component reactive transport code PFLOTRAN to achieve numerical simulation of the reactive transport process of heavy metal contaminants in the fractured network and quantitative assessment of mass fluxes. The study shows that the behavior of the fracture network gradually transforms into the transport in porous media as the density of the network increases; Both the density and orientation of fracture development affect the connectivity of the fracture network, which in turn affects the migration pattern and flux assessment of different components in fractured rock groundwater flow, where the migration behavior of conservative components and various reactive components are significantly different.Meanwhile, it is shown that roughness has an important influence on the migration process and flux assessment of the transport components in the fracture network.This paper provides an effective simulation and quantitative assessment tool for the reactive transport of heavy metals and groundwater flow in the fractured field.