MT3DMS: A Modular Three-Dimensional Multispecies Transport Model for Simulation of Advection, Dispersion, and Chemical Reactions of Contaminants in Groundwater Systems; Documentation and User's Guide

摘要

This manual describes the next generation of the modular three- dimensional transport model, MT3D, with significantly expanded capabilities, including the addition of (a) a third-order total-variation-diminishing (TVD) scheme for solving the advection term that is mass conservative but does not introduce excessive numerical dispersion and artificial oscillation, (b) an efficient iterative solver based on generalized conjugate gradient methods and the Lanczos/ORTHOMIN acceleration scheme to remove stability constraints on the transport time-step size, (c) options for accommodating nonequilibrium sorption and dual-domain advection-diffusion mass transport, and (d) a multicomponent program structure that can accommodate add-on reaction packages for modeling general biological and geochemical reactions. MT3DMS can be used to simulate changes in concentrations of miscible contaminants in groundwater considering advection, dispersion, diffusion, and some basic chemical reactions, with various types of boundary conditions and external sources or sinks. The basic chemical reactions included in the model are equilibrium-controlled or rate- limited linear or nonlinear sorption and first-order irreversible or reversible kinetic reactions. MT3DMS can accommodate very general spatial discretization schemes and transport boundary conditions, including: (a) confined, unconfined, or variably confined/unconfined aquifer layers, (b)inclined model layers and variable cell thickness within the same layer, (c) specified concentration or mass flux boundaries, and (d) the solute transport effects of external hydraulic sources and sinks such as wells, drains, rivers, areal recharge, and evapotranspiration.