A multiple species transport model with sequential decay chain interactions in heterogeneous subsurface environments

Journal Article · Sun Aug 01 00:00:00 EDT 1993 · Water Resources Research; (United States)

DOI:https://doi.org/10.1029/93WR00964· OSTI ID:5484411

McNab, Jr, W W; Narasimhan, T N ^[1]

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1. Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley, CA (United States)

The spatial and temporal distribution of solutes in groundwater is controlled by several physical and chemical processes. Among the chemical processes, sequential degradation phenomena play an important role in determining the fate of radioactive materials and certain types of organic compounds. The authors present a numerical model designed to evaluate the simultaneous transport and kinetically controlled sequential degradation (straight and branched chains) of several dissolved components in groundwater systems. The model utilizes a two-step quasi-linearization algorithm to solve the equations of chemical transport and transformation. The transport equations are solved explicitly using the integral finite difference method. The chemical transformation equations are solved using an implicit finite difference (in time) algorithm for each volume element in the discretized flow domain. Although this algorithm is designed to solve problems involving first-order kinetics, it may be modified in certain instances to accomodate rate mechanisms other than first order. The chemical transformation module and the transport module are coupled via a source/sink term in the transport equation. This combination results in a numerical code that is computationally efficient. The authors have found that the model yields solutions which are in excellent agreement with available analytical solutions. Solution of a test problem based on the sequential degradation of the pesticide aldecarb demonstrates that the model can provide useful insights into the fate of solutes subject to certain degradation regimes in heterogeneous groundwater systems. Although the illustrative examples presented are one dimensional, the model itself is capable of handling two- and three-dimensional problems. In addition, the modular structure of the model is built upon user-specified chemical reactions. 25 refs., 8 figs., 1 tab.

• OSTI ID: 5484411
• Journal Information: Water Resources Research; (United States), Vol. 29:8; ISSN 0043-1397
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ENVIRONMENTAL TRANSPORT
MATHEMATICAL MODELS
GROUND WATER
CONTAMINATION
SOLUTES
SPATIAL DISTRIBUTION
CHEMICAL REACTION KINETICS
FINITE DIFFERENCE METHOD
NUMERICAL SOLUTION
RADIOACTIVE MATERIALS
CALCULATION METHODS
DISTRIBUTION
HYDROGEN COMPOUNDS
ITERATIVE METHODS
KINETICS
MASS TRANSFER
MATERIALS
OXYGEN COMPOUNDS
REACTION KINETICS
WATER
540220* - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)
540230 - Environment
Terrestrial- Radioactive Materials Monitoring & Transport- (1990-)
990200 - Mathematics & Computers