Application to Landfill Leachate into Aquifers

The Geochemist s Workbench program react now includes procedures to calculate reaction kinetics of biotransformations, and the phreeqc documentation gives an example of similar calculations in phreeqc. 

Hunter et al. (1998) used a kinetic model to simulate reactive transport and ground-water evolution upon the intrusion of landfill leachate into an oxic aquifer. Most interestingly, they found that the patterns of redox fronts are similar to what have been seen in marine sediments. Hunter et al. (1998) first developed a one-dimensional multi-component reactive transport model biorxntrn and then conducted a numerical experiment using this code. The actual model is quite complex we describe here the essentials of it so that we can see what can be done. 

DOC is depleted at about 280 m, a reverse zonation occurs before it returns back to aerobic conditions of the uncontaminated aquifer. 

We should note how Hunter et al. (1998) treat the kinetics in their model. They first divided reactions into different types. 

We have already stated ( 1.4.2 and 2.5) that the subject of chemical reaction kinetics is both important and poorly understood in geochemical modeling. The problem is that this subject is much more difficult than equilibrium thermodynamics. The kinetics of a few reactions are fairly well understood, but a great many more have completely unknown kinetics. Furthermore, those that are understood have usually been studied in fairly clean systems, and the effect of added components is uncertain. Even if some reactions were perfectly understood, the usefulness of including the kinetics of 

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