A Steady-State Approach to Predict Degradation Rates

5 A Steady- State Approach to Predict Degradation Rates 

The consumption of a reactant at steady-state can be described using chemical kinetics. A reactant is degraded with a rate constant kj to form product 1, which is subsequently degraded to form product 2 with a rate constant k2. 

If the concentration of the reactant is larger than that of the product then the consumption of the product is faster than its formation. 

According to this concept concentration ratios allow prediction of the relative degradation rate of the individual reactants. In Fig. 15.4 the ratios from the median concentration values shown in Fig. 15.3 are plotted on a logarithmic scale for the various redox conditions. The ratio PCE/TCE was omitted because no discrimination can be made between TCE as a contaminant somce or as a product of the degradation of PCE. 

In analogy to the partial equilibrium approach, the assumption of the degradation sequence of chlorinated ethenes to occur at steady-state can be used also to derive equilibrium potentials for their degradation according to 

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