Degradation of polycyclic aromatic hydrocarbons: Model simulation for bioavailability and biodegradation

A mathematical model for a one‐dimensional convective‐dispersive solute transport in a soil matrix is presented. The interplay of linear equilibrium sorption and first order degradation were incorporated into the formulation of the model. The model took into consideration the overall effects of the solid and liquid phase mass transfer resistances. Data from experiments were analysed using the temporal moments method (MOM) and CXTFIT curve‐fitting technique. The functional parameters; dispersion coefficient, first order degradation rate constant and the retardation factor were estimated using both first and second normalised moments. The solution to the model equations was achieved by the use of the backward finite difference scheme. Results obtained showed that naphthalene was more selectively degraded than pyrene and anthracene with a residual concentration of naphthalene 1.12E ? 5 mg/L, 1.48 mg/L; pyrene 3.11E ? 4 mg/L, 1.58 mg/L; and anthracene 7.67E ? 4 mg/L, 1.61 mg/L in the axial and radial directions, respectively. Concisely, the modeling results showed the occlusion of these compounds within the fissures and cavities of the soil particles, which renders them not readily bioavailable and thus inaccessible to microbial degradation.