Cleanup of soil contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is usually done using high-temperature incineration, but an in situ method is being developed which could be more cost-effective and less destructive to the site. This is based on the fact that TCDD can undergo photolysis by sunlight under the proper conditions. An organic solvent mixture is added to the contaminated soil, and time is then allowed for TCDD solubilization, transport, and photodegradation. These studies focus on the mathematical description of the decontamination process. The model that has been developed can be used to further optimize the cleanup conditions. This model uses two sets of equations to describe the fluid flow and the TCDD movement and photodegradation. It considers convective transport (driven by evaporation) and diffusive transport of the TCDD. Once the contaminant reaches the soil surface, it is photodegraded or it can accumulate in a film of TCDD at the surface of the column.

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The transport of 2,3,7, in soils containing various organic liquids has been measured experimentally. A model has been developed that considers diffusive transport in the liquid phase and takes into account the rate of adsorption and desorption of TCDD from the soil particles. Effective diffusion coefficients for TCDD were fit to the data, and the results compared well with estimates using the Wilke-Chang correlation.

Literature data show that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is extremely persistent when applied to soil in waste oil. One method of soil decontamination involves adding organic solvents to the soil and then allowing time for diffusion to the surface where TCDD can be decomposed by sunlight. Before such a method becomes feasible, it was determined that a study of the reasons the persistence of the chemical when applied in waste oil would be useful. Therefore an estimate of possible photodegradation of TCDD in oil was made, and it was concluded that the probable high UV absorbance of the waste oil in which the TCDD was applied was a very likely reason for the lack of observed photodegradation.