Application of an Intraparticle Diffusion Model to Describe the Release of Polyaromatic Hydrocarbons from Field Soils

The fate and transport of chemicals of concern released from field soils must be known to protect human and ecological receptors. A mechanistic approach to modeling chemical release from soil is advantageous to implement effective remediation strategies at an impacted site. The focus of this research was to gain an understanding of the processes causing slow release of polyaromatic hydrocarbons (PAHs) from field soils collected at sites with historical releases. A mechanistically based intraparticle diffusion model was applied to experimentally measured hydrocarbon release data and particle size distributions obtained from three field soils. For these field soils, the intraparticle diffusion model was able to describe the measured chemical release data. Fitted effective diffusion coefficients $\left(D_{\mathrm{eff}}\right)$ of the intraparticle diffusion model correlated to expected results. Trends were found to exist between the $D_{\mathrm{eff}}$ and both the molecular weight (MW) and the octanol–water partition coefficient $\left(K_{\mathrm{ow}}\right)$ of the PAH analyzed for the field soils with low organic carbon content. For these soils, the relationships suggest that intraparticle diffusion processes may be responsible for slow desorption and it may be possible to estimate $D_{\mathrm{eff}}$ values for a soil or contaminated media with similar intraparticle properties using a readily measured chemical characteristic such as MW and $K_{\mathrm{ow}}$ .