The Effect of Water-Soluble Organic Material on the Transport of Phenanthrene in Soil

Environmental fate modeling involves the difficult task of quantitatively describing the natural mechanisms that affect the mobility and concentration of a pollutant in the environment. Of primary importance for modeling the subsurface transport of many contaminants are dissolution in groundwater, which allows transport by advection, diffusion, and dispersion; and sorption to stationary soil particles, which retards transport. Many environmental contaminants, such as polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and dioxins, are hydrophobic and have low aqueous solubilities. Consequently, these compounds typically sorb strongly to soil and the risk to potential receptors distant from the waste site is assumed to be low. However, if dissolved macromolecules or colloidal particles are dispersed in the groundwater, they may sorb the pollutants, allowing them to be transported with these mobile carriers through the subsurface environment. The processes resulting in such “facilitated transport” are generally not incorporated into environmental fate models.