Kai Uwe Totsche

Carrier Influenced Transport of Pollutants in Porous Media: Mathematical Modeling

Dissolved organic Carbon(DOC) in soils and aquifers is considered as a sorbent and carrier for organic contaminants. The knowledge of the interaction between hydophobic organic chemicals (HOC) and soil or aquifer materials in the presence of mobile carriers, such as DOC, plays an important role in understanding of the transport behavior of the HOC. Several studies focused on the influence of the chemical characteristics of the contaminant on solubility enhancement by DOC [6]. Enhanced transport of pesticides and hydrophobic organic chemicals mediated by the presence of DOC in soils and other porous media has been documented by a number of studies [14]. In these studies, it is generally assumed that DOC is an non-reactive component of the aqueous phase with respect to interactions with bulk soil material (BSM). This inhanced mobility or leaching of the contaminant may have impact on risk assessment studies. Recently, there is experimental evidence that also the carrier DOC itself and the HOC-DOC compounds undergo adsorption to the soil matrix [3]. This process reduces again the mobility of the contaminant such that the overall result is not clear.

Carrier-Influenced Transport of Pollutants in Porous Media: Experimental Assessment

The association of organic contaminants with colloidal DOC (dissolved organic carbon) has been demonstrated to have an effect on the mobility of these compounds in groundwater (McCarthy and Zachara, 1989). High concentrations of DOC are produced in surface soils from the forest floor (David and Vance, 1991) or from organic amendments such as manure, compost, and sewage sludge (et al., 1993). The present study focusses on the experimental assessment of DOC-influenced transport of polycyclic aromatic hydrocarbons (PAHs) in the vadose zone of soils. The processes we consider (Fig. 1) are sorption of the contaminant to the soil matrix and also to a mobile sorbent, such as DOC. Additionally, the carrier DOC is considered to undergo adsorption to the soil matrix as well (Knabner et al., 1993). Thus, we can elucidate the significance of natural DOC for the transport of PAHs in soils.