Pitfalls Associated with the Assumption of a Constant Partition Coefficient in Modeling Sorbing Solute Transport Through the Subsurfaceby Basilis N. Stephanatos, Environmental Resources Management, (ERM), Exton, United States,
Kevin Walter, Environmental Resources Management, (ERM), Exton, United States,
Alan Funk, Environmental Resources Management, (ERM), Exton, United States,
Alan MacGregor, Environmental Resources Management, (ERM), Exton, United States,
Abstract: This paper presents several case studies where the estimation of the adsorption coefficient, Kd, by means of the Koc-foc model resulted in significant errors in the prediction of the fate and transport of sorbing solutes through the subsurface. One important finding of this work is that the linear equilibrium approach to sorption is not adequate for many real-world situations. Alternative nonlinear equations for predicting the adsorption coefficient are presented for arsenic, trichloroethylene, and total volatile organics. These nonlinear relationships indicate that arsenic and volatile organics are more strongly sorbed to soil at low concentrations than at high concentrations. These findings have important implications for the prediction of groundwater cleanup time and for the evaluation of the effectiveness of a remedial alternative at a particular hazardous waste site. If a constant partition coefficient is estimated by the Koc-foc model, then a significant underestimation of the actual time to aquifer cleanup would result.
Subject Headings: Hydrologic models | Soil pollution | Water pollution | Case studies | Model analysis | Adsorption | Errors (statistics) | Arsenic
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