Evaluation of Modeling Approaches for Sorption–Desorption Processes in Flow-Through Soil Columns

Abstract

The influence of soil organic matter and pore water velocity on the transport of naphthalene in flow-through columns was investigated. Pulse injection experiments were conducted using three different soils (with 0%, 1.9%, and 3.9% organic content by weight) and flow rates (0.05, 0.1, and 0.2 mL/min) and solvent extractions were performed to measure the nondesorbable naphthalene fraction. To describe interactions between contaminants in the aqueous and solid phases, observed breakthrough data were described using two-site models, four different formulations of a three-site model, and two fully kinetic models. While the two-site models did not adequately describe the breakthrough data for all cases, simulations based on the three-site models matched the observations well with the exception of high organic content soils and high flow rates. For soils with high organic content, the fully kinetic models described the observed data better compared to the three-site models. Results indicate that as long as the equilibrium, rate-limited, and irreversible sorption domains are included in the models, different conceptualizations about how contaminants interact in the aqueous and solid phases do not produce significantly different results.