The Long-Term Dissolution Characteristics of a Residually Trapped BTX Mixture in Soil

Abstract

ABSTRACT A mass transfer limited model is presented to describe the long-term dissolution of organic compounds from a benzene, toluene, and xylenes (BTX) mixture residually trapped in a sandy soil. The model is an extension of a previously presented equilibrium dissolution model [1] which takes into consideration mass transfer limitations that develop later in the leaching process and is similar to that presented by Borden and Kao [2] for modeling BTX dissolution from residually trapped gasoline. The residual nonaqueous phase liquid (NAPL) is divided into multiple regions: one region which undergoes equilibrium dissolution and additional regions in which mass transfer is progressively limited. Application of the model to BTX column effluent data indicates that the initial dissolution (exponential decay region) of BTX can be effectively described by equilibrium dissolution. When applied to later dissolution times (asymptotic region) a multiple-region model is required to rationalize the data for all three ...