Modeling coupled degradation, sorption, and transport of 17β-estradiol in undisturbed soil

The presence of 17 beta-estradiol in the environment, even at parts-per-trillion concentrations, raises significant concern regarding the health of aquatic organisms. Once 17 beta-estradiol is released into the environment from human and animal sources, its fate and transport is controlled by factors such as sorption and transformation, which need to be understood to fully assess potential exposures. The objective of this study was first to discern, through controlled batch experiments, the simultaneous transformation (i.e., chemical and biological) of natural estrogenic compounds and their mass exchange between the aqueous and solid phase (i.e., reversible and irreversible sorption sites). In addition, a model was developed that used a series of first-order expressions to describe the various fate and transport processes of parent and metabolite estrogens in the nonequilibrium batch experiments. A global optimization method was used to estimate the parameters of this nonequilibrium batch model. The model provided a good description of the data, and the parameter estimates were reliable. The batch studies parameter estimates were then incorporated into a convective-dispersive model to describe two undisturbed column experiments. The consistency of parameter estimates between the batch and column experiments indicated a high capability and reliability of this model and the parameter values.