Novel Analytical Solution Library for Multi-Species Transport of Degradable or Decaying Contaminants in Rivers with Stagnant Water and Hyporheic Zones (II)

In rivers there is continuous exchange of water and dissolved chemicals with their surrounding stagnant water zone and the hyporheic zone. Analytical models are widely used to obtain a better understanding and make accurate predictions of the transport and fate of contaminants in rivers. One approach for modeling mass exchange of dissolved chemicals between the river channel and the stagnant zone is the transient storage model (TSM) in which the first-order reaction mass transfer between the river channel and stagnant water zones is assumed. A more refined approach is the so-called hyporheic diffusion model (HDM) where mass transfer from the river channel into the stagnant water zones or more generally the entire hyporheic zone is assumed to be controlled by diffusion and the Fick’s law is followed to describe solute diffusion. Although some analytical solutions for the TSM and HDM have already been reported in the literature, analytical solutions for TSM and HDM for the transport of multiple species in rivers have not yet been developed. Such solutions for TSM and HDM would be effective tools for simultaneously and more accurately predicting the transport behavior of both the parent species and the daughter species of degradable or decaying contaminants in rivers. These degradable or decaying constituents may contain a wide spectrum of contaminants resulting from specific natural processes and anthropogenic activities such as toxic trace elements, radionuclides, industrial chlorinated solvents, pesticides, nutrients and pharmaceuticals which generally involve a more complicated series of first-order or pseudo first-order decay or degradation chain reactions. In this two-year project we aim to develop novel analytical solutions for TSM and HDM for the purpose of describing the transport of degradable and decaying contaminant in rivers with stagnant water and/or hyporheic zones. In the on-going research of this two-year project, we have already derived a series of analytical solutions for TSMs subject to different types of boundary conditions. As a subsequent research of an on-going MOST project, this project attempts to develop novel analytical HDM solutions for describing the movement of degradable and decaying contaminant in rivers. A solution library will be systematically constructed by integrating the achievements of these two-year tasks.