Coupled hydrological and

Coupled Hydrological and Geochemical Processes Governing the Fate and Transport of Sr and U in the Hanford Vadose Zone... 

The goal of this paper is to provide an overview of coupled hydrological and geochemical processes observed in large intact cores of Hanford sediments. A multiple nonreactive tracer technique will be utilized to quantify physical hydrology under saturated and unsaturated conditions. Adsorption isotherms will quantify the sorption of SrEDTA and U(VI) under kinetic and equilibrium... 

Figure 5. Coupled hydrology and geochemistry of the adsorption and displacement of Sr and SrEDTA through the Hanford flood deposits, (a) Observed displacement of nonreactive tracer Bf, and reactive SrEDTA through repacked sediments, (b) Enlarged view of (a) to show the co-elution of nonreactive tracer Br and EDTA" formerly complexed with (c) Observed...

Remediation is a process of restoration. In order to conduct remedial activities, we must first understand both the process which generated the contaminants, the contaminant chemistry, the soil geology, the site hydrology, and the nature and kind of interactions between the soil, water, and the contaminants. In this brief exposition, weTl discuss a couple of different types of sites and see the limits of remediation technology. 

Fig. 7.1 Schematic description of MCCM as used on the local and regional scale for air quality simulations, and for simulation of the regional climate including the introduced coupled models to hydrology and biosphere compartments...

A variety of adsorption models, from A, to the electrostatic adsorption models in MINTEQA2, have been coupled with hydrologic transport models. Available coupled codes and their attributes have been described and compared, in some detail, by Mangold and Tsang (1991) (see also Lichtner et al. 1996) and will not be considered here. 

Each individual flux in the two preceding equations is a function of combinations of environmental factors. These factors, and the coupling between the chemical and macroscopic transport processes in the surficial environment, will be discussed in the subsequent sections of this chapter. The discussion will focus on the coupling between the chemical, hydrological, and physical processes and will deal with the global average fluxes of water, solid and dissolved materials that are products of the three interaeting classes of forces and processes... 

It is, however, simpler to consider for the totality of chemical kinetic and transport processes that operate on different physical and time scales in the surficial environment three main classes of driving forces—physical, hydro-logical, and chemical—and responses to these forces in various physical, hydrological, and biogeochemical processes. This is illustrated schematically in Table 1, which gives a matrix of 3 x 3 couplings between physical, hydrological, and chemical forces and their environmental effects as far as these concern transport. 

TABLE 1. Coupling among Macroscopic Transport Processes and Physical, Hydrological, and Chemical Driving Forces... 

The interactions of the chemical kinetic and macroscopic transport processes depend to a variable extent on each of the nine couples given in Table 1. For example, transport of solutes by water runoff is a result of atmospheric precipitation, land exposure to water, chemical reactivity of solids in an aqueous solution, and flow of water over the continental surface. The net result of this process is controlled by coupling among the physical, hydrological and chemical entities in Table 1, as shown below ... 

The long-term performance of the repository at Yucca Mountain will be affected by the coupling of thermal, hydrological and chemical (THC) processes in the rock around the emplacement drifts. The transport of heat, fluid, and vapor will result in changes in water and gas chemistry, as well as mineral dissolution and precipitation which may lead to permanent changes in porosity, permeability and unsaturated hydrological properties. The purpose of this contribution is to describe the approach used to model reaction-transport processes in the Drift Scale Test (DST) with comparisons of simulation results to measured geochemical data on water, gas, and minerals. 

So as to predict precisely the near-field behaviour for long-term performance analysis by inclusion of the near-field chemical evolution, we think it important to take into account the interactive model from thermal, hydrological and mechanical processes to chemical process as the first step of this research. After this step, we can really introduce the interactive model from chemical process to other processes, and then we can realize the fully coupled T-H-M-C model. 

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