Transport in the Subsurface

Gerba.C. P., Yates, M. V. Yates, S. R. (1991). Quantitation of factors controlling viral and microbial transport in the subsurface. In Modeling the Environmental Fate of Microorganisms, ed. C.J. Hurst, pp. 77-88. Washington, D.C. American Society for Microbiology. 

Electric fields use in soil restoration has been focused on contaminant extraction by their transport under electroosmosis and ionic migration. Contaminant extraction by electric fields is a successful technique for removal of ionic or mobile contaminants in the subsurface. However, this technique might not be effective in treatment of soils contaminated with immobile and/or trapped organics, such as dense non aqueous phase liquids (DNAPLs). For such organics, it is possible to use electric fields to stimulate in situ biodegradation under either aerobic or anaerobic conditions. It is necessary to evaluate the impact of dc electric fields on the biogeochemical interactions prior to application of the technique. It is not clear yet how dc electric fields will impact microbial adhesion and transport in the subsurface. Further, the effect of dc fields on the activity of microorganisms in a soil matrix is not yet well understood. 

Transport in the subsurface environment is slow compared with the other environmental media. Contaminants may move only tens of meters per year by advection, contrasting sharply with surface waters, which travel this far in minutes or hours, and air, which may travel this far in seconds (as discussed in the next chapter). Similarly, Fickian transport coefficients are rarely higher than thousandths of a square centimeter per second and are often no larger than a fraction of the molecular diffusion coefficient in free water. Many organic compounds that would rapidly volatilize into the atmosphere from surface waters may reside in groundwaters for decades or longer. 

Multiphase flow theory is very well developed because of applications such as interfacial separations, petroleum production, and vadose-zone hydrology yet, it remains a mostly empirical science. This is a consequence of the complex physics of flow and because the parameters describing multiphase flow are highly sensitive to pore structure and interfacial configurations. Though three-phase flow is important in applications such as oil production and contaminant transport in the subsurface, we limit the following discussion to two-phase flow for simplicity. 

Contents indude Interactions of bacteria with metals, particle transport In the subsurface, and chemical and physical Influences. 

Accurate model prediction, no matter how practical it is, can be obtained only by understanding the underlying science. In this case, the prediction of mass transport in the subsurface can only be accurate if we understand the geochemical reactions that occur in the aquifer. This requires that we understand the geochemical properties of the aquifer, have the thermodynamic and kinetic properties of the chemical system in hand, and understand the interplay among chemical, physical, and biological processes. 

Yang GCC, Tu HC, Hung CH. (2007). Stability of nanoiron slurries and their transport in the subsurface environment. Separation and Purification Technology 58(1) 166-172. 

Energy transport in the subsurface is attributable to heat conduction in the porous matrix as well as heat transport by fluid motion (advection). In the absence of fluid movement, energy flow by conduction only is described by the relationship... 

S Flow and transport in the subsurface could be affected by a feedback... 

Explain how magma was transported in the subsurface while showing little evidence of contamination by crustal rocks (e.g., they contain few if any crustal xenoliths). 

Waite, T.D., andT.E. Payne. 1993. Uranium transport in the subsurface environment Koongarra Acase study, p. 349-410. In H. Allen et al. (ed.) Metals in groundwater. Lewis Publ., Ann Arbor, MI. 

The subject of advective porewater flux and associated chemical transport is covered in Chapter 11 in the context of aquatic bed-sediment systems, which include surface soil-derived particle layers on the bottom of streams, rivers, lakes, estuaries, and the near-shore marine environment. This soil system is a saturated porous medium and therefore the fundamentals of the transport processes and related parameters within this system are identical to that of surface soils. A brief review of advective transport in the subsurface follows. 

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