In groundwater transport

Ryan JN, Elimelech M (1996) Colloid mobilization and transport in groundwater. Colloid Surf A-Physicochem Engin Aspects 107 1-56... 

Frind, E.O., Simulation of long-term transient density-dependent transport in groundwater, Adv. Water... 

At the same time, reaction modeling is now commonly coupled to the problem of mass transport in groundwater flows, producing a subfield known as reactive transport modeling. Whereas a decade ago such modeling was the domain of specialists, improvements in mathematical formulations and the development of more accessible software codes have thrust it squarely into the mainstream. 

Hoag, G. E., Bruell, C. J., and Marley, M. C., 1984, Study of the Mechanisms Controlling Gasoline Hydrocarbon Partitioning and Transport in Groundwater Systems Institute of Water Resources, University of Connecticut, U.S. Department of the Interior Research Project No. G832-066, 51 pp. 

Enfield, C.G. and Yates, S.R. Organic chemical transport in groundwater, in Pesticides in the Soil Environment Processes, Impacts, and Modeling, Soil Science of Society of America, Cheng. H.H., Ed. (Madison. WI SSSA, 1990), pp. 271-302. 

Gerba, C. P. (1999). Virus survival and transport in groundwater. J. Ind. Microbiol. Biotechnol. 

Figure 9.6 Illustration of the retardation of 1,4-dimethylbenzene (DMB) transport in groundwater due to (1) reversible sorptive exchange between water and solids, and (2) limiting transport of DMB to that fraction remaining in the flowing water. As dissolved molecules move ahead, they become sorbed and stopped, while molecules sorbed at the rear return to the water and catch up. Thus, overall transport of DMB is slower than that of the water itself.

Illustrative Example 11.4 Estimating the Retardation of Trinitrotoluene Transport in Groundwater... 

Illustrative Example 11.4 Estimating the Retardation of Trinitrotoluene Transport in Groundwater Problem Due to past munitions production and use, the explosive NAC, trinitrotoluene (TNT), occurs in a ground water at 0.1 pM. You need to evaluate this compound s mobility in this oxic aquifer knowing it has the characteristics shown below. Mineralogy 75% quartz, 20% feldspar, 5% illite, 0.2% organic matter (NOM) Density of aquifer material ps = 2.6 kg L"1... 

This expression describes the fastest and most important mode of transport in groundwater. In fact, an important task of the hydrologist is to develop models to predict the effective velocity u (or the specific flow rate q). Like the Darcy-Weis-bach equation for rivers (Eq. 24-4), for this purpose there is an important equation for groundwater flow, Darcy s Law. In its original version, formulated by Darcy in 1856, the equation describes the one-dimensional flow through a vertical filter column. The characteristic properties of the column (i.e., of the aquifer) are described by the so-called hydraulic conductivity, Kq (units m s"1). Based on Darcy s Law, Dupuit derived an approximate equation for quasi-horizontal flow ... 

Backhus, D. A., and P. M. Gschwend, Fluorescent polycyclic aromatic hydrocarbons as probes for studying the impact of colloids on pollutant transport in groundwater , Environ. Sci. Technol., 24,1214-1223 (1990). 

Brown, B.V. (2005) Arsenic transport in groundwater, surface water, and the hyporheic zone of a mine-influenced stream-aquifer system. Master s Thesis, Virginia Polytechnic Institute and State University, p. 44. 

Sorption and Desorption Isotherms. To model radionuclide transport in groundwater through geologic media, it is necessary to mathematically describe sorption and desorption in terms of isotherms. The Freundlich isotherm was found to accurately describe sorption and desorption of all radionuclides studied in the interbed-groundwater systems, except when precipitation of the radionuclide occurred. 

Chemicals may enter groundwater as landfill leachates or from deep-well injection of hazardous wastes, leaching from soil and water, or septic tanks. Diffusion and advection are the typical mechanisms of chemical transport in groundwater. Groundwater may be taken up via human use or empty onto the surface waters via a natural spring. 

As may be apparent from many of the examples presented above, models of processes that affect the fate and transport in groundwater of petroleum hydrocarbons and chlorinated aliphatic hydrocarbons are much more prevalent than models of other contaminants. Much research has yet to be accomplished to improve our understanding and ability to model transformation processes, particularly for contaminants like polynuclear aromatic hydrocarbons, nitro-aromatics, and pesticides. 

Walter A.L. et al., Modeling of multicomponent reactive transport in groundwater 1. Model development and evaluation, Water Resour. Res., 30, 3137, 1994. 

Walter A. L., Frind E. O., Blowes D. W., Ptacek C. J., and Molson J. W. (1994b) Modelling of multicomponent reactive transport in groundwater 2. Metal mobility in aquifers impacted by acidic mine tailings discharge. Water Re sour. Res. 30, 3149-3158. 

One has to distinguish between transport in groundwater aquifers, which are saturated with water, and transport in the unsaturated subsurface zone, where pores contain water and air (this might lead to a very heterogeneous flow structure). 

Higher concentrations of As tend to be found more in groundwater than in surface water sources of drinking water therefore, the emphasis of this paper is on the geochemical processes that affect As transport in groundwater. However, many of the processes discussed are also applicable to surface waters and the variably saturated zone above the groundwater table. 

Backus, D. A. Geshwend, P. M. Fluorescence Polycyclic Aromatic Hydrocarbons as Probes for Studying the Impact of Colloids on Pollutant Transport in Groundwater Environmental Science and Technology 1990,24 p. 1214-1223. 

DOI. 1984. A study of the mechanisms controlling gasoline hydrocarbon partitioning and transport in groundwater systems. Contract no. 14-08-001-G-832. Reston, VA U.S. Geological Survey, U.S. Department of the Interior. Project no. 370706. 

Water flow and contaminant transport in groundwater are difficult to study and investigations of pesticides at the aquifer level are scarce. The tendency has been to isolate the processes that control the chemical composition and to investigate each separately. Studies at the level of the aquifer that have... 

Even though new MTBE plants are not being built in North America, CD is used currently for the production of other oxygenates such as TAME or ETBE, which being less soluble in water (i.e., less tendency to be transported in groundwater) are being considered or used as alternative octane enhancers. Ethyl-tert-butyl ether is produced from the etherification of ethanol and isobutylene while TAME production requires isoamylene and methanol. A simulation of the industrial production of a green octane enhancer from... 

McCaithy and Degueldre (1993), Degueldre (1993), and Triay et al. (1995) discuss colloidal transport in groundwater a it relates to the transput of contaminants, including radionuclides. 

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