Transport in soil

Other studies have investigated transport in soil and at DOE waste disposal sites (Fowler et al. 1981 McCarthy et al. 1998a, 1998b Penrose et al. 1990). As a result of these studies, the environmental fate of americium is reasonably well understood. 

Fischer, U., Hinz, C., Schulin, R. and Stauffer, F., Assessment of nonequilibrium in gas-water mass transfer during advective gas-phase transport in soils, J. Contam. Hydrol., 33, 133-148, 1998. 

Corapcioglu, M. Y. and Baehr, A. L., 1985, Immiscible Contaminant Transport in Soils and Groundwater with an Emphasis on Gasoline Hydrocarbons System of Differential Equations vs. Single Cell Model Water Science and Technology, Vol. 17, No. 9, pp. 23-37. 

The root time method of data analysis for diffusion coefficient determination was developed by Mohamed and Yong [142] and Mohamed et al. [153]. The procedure used for computing the diffusion coefficient utilizes the analytical solution of the differential equation of solute transport in soil-solids (i.e., the diffusion-dispersion equation) ... 

Rouen D, Scher H, Blunt M (1997) On the structure and flow processes in the capillary fringe of phreatic aquifers. Transp Porous Media 28 159-180 Rose CW (1993) The transport of adsorbed chemicals in eroded sediments. In Russo D, Dagan G (eds) Water flow and solute transport in soils. Springer, Heidelberg, pp 180-199 Rosenberry DO, Winter TC (1997) Dynamics of water-table fluctuations in an upland between two prairie-pothole wetlands in North Dakota. J Hydrol 191 266-289 Russo D (1997) On the estimation of parameters of log-unsaturated conductivity covariance from solute transport data. Adv Water Resour 20 191-205 Russo D, Toiber-Yasur 1, Laufer A, Yaron B (1998) Numerical analysis of field scale transport of bromacU. Adv Water Resour 21 637-647... 

Brusseau, M. L., The influence of solute size, pore water velocity, and intraparticle porosity on solute dispersion and transport in soil , Water Resour. Res., 29,1071-1080 (1993). 

Corapcioglu, M. Y. Haridas, A. (1985). Microbial transport in soils and groundwater a numerical model. Advances in Water Resources, 8, 188—200. 

Rao, P. S. C., Beilin, C. A. Brusseau, M. L. (1993). Coupling biodegradation of organic chemicals to sorption and transport in soils and aquifers paradigms and paradoxes. In Sorption and Degradation of Pesticides and Organic Chemicals in Soil, pp. 1-26. Madison, WI Soil Science Society of America. 

This chapter describes the effects of dc fields on ions transport in soils, electrolysis and geochemical reactions, microbial adhesion and transport, and microbial activity. The interest in these in these processes is derived from the potential of using electric fields for transporting and mixing contaminants, biostimulants, and bioaugmentation inoculants to enhance in situ bioremediation. 

Chen, W. and RJ. Wagenet (1997). Description of atrazine transport in soil with heterogenous nonequilibrium sorption. Soil Sci. Soc. Am. J., 61 360-371. 

Kookana, R.S., L.A.G. Aylmore, and R.G. Gerritse (1992). Time-dependent sorption of pesticides during transport in soils. Soil Sci., 154 214-225. 

Ma, L. and H.M. Selim (1996). Atrazine retention and transport in soils. In G.W. Ware, ed., Review of Environment Contamination and Toxicity. New York Springer-Verlag, pp. 129-173. 

Specific management practices influence triazine runoff and leaching, including fertilizer type, tillage crop residues, and previous crop history, as well as triazine application, formulation, and placement (Baker and Mickelson, 1994). Tillage systems affect various soil properties, such as soil moisture, temperature, pH, organic matter, water flow, and microbial populations, especially at and near the soil surface. These factors can affect transformation, retention, and transport of herbicides in soil. Interactions of and compensations between these processes can influence our prediction of triazine transport in soil. Therefore, triazine movement is usually studied under one management practice at a time. 

A number of investigators have modeled solute transport in soils assuming an equilibrium occurs between solution and solid phases. This assumption is often not valid in heterogeneous soil systems, and has been the impetus for the development of a number of nonequilibrium models. Some researchers have assumed that the nonequilibrium is caused by stagnant zones, which result in tortuous diffusional processes between solution and sorbed phases (Rao et al., 1979). Other researchers have attributed the nonequilibrium to kinetic effects. 

Mechanistic Multiphase Model for Reactions and Transport of Phosphorus Applied to Soils. Mansell et al. (1977a) presented a mechanistic model for describing transformations and transport of applied phosphorus during water flow through soils. Phosphorus transformations were governed by reaction kinetics, whereas the convective-dispersive theory for mass transport was used to describe P transport in soil. Six of the kinetic reactions—adsorption, desorption, mobilization, immobilization, precipitation, and dissolution—were considered to control phosphorus transformations between solution, adsorbed, immobilized (chemisorbed), and precipitated phases. This mechanistic multistep model is shown in Fig. 9.2. 

Selim et al. (1976a) proposed a mathematical model for potassium reactions and transport in soils. Kinetic reactions were assumed to govern the transformation between solution, exchangeable, nonexchangeable (secondary minerals), and primary mineral phases of potassium shown in Fig. 9.3. 

Selim, H, M., Davidson, J. M., and Mansell, R. S. (1976a). Evaluation of a two-site adsorption-desorption model for describing solute transport in soils. Proc. Summer Comput. Simul. Conf. pp. 444-448. 

A two-site model has been used (18) to model cesium transport in soils. In this model a Langmuir-type model, Equation 3,was used to represent surface sorption and a first-order model, Equation 1, was used to approximate interparticle diffusion. Extraction with CaC was used to verify the exchangeable site inventory. 

Contaminant distribution in soil and water depends on such factors as soil properties the physical and chemical properties of the contaminant contaminant fate and transport in soil, groundwater or surface water and even the manner in which the contaminant was introduced into the environment. The knowledge of these issues coupled with available information on site history and background allows us to make valid assumptions in the planning phase on contaminant distribution and variability at the site. 

Giovine, P., and Palumbo, A. (2003) Modeling Contaminant Transport in Soils. Proc. Medit. Conf. on Modelling and Simulation 03, Reggio Calabria, June 2003, Session on Modeling, Tech. Note No. 178 on CD Rom NeuroLab... 

Yeung, A.T. (1994) Effects of electro-kinetic coupling on the measurement of hydraulic conductivity. In Hydraulic Conductivity and Waste Contaminant Transport in Soils, ASTM STP 1142 (D.E. Daniel and S.J. Trautwein, eds.). Am. Soc. for Testing Materials, Philadelphia... 

The current view is that in a porous medium, two liquid-phase regions can be identified on functional grounds (Yaron et al., 1996). The first is near the solid phase and is considered the most important surface reaction zone of the porous medium system. This near-surface water also controls the diffusion of the mobile fraction of the solute in contact with (sorbed on) the solid phase. The second region covers the free water zone, which governs the water flow and solute transport in soils (Fig. 10.2). 

Parker JC, KatyalAK, Kaluarachchi JJ, Lenhard RJ,Johnson TJ,Jayaraman K,Onlii K,Zhu JL (1991) Modeling multiphase organic chemical transport in soils and groundwater. US Environmental Protection Agency Project CR-814320, Washington D.C., USA... 

Contaminants in the soil compartment are associated with the soil, water, air, and biota phases present. Transport of the contaminant, therefore, can occur within the water and air phases by advection, diffusion, or dispersion, as previously described. In addition to these processes, chemicals dissolved in soil water are transported by wicking and percolation in the unsaturated zone.26 Chemicals can be transported in soil air by a process known as barometric pumping that is caused by sporadic changes in atmospheric pressure and soil-water displacement. Relevant physical properties of the soil matrix that are useful in modeling transport of a chemical include its hydraulic conductivity and tortuosity. The dif-fusivities of the chemicals in air and water are also used for this purpose. 

Environmental Fate. Tetryl released to the environment partitions mainly to water and soil (Army 1987d Lyman et al. 1982 Navy 1984b). Tetryl is transported in soil, surface water, and, rarely, in groundwater (Army 1987d Swann et al. 1983). Because of its very low vapor pressure, it is unlikely to partition to air (Army 1987d). No data were located regarding atmospheric transport of tetryl. 

A Web-Based Three-Dimensional Simulation System for Solute Transport in Soil... 

Hering, J.G., Implication of complexation, sorption and dissolution kinetics for metal transport in soils, in Metal Speciation and Contamination of Soil, Allen, H.E., Huang, C.P., and Bailey, G.W., Eds., CRC Press, Boca Raton, FL, 1995, p. 59. 

Understanding sulfate transport and retention dynamics in forest soils is a prerequisite in predicting S04 concentration in the soil solution and in lake and stream waters. In this study, forest soil samples from the Gardsjon catchments, Sweden, were used to study S04 transport in soil columns from the upper three soil horizons (E, Bs, and BC). The columns were leached using a sequential leaching technique. The input solutions were CaS04 equilibrated with forest floor material. Leaching behavior of S04 and concentration in the effluent were measured from columns from individual horizons. S04 was always retained in the Bs and BC horizons, while... 

Generally speaking, matter transport in soil is slow (gronnd water tends to move a few m/year), permitting construction of steep chemical gradients inside soil which inflnence all mobility, speciation and bioavailability of qnite a nnmber of chemical elements. Elements may be kept from takeup from certain soil horizons, or stick to them in vertical transport or be volatalized snbseqnent to hydride or aUcyl formation (Wood 1975 Thayer 1995). 

Tokunaga T., Zawislanski P., Johannis P., Lipton D., and Benson S. (1994) Field investigations of selenium specia-tion, transformation, and transport in soils from Kesterson Reservoir and Lahontan valley. In Selenium in the Environment (eds. W. T. Frankenberger and S. Benson). Dekker, New York, chap. 5, pp. 119-138. 

By examining the effect of alkaline earth, lanthanide and yttrium metal ions on alginates, we can begin to understand how these metals interact with simple components of soil matter. After laying the groundwork with these studies, we can then predict possible mechanisms for ion transport in soils. 

In order to understand how chemical species are transported in soil, it is important to recognized that the soil column needs to be viewed as having at least three distinct reservoirs for contaminants. These reservoirs are - (1) the surface-soil layer, (2) the rooting zone, and (3) the deeper unsaturated zone. The nature of these soil components is described below. These layers are illustrated in Figure 1. 

Corapcioglu MY, Baehr A. 1985. Immiscible contaminant transport in soils and groundwater with an emphasis on petroleum hydrocarbons System of differential equations vs single cell model. Water Science and Technology 17 23-37. 

Physicochemical models of partitioning at the solid-water interface, such as that used here to model ion exchange, require detailed knowledge about the particles. The surface properties of the mineral phases present, as well as equilibrium constants for ion binding to both fixed and variable charge sites associated with each phase, are required. These data requirements and the uncertainty about modeling sorption in mixtures of minerals (e.g., 48-50) make such models difficult to apply to complex natural systems. This is especially the case for modeling solute transport in soil-water systems, which... 

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