Soil-column techniques

Analytical solutions to transport equations that simultaneously consider adsorption and transformation, when used in concert with appropriate soil column techniques, offer substantial promise for study of the environmental fate of organic chemicals. Such methods can be widely used since a number of such solutions already exist in the scientific literature. It remains only to design research programs in which those who understand such equations are working with those who can design and execute complementary chemical studies. 

The soil-column techniques fall into four major categories based on the solvent involved, namely (Fuller Warrick, 1985) ... 

The soil-column technique requires that only the readily measurable properties of the disposal system be determined. These include (1) soils data (physical and chemical), (2) transport fluid data (e.g., total organic carbon, soluble common salts, pH, etc.), (3) soil-column data, and - in particular - (4) breakthrough curves and statistical analyses (Fuller Warrick, 1985). 

Weng L, Temminghoff EJM, van Riemsdijk WH. Determination of the free ion concentration of trace metals in soil solution using a soil column Donnan membrane technique. Ear. J. Soil Sci. 2001 52 629-637. 

The analytical technique assumes that the calculated diffusion coefficients for various individual pollutants represent average values throughout the length of the soil column. Although the interactions established between the pollutant and the soil cause continuous alteration in the transmissivity characteristics of the soil, the procedure which uses the analytical solution can only provide average values, because the values of Ce are obtained at the outlet end of the test sample. Thus, a representative diffusion coefficient should be calculated for individual layers in the soil column, and/or each pore volume passage of ef-... 

Mansour, M., Thaller, S., andKorte, F. Action of sunlight on parathion. Bull. Environ. Contam. Toxicol, 30(3) 358-364,1983. Manzurola, E. and Apelblat, A. Solubilities of L-glutamic acid, 3-nitrobenzoic acid, p-toluic acid, calcium-L-lactate, calcium gluconate, magnesium-DL-aspartate, and magnesium-L-lactate in water, J. Chem. Thermodyn., 34 (7) 1127-1136, 2002. Maraqa, M.A., Zhao, X., Wallace, R.B., and Voice, T.C. Retardation coefficients of nonionic organic compounds determined by batch and column techniques. Soil Sci. Soc. Am. J., 62(1) 142-152, 1998. 

In a review of deep soil mixing techniques, Bruce et al. stated that large-scale soil mixing systems may cost 80,000 to 200,000 to mobilize (costs were reported to be lower for methods such as lime cement columns). Typical treatment prices for deep soil mixing technologies were estimated to range from 50 to 100/m (D207238, p. 4). 

Subsurface environmental conditions are suboptimal with low temperatures and low concentrations of growth nutrients. The decline of bacterial inoculae by protozoan predation is of major concern in soil (Acea etal., 1988 Acea Alexander, 1988 Casida, 1989) but may not be a factor in saturated subsurface environments. Immobilization of cells to carrier material may enhance microbial survival in the environment through control of predation and supply of nutrients and moisture. Stormo Crawford (1992) developed a cell immobilization technique for production of small beads (2-50 /rm) consisting of agarose and cells of PCP-degrading Flavobacterium sp. Microencapsulated Flavobacteria efficiently degraded PCP and survived for two years in soil columns at environmental conditions (Stormo Crawford, 1994). These results show that microencapsulation may be a very useful tool in in situ bioremediation. 

Miscible displacement or packed column techniques also are widely used (i.e., Brusseau et al., 1990 Lee et al., 1991). In this approach, the chemical of interest is pumped through a soil column and the concentration of the chemical in the column effluent is monitored over time. The resulting concentration versus time curve is subtracted from that of a conservative (non-sorbed) tracer, pumped through the column at the same time or in a different experiment, to calculate the extent of sorption. 

Maraqua, M.A., X. Zhao, and T.C. Voice. 1998. Retardation coefficients of nonionic organic compounds determined by batch and column techniques. Soil Sci. of Am. J. 

The development of electrophoretic techniques afforded possibilities for fractionations based on charge density differences. Duxbury (1989) has reviewed applications of different electrophoretic separation methods, including zone electrophoresis, moving boundary electrophoresis, isotachophoresis, and isoelectric focusing (IEF). Preparative column electrophoresis (Clapp, 1957) and continuous flow paper electrophoresis (Hayes, 1960 summarized by Hayes et al., 1985) methods have been used to separate components isolated from sapric histosol soils. These techniques allowed separation of polysaccharides from the colored components the electrophoretograms of the colored components were diffuse, showing a continuum of components of different charge densities. 

The packed column technique is also widely used (Lee et al., 1991 Macintyre et al 1991), in which a solution of the chemical under investigation is pumped through a soil column, with the effluent concentration being monitored over time. Good agreement between batch and column methods has generally been observed (Doucette, 2003), although some appreciable differences have been noted (Maraqua et al., 1998). 

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... 

Use of surfactants may prove to be a good technique for separating diesel fuel fit>m a soil as indicated in results obtained in preliminary screening tests (removal efficiencies up to 97%) and from results of other studies performed on laboratory-packed soil columns (removal efficiencies up to 8.6%), assuming flow through the bulk matrix. Results presented here using undisturbed, diesel-fuel-contaminated soil cores taken from a site indicate, however, that removal of diesel fuel from the soil flooded with surfactant solution was generally less than 1%. Low removal efficiencies in these soil... 

The technique of positron emission tomography (PET), developed for medical applications, offers also the capability to map flow distributions in geological layers. Conservative tracers, marked with a positron emitting radionuclid, can be used for hydrodynamic studies in soil columns. Suitable tracers for such studies are for example kali-umfluoride- or cobalthexacyanocomplex, marked with the positron emitting isotops F-18 and Co-58 respectivly. 

Ayadat, T. and Hanna, A.M. 2005. Encapsulated stone columns as a soil improvement technique for... 

The stone column technique comprises the insertion of compacted columns of granular material into the soils to be treated. These columns displace the existing deposits and are tightly interlocked with the surrounding soil. 

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