Soil particle surfaces

Cations form a diffuse layer of ions called the diffuse double layer or the electrical double layer around soil particles as depicted in Figure 5.10. The existence of the diffuse double layer means that the ions are not evenly distributed throughout the solution rather, cations are more concentrated close to soil particle surfaces and are less concentrated further away. This phenomenon must be kept in mind, particularly when electrochemical analytical methods of analysis are developed [5,7],... 

Thus, one approach to the liberation of electrostatically-bound ions from soil particle surfaces involves the use of partial leaches containing complexing ligands (such as halide salt solutions). These liberate the adsorbed metals by forming complexes, thereby out-competing the adsorption surfaces for these metals. 

Thirty-two soil samples on a N-S traverse were collected from the brunisolic B-horizon (20 cm average depth) in May, 2008 over the drill-defined Northeast Zone of the Gay s River carbonate hosted massive sulfide (CHMS) Zn-Pb deposit, Stewiacke, Nova Scotia. This mineral target is buried by up to 10 m of exotic till and c. 10 m of gypsum, and so represents an ideal location to evaluate the exploration performance levels of partial digestions designed to extract labile elements from soil particle surfaces. 

Klohn-Crippen Consultants, Ltd., has developed the ex situ ChemTech soil treatment process for the removal of heavy metals and organic contaminants from contaminated soil and sediment. The ChemTech process uses two mechanisms to remove contaminants physical scouring of the soil particle surface and chemical leaching of the contaminants from the soil particles. Processing takes place using a three-phase fluidized bed. The technology has been evaluated in pilot-scale... 

Strips the sorbed hydrocarbon phase from soil particle surfaces, enabling rapid biodegradation. 

G.L. Gresham, G.S. Groenewold, A.D. Appelhans, J.E. Olson, M.T. Benson, M.T. Jeffery, B. Rowland and M.A. Weibel, Static secondary ionization mass spectrometry and mass spectrom-etry/mass spectrometry (MS2) characterization of the chemical warfare agent HD on soil particle surfaces, Ini. J. Mass Spectrom., 208, 135-145 (2001). 

The ratio of to would be expected to be unity as long as the uranium stays locked inside undisturbed crustal rock in secular equilibrium with its progeny, but measurements show that the ratio is typically different than unity (EPA 1994). This disequilibrium occurs when the rock is disturbed by chemical or physical changes involving water. In the environment, a portion of the separates from the by what is theorized to be a physical process (alpha recoil ejection of the Th decay product from surfaces of soil particles) or a combination of physical and chemical processes (a transformation at the soil particle surface fractures the surface allowing access for water to dissolve the more soluble Th product) (NCRP 1984a). These processes can change the uranium isotope ratios in air, soil, and water. 

Sorption and Desorption Processes. Sorption is a generalized term that refers to surface-induced removal of the pesticide from solution it is the attraction and accumulation of pesticide at the soil—water or soil—air interface, resulting in molecular layers on the surface of soil partides. Experimentally, sorption is characterized by the loss of pesticide from the soil solution, making it almost impossible to distinguish between sorption in which molecular layers form on soil partide surfaces, precipitation in which either a separate solid phase forms on solid surfaces, covalent bonding with the soil particle surface, or absorption into soil partides or organisms. Sorption is generally considered a reversible equilibrium process. 

Non-polarised gases such as methane and helium can be adsorbed onto soil particle surfaces via molecular attraction. This attraction is weak and the gases can be separated from the soil by gentle heating, pressure reduction, or the combination of these two procedures. This mode of gas occurrence is less influenced by meteorological conditions than the free-molecule mode, and so the results are more repeatable. The samples are easier to handle but the desorption procedures need to be strictly controlled complete desorption is not necessary, but artifacts in the data due to variations in desorption... 

Aringhieri, R., and G. Pardini. 1989. Kinetics of the adsorption of potential-determining ions by positively charged soil particle surfaces. Soil Sci. 147 85-90. 

Only Al3+ is a common exchangeable cation in soils and is significant only in moderately to strongly acid soils, pH < 5.5. A1 and Fe are usually the second and third most common cations in total soil content, but only tiny fractions are exchangeable on soil particle surfaces and dissolved in the soil solution. 

Soil particle surfaces are also charged so they attract ions and water dipoles. The charge can be an atomic layer beneath the crystal surface so the interaction between, soil particles and water is weaker than between ions and water. At the edges of crystals, the charge is weaker but at the surface. 

One school of thought maintains that certain sites on soil surfaces can retain these cations strongly radiographs show the cations are both bunched and spread out on soil surfaces. Another school suggests that these adsorption sites are where the cations can mix as solid solutions with the other ions on the surfaces. The free energy of mixing on the surfaces (Appendix 3.2) is responsible for the strong retention rather than any uniquely favorable adsorption spots on soil particle surfaces. In any case, soil retention can reduce the aqueous solubility of these ions to well below that in equilibrium with their pure hydroxyoxides. 

As with cations and anions, soil interaction with molecules happens only if the substance contacts soil particles. Surface spreading or burial is insufficient the wastes must be mixed with the soil to react with it. The sensational Love Canal case, for example, involved the burial of organic liquids in 55-gallon (215-L) drums stacked in shallow trenches underground. I-tad the organic liquids been mixed and allowed to interact with the soil, the leakage and movement after the thin steel drums corroded might never have happened, and it certainly would have been less severe. 

Adsorption water accounts for water molecules bound to the soil particle surfaces by electrostatic forces, hydrogen bonds and van der Waals forces. 

CHANGE OF ZETA POTENTIAL OF SOIL PARTICLE SURFACES... 

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