Geochemical immobilization

This case study is interesting in that one hazardous waste (acrylonitrile) was quickly rendered nonhazardous after injection, whereas another (sodium thiocyanate) showed no evidence of decomposition during the duration of the study. The implication for geochemical fate assessment is that research should focus on the compounds likely to be most resistant to decomposition or immobilization, as they will be the ones most critical in demonstrating containment in a no-migration petition. 

Winchester, J.A. Floyd, P. A. 1977, Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chemical Geology, 20, 325-343. 

Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002).

The immobilization of dissolved chemical species by adsorption and ion exchange onto mineral surfaces is an important process affecting both natural and environmentally perturbed geochemical systems. However, sorption of even chemically simple alkali elements such as Cs and Sr onto common rocks often does not achieve equilibrium nor is experimentally reversible (l). Penetration or diffusion of sorbed species into the underlying matrix has been proposed as a concurrent non-equilibration process (2). However, matrix or solid state diffusion is most often considered extremely slow at ambient temperature based on extrapolated data from high tem-... 

Geochemical detection of uranium deposits in sandstone-type deposits depends on the geochemical behavior of U and pathfinder elements (Rose Wright 1980). Uranium is dispersed under oxidizing conditions but is immobile under reducing conditions. Adsorption on freshly precipitated Fe-oxides and certain types of organic matter also limits dispersion unless high concentrations of or... 

Fluor Daniel GTl, Inc. (now part of the IT Corporation), has developed in situ geochemical fixation technology to immobilize metallic contaminants in soil, sediment, sludge, and groundwater. The technology uses a site- and contaminant-specific combination of reagents to convert ionic contaminants to less soluble forms. In situ geochemical fixation has been used to remediate sites contaminated with chromium, uranium, molybdenum, and copper. 

This book focuses on geochemical approaches in immobilizing, isolating, or neutralizing waste derived from energy production and consumption. 

Estimates of storage capacity based on simple flow and equilibrium geochemical models indicate that the Rose Run Sandstone, by itself, potentially can store 30 years of emissions from the five largest coal-burning power plants in eastern Ohio. Ultimately the injected C02 can dissolve into the brine and be converted to the stable, immobile, carbonate mineral phases, primarily siderite, dawsonite, and calcite. 

Knicker, H. (2002). The feasibility of using DCPMAS 15N 13C NMR spectroscopy for a better characterization of immobilized N-15 during incubation of 13C and 15N enriched plant material. Org. Geochem. 33, 237-246. 

In contrast to the conventional PRB, a permeable reactive treatment zone (PRTZ) is a geochemically manipulated subsurface zone where aquifer material is altered to promote destruction or immobilization of target chemicals (e.g., flushed with sodium dithionite to create a zone of reduced iron [20-23]). Passive reactive wells (PRWs) are a series of wells or caissons containing a treatment material, through which water flows because of a permeability contrast between the wells and aquifer. A biologically reactive barrier (BRB), sometimes called a biocurtain, is a subsurface zone where microbiological activity is enhanced or modified to provide treatment of target chemicals. 

Considering the pH range 4—10 as the geochemical range, the redox potential due to the breakdown of water due to redox processes, the rare earths are predominantly present as Ln(III). Since the anions OH- and CO2 are present in natural environments, rare earths combine with these anions to form insoluble hydroxides and carbonates and hence immobilized. At lower pH, rare earth ions are adsorbed on clays, which are natural ion exchangers. The interactions of rare earth ions with humic and fulvic acids in soils, and Fe/Mn oxides are so strong, that they become immobile. 

Immobilization of P in the soil in the short or long term by geochemical fixation processes might, in some situations, play an important role in the cycling of P in pasture ecosystems. However, unlike in the acid savanna soils, where high P fixation is prevalent, only a relatively small proportion of Amazon soils (mainly Oxisols and Ultisols of... 

Aqueous Pb concentrations are critical for evaluating the effectiveness of P-induced Pb immobilization, since it is directly related to Pb bioavailability in contaminated soils (Ma and Rao, 1997). However, geochemical forms of Pb in soil affect its solubility, therefore directly influencing its bioavailability. Thus, assessing environmental impacts of Pb in soils by its aqueous concentrations alone is incomplete. In addition, knowledge of Pb distribution in different geochemical... 

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