Geochemical partitioning

Empirically determined retardation factors (either partition coefficients or breakthrough curve measurements, which are the change in solute concentration measured over time in laboratory or field experiments) have been widely used because of their inherent simplicity.162 Modeling of specific geochemical partition and transformation processes is not necessary if the retardation factor can be determined empirically. 

Deuel, L.E. and Holliday, G.H. (1998) Geochemical partitioning of metals in spent drilling fluid solids./. I inerg. Resour. Technol. — Irons. ASME, 120, 208-214. 

Phosphorus Biogeochemistry and Cycling Current Research Table 4 Geochemical partitioning of reactive-P burial fluxes. 

Blundy J, Wood B (2003) Mineral-melt partitioning of uranium, thorium and their daughters. Rev Mineral Geochem 52 59-123... 

While over the past ten years, our ability to measure U-series disequilibria and interpret this data has improved significantly it is important to note that many questions still remain. In particular, because of uncertainties in the partition coefficients, fully quantitative constraints can only be obtained when more experimental data, as a function of P and T as well as source composition, become available. Furthermore, the robustness of the various melting models that are used to interpret the data needs to be established and 2D and 3D models need to be developed. However, full testing of these models will only be possible when more comprehensive data sets including all the geochemical parameters are available for more locations and settings. 

Blatter DL, Carmichael ISE (1998) Hornblende peridotite xenoliths from central Mexico reveal the highly oxidized nature of subarc upper mantle. Geology 26 1035-1038 Blundy J, Wood B (2003) Mineral-melt partitioning of uranium, thorium and their daughters. Rev Mineral Geochem 52 59-123... 

Lundstrom CC, Shaw H, Ryerson F, Phinney D, Gill J, Williams Q (1994) Compositional controls on on the partitioning of U, Th, Ba, Pb, Sr and Zr between clinopyroxene and haplobasaltic melts implications for uranium series disequilibria in basalts. Earth Planet Sci Lett 128 407-423 Lnndstrom CC (2003) Uranium-series disequilibria in mid-ocean ridge basalts observations and models of basalt genesis. Rev Mineral Geochem 52 175-214... 

Quigley MS, Honeyman BD, Santschi PH (1996) Thorium sorption in the marine enviromnent equilibrium partitioning at the Hematite/water interface, sorption/desorption kinetics and particle tracing. Aquat Geochem 1 277-301... 

At the simplest level, the processes that most influence geochemical fate can be divided into three groups partition, transformation, and transport ... 

Table 20.4 presents the partition and transformation processes known to occur in the near-surface environment along with the special factors that should be considered when evaluating data in the context of the deep-well environment. Geochemical processes affecting hazardous wastes in deep-well environments have been studied much less than those occurring in near-surface environments (such as soils and shallow aquifers). Consequently, laboratory data and field studies for a particular substance may be available for near-surface conditions, but not for deep-well conditions. 

In recent years, there has been an increasing level of interest in the use of 234Th/238U disequilibrium in the marine environment to study geochemical processes with short time scales (up to 100 days), particularly those associated with carbon cycling in the oceans [34-36] and the partitioning of pollutants between the dissolved and particulate phases [37,38]. However, the analysis of 234thorium is constrained by its short half-life and its low concentration in seawater, so appropriate analytical techniques must be rapid and sensitive and preferably should allow shipboard analysis. 

The partitioning of As in the aquifer solid-water interface can best be explained with the distribution coefficient, Kd (a ratio of solute adsorbed in sediment to that of dissolved in groundwater). Due to being simplistic in nature, Kd has long been well appreciated as well as applied by geochemical modelers. 

Honeyman, B. D., and J. O. Leckie (1986), "Macroscopic Partitioning Coefficient for Metal Ion Adsorption Proton Stoichiometry at Variable pH and Adsorption Density", in J. A. Davis and K. F. Hayes, Eds., Geochemical Processes at Mineral Surfaces, ACS Symposium, Washington, DC. 

The geochemical fate of most reactive substances (trace metals, pollutants) is controlled by the reaction of solutes with solid surfaces. Simple chemical models for the residence time of reactive elements in oceans, lakes, sediment, and soil systems are based on the partitioning of chemical species between the aqueous solution and the particle surface. The rates of processes involved in precipitation (heterogeneous nucleation, crystal growth) and dissolution of mineral phases, of importance in the weathering of rocks, in the formation of soils, and sediment diagenesis, are critically dependent on surface species and their structural identity. 

Bigeleisen and Mayer (1947) simplified the reduced partition function by observing that vibrational frequency shifts caused by isotope substitution are relatively small (except when deuterium is substituted for normal hydrogen). When the dimensionless quantity hv/kr is of the order 5 or less (corresponding to a typical 1000 cm vibration at 288 K)—a condition applicable to most geochemical situations. 

Gas-liquid relationships, in the geochemical sense, should be considered liquid-solid-gas interactions in the subsurface. The subsurface gas phase is composed of a mixture of gases with various properties, usually found in the free pore spaces of the solid phase. Processes involved in the gas-liquid and gas-solid interface interactions are controlled by factors such as vapor pressure-volatilization, adsorption, solubility, pressure, and temperature. The solubility of a pure gas in a closed system containing water reaches an equilibrium concentration at a constant pressure and temperature. A gas-liquid equilibrium may be described by a partition coefficient, relative volatilization and Henry s law. 

Watson E. B. (1976). Two-liquid partition coefficients Experimental data and geochemical implications. Contrib. Mineral Petrol, 56 119-134. 

Wright I, Grady MM, PUlinger CT (1990) The evolution of atmospheric C02 on Mars the perspective from carbon isotope measurements. 1 Geophys Res 95 14789-14794 Wunder B Meixner A, Romer R, Wirth R, Heinrich W (2005) The geochemical cycle of boron constraints from boron isotope partitioning experiments between mica and fluid. Lithos 84 ... 

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