Geochemical partitioning coefficients

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. 

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. 

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. 

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. 

The ionic radius criterion for interpreting geochemical distributions of trace elements was given a boost in the early 1970 s when correlations were shown to exist between ionic radii and partition coefficients of some trace elements (Onuma et al., 1968 Higuchi and Nagasawa, 1969 Jensen, 1973). The influence of cation radius and charge on trace element distribution patterns was demonstrated by measurements of the distribution coefficient, >, defined by... 

Nowosielski, B.E., Fein, J.B. (1998) Experimental study of octanol-water partition coefficients for 2,4,6-trichlorophenol and pentachlorophenol Derivation of an empirical model of chlorophenol partitioning behaviour. Appl. Geochem. 13, 893-904. 

Boron is present in freshwater as nonionized boric acid and negatively charged borate ion (B(0H)4 ). The ability of boron to adsorb on surfaces is a well-known characteristic of its geochemical cycle at the surface of the Earth. Spivack et al. (1987) determined partition coefficients of boron in the marine sediments off... 

Is the core a plausible reservoir These calculations indicate that, using presently available constraints, the core remains a plausible source of the He found in OIB. Measured high He/" He ratios would then be the result of mixtures of He from the core that has a solar nebula He/" He ratio with radiogenic " He from the mantle. However, the implications for other geochemical parameters also must be considered. Other elements that would be affected by bulk transfer of core material into the mantle include the Pt-group elements and volatiles that may be relatively abundant in the core, such as H and C. While some limits on the amount of transferred core material are provided by these (Porcelli and Halliday 2001), it should be noted that the amount needed to sustain the He flux is still very uncertain, and it is possible that upward revisions in the amount of noble gases within the early Earth, or in the metal/silicate partition coefficients, could reduce the required flux of core material by an order of magnitude or more. 

In practical geochemical and ecologic studies the composition of natural organic matter (liquid or solid) is in most cases unknown. So, as a rule, partition coefficients of a component i for a complex natural solution of unknown composition have to be dealt with. They are called absorption partition coefficient with organic matter. This coefficient Kw,i is experimentally determined and is equal to the ratio of balanced weight concentrations component i in organic matter and in water, according to equations 1.20 in (see Tikhomirov, 2016, v.l) and (2.314), i.e.,... 

Curti, E. (1999). Coprecipitation of radionuclides with calcite Estimation of partition coefficients based on a review of laboratory investigations and geochemical data. 

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. 

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