Speciation using calculator

The samples were collected in polyethylene bottles and stored at 4°C. Water samples were stabilized for arsenic speciation using phosphoric acid to yield a final concentration of 10 mM [2]. Wet material was used for the extraction and the dry weight was calculated by weighing a different part of the sample after drying (105°C). 

For these reasons, it is useful to evaluate the effects of forming or not forming aqueous sulfide complexing agents and sulfide precipitates on radionuclide solubilities and aqueous speciation. Therefore, calculations were performed for key radionuclides for two cases (1) reduction of sulfate to sulfide and bisulfide was allowed to occur as Eh was lowered and (2) sulfate reduction as a function of Eh was prohibited so that sulfate was the only sulfur complexing agent available at all Eh values. 

The lead contents of 206 soil samples determined by AAS indicated that such determination provides a useful parameter for soil comparison and discrimination in forensic science (Chaperlin 1981). Soil investigations near a former smelter in Colorado revealed that historic use of arsenical pesticides has contributed significantly to anthropogenic background concentrations of arsenic on certain residential properties. A variety of forensic techniques including spatial analysis, arsenic speciation and calculation of metal ratios were successful in the separation of smelter impacts from pesticide impacts (Folkes, Kuehster, and Litle 2001). 

The calculations described below are of two types first, recalculation of metal-ligand speciation and comparison with previous results, and secondly, interpretation of the toxicity data in terms of speciation using factor analysis and multiple regression. The speciation calculations were performed using REDEQL2 ( ) and SPSS (9) was used for factor analysis and multiple regression. 

Figure VII-15 Solubility data for Th02(am, hyd) in 0.5 M NaC104 a) from [1989MOO] and b) from [19940ST/BRU] (filled squares eaibonate-free solution open squares under C02(g) atmosphere which has, however, no effect on the speciation at pH < 4.5). The solubility constant and aqueous speciation are calculated using the hydrolysis constants and SIT coefficients selected in the present review...

Figure VII-18 Solubility data from [1965BAE/MEY] for Th02(cr) at 95°C. The solubility constant and aqueous speciation are calculated using hydrolysis constants selected in the present review for 1 M NaC104 at 95°C (c/ Section VII.3.5.1).

It is clear from the discussion earlier that in almost all cases where stability constants are obtained by fitting a function to some experimental points where there is more than one variable, the constants will be partially interdependent. Essentially this means that if the stability constant uncertainties are used, for example, for a speciation uncertainty calculation, then it will not be correct to use them as independent uncertainties (refer to Figure 3.13). 

In Figure 2 the solubility and speciation of plutonium have been calculated, using stability data for the hydroxy and carbonate complexes in Table III and standard potentials from Table IV, for the waters indicted in Figure 2. Here, the various carbonate concentrations would correspond to an open system in equilibrium with air (b) and closed systems with a total carbonate concentration of 30 mg/liter (c,e) and 485 mg/liter (d,f), respectively. The two redox potentials would roughly correspond to water in equilibrium wit air (a-d cf 50) and systems buffered by an Fe(III)(s)/Fe(II)(s)-equilibrium (e,f), respectively. Thus, the natural span of carbonate concentrations and redox conditions is illustrated. 

DOE. 1995c. Solubility-limited concentrations and aqueous speciation of U, Pu, Np, Am and Tc Comparison between results of Bruno and Sellin (1992) and calculations using GEMBOCHS (version R16). Washington, DC U.S. Department of Energy. NTIS/DE95015124. 

Garcia-Monco Carra et al. [296] have described a hybrid mercury film electrode for the voltammetric analysis of copper (and lead) in acidified seawater. Mercury plating conditions for preparing a consistently reproducible mercury film electrode on a glassy carbon substrate in acid media are evaluated. It is found that a hybrid electrode , i.e., one preplated with mercury and then replated with mercury in situ with the sample, gives very reproducible results in the analysis of copper in seawater. Consistently reproducible electrode performance allows for the calculation of a cell constant and prediction of the slopes of standard addition plots, useful parameters in the study of copper speciation in seawater. 

In a final example of the use of a sliding activity path, we calculate a speciation diagram, plotted versus pH, for hexavalent uranium in the presence of dissolved phosphate at 25 °C. We take a 10 mmolal NaCl solution containing 1 mmolal each ofUO +, the basis species for U(VI), and HPO4... 

Interactive Version 2.15.0 (Parkhurst Appelo 1999). The llnl.dat database distributed with PHREEQC was used for all calculations. Geochemical modeling was used to speciate the components of the tailings pore-water at discrete depths and to investigate the thermodynamic stability of mineral phases through out the tailings. 

With these experimental surface reaction parameters and the speciation program MICROQL the species distribution in the river using metal and particle concentrations, pH and alkalinity measured in the river at the concerned sampling data was calculated. Various assumptions for the complexation in solution may be used, which affect ai and thus Kd-... 

At equilibrium, the reactant concentrations and products can be used to define a mass ratio called an equilibrium constant (A). This constant can then be used to predict the equilibrium concentrations of the reactants and products from the total amount of C or from either the equilibrium concentration of the products or the reactants. Although K is referred to as an equilibrium constant, it is a function of salinity, temperature, and pressure. With the appropriate value of K, calculations can be made to predict the equilibrium speciation of elements in seawater. The procedure for doing this is provided in the next section along with an expansion of K to multicomponent chemical systems. 

Although computer programs are now used to perform speciation calculations, examining how these calculations are performed provides important insights into the limitations of the model predictions. Thus, we will step through a small part of the calculation used to generate the results presented in Figure 5.4, which represents the iron... 

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