Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Seawater species distributions

Solutions of equations (12.1)—(12.3) using selected ion pairing constants appropriate at 25°C and 0.7 mol kg 1 ionic strength (Garrels and Thompson, 1962 Millero and Schreiber, 1982) are consistent with the seawater species distributions shown in Table 12.2. [Pg.325]

When they calculated the species distribution in seawater, Garrels and Thompson (1962) were probably the first to apply chemical modeling in the field of geochemistry. Modern chemical analyses give the composition of seawater in terms of... [Pg.3]

It is clear from the species distribution that the dissolved components in seawater react to varying extents to form complex species (Table 6.5). Components Na+ and Cl- are present almost entirely as free ions. Only a few percent of their masses appear in complexes, most notably the ion pairs MgCl+, NaSOJ, CaCl+, and NaCl (Table 6.4). Components Ca++, SOJ-, and HCO3, on the other hand, complex strongly complex species account for a third to a half of their total concentrations. [Pg.84]

The resulting species distribution (Table 6.7), as would be expected, differs sharply from that in seawater (Table 6.4). Species approach millimolal instead of molal concentrations and activity coefficients differ less from unity. In the Amazon River water, the most abundant cation and anion are Ca++ and HCOJ in seawater, in contrast, Na+ and Cl- predominate. Seawater, clearly, is not simply concentrated river water. [Pg.94]

The species distribution (Table 6.9) calculated for the brine differs from that of seawater and Amazon River water in the large molalities predicted and the predominance of ion pairs such as NaCl, CaCl+, and MgCl+. The complex species make up a considerable portion of the brine s dissolved load. [Pg.99]

Calculated copper species distribution in seawater by different authors (in %). [Pg.7]

The unit used for the input of concentrations can be defined with the keyword units. Possible units are mass or moles per liter solution, moles per kg solution or moles per kg water. Concentrations thereby can be given in g, mg, ug (not pg) or mol, mmol, and umol. Temperature (temp) is denoted in °C. The density (density) can be entered in g/cm3, with a default of 0.9998. That information is especially important for highly mineralized waters, like e.g. seawater. To input the measured Eh value a conversion to the pE value is necessary (see chapter 1.1.5.2.2, Eq. 65). If no pE value is given, pE is assumed to be 4 by default. A redox couple (redox) can be defined to calculate the pE value that will be used to model the species distribution of redox sensitive elements if no pE is given. [Pg.86]

The complexation constants of the individual major seawater ions with otFeOOH determined in single salt solutions can be used to predict the titratable charge and surface species distribution of goethite in seawater. This prediction can then be compared with the experimentally determined charge of goethite in a mixed seawater type electrolyte. [Pg.288]

Table II is a summary of the surface species distributions with pH. These were used to calculate a titratable charge. The effect of the ionized surface species (FeO and FeOHj) on the titratable charge and surface species distributions is less than the effect of the potassium complexes. Also included in Table II are the % contributions of the individual complexes to the total calculated charge. In Figure 7 the calculated charge is compared with the titratable charge determined by the potentio-metric titration of aFeOOH in a major seawater ion electrolyte. Also included in Figure 7 is a compilation of the titration data used in determining the calculated charge. Table II is a summary of the surface species distributions with pH. These were used to calculate a titratable charge. The effect of the ionized surface species (FeO and FeOHj) on the titratable charge and surface species distributions is less than the effect of the potassium complexes. Also included in Table II are the % contributions of the individual complexes to the total calculated charge. In Figure 7 the calculated charge is compared with the titratable charge determined by the potentio-metric titration of aFeOOH in a major seawater ion electrolyte. Also included in Figure 7 is a compilation of the titration data used in determining the calculated charge.
The simplified mass and proton balance model determined what the surface species distribution of goethite would be in a mixed, seawater type electrolyte. This surface species distribution was used to calculate a surface charge for goethite. [Pg.294]

The other approach employs a geochemical computer model, such as PHREEQC (Parkhurst 1995 also Chap. 15) with an input of a complete seawater analysis. Such a model will then calculate the activity coefficients and the species distribution of the solution according to the complete analysis and the constants of the thermodynamic database used. These constants are well known with an accuracy which is usually better than the accuracy of most of our analyses at least for the major aquatic species. Together with the real constant of the solubility product a reliable saturation index (SI = log Q) is then calculated. The constants of solubility products are not accurately known for some minerals, but for calcite, and also for most other carbonates, these constants and their dependence on temperature and pressure are very well documented. [Pg.318]

Fig. 9.4 Distribution of carbonate species (a and c) and calcium species (b and d) in seawater after Nordstrom et al. 1979 (a and b) and in an anoxic pore water (c and d). The pore water sample was extracted from the core previously shown in Figure 3.1 and was taken from a depth of 14.8 m below the sediment surface. The calculation of species distributions was performed with the program PHREEQC (Parkhurst 1995)... Fig. 9.4 Distribution of carbonate species (a and c) and calcium species (b and d) in seawater after Nordstrom et al. 1979 (a and b) and in an anoxic pore water (c and d). The pore water sample was extracted from the core previously shown in Figure 3.1 and was taken from a depth of 14.8 m below the sediment surface. The calculation of species distributions was performed with the program PHREEQC (Parkhurst 1995)...
Fig. 11-7 Distribution of dissolved carbon species in seawater as a function of pH. Average oceanic pH is about 8.2. The distribution is calculated for a temperature of 15°C and a salinity of 35%o. The equilibrium constants are from Mehrbach et al. (1973). Fig. 11-7 Distribution of dissolved carbon species in seawater as a function of pH. Average oceanic pH is about 8.2. The distribution is calculated for a temperature of 15°C and a salinity of 35%o. The equilibrium constants are from Mehrbach et al. (1973).
Stolzberg [143] has reviewed the potential inaccuracies of anodic stripping voltammetry and differential pulse polarography in determining trace metal speciation, and thereby bio-availability and transport properties of trace metals in natural waters. In particular it is stressed that nonuniform distribution of metal-ligand species within the polarographic cell represents another limitation inherent in electrochemical measurement of speciation. Examples relate to the differential pulse polarographic behaviour of cadmium complexes of NTA and EDTA in seawater. [Pg.151]

For a first chemical model, we calculate the distribution of species in surface seawater, a problem first undertaken by Garrels and Thompson (1962 see also Thompson, 1992). We base our calculation on the major element composition of seawater (Table 6.2), as determined by chemical analysis. To set pH, we assume equilibrium with CO2 in the atmosphere (Table 6.3). Since the program will determine the HCOJ and water activities, setting the CO2 fugacity (about equal to partial pressure) fixes pH according to the reaction,... [Pg.82]

The purpose of this chapter is to outline the simplest methods of arriving at a description of the distribution of species in mixtures of liquids, gases and solids. Homogeneous equilibrium deals with single phase systems, such as electrolyte solutions (e.g., seawater) or gas mixtures (e.g., a volcanic gas). Heterogeneous equilibrium involves coexisting gaseous, liquid and solid phases. [Pg.318]


See other pages where Seawater species distributions is mentioned: [Pg.5]    [Pg.851]    [Pg.10]    [Pg.295]    [Pg.858]    [Pg.861]    [Pg.4481]    [Pg.648]    [Pg.851]    [Pg.6996]    [Pg.6]    [Pg.7]    [Pg.432]    [Pg.281]    [Pg.217]    [Pg.312]    [Pg.330]    [Pg.81]    [Pg.165]    [Pg.168]    [Pg.875]    [Pg.91]    [Pg.614]    [Pg.1580]    [Pg.1711]    [Pg.124]    [Pg.359]    [Pg.222]    [Pg.55]   
See also in sourсe #XX -- [ Pg.3 , Pg.82 , Pg.83 , Pg.84 , Pg.85 , Pg.86 , Pg.87 , Pg.88 , Pg.89 , Pg.90 , Pg.91 , Pg.92 ]

See also in sourсe #XX -- [ Pg.6 , Pg.80 , Pg.81 , Pg.82 , Pg.83 , Pg.84 , Pg.85 , Pg.86 , Pg.87 , Pg.88 , Pg.89 , Pg.90 ]




SEARCH



Species distribution

© 2024 chempedia.info