Truesdell-Jones model

Truesdell-Jones model SIT model Pitzer model... 

The water is dominantly a NaCl brine with important amounts of Ca and Mg. The analysis indicates a stoichiometric ionic strength of 2,88 mol/kg, too high to justify use of the Davies equation. Because solubility of the akaline earth sulfates is directly proportional to the activity coefficients of Ca ", Sr +, Ba +, and SO ", we are interested in their values in the brine. We will compute the activity coefficients using the Truesdell-Jones (TJ) and SIT models. 

Chemical analyses of 10 groundwaters from springs and wells in carbonate rocks are shown in Table 6.7, along with their apparent CO2 pressures and saturation indices with respect to calcite and dolomite, which have been calculated using the computer model SOLMINEQ.88 (Kharaka et al. 1988). The composition of seawater and its modeled carbonate-mineral saturation state is also shown. SOLMINEQ.88 calculates the concentrations of ion pairs, such as CaHCO and MgSO, and uses the Truesdell-Jones equation to compute ion activity coefficients. (See Chap. 4.)... 

Garrels and Thompson s calculation, computed by hand, is the basis for a class of geochemical models that predict species distributions, mineral saturation states, and gas fugacities from chemical analyses. This class of models stems from the distinction between a chemical analysis, which reflects a solution s bulk composition, and the actual distribution of species in a solution. Such equilibrium models have become widely applied, thanks in part to the dissemination of reliable computer programs such as SOLMNEQ (Kharaka and Barnes, 1973) and WATEQ (Truesdell and Jones, 1974). 

The computerized aqueous chemical model of Truesdell and Jones (, 3), WATEQ, has been greatly revised and expanded to include consideration of ion association and solubility equilibria for several trace metals, Ag, As, Cd, Cu, Mn, Ni, Pb and Zn, solubility equilibria for various metastable and(or) sparingly soluble equilibrium solids, calculation of propagated standard deviation, calculation of redox potential from various couples, polysulfides, and a mass balance section for sulfide solutes. Revisions include expansion and revision of the redox, sulfate, iron, boron, and fluoride solute sections, changes in the possible operations with Fe (II, III, and II + HI), and updating the model s thermodynamic data base using critically evaluated values (81, 50, 58) and new compilations (51, 26 R. M. Siebert and... 

A sixth source of difference, which was unavoidable in preparation of the test cases, is the various ways each program handles the carbonate system. From a practical standpoint, the inorganic carbon system of natural waters is usually determined from the titration alkalinity. Because the titration alkalinity includes both carbonate and non-carbonate alkalinity, the titration alkalinity must -be corrected for noncarbonate alkalinity. Most models correct for the presence of H2BO0 and H SiOT but many other minor species should be considered and there is no general agreement as to the precise correction for non-carbonate alkalinity. In devising the correction used originally in WATEQ, Truesdell and Jones also... 

Zero-dimensional geochemical models are concerned with the contents of solutions of an aquatic subsystem (e.g. pore water, ocean water, precipitation, groundwater), the equilibria between the various dissolved species as well as their adjoining gaseous and solid phases. A computer model by the name of WATEQ (derived from water-equilibria) was published for the first time by Truesdell and Jones (1974). Unfortunately, this was done in the computer language PLl which has... 

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