Programs phreeqc

Aqueous geochemical modeling was performed using the program PHREEQC... 

The program PHREEQC dates back to 1980 (Parkhurst et al. 1980), at that time written in FORTRAN and named PHREEQE. The option of the program comprised ... 

The data sets WATEQ4F.dat, MINTEQ.dat, PHREEQC.dat and LLNL.dat are automatically installed with the program PHREEQC and can be chosen from the menu item Calculations/File under Database File. The internal structure of these thermodynamic data sets has already been explained in great detail in chapter... 

Charlton S. R., Macklin C. L., and Parkhurst D. L. (1997) PHREEQCI—A Graphical User Interface for the Geochemical Computer Program PHREEQC. US Geol. Surv. Water-Resour. Invest. Report 97-4222, 9pp. 

Figure 9.4 shows the distribution of carbonate and calcium species in ocean water and in an anoxic pore water, calculated with the program PHREEQC (Parkhurst 1995). It is evident that about 10 % of total calcium is prevalent in the form of ionic complexes and 25 - 30 % of the total dissolved carbonate in different ionic complexes other than bicarbonate. These ionic complexes are not included in the equations of Sections 9.3.1 and 9.3.2. Accordingly, the omission of these complexes would lead to an erraneous calculation of the equilibrium. The inclusion of each complex shown in Figure 9.4 implies further additions to the system of equations, consisting in another concentration variable (the concentration of the complex) and a further equation (equilibrium of the complex concentration relative to the non-... 

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)...

Table 9.3 Model calculation applying the computer program PHREEQC (Parkhurst 1995) to a sample of ocean water in a water depth of approximately 1000 m, near the equator. The constant of the solubility product for calcite is corrected for temperature and pressure. The decomposition of organic substance due to the presence of free oxygen in the water column has been included.

Table 15.2 For an analysis of Table 15.1, this allocation of the aquatic species was calculated with the geochemical model program PHREEQC.

The only hmitation is one s own knowledge as to the process to be modeled. The program PHREEQC can be obtained from the internet as public domain software, including an elaborate, very informative description and many examples, at ... 

The examples presented in the following and in Section 9.2 have been calculated exclusively with the program PHREEQC. 

Fig. 15.3 Geochemical model calculation using the program PHREEQC. To an oxic seawater with calcite in equilibrium (cf. Table 15.4) an organic substance is gradually added automatically leading to a redox reaction. The system should continue to be open to calcite equilibrium, but sealed from the gaseous phase...

Table 15.4 In the seawater analyses shown in Tables 15.1 to 15.3, an equilibrium adaptation to the mineral calcite (SI = 0) and to the atmosphere with log pC02 = -3.47 (equivalent to pC02 = 0.00034) and log p02 = -0.68 (equivalent to p02 = 0.21) was calculated. This model calculation was performed with the program PHREEQC (Pankhurst 1995, Parkhurst and Appelo 1999).

Fig. 15.4 Geochemical model calculation using the program PHREEQC. In an anoxic system (state at the end of the model calculation from Fig. 15.3), the gradual addition of organic matter to the redox reaction is continued, whereby the system is kept open for calcite equilibrium and sealed from the gaseous phase. Initially, the dissolved sulfate will be consumed, in the course of which low amounts (logarithmic scale) of methane will emerge. Only after the sulfate concentration has become sufficiently low, will the generation of methane display its distinct increase.

For example, the database (llnl.dat) for program phreeqc, an excellent and versatile program from the USGS, contains the following lines ... 

Diamonds calculated by program phrqpitz. Circles calculated by program GYPSUM (see Appendix E). Dash-dot line calculated by program phreeqc. 

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