Chemical Modeling of Aqueous Systems II - American Chemical Society

Chapter 11

Reconstruction of Reaction Pathways in a Rock-Fluid System Using MINTEQ Hannah F. Pavlik

1,3

2

and Donald D. Runnells

1

F. G. Baker Associates, 2970 Howell Road, Golden, CO 80401 Department of Geological Sciences, University of Colorado, Boulder, CO 80309-0250

Downloaded by UNIV OF PITTSBURGH on February 13, 2016 | http://pubs.acs.org Publication Date: December 7, 1990 | doi: 10.1021/bk-1990-0416.ch011

2

The mass transfer model MINTEQ was used to evaluate probable reaction pathways driving the reaction of processed oil shale leachate (Lawrence Livermore L2 leachate) with a sandstone of the Uinta Formation collected near Parachute, Colorado. The purpose of the study was to model the chemical interactions associated with the accidental discharge of oil shale leachate into the subsurface. The geochemical interaction of leachate and sandstone was reconstructed in consecutive steps that were considered additive toward the attainment of final equilibrium. The outcome of each hypothetical equilibration step was used as the starting point for successive chemical mass balance calculations. Modeling results suggest that the approach to chemical equilibrium is controlled by the recarbonation of the leachate, during which Ca activity and pH are driven by precipitation of calcite. Recarbonation is accompanied by the apparent precipitation of sepiolite from the leachate, dissolution of magnesium from an inferred magnesium carbonate mineral in the sandstone, and partitioning of lithium and fluoride between liquid and solid phases. The adsorption isotherms for Li and F were linear and insensitive to the system parameters, and therefore a constant Kd was used to model surface reactions involving Li and F. Modeling results compare favorably with laboratory studies of the interaction between sandstone and leachate. 2+

This paper is the result of research conducted to evaluate the use of distribution coefficient (Kd) values and mineral solubility data to simulate migration of contaminants from disposal sites of oil shale waste planned in the Piceance Creek Basin of western Colorado. In a broad context, the purpose of the research was to simulate geochemical impacts of the accidental discharge of oil shale leachate into the subsurface. The aquifer of concern was a sandstone member of the Uinta Formation, the bedrock that underlies potential disposal sites for oil shale waste near Parachute, Colorado. The contaminant fluid was a leachate derived from the Lawrence Livermore L2 modified in-situ processed shale. The interaction of leachate and sandstone was studied in a series of batch experiments in which crushed samples of Uinta Sandstone were reacted with the leachate for five days. The contact time was determined in previous screening experiments which showed that major chemical constituents in the leachate had attained a steady-state composition during this period. During the experiments, the initial and final compositions of the leachate were determined. Characterization of the Uinta Sandstone and the L2 leachate and details of the analytical methods used in these studies have been described elsewhere (I). MINTEQ (2) was the equilibrium mass-transfer code chosen to model the geochemical interaction between leachate and sandstone. The model was selected to perform three functions for which it is well-suited: (1) To compute the activity of major inorganic species in the L2 leachate before and after reaction with the sandstone; (2) To calculate and evaluate the solubility controls imposed on the geochemical system during recarbonation; and, 3

Current address: EBASCO Services, 143 Union Boulevard, Lakewood, CO 80228 0097-6156/90/0416-0140$06.00/0 c 1990 American Chemical Society

In Chemical Modeling of Aqueous Systems II; Melchior, Daniel C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

11.

PAVLIK & RUNNELLS

Reconstruction of Reaction Pathways

141

(3) To model the partitioning of lithium and fluoride between solid and liquid phases. Hypothetical reaction pathways were evaluated in four general stages. First, the chemical composition of the L2 leachate before and after reaction with the sandstone was examined and plausible reactions that might represent stages of partial equilibrium were selected. Second, MINTEQ was used to compute the equilibrium composition of the leachate at each reaction step, given the precipitation or dissolution of plausible minerals and assuming that the system was closed to C 0 . Third, the outcome of each hypothetical equilibration step was used as input for subsequent mass balance calculations. And fourth, after each equilibration step, progress toward equilibrium was reevaluated through comparison of predicted and observed leachate chemistry. Because of the complex mineralogy of the Uinta Sandstone and the complex chemistry of the leachate, it was impractical to measure all of the parameters needed to simulate surface reactions using the complexation algorithms in MINTEQ. Therefore, the more generalized approach of using empirical Kd values for L i and F was tested and found to be appropriate. The Kd parameter represents a general descriptor of the surface reactions occurring in this rock-fluid system. As is well known, the Kd is not a universal parameter but must be tested and verified for each system of interest.


2

Composition and Properties of the Uinta Sandstone The Uinta Formation is the stratigraphie unit that overlies the Tertiary Eocene oil shale deposits of the Green River Formation in western Colorado. This stratigraphie unit contains interbedded fluviatile and lacustrine beds marking the margins of ancient Lake Uinta (3-6). It is characterized by tuffaceous siltstones and dolomitic limestones which grade into medium to fine grained orange sandstones. Tuff beds containing diagenetic zeolite minerals are abundant in both the Green River and Uinta Formations (7). The suite of minerals found in the Uinta Sandstone collected from Parachute Creek reflects the unique geochemical environment provided by Lake Uinta. The dominant minerals in the fresh sandstone are quartz, sodium plagioclase feldspars, and potassic feldspars as indicated by X-ray diffraction analysis ( 1). Important accessory minerals are calcite, nahcolite, dolomite-ankerite, and talc. Trace minerals include iron-enriched magnesite in the siderite-magnesite series, pyrite, pyrrhotite, and hematite. Chemical properties of representative samples of the Uinta Sandstone are summarized in Table I. Characterization of L2 Oil Shale Leachate The fluid generated by agitating the L2 processed shale in water in closed containers for 30 days attained a pH of 11.8. The geochemistry of high-pH oil shale leachates has been studied by a number of investigators as part of the U.S. Department of Energy Oil Shale Program (for example, 8-10). The high pH has generally been attributed to the hydrolysis of calcium and magnesium oxides produced by the decomposition of carbonates during retorting (11,12). The L2 leachate is essentially a sodium-sulfate solution containing significant concentrations of K, Ca, Mo, F, Li, Si, inorganic carbon, OH, and CI. The ionic strength ranges from 0.08 to 0.09. Arsenic is present in trace concentrations. The organic fraction of the L2 leachate was not characterized in this study; however, the concentration of total dissolved organic carbon in the leachate was 8 mg/L. In view of the high concentrations of sulfate (2765 mg/L) and carbonate (428 mg/L) as complexing ligands, we do not believe that the dissolved organic carbon in the leachate will play a significant role in complexation. Speciation of the fluid was modeled using MINTEQ. The major inorganic species in the L2 leachate are listed in Table II. The thermodynamic data base for MINTEQ was adapted from that of WATEQ3 (Τ3-15)· The V A X version of the model used in this study was obtained from Battelle Pacific Northwest Laboratory and implemented at the University of Colorado by Davis (16). PRELIMINARY SCREENING OF PLAUSIBLE REACTIONS Batch reaction experiments were conducted and the data obtained were examined to establish changes in aqueous speciation that had occurred in the L2 leachate during contact with the Uinta Sandstone. The rock-fluid system was assumed to have attained a state of "apparent equilibrium" during the batch experiments; that is, it was assumed that both equilibrium and non-equilibrium



C H E M I C A L M O D E L I N G O F A Q U E O U S S Y S T E M S II

T A B L E I. Chemical Properties of the Uinta Sandstone

Analysis

Results

pH (1:1 distilled H 0 after 2 hr)

8.4 ± 0.02

2

Specific Conductance (1:1 distilled H 0 after 2 hr) 2

Oxid. org. C

0.18 ± 0.03 wt %

Total carbonate C

0.97 ± 0.64 wt %

Total free Fe

2.1 ± 0 . 3 wt %

Amorphous Fe

0.30 ± 0.04 wt %

Total free Si

0.5 ± 0 . 1 wt %

Exchangeable Ca

1.2 ±

0.1 wt %

Exchangeable Mg

0.5 ±

0.1 wt %

Zero net surface charge (Na S0 )

pH = 6.7

2

4

Cation exchange capacity (Na saturation)

10.4 ± 0.3 meq/100g

Anion exchange capacity (CI exchange)

0.07 ± 0.02 meq/100g

BET Surface Area Crushed bedrock CaC0 (s) + 2 H 2

2

+

(1)

3

Carbon dioxide partial pressure was not directly measured during the batch experiments. However, it was observed that in the absence of Uinta Sandstone, when the fluid is open to atmospheric carbon dioxide (theoretical log pCO = -3.57 atm. at the University of Colorado), it gradually recarbonates and the pH drops from 11.8 to 9.6 after 36 days. Based on a knowledge of the mineralogy of the Uinta Sandstone, the mineral phases most likely to be controlling the solubility of Ca in the sandstone - L2 leachate system are calcite, dolomite, gypsum, and fluorite. Stability lines and saturation indices calculated for these minerals are presented in Figure 1 and Table III, respectively. The observed data point (black circle) plotted in Figure 1 represents the measured pH and log C a activity in the L2 leachate after reaction with the Uinta Sandstone. The log C 0 gas partial pressure of -2.95 atmosphere is based on the measured pH and alkalinity of the reacted solution. The open circle represents the log Ca activity and pH calculated by MINTEQ for the raw leachate recarbonated to a log C 0 partial pressure of -2.95 atmosphere. The leachate apparently developed a C 0 gas overpressure because equilibrium with calcite was attained in scaled containers at the relatively low pH of 7.91 (18). The calcite-dolomite line shown in the figure represents the pH-dependent activity of Ca in equilibrium with both calcite and dolomite. The data presented in Figure 1 and Table III illustrate that upon recarbonation and exposure to the sandstone, the activity of Ca in the leachate most closely approaches equilibrium with calcite. Both before and after reaction with the sandstone, Ca activity is undersaturated with respect to gypsum and fluorite and oversaturated with respect to dolomite. The gypsum and fluorite solubility lines in Figure 1 were developed using S0 and Ρ activities calculated in the raw leachate. A summary of the response of the leachate-sandstone system to recarbonation is presented in Figure 2. The figure illustrates that the approach to equilibrium with calcite (according to Equation 1) can be simulated by the progressive dissolution of C 0 gas into the leachate and by equilibration of the leachate with calcite in the Uinta Sandstone. The recarbonation pathway for the system was simulated by MINTEQ as follows (Figure 2). First, MINTEQ was used to calculate the partial pressure of C 0 gas in equilibrium with the two fluids listed in Table III. Based upon measured alkalinity and pH, the raw L2 leachate (point 1, Figure 2) was computed to have a C 0 pressure of 10* atmosphere. After 5-day reaction with the Uinta Sandstone (point 4, Figure 2), the measured pH and alkalinity of the fluid yielded a calculated C 0 pressure of 10 · atmosphere. Leachate recarbonation was simulated by fixing the C 0 gas partial pressure of the unreacted fluid in the absence of sandstone at the theoretical value of 10 atmosphere (point 2, Figure 2), and in the presence of sandstone at the value of 10 atmosphere calculated from leachate chemistry (point 3, Figure 2). It is assumed that, when open to the atmosphere, the system will ultimately approach equilibrium with ambient C 0 pressure (in Boulder) of 10 · atmosphere (point 5, Figure 2). z

2+

2

2+

2

2

2+

2+

2+

2r

4

2

2

23

2

2 95

2

2

157

195

2

3 57



PAVLIK & RUNNELLS


T A B L E ID. M I N T C Q < ^ t a i l a t e d Saturation Indices for Selected Minerals i n the L 2 Leachate Before and After Reaction with the Uinta Sandstone

Mineral

Calcite Gypsum Fluorite Dolomite Talc Sepiolite Magnesite Hydromagnesite Nesqehonite Brucite Diopside

SI Before Reaction

Log SI After Reaction

2.71 -0.26 -0.30 1.97 4.15 0.21 -1.24 -11.17 -3.65 0.34 5.78

0.25 -0.14 -0.81 0.31 -0.45 -2.12 -0.44 -12.45 -2.85 -4.15 -2.02


145


146

CHEMICAL MODELING OF AQUEOUS SYSTEMS II

(1) Observed raw leachate at p C 0 = 10atm 2

(2)

22

h

8

2

2

Simulated recarbonated leachate at p C 0 = 10atm 2

Simulated recarbonated leachate at p C 0 = 103

(3)

3

(4)

5

7

atm

2

Leachate observed after reaction with sandstone at p C 0 = 10- - atm 2

2

(1)

(5)

20

95

Leachate observed after reaction with sandstone at 10" - atm 3

•L ™ +

9 5

57

18 Closed system

16

14

12

• Observed data point Ο Predicted data point

-8

-L -7

_L -6

Open system

-5

-4

-2

log C 0 ( g ) Pressure 2

Figure 2. Simulated recarbonation of the L2 leachate and the approach to system equilibrium with calcite (error bars fall within the area of the black circles).


11.

PAVLIK & RUNNELLS


147

Magnesium and Silica Solubility Controls 2+

2+

Recarbonation of the L2 leachate affects the activity of both C a and M g by lowering the pH. Key mineral phases in the sandstone-leachate system which might control the activity of M g are shown in Figures 3 and 4. In the computations for these diagrams, dissolved silica activity and pH were fixed at the values observed after reaction with the sandstone. Calculated saturation indices for selected Mg-bearing minerals are given in Table III. As shown by the raw L2 leachate data point (empty circle) in Figure 3, the leachate is initially supersaturated with respect to (at least) calcite, dolomite, talc, magnesite, sepiolite, hydromagnesite, nesquehonite, and brucite. After reaction with the Uinta Sandstone (indicated by the solid circle, point L2-USS in Figure 3), M g activity appears to be most nearly controlled by the solubility of magnesite. Tb better understand the magnesium and silicate chemistry of the rock-fluid system, the solubilities of talc, sepiolite, and diopside are compared in Figure 4. These three minerals were plotted because they have been reported to be stable in high silica, alkaline systems similar to the one under study (l_9-23). The mineral stability lines were developed using the following equations: 2+


2+

3Mg

2+

4Mg

2+

Mg

2+

+ 4H4Si0 ° "•Mg Si O (OH) + 4 H 0 + 6 H (talc) 4

3

4

10

2

+ o r ^ S K V - M&Si.O^Orfy.oHP + 8 H (sepiolite) + Ca

2+

+

(2)

2

+

(3)

+

+ 2H Si0 ° +MgCaSi 0 + 4 H + 2 H 0 (diopside) 4

4

2

6

2

(4)

Inspection of Figure 4 indicates that after reaction with the Uinta Sandstone for five days (see data point L2-USS in the figure), the activity of M g in solution most closely approaches apparent equilibrium with talc or sepiolite. However, these results must be interpreted with caution. The published literature contains large discrepancies in the thermodynamic data available for the stabilities of talc and sepiolite (24,25). Garrels and Mackenzie (23}, among others, have reported that sepiolite precipitates preferentially to talc in silica-rich, alkaline fluids. Similarly, Nordstrom and Munoz (24) noted that error in the existing thermodynamic data is sufficiently large to reverse the relative stabilities of these two magnesium silicate minerals. On the basis of the data plotted in Figure 4, and the field evidence for occurrences of sepiolite (20,22), it seems reasonable to assume that sepiolite is the solid phase most likely to control the chemistry of magnesium in the presence of dissolved silica in this system. 2+

Partitioning of Lithium and Fluoride Information on the partitioning of dissolved lithium and fluoride species between liquid and solid phases was obtained from sorption isotherms derived for the rock-fluid system in a parallel research effort (1_,26). These studies showed that the distribution coefficient parameter successfully integrated the surface interactions of lithium and fluoride with the Uinta Sandstone; this approach provided a usefulfirst-approximationfor modeling sorption in the system. Isotherm data indicated that for both lithium and fluoride: (1) equilibrium, reversible partitioning occurred, (2) the slope of the partitioning function was constant and linear, (3) the choice of solid/solution ratio (from 1:5 to 1:20) had no statistically significant effect on the determination of the distribution coefficient, and, (4) the Kd value was independent of concentration, pH, and ionic strength effects after equilibrium was attained. Experimental Kd values obtained for lithium and fluoride in the Uinta Sandstone-L2 leachate system were 0.6 + 0.1 mL/g and 2.2 +_ 0.5 mL/g, respectively.

American Chemical Society. Library

1155 16thSystems St., N.W. In Chemical Modeling of Aqueous II; Melchior, Daniel C., et al.; ACS Symposium Series; American Chemical Washington. DX. Society: 20036 Washington, DC, 1990.


148


Thermodynamic Data Sources (12) (15) (15)a (1_5)£ (15)ED (22)

Ball et al., 1980 Truesdell and Jones, 1974 Ibid (amorphous sepio.) Ibid (crystalline sepio.) Ibid ( M g hydromag.) Plummer et al., 1976 5

(22) (2S)m (22) (2fJ) (2ΰ)Γϋ

Stumm and Morgan, 1981 Ibid ( M g hydromag.) Lindsay, 1979 Robie et al., 1979 Ibid ( M g hydromag.) 4

5

Figure 3. Mineral stability lines for solid phases potentially controlling Mg activity at log pC0 = -2.95 (error bars fall within the area of the data points). 2


11.

PAVLIK & RUNNELLS


149

MINTEQ SIMULATION OF SYSTEM BEHAVIOR Hypothetical reaction pathways chosen to model the L2 leachate-Uinta Sandstone system are illustrated in Figure 5. As a first approximation, dissolution/precipitation reactions affecting the mass balance of Na, K, Mo, S0 , and CI were not considered. Instead, based upon the solubility controls discussed in the previous sections of this paper, the working hypothesis for the simulations is that the recarbonation of L2 leachate drives the reactions toward equilibrium. Along the path toward equilibrium, recarbonation is accompanied by the precipitation and dissolution of sepiolite, calcite, and an inferred hydrated magnesium carbonate mineral such as hydromagnesite. Dissolution of hydromagnesite appears to be one reasonable mechanism for releasing M g into the L2 leachate for several reasons. First, small intensity peaks for hydromagnesite were detected during X-ray diffraction of the Uinta Sandstone (1). Although these were not conclusive, the presence of a magnesium carbonate mineral of similar composition can be inferred in the sandstone. A mass balance calculation on magnesium indicates that the increase in Mg in solution can be explained by dissolution of approximately 1 percent hydromagnesite from the sandstone. Data presented in Figure 3, supported by MINTEQ mineral saturation index calculations (Table III), show that hydromagnesite should dissolve in the leachate. However, saturation indices given in Table III indicate that other dissolution and precipitation reactions involving Mg-bearing minerals are also possible, such as dissolution of magnesite and precipitation of either dolomite or talc. The results from one reaction-path simulation of the L2 leachate-Uinta Sandstone system are presented in Figure 6. The series of reactions chosen for this simulation are as follows: (1) Sepiolite precipitates from the silica-rich alkaline fluid according to the reaction: 4


2+

2Mg (2)

+ 3H,Si0 ° -> Mg2Si 0 (OH) + 2 H 0 + 4 H 4

3

6

4

+

(5)

2

Recarbonation of the fluid occurs, causing calcite to precipitate, and driving the pH of the system down according to the reaction: Ca

(3)

2+

2+

+ C0 (g) + H 0 -* CaC0 + 2 H 2

2

+

(6)

3

Continued recarbonation lowers pH further causing hydromagnesite in the Uinta Sandstone to dissolve as follows: +

Mg5(C0 ) (OH) .4H 0 + H -+ 5Mg 3

4

2

2

2+

+ 4C0 * + 6 H 0 3

2

(4)

(7)

Lithium and fluoride partitioning between liquid and solid phases reaches a steadystate. In Figure 6, column (1) represents the initial chemical composition of the leachate observed prior to contact with the sandstone. Column (5) summarizes the solution composition observed after reaction with the sandstone for five days. Columns (2)-(4) represent intervening steps in the reaction-path simulation. The major changes in chemistry observed between columns (1) and (5) are an increase of three orders of magnitude in the concentration of Mg and significant decreases in total dissolved carbonate, fluoride, and silica. The data presented in columns (3) and (4) of Figure 6 illustrate the effect of lithium and fluoride Kd mass action equations on the simulation of system equilibrium. In column (3) of Table i y where the Li-Kd constant was used to simulate adsorption, predicted and observed concentrations of lithium match quite closely. However, fluoride levels are overestimated. In column (4), where the F-Kd constant was used to simulate adsorption, the match between predicted and observed fluoride in solution is improved. In this case, however, the predicted concentration of lithium in the leachate is overestimated.



150


Thermodynamic Data Sources (15) Truesdell and Jones, 1974 (1_5)a Ibid (amorphous sepio.) (1_5)c Ibid (crystalline sepio.)

(22) (£9) (££)

Plummer et al., 1976 Lindsay, 1979 Robie et al., 1979

Figure 4. Mineral stability lines for talc, sepiolite, and diopside after the 5-day reaction period (error bars fall within the area of the black circle).

Recarbonation: ρ 0 Ο increases pH decreases 2

Initial leachate observed before contact with the sandstone log p C 0

2

Partitioning of lithium and fluoride

= -8.23

pH = 11.84

log p C 0 C a - Mg solubility controls

Sepiolite precipitates Calcite precipitates Figure 5. system.

Final leachate observed after contact with the sandstone

TT

2

= -2.95

pH = 7.91

System approaches equilibrium with calcite Hydromagnesite dissolves

Schematic diagram showing the modified reaction-path simulation of the



11.

PAVLIK & RUNNELLS


r^TtTtcvJcvii^cvicvj^eoeoTt

CO Q_

0)oiOr-o)Ncooinoimo

< _l => CO

< ID σ LU CO

ο ο ο ί Λ Ο Ν ί ο Μ Ν ^ τ ί - ι η τ -

_5 χ .

ο +

c\j +

_ Ο

+ +

y

α! σ> tu

m-

au.2ïJWu2ziu

Ο Ο _

ο


151

152


CONCLUSIONS MINTEQ reaction-path simulations supported by mineral saturation data suggest that the chemical equilibrium of the Uinta Sandstone-L2 leachate system is controlled by recarbonation of the leachate, during which calcite precipitation largely controls C a activity and pH. Recarbonation is accompanied by the apparent precipitation of sepiolite from the leachate, dissolution of magnesium from an inferred magnesium carbonate mineral in the sandstone, and partitioning of lithium and fluoride between liquid and solid phases. The modeling results are reasonable in light of the observed mineralogy, measured Kd values, and observed changes in chemical composition of the leachate. In this modeling effort, the complex interaction of oil shale leachate and Uinta Sandstone was reconstructed in consecutive steps that were considered additive toward the attainment of final equilibrium. The predicted outcome of each equilibration step was used as the starting point for successive mass balance calculations. In this way, plausible reaction pathways along which the leachate and sandstone approach chemical equilibrium were hypothesized and evaluated. It should be noted that given the number of plausible phases that may be reacting in the system, predictions of solution composition along the path to heterogeneous equilibrium are likely to be non-unique. Despite this fact, and as illustrated in this work, the value of the reaction-path modeling approach lies in its use of equilibrium concepts to distill a complex set of hypothetical geochemical processes into a few major reactions that are likely to improve our understanding of system behavior.


2+

ACKNOWLEDGMENTS The research in this paper was performed in partial fulfillment of a Ph.D dissertation completed by the senior author at the University of Colorado-Boulder. Financial support from the U.S. Department of Energy, Atlantic Richfield Foundation, Inc., and the University of Colorado Department of Geological Sciences are gratefully acknowledged. We also wish to thank A l Burnham and Bill Miller of Lawrence Livermore National Laboratory for providing samples of L2 retorted oil shale. LITERATURE CITED 1. 2.

3. 4. 5. 6. 7. 8.

9.

10.

11. 12.

Pavlik, H. F. Ph.D. Thesis, University of Colorado, Boulder, 1987; p 207. Felmy, A R.; Girvin, D. C.; Jenne, E. A. MINTEQ, a Computer Program for Calculating Aqueous Geochemical Equilibria; Final Project Report, Contract 68-03-3089, U.S. Environmental Protection Agency: Athens, GA, 1983; p 87. Miknis, F. P.; McKay, J. F., Eds. Geochemistry and Chemistry of Oil Shales; ACS Symposium Series No. 230; American Chemical Society: Washington, DC, 1983; p 565. Bradley, W. H. U.S. Geol. Survey Prof. Paper 168, 1931; p 58. Juhan, J. P. The Mountain Geologist 1965, 2, 123-128. Cashion, W. B.; Donnell, J. R. U.S. Geol. Survey Bull. 1394-G, 1974; p 9. Surdam, R. C.; Parker, R. B. Geol. Soc. of Amer. Bull. 1972, 83, 689-700. Runnells, D. D.; Glaze, M.; Saether, O.; Stollenwerk, Κ. In Trace Elements in Oil Shale; Chappell, W.R., Ed.; Progress Report 1978-79, Center for Environmental Sciences, University of Colorado: Denver, CO, 1979; p 134. Runnells, D. D.; Esmaili, E. In Trace Elements in Oil Shale; Chappell, W.R., Ed.; Progress Report 1980-81, Center for Environmental Sciences, University of Colorado: Denver, CO, 1981; p 163. Peterson, Ε. J.; Henicksman, A.; Wigner, P. Investigations of Occidental Oil Shale, Inc., Retort 3E Spent Shales; Report LA-8792-MS, Los Alamos National Laboratory: Los Alamos, NM, 1981; p 39. Park, W. C.; Lindemanis, A. E.; Raab, G. A. In Situ 1980, 3, 353. Burnham, A. K.; Subblefield, C. T.; Campbell, J. H. Effects of Gas Environment on Mineral Reactions in Colorado Oil Shale; Report UCRL-81951, Lawrence Livermore National Laboratory: Livermore, CA, 1978.


11. 13. 14. 15. 16. 17.


18. 19. 20. 21. 22. 23.

24. 25.

26.

27. 28. 29. 30.

PAVLIK & RUNNELLS


153

Ball, J. W.; Nordstrom, D. K.; Jenne, E. A. U.S. Geol. Survey Water Resources Invest. 78116, 1980, pp. 78-116. Ball, J. W.; Jenne, E. A.; Cantrell, M. W. U.S. Geol. Survey Open File Report 81-1183, 1981; ρ 81. Truesdell, A H.; Jones, Β. F. U.S.Geol. Survey Jour. Res. 1974, 2, 233-248. Davis, A. O. Ph.D. Thesis, University of Colorado, Boulder, 1985; ρ 214. Plummer, L.N.; Parkhurst, D.L.; Thorstenson, D.C. Geochim. Cosmochim. Acta 1983, 47, 665-686. Drever, J. I. The Geochemistry of Natural Waters; 2nd ed.; Prentice-Hall: New Jersey, 1988; Figure 4.4, pp. 61. Reddy, K J.; Lindsay, W. L. Jour. Environ. Qual. 1986, 15, 1-4. Wollast, R.; Mackenzie, F. T; Bricker, O. P. Am. Mineral 1968, 53, 1645-1662. Bricker, O. P.; Nesbitt, H. W.; Gunter, W. D. Am. Mineral 1973, 58, 64-72. Hathaway, J. C.; Sachs, P. L. Am. Mineral 1965, 50, 852-867. Garrels, R. M.; Mackenzie, F. Τ In Equilibrium Concepts in Natural Water Systems; Jenne, E. A , Ed.; Advances in Chemistry Series No. 67; American Chemical Society: Washington, DC, 1967; pp. 222-242. Nordstrom, D. K.; Munoz, J. Geochemical Thermodynamics; Benjamin/Cummings: San Francisco, CA, 1985; ρ 477. Bassett, R. M.; Kharaka, Y. K; Langmuir, D. In Chemical Modeling in Aqueous Systems; Jenne, E. A., Ed.; ACS Symposium Series No. 93; American Chemical Society: Washington, DC, 1979; pp. 389-400. Pavlik, H. F.; Runnells, D. D. "Evaluation of the Validity and Statistical Variability of Lithium and Fluoride Distribution Coefficient Values in a Complex Geochemical System''; Research Highlights, DOE/ER-0261, U.S. Department of Energy: Washington, DC, 1986; ρ 16. Plummer, L. N.; Jones, Β. E; Thiesdell, A H. U.S. Geol. Survey Water Resources Invest. 73-13, 1976; ρ 61. Stumm, W.; Morgan, J. J. Aquatic Chemistry, 2nd ed.; Wiley-Interscience: New York, 1981; pp. 273. Lindsay, W. L. Chemical Equilibria in Soils; Wiley-Interscience: New York, 1979; pp. 107108. Robie, R. A.; Hemingway, B. S.; Fisher, J. R. U.S. Geol. Survey Bulletin No. 1452, 1978; ρ 456.

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Chemical Modeling of Aqueous Systems II - American Chemical Society

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