Ground Water and Their

GEOLOGICAL SURVEY PROFESSIONAL PAPER 498-D

Prepared in cooperation with the 

Governments of Nigeria^ the United 

Arab Republic^ and Wed Pakistan)

under the auspices of the United i j

States Agency for International 

Development
Chemical Properties of 

Ground Water and Their 

Corrosion and Encrustation 

Effects on Wells

By IVAN BARNES and FRANK E. CLARKE

HYDROLOGY OF AQUIFER SYSTEMS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 498-D

Prepared in cooperation with the 

Governments of Nigeria, the United 

Arab Republic, and W^est Pakistan, 

under the auspices of the United States 

Agency for International Development

Studies of well waters from Nigeria, 

Egypt, and Pakistan and use of equilibrium 

data on calcite and ferric hydroxide in 

predicting magnitude of corrosion and 

encrustation problems

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

First printing 1969 

Second printing 1983

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304
CONTENTS

Symbols. _ _________________________

Abstract-__________________________

Acknowledgments __________________

Purpose and scope._________________

Previous studies.___________________

Interception of ground water by wells. 

Methods of sampling and analysis. _ _. 

Corrosion testing.__________________

Examination of deposits_____________

Theory.___________________________

Data analysis ______________________

Page

IV

Dl

1

1

2

3

3

3

4

5

15

Reactions causing deposition of solids _________________

Corrosion and encrustation of wells _______-___--_-__._

Summary- _______________-_-_-_-__-___--__--__-.___

Conclusions. ___________-___--_--_-_-----_--_--_--__

References. _ ___________-___-___-___-_-_---_-__--___

Appendix 1. Digital computer program for constituent 

analysis. ______________-_-___-_____---__--__---__

Appendix 2. Computer analysis, ground-water data, 

Egypt, Nigeria, and West Pakistan; key to computer 

program column headings. ___________----_---.__ .____

Page

D19

20

28

33

35

36

37

48

ILLUSTRATIONS

Page

FIGURE 1. Photograph of corrosion probe_______-_-_-____-______-_______-___________-_--_-__--_-----_-_---_-- D4

2. Diagrammatic sketch, encrustation plug, corroded steel casing slot, Shadman well 34, West Pakistan____-_ 20

3. Photograph of encrustation plug, steel casing slot, Shadman well 34, West Pakistan.___________--__-__- 20

4. Photograph of encrusted slotted casing, Shadman well 34, West Pakistan._____________________________ 26

5-13. Graphs showing corrosion curves, mild steel:

5. Dalori well, Nigeria.___-_-_-_-_-______________-________-___-___-_--__-------__----_---_- 27

6. Ngala well, Nigeria.._____________________________________________________________________ 27

7. Kharaga well 1, Egypt____-___-_______________________-___-_-___---___-_---_----------- 27

8. Nasser well 1, Egypt.-___________________________________________-__---_-__-_----------- 27

9. Nasser well 3, Egypt- ------------------------------------------------------------------- 27

10. Shadman well 27, West Pakistan ___-_____-_-_-_-___-_______-___-_-__--------_----_---_-- 28

11. Shadman well 47, West Pakistan_-___--____-___________--__-----_-___-_------------------- 28

12. Shahkot well 251, West Pakistan --..---.--.______--__----_-----_---_---_-----------.--- 28

13. Shahkot well 252, West Pakistan...._.___.___________-_______-_.---_.-_--.----.--------.-- 28

14-20. Graphs showing average corrosion rates plotted against reaction states:

14. FeCO3 -_--___--_______-___________._______________-_______-___-__-____--_----_-----_--- 29

15. CoGQz.-------,-------.---.---^.-------------------------------------------------------- 29

16. Fe(OH),___..-.--_.-.-_---.---..--._ _.._.___.. _ __.-. ._-__ _._ _-_._-.___ 29

17. Fe3O4 _________ ------------.---,---^---,---.-------------------------------------------- 30

18. Iron metal-___________________________________________-__--_-_-___--_----_---_--------- 30

19. Mn3O4 ---_-.____-________.._._..__. _.___.____.__________--_- __-_-_- ------ -- 31

20. Cu(OH).....____.__._._...___..__.___.._.____._.___.__..__...._.._..___..._..-.-__.--_.- 31 

21-27. Graphs showing maximum corrosion rates plotted against reaction states:

21. CaCOs. _-_______-_______-_____________________________-__-___-_------ -------------.- 32

22. Fe(OH) 3 _________________________________________________________________________________ 32

23. FeCO3 ._____________________________________________________________ _--_-----_-___-_--- 32

24. Fe3O4 _______ -----------------.----------------.------------,---------------------------- 33

25. Iron metal___________-_____________________________________-___-__--__-------_---------- 34

26. Mn3O4 _____________________________.__________________________________----_-----_----_--- 35

27. Cu(OH) 2 ___________________________.____________________________-__-__-_---------_------- 36

III
IV CONTENTS

TABLES

Page 

TABLE 1. Identifications of solid phases found in slot filling of the mild-steel well casing removed from Shadman well

34, West Pakistan-____.__________----___--_____-_.-_____-____-__________-_____-__-_-____-____ D21

2. A comparison of the composition in weight percent by spectrographic analysis of materials found on the well

screen of Shadman well 34, West Pakistan-____________-___-____----___---_-----__-----_---___-__ 21

3. Ranges of numerical results of data analysis for possible reactions of waters and solids_________________ 23

4. A/-R for waters supersaturated with respect to solids that might precipitate from the well water as sampled

at the wellhead.______________________________________________________________________________ 24

5. States of reaction including all well waters and summary of phases found in samples from Shadman well 34,

West Pakistan.____________________________-___________-__---_-_-----_-_________________ 24

6. Results of chemical analysis and data analysis, Shadman well 34, West Pakistan. A, Intrinsic thermodynamic properties of water general characteristics. B, Intrinsic thermodynamic properties of water 

ionic data. C, Thermodynamic state of water with respect to coexisting solid phases undergoing hydrolysis 

reactions. D, Thermodynamic state of water with respect to coexisting solid phases undergoing oxidationreduction reactions_ _ ________________________________________________________________________ 24

7. Possible behavior of solid phases capable of protecting iron from corrosion________________.»____________ 28

SYMBOLS

A* A constant= 1824347.0.

a0 Distance of nearest approach of dissolved species.

o,&,c Components.

AP Activity product.

(aq) Dissolved aqueous species.

atm Atmosphere, pressure unit.

B* A constant = 50.297670.

Cv Is the heat capacity at constant pressure.

ealc Subscript for calculated property.

CR Ratio of cation concentration or activity actually

	found to cation concentration or activity at

	equilibrium.

D Dielectric constant of pure water.

d Exact differential.

dw Density of water.

E Electrical potential.

E° Standard state electrical potential.

e Electronic charge,

e~ Electrons involved in chemical reactions.

Eh Oxidation-reduction potential.

Ehm Measured oxidation potential.

EhTC Equilibrium oxidation potential calculated for the

	temperature measured in the field. 

Emf Electromotive force, 

cq Subscript for equilibrium properties. 

\$ Voltgram equivalent. 

G Gibbs free energy. 

G° Standard state Gibbs free energy. 

(?' Gibbs free energy at equilibrium. 

GFW Gram formula weight. 

H Enthalpy. 

i,j Species. 

7, /, K Phases. 

IPY Corrosion rate, expressed as inch penetration per

	year.

K Equilibrium constant.

k Is Boltzmann's constant.

L A time and cross-sectional area conversion factor.

In Logarithm base e.

m,

mm

N

n

obs

P

pH

ppm

Q 

R

r

S

S°

SCE

T

Tt

TOT

U

V

V°

W

Wel

7. 

A 

26

Amount of species i present.

Molality of species i.

Millimeter.

Avogadro's number.

Number of electrons.

Subscript for observed property.

Pressure.

Negative logarithm, base 10, of the hydrogen ion

activity.

Parts per million. 

Heat added to the system. 

Gas constant. 

Electrical resistance. 

Entropy.

Standard state entropy. 

Saturated calomel electrode. 

Temperature, degrees Kelvin. 

Duration of exposure of corrosion test specimen. 

Subscript to denote total amounts. 

Internal energy. 

Volume.

Standard state volume. 

Work done by the system. 

Electrical work.

Work of expansion against a pressure. 

Charge on ion i. 

Activity (molal) of species i. 

Ionic strength.

Activity coefficient of species i. 

Finite change or increment. 

Twice the glancing angle in X-ray diffraction. 

Chemical potential in a half cell. 

Chemical potential of species i. 

Standard state chemical potential of species i. 

Chemical potential at equilibrium. 

Sum of chemical potentials for a reaction.

Summation over all species of type i. 

Partial differential.
HYDROLOGY OF AQUIFER SYSTEMS

CHEMICAL PROPERTIES OF GROUND WATER AND THEIR CORROSION AND 

ENCRUSTATION EFFECTS ON WELLS

By IVAN BARNES and FRANK E. CLARKE

ABSTRACT

Well waters in Egypt, Nigeria, and West Pakistan were 

studied for their chemical properties and corrosive or encrusting 

behavior. From the chemical composition of the waters, reaction 

states with reference to equilibrium were tested for 29 possible 

coexisting oxides, carbonates, sulfides, and elements. Of the 29 

solids considered, only calcite, CaCO3 , and ferric hydroxide, 

Fe(OH) 3 , showed any correlation with the corrosiveness of the 

waters to mild steel (iron metal). All 39 of the waters tested 

were out of equilibrium with iron metal, but those waters in 

equilibrium or supersaturated with both calcite and ferric 

hydroxide were the least corrosive. Supersaturation with other 

solid phases apparently was unrelated to corrosion.

A number of solids may form surface deposits in wells and lead 

to decreased yields by fouling well intakes (screens and gravel 

packs) or increasing friction losses in casings. Calcite, CaCO3 ; 

ferric hydroxide, Fe(OH) 3 ; magnetite, Fe3O4 ; siderite, FeCO3 ; 

hausmannite, Mn3 04 (tetragonal); manganese spinel, Mn3O4 

(isometric); three iron sulfides mackinawite, FeS (tetragonal); 

greigite, Fe3S4 (isometric); and smythite, Fe3S4 (rhombohedral) 

copper hydroxide, Co(OH) 2 ; and manganese hydroxide, 

Mn(OH) 2 , were all at least tentatively identified in the deposits 

sampled.

Of geochemieai interest is the demonstration that simple stable 

equilibrium models fail in nearly every case to predict compositions of water yielded by the wells studied. Only one stable phase 

(calcite) was found to exhibit behavior approximately predictable 

from stable equilibrium considerations. No other stable phase 

was found to behave as would be predicted from equilibrium 

considerations. All the solids found to precipitate (except calcite) 

are metastable in that they are not the least soluble phases 

possible in the systems studied.

In terms of metastable equilibrium, siderite and ferric hydroxide behave approximately as would be predicted from equilibrium 

considerations, but bqth are metastable and the presence of 

neither would be anticipated if only the most stable phases were 

considered. The behaviors of none of the other solids would be 

predictable from either stable or metastable equilibrium considerations.

An unanswered problem raised by the study reported here is 

how, or by what paths, truly stable phases form if first precipitates 

are generally metastable.

The utility of the findings in well design and operation is in 

no way impaired by the general lack of equilibrium. Conditions 

leading to either corrosion (which is related to lack of supersaturatioif with protective phases), or encrustation (supersaturation with phases that were found to precipitate), or both, 

apparently can be identified. The application of the methods 

described can be of great importance in developing unexploited 

ground-water resources in that certain practical problems can be 

identified before extensive well construction and unnecessary 

well failure.

ACKNOWLEDGMENTS

The water well studies which yielded the data covered 

by this report were made in cooperation with the 

Governments of Nigeria, the United Arab Republic, 

and West Pakistan, under the auspices of the United 

States Agency for International Development 

(USAID).

The background references contain the names of 

many individuals who provided invaluable help from 

the Geological Survey of Nigeria (GSN); the Egyptain 

General Desert Development Organization (EGDDO) j 

the Water and Soil Investigation Division (WASID) 

of the Water and Power Development Authority 

(WAPDA) of West Pakistan; and personnel of the 

respective USAID missions. These references also 

acknowledge help of the following U.S. Geological 

Survey personnel. Valuable analytical assistance was 

provided by Pauline Dunton, Norman Beamer and 

associates, Blair Jones, and Roger Wolff. Acknowledgment is made herewith to Mary E. Mrose for special 

instrumental analyses, to Alfred H. Truesdell and John 

D, Hem for their thorough reviews and technical 

suggestions, to Mary E. Grisak for her patient typing 

of clear text from manuscript, and to Norma C. Grube 

for her excellent technical editing, constructive criticism of composition and format, and painstaking 

preparation of the final manuscript.

PURPOSE AND SCOPE

The purpose of this report is to describe the chemical 

properties found in water yielded from wells and to 

relate the chemical properties of the water to corrosion 

and encrustation of the well components. In addition 

to the practical results of the study, the data also

Dl
D2 HYDROLOGY OP AQUIFER SYSTEMS

provide insight into the behavior of naturally occurring 

solid phases (minerals) which are of interest in geochemical considerations.

A large amount of information is needed to achieve 

the purpose of such a study. Detailed analytical data 

on the water compositions, electrochemical measurements in the field (Eh and pH), and field measurements 

of unstable constituents (HCOs", dissolved oxygen, 

ferrous iron) all are needed properly to define the properties of the waters yielded by the wells. Chemical and 

mineralogic studies of the solids depositing on well 

parts and studies of the extent of corrosion attack and 

rate of corrosion attack are needed to relate chemical 

properties to practical consequences of corrosion or 

encrustation. The results reported here include all the 

considerations listed above, where possible, and hence 

provide a unique opportunity to accomplish the purpose of the report. The wells in these widely scattered 

localities were studied because serious corrosion and 

encrustation proved to be unexpected problems, and 

the magnitude of long-range ground-water developments warranted detailed studies at these sites. These 

studies are covered by Clarke (1963) and Clarke 

and Barnes (1964, 1965) in open-file publications 

of the U.S. Geological Survey.

The waters described in this report are not unstable 

in the sense that rapid spontaneous reactions occur. 

A thermodynamic treatment of the analytical data 

may help to explain the sluggishness of some of the 

reactions and the apparent failure of others to take 

place at all. The thermodynamic properties of the 

actual states may be calculated and compared to the 

state of equilibrium with possible coexisting solids. 

The calculations yield potentials existing in the solutions 

to drive reactions. If the potentials for a reaction are 

always low and the postulated reactants are present, 

the small values of the potentials may be regarded as 

presumptive evidence for a relatively fast reaction. If 

large potentials are found for a reaction and the postulated reactants are present, then presumably the 

reaction proceeds only slowly or there is unlimited 

supply of reactants. Direct observation is helpful in 

proving that the reaction does indeed occur. Hopefully, 

the accumulation of a large body of the kind of information that is presented here will lead to improved knowledge of how phases actually behave in the natural 

environment and to better understanding of geologic 

processes.

PREVIOUS STUDIES

Methods for the investigation of naturally occurring 

water have been developed for field use (Back and 

Barnes, 1961; Barnes, 1964). These methods are used 

for the measurement of the oxidation-reduction potential (Eh) and pH and bicarbonate (HCO3~) ion 

concentration to supplement the usual methods of 

chemical analysis as described by Rainwater and 

Thatcher (1960). By means of the more recent developments the interpretation of natural water compositions 

has been extended beyond the earlier excellent treatment of Hem (1959). Eh and pH measurement methods 

for natural materials also have been advanced by 

recent Russian work (Germanov and others, 1959; 

Solomin, 1965) but have served largely to classify 

waters or rocks as relatively reducing or oxidizing. 

The compilation of Baas Becking, Kaplan, and Moore 

(1960) listed pH and Eh data from natural environments; again, the variables were largely descriptive, 

and quantitative interpretations could not be made.

In spite of the complex systems found in nature, 

attempts have been made to interpret the chemical 

data including pH and Eh. To a large extent, the study 

here reported is an outgrowth of the pioneering work 

of Garrels (1960) and the numerous papers by Hem 

(1960 a, b, c; 1961 a, b; 1963 a, b, c, d, e; and 1964) who 

independently applied the same arguments to the 

equilibrium description of systems such as those reported here. At least partial success in interpreting 

the compositions of ground water was obtained by 

Back and Barnes (1965), Barnes and Back (1964a), 

Barnes and Clarke (1964), and Barnes, Stuart, and 

Fisher (1964). Back and Barnes in their work in southern Maryland chose an area in which limonite, lignite, 

and silicates predominated and the data collected and 

analysis, although admittedly simplified, were aimed 

at a resolution of the chemical behavior of limonite 

in natural environments. Taking the Eh, pH, and iron 

concentrations in the water and considering the ionic 

strength and ion pair formation, they concluded that 

the solubility of limonite apparently ranged between 

the solubility of Fe(OH) 3 (Hem and Cropper, 1959) 

and the solubility of Fe2O3 (hematite) given by Latimer 

(1952). Back and Barnes also found that, generally, 

the longer the contact time between the water and the 

lignite, the lower the Eh and the closer the solubility 

of limonite approached the limit imposed by hematite.

Barnes, Stuart, and Fisher (1964) extended the data 

analysis to include limonite and pyrjte. They were 

able to show that in some cases pyrite dissolved and 

apparently saturated coexisting aqueous solutions by 

the reaction:

FeS2 +8H2O=Fe+2 +2SO4-2+ 16H++ 14<r. (1)

In separately reported work, Barnes (1965) showed 

that in the rapidly varying ambient of a stream under 

subaerial conditions calcite supersaturation could be 

as much as 20 times the calcium activity for the car-
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D3

bonate activity of the water. Back (1963) found that 

in the slowly varying ambient conditions of groundwater flow, the departure on the supersaturated side 

of equilibrium rarely exceeded twice the calcium ion 

activity for the carbonate ion activity found.

The papers cited and briefly summarized above 

differ from the usual natural water chemical studies 

in that they consider the behavior of phases that might 

occur, or are known to occur, given the composition 

of the water and the approximate mineralogy of the 

rocks. The studies also depart from the usual geologic 

investigation because the studies included the measurement of the chemical properties of the wa er coexisting 

with the other geologic materials found. Many precautions have been necessary in the measurements of 

the chemical properties of natural aqueous solutions. 

Barnes (1964) showed that the pH must be measured 

in the field. Back, and Barnes (1961) showed that the 

measurement of the Eh is, at best, time consuming. 

Roberson, Feth, Seaber, and Anderson (1963) showed 

that significant changes in HCOs" concentrations may 

occur on sample storage. Barnes and Back (1964b) 

have shown that ground waters in limestones may 

often be supersaturated with calcite, and hence aliquots 

for subsequent laboratory analysis for calcium should 

be acidified (see also Barnes, 1965). Dissolved oxygen 

is a notorously unreliable analysis unless done in the 

field with due precaution. Iron in solution in ground 

water is chiefly as Fe+2 (Barnes and Back, 1964a), 

and aliquots should be collected, filtered if possible, 

and acidified for subsequent analysis. If the pH in 

the field be greater than 4.0, the total iron dissolved in 

the original sample should be nearly all Fe+2 (Barnes 

and Clarke, 1964).

INTERCEPTION OF GROUND WATER BY WELLS

In detail, the hydrology of a single well may be quite 

complicated. Permeability is not uniform in all directions and at all locations within an aquifer. Not only is 

an aquifer generally not isotropic (nonuniform permeability), but an aquifer is usually not homogeneous, 

physically or chemically. As a consequence, stratification or other variation in water compositions may be 

expected in a single aquifer. Depending upon the 

distribution of permeability and its directional variation 

and upon the interval (s) screened in the well and the 

method of well operation, water of different compositions may be mixed in the well and may yield precipitates. Intermittent operation of a well further complicates the hydrology, as the well may serve as a hydraulic 

path for relatively rapid flow between parts of the aquifer (a flow that might occur at a very slow rate, if at 

all, under natural conditions). During periods of well

operation the hydrology may be quite different from 

that during non opera ting periods.

As a consequence of the complex hydrology, the 

detailed chemical properties of water yielded by a well 

may be expected to vary with time and often to represent unnatural mixtures. It should be remembered that, 

however variable the hydrology and chemistry may be, 

the water yielded by the well may represent the solution 

that gave rise to troublesome corrosion or encrustation, 

and the water is thus of great practical importance. 

Geochemically, the water mixtures may represent 

extreme cases. If it can be demonstrated by the study 

of the waters yielded by the well that some reactions do 

not occur in spite of large potentials to drive the reactions or that other reactions are so rapid that large 

potentials cannot be achieved even by rapid mixing of 

incompatible solutions, then the results will be of 

geochemical importance.

METHODS OF SAMPLING AND ANALYSIS

The field methods used are those in references cited 

above. Eh was determined by the methods and with 

the equipment described by Back and Barnes (1961); 

pH and HCO3~, from the methods described by Barnes 

(1964). HCO3~ concentrations, obtained graphically 

(Barnes, 1964), agreed within 1 ppm (part per million) 

of the results of the computer program written by 

Fred Sower, of the U.S. Geological Survey, for the data 

repeated by Barnes (1965). In none of the wells was 

dissolved oxygen found below 10 feet from the surface 

when an oxygen probe with silver and gold electrode 

(Yellow Springs Instrument Co., Yellow Springs, Ohio) 

was used. Many of the chemical analyses were done in 

the U.S. Geological Survey laboratories, where the 

methods of Rainwater and Thatcher (1960) were used, 

and generally the results were in close agreement with 

analyses done in foreign laboratories by unspecified 

methods. Careful chemical analyses know no political 

boundaries.

Whether performed in the field or in the laboratory, 

the analysis of a water sample must be interpreted in 

the light of the representativeness and reliability of the 

sample. In general, the data obtained for this report 

were from samples of water discharged by flowing or 

pumping wells.

CORROSION TESTING

The inherent corrosiveness of water can best be 

studied with an electrically insulated specimen filament which eliminates the effects of long-line current, 

differential concentration cells, galvanic couples, and 

unusual velocity effects. The corrosion elements used 

in this study (fig. 1) consisted of 0.04-inch (1-mm)
D4 HYDROLOGY OF AQUIFER SYSTEMS

FIGURE 1. Corrosion probe.

diameter loops of test wire inserted through the well 

casing or water-discharge pipe by means of a threaded 

probe body. One part of the loop is enclosed in a sealed 

tube and thus is separated from the water so that resistance changes due to temperature changes may be measured. Electrical connections between the covered and 

uncovered parts of the loop allow the two, parts to be 

separate legs of a bridge circuit. Changes in electrical 

resistance resulting from corrosion of the test loop can 

be determined and converted to inch penetration per 

year (IPY) by the equation:

(2)

where:

Ar and ATe= change in resistance and elapsed

time of exposure, respectively; 

L=a time and cross-sectional area conversion factor.

The IPY ranges of 0 to 0.002, 0.002 to 0.02, 0.02 to 

0.05, and greater than 0.05 are considered to represent 

insignificant, moderate, severe, and extreme damage 

to mild steel.

The corrosion probe filament is more useful in assessing general corrosion than in predicting the extent of 

localized pitting. Although it cannot be used accurately 

to determine actual lives of well parts, it is useful in 

comparing several metals in a particular environment or 

effects of several environments on a single metal.

Metal loss data determined with corrosion probes 

can be related to actual metal lives of well parts only 

if there is some actual well field experience with the 

same metals, to establish relationships between corrosion of the insulated probes and the actual well construction materials. The latter, or course, are subject 

to other factors, such as galvanic effects, long-line 

currents, and concentration cells, as well as to the 

basic water-quality factors. Because corrosion probes 

generally are placed in the upper casing or discharge 

lines of wells, and thus sample the mixed discharge, 

field tests with actual well parts help one avoid overlooking severe local effects which may not be apparent 

in a small specimen exposed to an integrated discharge 

sample. Fortunately, experience in most deep-well 

studies has shown that waters flowing from the wells 

are approximately constant in chemical properties and 

that corrosion-probe data correlate rather well with 

performance of metal parts. This would appear to 

support the basic hypothesis of this paper: that the 

basic chemistry of the water discharged is as important 

as local effects in causing corrosion and encrustation in 

deep water wells and that installation of corrosion 

probes hi discharge lines is a reasonably representative 

device for assessing damage in such environments.

EXAMINATION OF DEPOSITS

Solid samples of deposits from well parts were 

examined with a binocular microscope, and, unless 

otherwise indicated, small parts of each specimen were 

ground to silt-clay size using agate mortar and pestle 

or a tungsten carbide grinding vial. For examination, 

the ground parts of some samples were mounted on 

glass slides. Other powdered samples were pressed into 

special aluminum holders. Samples thus prepared were 

examined by X-ray diffraction on a Norelco recording 

diffractometer employing nickel-filtered copper radia-
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D5

tion and a proportional counter for pulse-height discrimination, at scanning speeds of 1° 29 per minute.

Interpretations are based on comparisons with standard materials and the file-card data of the American 

Society for Testing and Materials (ASTM) and were 

checked against additional citations from the literature.

Pulse-height analysis did not entirely eliminate 

interference from iron fluorescence. It is unlikely that 

material was detected in quantities less than about 5 

percent by volume. Poorly crystallized iron minerals, 

such as goethite (FeOOH), sometimes cannot be positively identified in amounts less than 20 percent.

Where better-resolved X-ray diffraction measurements were needed, powder samples were photographed 

in manganese-filtered iron radiation by Mary E. Mrose, 

U.S. Geological Survey. These films were then measured 

by Blair F. Jones and compared with film, as well as 

diffractometer standards. X-ray fluorescence analysis 

for sulfur was done by Pauline J. Dun ton.

THEORY

Observations have been made of the physical and 

chemical properties of various aqueous solutions. A 

rational basis is needed for the comparison of observations to determine if any consistent relationships hold. 

Thermodynamic arguments seem the most reasonable 

bases for comparing the properties of the well waters 

studied because the arguments are rigorous. A direct 

test is also afforded of the departures from chemical 

equilibrium in the waters sampled. The use of thermodynamics then provides a quantitative comparison of 

the waters studied and also a direct test of the validity 

of postulated chemical equilibria.

Unfortunately, a fairly extensive derivation of thermodynamic relations is necessary. The systems studied 

are real and are to be compared to equilibrium states as 

references. There is in the literature no development of 

the theory needed to treat the systems here described, 

and thus the derivations are given.

The studies of the behaviors of naturally occurring 

substances have included two kinds of mineral-water 

reactions. The simpler type of reaction involves no 

electron transfer and the behavior of the solid substance 

can be described in terms of chemical parameters, 

temperature, and pressure. Calcite is an example of the 

simple case. Whether the reaction is written

CaCO3=Ca+2 +CO3-2 , (3)

CaCO3+H+=Ca+2 +HCO3-, (4)

CaCO3+H2O=Ca+2 +HCO3-+OH-, (5)

or other ways, tests for the behavior of calcite require 

knowing only the temperature, pressure, and chemical 

composition of the solution. The law of mass action is

the basis for testing the behavior of phases undergoing 

simple reactions.

Equally important are reactions involving electron 

transfer such as, for hematite,

3H2O+2Fe+2 =Fe2O3 +6H++2e-. (6)

Studies of reactions involving electron transfer 

require more information than the chemical composition 

of the solution, the temperature, and the pressure. 

the electrons produced are charges and induce electrical 

potentials so that the study of electron transfer reactions 

must also include a study of electrochemical properties.

Because this report is on both mass action reactions 

and electron transfer reactions, a general development 

of the theory is needed. Both types of reactions must be 

placed on the same formal basis to show the similarities 

and differences among the reactions described.

A system, as the term is used in this report, is any 

part of the universe isolated for consideration. The 

volume arbitrarily isolated may be considered theoretically or it may be isolated for measurements 

physical, chemical, or both. The boundaries of the 

system may be fixed, as the wall of a sample bottle, or 

moving, as for water flowing through a chamber in 

which measurements are made. If the boundaries to 

the system are moving, care must be taken that each 

volume of the water occupying the chamber is the same 

as every other volume; thus, monitoring the water 

properties in time may be necessary.

If the properties of a system are constant over a 

period of measurement, then the system will be termed 

stable. From this definition of stability, various degrees 

of stability may be found by observations made over 

varying lengths of time. In the flowing system (moving 

boundaries) monitoring or continually measuring the 

properties of interest is required to deteimine stability.

Fixed system boundar es are no guarantee of stability 

of a system. For example, a water sample in a bottle 

may change because of intrinsic long-term instability 

of the sample. On the other hand, the original water 

may be intrinsically stable, but if it is placed in a 

sample bottle which contains air, the air may not be 

compatible (stable) with the water, and both may 

change in properties (react). The air-water sample 

interaction is an example of an unstable system containing two substances, a gas and a liqu d. A clear 

distinction should be made between the stability of 

naturally occurring water in its natural environment 

and the stability or instability of water samples 

stored for subsequent analysis. If measurements of the 

properties of the water at the sampling site yield inconstant results during a period of measurement, then 

it should be concluded that the water is unstable, and

324-262 O-69 2
D6 HYDROLOGY OF AQUIFER SYSTEMS

great care must be exercised in the interpretation of 

the properties of the water. On the other hand, if 

a sample of water is collected and placed in a container 

for subsequent study, the system represented by the 

sample may be unstable over the period of transport 

to the laboratory and storage within the laboratory. 

In the discussion of previous studies examples are 

given of unstable samples. The demonstration of the 

stability of the sample requires proof that the measurement of properties, immediately upon capture of the 

sample, yield the same results as the same measurement at a later date. If such a proof is lacking, the 

properties of samples measured after storage cannot 

be used with confidence in the description of natural 

water. Reproducibility of measurements of properties 

of samples in the laboratory after sample storage cannot be used to prove that the sample represents the 

natural water, because they may be merely demonstrations that all such samples have reached a particular 

state (set of properties) and that state may not be the 

same as the natural state.

To facilitate the discussion of interactions between 

various substances, a phase is defined as a substance 

(liquid, gas, or solid) of fixed chemical potential for all 

components. A component is one of the necessary and 

sufficient chemical (compositional) variables to describe 

the compositions of all phases in a system. A constituent 

is a physically dependent compositional variable in that 

it cannot be varied at will without concomitant changes 

occurring. By the laws of electrostatics, for example, the 

concentration of an ion cannot be varied without inducing electrical potentials, or without a corresponding 

change in the concentrations of ions of the opposite 

sign. Species is the generic term including components 

and constituents.

The Gibbs free energy, G, is a fundamental thermodynamic property, and by use of the Gibbs free energy 

the necessary relations among the different types of 

reactions, compositions, and physical variables may be 

derived. There is no way of directly measuring G, and 

the absolute value of G is known only by definition. 

Changes in G can be determined by measurement of 

operational or experimental properties, such as electrochemical potentials, temperature, pressure, compositions, and the like. The dependence of G upon each of 

the operational variables used in this study will be 

considered separately in sequence and will lead to 

general relations.

The Gibbs free energy, G, is a state variable depending upon the temperature, pressure, and composition 

of the system as

(7)

where

T is the temperature, 

P is the pressure, and 

I is the amount of species i present.

Differentiating,

uGr = ( ^TT?,

P, Mi,M,- . . . \dP/T, Mi,Mj. . .

(8)

The Gibbs free energy may change with T, P, or 

composition. The change in G due only to composition 

changes is

P,

(9)

In the discussion of variation of G with composition, 

the partial derivatives have specified the change in 

concentration of a component or constituent without 

change in the composition of the phases. The physical 

process corresponding to the data analysis would be 

to use a sufficiently large sample such that no composition change would occur if the appropriate number 

of moles of a component were added. The free energy 

change from such a process is calculated and compared 

to the change if 1 mole gram formula weight (GFW) 

of the solid phase were added.

Consider the change in G if components such as 

a, b, c are added to the system containing phases 

/, J, K. Three phenomena may be observed. A component may be a solid and remain a solid (phase /), in 

which case, all other phases remaining constant,

a/T, P,

(10)

or it may dissolve in a solid solution 7 also containing 

components b and c, in which case

dM

a Mh,Me, Mj, MR, T, P

(11)

or it may dissolve in an aqueous phase 7 producing 

changes in the concentration of a number of constituents i, all derived from component a, in which 

case the change is summed individually over all species 

i, j, derived from the solution of component a,

dMt . (12)

Although the concepts remain unchanged, notation 

becomes simpler if the partial derivatives are defined
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D7

as chemical potentials. For constituents in a solution /,

and for components,

(14)

?,P,Mh,M,

A rich variety exists for the expression of M, from 

such archaic units as grains per gallon (sometimes used 

for potable waters) to conveniences such as mole fractions (for solid solutions). The solids are considered 

here as invariant in composition for the sake of simplicity, although the assumption is not valid in detail. 

For aqueous solutions the specific variable Mt will be 

used, where m* represents the moles per kilogram of 

solvent (water).

A criterion for equilibrium between two phases is 

that the chemical potential be the same for each 

component in both phases (Denbigh, 1955, p. 80-85). 

For equilibrium, then

(Ma)/=(Ma)y (15)

In keeping with the usual conventions, the Gibbs free 

energy content of the elements in their stable form at 

1 atmosphere pressure and 25° C (reference state) is 

zero,

G° elem, 25°C, 1 atm, stable form 0. (16)

Generally, for pure components at a temperature of 

25° C, 1 atm total pressure (standard state)

G°25°. 1 atm (17)

The reference state is a definition of the thermodynamic 

state, an arbitrary reference for subsequent work. The 

standard state, however, is merely a uniform set of 

conditions (pure component, at a temperature and 

pressure) chosen for the comparison of the free energies 

of the various components in different phases. For 

clarity, again, the process is to add a mole of solid to 

such a large amount of the solution studied that the 

composition of the solution-solid mixture remains 

unchanged; Under such conditions, for the solid,

G

(GFW), Ti =Mi (18)

For dissolved (aqueous) species the standard state 

used here, in keeping with standard practice, is an ideal 

1 molal solution. An ideal solution is defined as one 

for which.

RT In mi= Hi- (19)

where R is the gas constant, so that for the ideal 1 

molal solution, then,

RTln 1 = M ,- (20)

or the chemical potential of the solute (M*) is the 

standard state chemical potential

M i= (21)

For the solutes in the standard state we can make 

the statement that

G '(GFW) t~ (22)

Thus, Latimer's compilation of "free energies" is a 

compilation (Latimer, 1952) of molal free energies 

which are always numerically equal to and, if the 

experimental procedure is properly chosen, become 

identical to standard state chemical potentials. For an 

actual reaction such as

Cu2S+2H+=2Cu++H2S(aq> (23)

the proportions among reactants and products are 

given by the coefficients for the species. The Gibbs 

free energy is an extensive variable and thus depends 

on the amount of material. Consequently, the molal 

free energies or chemical potentials must be considered 

in the proper proportions. The chemical potentials are 

summed over products and reactants, the general case 

being

d- Zl^react , (24)

or

For the reaction cited,

A(?=26rc

and

 Mcu2 s 

The condition for equilibrium is

(25)

(26)

(27)

(28)

The solid, if present in the real systems studied, should 

neither increase nor decrease in amount. There should 

be neither a net dissolution nor a net precipitation, 

although, of course, the solid may recrystallize. If

A<7=Aju>0, (29)

then the products of the reaction have a higher Gibbs 

free energy or a higher sum for the chemical potentials. 

The condition for a spontaneous reaction

A<7<0 (30)
D8 HYDROLOGY OF AQUIFER SYSTEMS

may be met if the species on the left-hand side of the 

chemical equation (the "reactants") react to produce 

more of the species on the right. This is only a potential, 

however, and it cannot be inferred nor is it meant to 

be implied that such reactions indeed occur. Independent nonthermodynamic arguments must be supplied before the reaction can be shown to take place, 

even if large potentials exist to drive the reaction. The 

purpose of the present paper is to show such potentials 

that exist in real systems and then evidence to indicate 

what, if any, of the formal reactions considered do 

indeed occur.

In the tests for the states of reactions, the only 

unambiguous statement that can be made concerning 

solutions supersaturated with respect to a solid is that 

they are supersaturated. As a consequence, all that is 

known is that the sum of the chemical potentials of 

the postulated dissolved species is larger than the 

chemical potential of the solid.

Many methods may be used to compare states of 

reactions. A fundamental approach is by way of 

chemical potentials. Consider the reaction

Cu2S+2H+=2Cu++H2S (aQ) . (31)

for the standard state,

The changes in free energy may be written, in general,

^CU2S~2{7H+, (32)

(33)

and for the equilibrium state involving solid pure 

Cu2S,

/-#cu2S0 -2£H/. (34)

The equivalent arguments in terms of chemical potentials are, in general,

AjU = 2jUCu+ +jUH2 8(aa) MCu2S° 2MH+, (35)

standard state,

AjU 0=2jUCu+ 0 +jUH2 S(aa)° MCu2S° 2MH+, (36)

and, at equilibrium, if pure solid Cu2S be present,

(37)

Each of the equalities may be added or subtracted. 

For example, the standard state may be subtracted 

from the equilibrium state so that

/ MH2 S(aa)°)

~ (Mcu2 s' MCu2 s°) 2(/iH/ JUH+°) (38)

For ideal solutions, by definition,

For real solutions

where

(39)

(40)

(41)

7*, the activity coefficient, is used to describe real 

solutions (j^l) in terms of ideal solutions (7^=1). 

7i is calculated from an extension of the Debye-Hiickel 

limiting law. By substituting for (ju' f M°*) for the 

ideal solution postulated, if Cu2S be present,

(42)

(43)

and because

the familiar formulation for ideal solutions may be 

derived

(44) l(mH+) 2 

and, of course, the expression

(mcu+) 2 (mH2s)

(45)

is the equilibrium constant KI assuming an ideal 

solution. For real solutions, if Cu2S be assumed present, 

the same treatment yields

(46)

Thus far the properties of the equilibrium state for 

both ideal and real solutions have been developed, but 

both are special cases. The general case of real solutions 

can be obtained by adding the chemical potentials for 

any state to the standard state. So, for the reaction 

cited,

Upon substitution of

the relation becomes

 Mcu2 s°) 2GuH+ MH*°)- (47)

(48)

+. (49)
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS

Combining the last terms,

The product

(«cu2 s) (c

(50)

(51)

is defined as the activity product. At equilibrium the 

activity product (AP) is equal to the equilibrium 

constant, K. If

AP>K,

the solution is supersaturated, or if

AP<K, 

the solution is unsaturated. If

AP=K, 

then the solution is in equilibrium and

The equations

and

may be added, and

results in

AP 

K

~

/IP 

(52)

(53)

(54)

(55)

(56)

The natural logarithm of the AP/K ratio times the 

gas constant and absolute temperature, then, gives a 

direct measure of the sum of the chemical potentials 

of species involved in the reaction, and hence gives a 

direct measure of the potential existing for the reaction 

under consideration. From the above considerations, 

only a sum of the chemical potentials may be determined, and only a ratio of AP to K for real solutions. 

The choice is entirely arbitrary as to which species is 

considered to be present in supersaturated or unsaturated concentration for solids which, barring solid 

solution or extremely fine grain size, may have only 

a=l.

To be consistent and orderly in the presentation of 

the data, an entirely arbitrary decision was made to 

assign the excess (or deficiency) in the chemical potential entirely to the metallic cation in solution. Others for 

particular reasons may wish to assign the departures

from equilibrium to the anion, hydrogen ion, or some 

other species. The hydrogen ion, being involved in most 

geochemical reactions, apparently merits special consideration in that nearly all departures from equilibrium 

could be expressed in a pH difference between actual 

and equilibrium states. Of course, to bring about a pH 

change some other species would have to be gained or 

lost from solution, and so the description of states 

solely in terms of pH differences may be misleading 

and obscure other and equally important consideration. 

Having in hand methods for treating systems of 

varying composition, arguments for systems of varying 

physical properties are necessary. The differential

dG=(~ dT

Tt p,

(57)

will be simplified by assuming constant compositions 

for all phases of the systems discussed. For the constant 

composition case

(58)

The significance of bothf ^

falls from the definition of G,

G=H-TS.

and ^-

i M .

(59)

For systems undergoing physical processes at a constant 

composition, by differentiation,

dG=dH-TdS-SdT, 

where

S is entropy and 

H is the enthalpy, given by

(60)

dH=dU+PdV+VdP, (61)

where

V is the volume and

U is the internal energy and is given by

dU=dQ-dW, (62) 

where

Q is the heat added to the system and 

W is the work done by the system, 

which is a statement of the law of conservation of 

energy (first law of thermodynamics). Upon substitution,

dG=dQ-dw+PdV+VdP- TdS-SdT. (63)

For re versible reactions

dQ=TdS. (64)
D10 HYDROLOGY OF AQUIFER SYSTEMS.

The work of expansion against a pressure (Wexp) may 

be expressed for constant pressure conditions as

(65)

For mass-action reactions the only work done is the 

work of expansion. Also, the equilibrium state is of 

interest as a reference.

Reversibility will be postulated for all reactions 

considered to calculate the properties of the equilibrium 

(reference), which will be compared to the actual 

states for the reactions. Postulating reversibility (which 

is to be tested), the dependence of 0° on physical 

conditions reduces to

dO°=PdV°-S°dT. (66)

The aqueous solutions studied are nearly incompressible 

and, at the shallow depths found,

The temperature dependence of Q° is, then, 

dGc

dT

__ _ cro

Substituting for S°,

dO° G°-HC

(67)

(68)

(69)

Dividing by T2 and rearranging,

dT ~ T2 

The equilibrium constant is related to G

and so

dluK H°

dT RT2

(70)

(71)

(72)

which is the van't Hoff equation which is used extensively in the data analysis to compute equilibrium 

states at the temperatures actually found in the field 

study.

In the treatment of electrochemical state the concern 

is with both chemical changes such as

Fe+2-+Fe+3 , (73)

and the concomitant physical changes as electrons are 

transferred as

Fe+2=Fe+3 +e-. (74)

In consequence, the two common formulations must 

be combined. If in general

and at fixed composition

dG=dH-TdS-SdT,

then

dT=dH-TdS-SdT.

(75)

(76)

(77)

The Gibbs free energy change then may be stated as

dmt. (78)

Combining the definitions of internal energy and 

enthalpy with the free energy,

dG=dQ-dW +PdV+ VdP- SdT- TdS+

" (79)

dQ and dW are dependent upon the path of any change 

occurring in the system of interest. If spontaneous 

changes occur there may also arise conditions for which 

dG may not be determined because of the uncertainty 

of state properties (P, T, V among others). The objective of the data analysis reported here is to determine 

states of solutions, some of which may react very slowly, 

if at all. Given the constancy of state P, T, composition, Emf (electromotive force) the thermodynamic properties of the systems may be defined. In 

the derivations of the functions of interest it will be 

assumed that the states of the solutions found were 

attained along reversible paths so that exact values 

of the properties may be obtained. For reversible paths

dQ=TdS. (80)

The work of expansion against a confining pressure 

(work done) P is given by

If the only work done by the system consists of electrical work done on the system, and the work of 

expansion, then

dmt. (82)

If the system is held at a constant pressure and temperature (dT dP=ff) and the definition

(83)
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS Dll

is used, then

Returning to the example used, of

Fe°=Fe+2 -f2e-,

(84)

(85)

the free energy change for infinitesimal changes in the 

composition of the system is

jUFe°- (86)

In oxidizing one equivalent of Fe° to Fe+2 , a free energy 

change occurs. If one equivalent of Fe° is oxidized to 

Fe+2 in such a large amount of solution that the composition remains virtually unchanged, then, again, 

the identifications

(87)

The problem with such a thought experiment is the 

very large increase in the electrical potential due to the 

accumulation of electrons. Guggenheim (1950, p. 330- 

412) gives an extended discussion of the point and 

shows there is no way of separating the individual m 

values of the reaction. No experimental method exists 

for the measurement of jjFe« independently of n e~ in 

the example given here. A convenient but entirely 

arbitrary convention is adopted here. The convention is

from which, for the example cited,

(88)

(89)

The convention assigns all chemical potential differences 

to the chemical species and the electrons represent the 

resulting electrical charges. The sum of the charges 

over a reaction is the charge or quantity of electrical 

energy transferred in the course of the reaction.

If two half cells, one with an oxidizing reaction 

(yielding electrons) such as

Fe°->Fe+2 +2e- (90)

and one with a reducing reaction (consuming electrons), 

such as the reaction to produce hydrogen gas, H2(g) ,

L2(g) (91)

are connected in an electrical circuit, the charge transfer across the existing potential difference may be 

measured. Electrical work is the product of charge

times the voltage difference. Along the conductors 

there is a demonstrably negligible change in the composition owing to electron flow. The law of conservation 

of energy, if obeyed, requires that the energy measured 

in the charge transfer be equal to the energy changes 

in the system. Along the conductor

dWel=EdQ, (92)

where E is the electrical potential. In each half cell an 

identical energy change takes place as in the oxidation 

reaction

(93)

(94)

and in the reduction reaction

The energy yielded by one reaction is consumed in 

the other.

For one equivalent of electrons,

W^=E. (95)

As with the hydrolysis reactions, the proportions of 

reactants and products must be considered, and if 

n electrons are produced or used in a reaction, then

Wel=nE. (96) 

For each half cell, from the convention adopted,

i 

0>(rhalf cell = S MidtYlj- (. *')

From the discussion thus far, it is possible to formulate 

useful functions for the description of the states of 

redox reactions in natural systems. For two half cells,

such as

Fe°=Fe+2 +2e- (98)

and

2H++2e-=H2(g) , (99)

imagine a situation in which the electrodes (the electron 

acceptors from or donors to the solutions in the half 

cells) are in intimate contact with such a large amount 

of solution that allowing an integral number of moles 

to react will not change the composition of the solutions. 

Then the internal changes to the chemical system are

eaction s ^products ^_j"reactaiits =

 XjMreactants ( 1 00)

and the external changes (the electrical work measured 

on the electrical path)

(101)
D12 HYDROLOGY OF AQUIFER SYSTEMS

where 

so that

is the voltgram equivalent of the G units,

(102)

Abaction is ambiguous, there being two reactions that 

must be coupled to preserve electrical neutrality. For 

clarity, the convention used is that for the reaction 

(half cell reactions will for brevity be referred to as 

reactions) in the state specified (the standard state)

1 atm, r) = (103)

(104)

(105)

where E° is the potential for half cells in which all 

reactants and products are in their standard states.

For half cells measured against the hydrogen half 

cell, which is the reference half cell for all the subsequent 

discussion, the free energy change is merely the free 

energy change of the half cell. The total free energy 

change due to chemical reactions in the two half cells is

ACr = ( / itr ^_i^reactants)half cell

 ^_/lJreactants)half cell, (106)

and for the special case of a potential referred to a 

standard hydrogen half cell,

A6?= ( S^products S^reactants)half cell 0. (107)

The relation between free energy and potential is

(108)

where Eh is the potential of the half cell as measured or 

referred to the standard hydrogen half cell. For reactions 

in which all reactants and products are in their standard 

states,

&G°=n$E° (109)

where E° is the standard electrode potential. The standard potentials are of course referred to the standard 

hydrogen half cell just as are all nonstandard potentials 

(Eh).

From an analogous argument to that used for the 

activity product, the relations among compositions of 

half cells, the chemical potentials, and electrical 

potentials may be derived. The case is slightly different 

because in the general case two reactions are considered, 

one in each half cell. For each half cell the reactants and 

products may be related to the standard state as

=. 2_i (jU j products0 Mi reactants°) (110)

and in general

=^i(iJ.i products M» reactants) 

For the example chosen

MFe°

and in general

(1 1 1)

(112)

(H3)

(114)

because the pure Fe metal is in its standard state (the 

stable modification at 1 atmosphere pressure). The 

equations may be subtracted to give, respectively, the 

general case referred to the standard hydrogen half cell

 Mi°) reactants,

and for the example used,

From the definition of the activity of a species,

(117)

the equations become

and

~~]C(m ai) reactants f~ (H8)

(119)

The transformation to the well-known Nernst equation 

follows directly as

reactants

and

Because the iron metal is in its standard state

(120)

(121)

(122)

which can only be true if
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D13

The form of the Nernst law given contains two 

conventions:

1. The departure of the state of the half cell from the 

standard state given by the term

n aj)products reactants. (124)

2. The departure of the standard state from equilibrium 

with the standard hydrogen half cell given by 

the term E°. 

Equations important in the analysis of the data

reported in this paper fall from the derivations. First,

from

(125)

* reactants

Identifying

reactants

it follows that

^products ^ '"'reactants'

(127)

(128)

Alternatively put, because, by definition for the 

standard hydrogen half cell,

A/i°=2/i° -\-2/j.°e - uw =0, (129) ±1 ±±2

the sum of the chemical potentials over the half cell of 

interest,

i i 

Vi = ZX products"IXeactants^71 ^- (I 30)

A/x*j does not constitute the difference between the 

equilibrium state of the half cell and the observed state 

of that half cell. Consistent with the theory developed 

in the section devoted to mass action reactions, A/UJ 

is used for the chemical potential difference between 

observed states and equilibrium states. The nature of 

the A/x*j for the half cell is quite different from the 

A/ij for the mass action reactions, such as hydrolysis, 

discussed earlier. The half cell reactions are compared 

to an external reference, and one necessary but not 

sufficient requirement for equilibrium between two 

half cells at the same T and P is that

or that

(131)

(132)

However, another requirement, independent of the

first, is that all species be common to the two half 

cells and

(133)

from which, using the same standard state for species 

i in both half cells,

(a<) a=(at) 6 . (134)

The criteria for equilibrium among the electrochemical 

reactions considered in the water are that the solutions 

have the same Eh, pH, and identical activities for all 

other species in addition to the hydrogen ion.

A last problem in the data analysis is the relation of 

the measured electrochemical properties to the values 

calculated for an equilibrium between various phases 

and the water. The problem is analogous to the relations 

among the chemical potentials, the activity products, 

and the equilibrium constants except for the additional 

complication of having to refer the electrochemical relations to an external standard, the standard hydrogen 

half cell.

In operational terms, the measuring device consists 

of an inert electrode (platinujn) and an electrode of 

either known and fixed Eh or one having a constant Eh 

that can be measured (calibrated) in the field. The two 

electrodes may then be immersed in the water to be 

studied, and, taking appropriate precautions as discussed under "Methods of sampling and analysis," 

a measured Eh (Ehm) may be obtained. Experience 

has shown that the Ehm values may be reasonably 

uniform in time or, in other words, the measurements 

are reproducible. Early work also showed at least 

partial success in the interpretation of the Ehm in 

terms of states of chemical reactions of iron oxyhydroxides and oxides. In spite of the apparent success, 

in none of the work at any time have the specific 

reactions controlling the electrode potentials been 

known. The closest that one may come to such a knowledge is to find an agreement between the Ehm and an 

Eh calculated (EhTC) for a particular half cell at the 

temperature of the solution. It must be borne in mind 

that the agreement may be fortuitous or causal, and 

there is no way at present for distinguishing accidental 

agreement from the causal relation. The consistent 

results obtained earlier, along with those reported in 

this paper, indicate that the Ehm data obtained thus 

far are fundamental properties of the solutions studied 

and warrant further use in geochemical investigations. 

Put another way, the pH of a solution is a specific 

property that determines the behavior of a single 

species; the Ehm is a general property that cannot at 

present be related to a single specific reaction, but the 

Ehm must be used in the study of reactions involving 

electron transfer.

324-262 O-69 3
D14 HYDROLOGY OF AQUIFER SYSTEMS

The analysis of the Ehm data may take several 

forms, as discussed in the section on "Data analysis," 

The concern here is the theoretical basis for the data 

analysis. In general, one of two cases may be found in 

the analysis of the Ehm data in terms of equilibrium 

with possible phases with the solution, or in terms of 

tests for an internal equilibrium distribution of dissolved species. The cases are the equilibrium case and 

the disequilibrium case. Taking the corrosion of iron, 

for example,

(135)

(136)

and compared to the Ehm value from observation. 

(Subscript obs indicates observed; calc indicates calculated.) If there is internal equilibrium, then

a value for EhTC may be calculated from

7P77

and

EhTC=Ehm

obs=(A/ii*) calc.

(137)

(138)

At equilibrium, the difference in the chemical potentials 

between the actual and equilibrium states, AMI, is zero. 

For the case in which

(A/it*)obs^(A/ii*)calc (139)

the departure from internal equilibrium can be put on 

the same formal basis as the departure from equilibrium in the mass action reactions.

The formulation falls readily out of the considerations above. The same convention is used also. The 

difference between (A/^*)^ and (A/ii*) calc is arbitrarily assigned to the metal cation. Using the example of 

iron corrosion, Ehm can be used for the calculation of 

the equilibrium /iFe+2 at the Ehm as

Fe°=Fe+2+2<r

i

(140)

(141)

where the subscript eq would be the equilibrium value 

for appropriate species in the water of interest.

Alternatively, from

»=Mi-Mi, (142)

(143)

and

] (MFe° MFe°)eq-

(144)

The test for equilibrium tacitly assumes the phase of 

interest present; and, if the phase is solid and of only 

one component, then by definition

M Solid phase MSolid phase- (145)

As a consequence

(146)

More generally, for any reaction involving a solid,

_ i 

H% (Ehm E7r)) = Xj(Mi~Mi

I Mi°)reactants, eq=A(/ii*) eq . (147)

where the summation is over all species except the 

solid phase (s).

If

*) 0bS (148)

then a value for the Eh may be calculated from the 

actual composition of the sample, for example, for iron 

corrosion,

Fe°=Fe+2+2<r (149) 

. w° i RT i / ("F^

(aFe°)

 

obs 1r'

obs J

(150)

A treatment identical to the treatment of the equilibrium case leads to

or, in general,

Mi°)products, obs

 / i(Ui Mi )reaetants, obs-

(152) 

Subtracting the equilibrium state from the actual state

 / i (/if /i i ) products, obs

i

 ^LjvMi Mi )reactants, obs

i

 xAMf Mi )products,eq

t Mi°)reactants, eq (153)
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D15

and simplifying

ng(EhTC Ehm) ==/uf products, obs Mireactants, abs

' -' 

X_/(,Mi)products, en~T~ / /(/UiJrp.arttants. ei

z i 

/ /VUi )products. ohs~r x AUi jreactants, obs

i i 

~r x Au» )products, eq / i(^J jre^ctants, eq- (154)

In the calculations, the identical species are considered 

and hence, under the same physical conditions, using 

the same reference state,

and hence,

(155)

(156)

Care must be used in the interpretation of the potentials calculated and measured and of the relation 

between them. If, as may be found,

EhTC^Ehm, (157)

then it may be immediately concluded that Ehm is not 

controlled by the particular reaction under study, and 

the inference is drawn that the reaction is insufficiently 

rapid to control the Ehm of the solution. The equilibrium state is indicated by the Ehm and sums of the /u/s 

for each of the reactions. A seeming alternative explanation for differences between an EhTC value and 

the Ehm is that, for the particular reaction, the rate is 

so slow that the reaction does not control the composition of the solution. In fact, both the conclusions are 

the same; that is, if EhTC^Ehm, then the reaction is 

slow in comparison to the reaction (s) which do control 

the Ehm and is also too slow to affect the solution composition over as short a period of time as the measurement required. More fundamentally, the Nernst law 

gives the functional relationship between potential and 

composition and either or both may be chosen as the 

independent variable(s).

The variable A/u/ has exactly the same significance in 

redox considerations as in mass-action considerations. 

It represents the difference in the chemical potential 

summed over the reaction as it actually is, less the 

equilibrium value, and gives the existing potential to 

drive the reaction. If more than one species is involved, 

as often happens, the assignment of the departure from 

equilibrium to any single species is arbitrary and without thermodynamic justification. The laws of electrostatics, from which the law of electrical neutrality is 

derived, forbid the addition or subtraction of a single 

charged species without corresponding large electrical 

potentials. If the disequilibrium state changes toward 

an equilibrium, the change cannot be by changing the 

activity of a single ion without concomitant changes. 

The path to equilibrium may be complicated if the 

activity of an ion involved in the reaction is varied 

(coupled with a nonreacting ion of opposite charge, in 

keeping with the requirement of electrical neutrality) 

because hydrolysis in the solution may bring about a 

change in the activities of some or all of the other 

reacting species.

For those more familiar with concentration data or 

activity data, however, the departures from equilibrium 

are also calculated in concentration and activity terms, 

and to the metal ion is assigned the whole value of A/u. 

Equilibrium concentrations of the metal ion are calculated keeping all other /u/s constant. This is an entirely 

arbitrary convention and does not state how any system will change, but is offered as a convenient mode of 

expression of the fundamental properties in terms of 

familiar operational variables.

DATA ANALYSIS

Given the constituents found in the water, the 

solubilities of possible phases for which free energy 

data are available were calculated. The reactions used 

are strictly formal. They do not necessarily indicate 

a reaction mechanism or path.

The data analysis is broken into parts as follows:

1. Corrections for nonideal behavior of measuring 

systems.

2. Distributions of chemical species from the properties 

of the solutions.

3. Tests for the apparent behavior of the possible 

solids from available free energy data.

The pH data from field observations must be 

corrected to true data, and this was done using the 

procedures of Barnes (1964), including the measurement of the observed pH of two buffers.

Practical experience has shown that there may be 

discordance among saturated calomel electrode (SCE) 

potentials when measured against one another. Experience also has shown that the potential of a single 

SCE varies not only with temperature but with its 

history. The problem is not great in measuring pH 

because the potential of the SCE is Opposed in the 

calibration of glass electrode-SCE pairs. In Eh 

measurement, however, an absolute Emf for the SCE 

is required, not merely a constant Emf. The solution 

cited by Garrels (1960, p. 168) and his temperature 

compensation functions were used to obtain absolute
D16 HYDROLOGY OF AQUIFER SYSTEMS

values of the Eh of the SCE. All measurements in 

the field were so calibrated where possible. For other 

field studies, Garrels' function (1960, p. 67) for the 

Emf of the SCE as a function of temperature was 

verified experimentally and used.

The second step in the data analysis is prone to more 

uncertainty than the problems of correcting observation to true values. The distribution of species perforce 

assumes equilibrium distributions of species in the 

aqueous phase. Hem (1963a) gives stability constants 

for ion pairs formed between Mn+2 and HCO3~ and 

Mn+2 and SO4~2 . Using Hem's constants, the actual 

concentration of Mn+2 (molal) is given by

W Mn TOT

(158) 

where

WMII TOT is the total molality of Mn+2 by analysis, 

7Mn+2 is the activity coefficient for Mn+2, 

a so+ 2 is the product of the molality of SO^ 2 

times the activity coefficient of SO4~2 , and 

m-Hco- is the molality of the HCO3~ as reported by 

analysis.

Tacit in the above calculation is not only the equilibrium among the Mn species but also the presumed 

validity of individual ion activity coefficients. The 

question of the validity of individual ion activity 

coefficients has been argued for some years in the 

chemical literature. Many formulas have been proposed 

and their relative merits discussed. For details the 

reader is referred to Harned and Owen (1958), Robinson 

and Stokes (1959), and Guggenheim (1950). Both the 

rigor and accuracy of any formula used may be 

debatable. In dealing with naturally occurring solutions, 

however, which are invariably mixed electrolytes of 

widely ranging compositions, some model must be 

selected. The choice is arbitrary but made with the 

belief that a consistent and clearly defined treatment is 

to be preferred. The lack of data on individual or 

mean ion activity coefficients in the solutions studied 

and the impossibility of obtaining such data in the 

study here reported preclude an empirical check on 

the validity of the argument used. However, it seems 

safe to assume the activity coefficients calculated 

here are not more than one order of magnitude in error, 

and even an error of this magnitude would not vitiate 

the conclusions reached by the current data analysis.

The formula used for the computation of individual 

ion activity coefficient is:

 In Vi=

T1/2

T1/2 (159)

where

7i is the ion activity coefficient of the ith ion, 

A* is a constant involving only fundamental

constants, * 

B* is a constant involving only fundamental

constants,

dw is the density of pure water, 

D is the dielectric constant of pure water, 

T is the temperature in degrees centigrade, 

T is the ionic strength, 

zt is the charge of the 'ith ion, and 

a 0 is the distance of nearest approach of solutes

(Kielland, 1937).

(160)

where mt is the molality of the iih ion; A* and B* are, 

respectively,

(161)lblj

V1000&/ (162)

where

e is the electronic charge, 

N is Avogadro's number, and 

k is Boltzmann's constant.

Values of A* and B* have been calculated from the 

values cited in the U.S. National Bureau of Standards 

(1963) and are:

A*= 1824347. 0

J5*- 50. 297670

The density of water has been calculated from the 

function of Keenan and Keyes (1936, p. 21). The 

dielectric constant of water is calculated from the 

equation given by Jefiries Wyman and E. N. Ingalls 

as cited by Harned and Owen (1958, p. 159) up to 

100° C. For flexibility not required for the studies 

reported here, the program listed in "Appendix 1" of 

this report gives the dielectric constant for the watervapor saturated conditions from 100° C up to 360° C 

from the function of Akerlof and Oshry (1950).

The distribution of manganese species as cited above 

is simple in comparison to the distribution of copper 

species in solution. The pertinent reactions are:

Cu+=Cu+2+<T, 

2Cu+2 +2H2O=Cu2 (OH) 2+2 +2H+

(163)

(164)

and

Cu ToT=Cu+2+Cu+1 +2Cu2 (OH) 2+2. (165)

The equations may be solved readily for the distribution 

of copper. For example, a solution would be
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D17

7Cu2 (OH) 2+2

''0) \

J

TCu+2

(166)

where

m is molality of the appropriate ion,

a is the activity of the appropriate ion,

g is the volt gram formula weight equivalent,

R is the gas constant,

Ehm is the measured redox potential,

En° is the standard state potential for the reaction

2Cu+1 +2H2O=Cu2 (OH) 2+2+2H++2<r,

(167)

En° is the standard state potential for the reaction

Cu+1 =Cu+2 +<T, and (168) 

CUTOT is the total molality of copper species.

The function is a simple quadratic and, although 

cumbersome, would not be intractable except that

JT2 7^

7cu+2 LL 7cu2 (OH) 2+2

In all three actual solutions examined as test cases 

for copper speciation, the exact solution would require 

accuracy to more than two significant figures for the 

copper analysis, but the analysis is not reliable to more 

than two significant figures. Several alternate methods 

of distributing copper species were tried. The one selected has the virtue of working and, although it requires 

significant programming, it is efficient in use of computer 

time and becomes increasingly efficient as any one of 

the species considered diminishes in importance. Again, 

it should be remembered that the speciation assumes an 

equilibrium distribution of dissolved species and valid 

ion activity coefficients.

As other copper species become important in other 

natural solutions, the data analysis will become more 

complex. The selection of Cu+, Cu+2 , and Cu2 (OH) 2+2 

was made after preliminary calculations showed other 

species less important.

The distribution of sulfide species was based on an 

analysis of the data presented by Wright and Maas 

(1932). The data of Wright and Maas are still considered the most reliable obtained as a function of 

temperature. For the pH values of natural waters the 

reaction is

H2S(aq) =H+-r-HS-. (170)

The results of Himmelblau and Loy (1961) are suspect 

because, in the dilute solutions they chose, adsorbed 

oxygen on their apparatus would pose serious problems. 

Two sets of finite difference calculations for &H° from 

Wright and Maas' data gave erratic results. A smooth 

curve was drawn through their data and the slopenormal method described by Swartzendruber and Olson 

(1963) was applied to obtain &H°. From the &H° data 

obtained by the slope-normal method &CP (the heat 

capacity differences at constant pressure) was calculated. The resulting equations are:

A(7p= 0.0724454 kcal per mole (kilo calorie per mole),

(171)

- 0.0724454 T+ 27.4746 kcal per mole, (172)

(173)

log #=-36.456001 log T 6. 003400 X103 

+103.366829.

Many more significant figures are carried than justified 

by the original data. It should be remembered that 

digital computers commonly carry 12 digits so that the 

best values of the functions are given to avoid rounding 

errors in extensive computation.

The tests for the behavior of each solid considered 

rely on the data of Latimer (1952), Garrels (1960), 

and Larson and Buswell (1942). The chemical reactions 

that are considered (and, again, are formal, using 

directly measured variables where possible) are:

Computer

program

reaction

Nos.

0_ _ _ _

2_ _ _ _

3____

Hydrolysis reactions 

Cuprite :

Cu2O+2H+=2Cu++H2O. 

Tenorite:

CuO+2H+ = Cu+2 +H2 O. 

Copperhydroxide (no mineral name) :

Cu(OH) 2 + 2H+=Cu+2 +2H2O. 

Azurite:

(174)

(175)

(176)

.

(177) 

4____ Malachite:

Cu2 (OH) 2C03 +2H+ = 2Cu+2+C03-2 +2H2 0. (178) 

5____ Covellite:

CuS+2H+ = Cu+2+H2S(aQ) . (179) 

6____ Chalcocite:

(180)

(181)

(182)

(183)

(184)

7 _ _ _ _ Rhodochrosite :

MnC03=Mn+2+C03-2. 

8_ _ _ _ Ferrous hydroxide (no mineral name) :

Fe(OH) 2 +2H+=Fe+2 + 2H2 O. 

9____ Siderite:

FeCO3 =Fe+2 +CO3-2 . 

10_ _ _ Magnesite :

= Mg+2 +C03-2.
D18 HYDROLOGY OF AQUIFER SYSTEMS

(185)

(186)

(187)

Redox reactions

Computer 

program 

reaction

Nos. Hydrolysis reactions

!!___ Dolomite:

CaMg(C03) 2=Ca+2 +Mg+2 +2C03-2 . 

12___ Calcite:

CaCO3 =Ca+2 +CO3 -2 . 

1 3 _ _ _ Mackinawite :

FeS+2H+=Fe+2 +H2SUq) . 

14 _ _ _ Chalcopyrite :

CuFeS2 +4H+=Cu+2 +Fe+2 +2H2S(aq) . 

15_ __ Bornite:

Cu5FeS1 + 8H+=4Cu+ + Cu+2 +Fe+2 +4H2S(aq) . 

1 6 _ _ _ Manganous hydroxide (no mineral name) :

Mn(OH) 2 + 2H+ = Mn+2 + 2H2O. 

17___ Anhydrite:

CaSO1 = Ca+2 +SOr2 . 

18_ __ Gypsum:

CaSO,-2H2O=Ca+2 +SOr2 +2H2O.

Computer 

program 

reaction

Nos.

0____ Iron:

Fe=Fe+2 +2e~. 

1 _ _ _ _ Magnetite :

3Fe+2+4H2O=Fe3Oi 

2_ _ _ _ Ferric hydroxide (most soluble form of limonite) :

Fe+2 +3H2 0=Fe(OH) 3 + 3H+ + e-. (192) 

3 _ _ _ _ Hydrogen sulfide :

H2S(aQ) + 4H2 0=SOr2+10H++8e-. (193) 

4____ Pyrolusite:

Mn+2 +2H2O=MnO2 + 4H++2e-. (194) 

5 _ _ _ _ Hausmannite :

3Mn+2 +4H2O=Mn3O|+8H+ + 2e-. (195)

6____ Bixbyite:

2Mn+2 +3H2O=Mn2O3 +6H++2e-. (196) 

7_ __ Pyrite:

Fe+2 +2H2S(aq) = FeS2 + 4H+ + 2e-. (197) 

8____ Copper:

Cu=Cu+2 +2<r. (198) 

9____ Hematite (least soluble form of limonite) :

2Fe+2 +3H2O=Fe2O3+6H++2e-. (199) 

10___ Pyrite:

FeS2 + 8H2O= Fe+2 + 2SOr2 + 16H++ 14e~. (200) 

ll_-_ Used to distribute copper species:

Cu+=Cu+2+e-. (201) 

12___ Used to distribute copper species:

2Cu+ + 2H2O==Cu2 (OH) 2+2 +2H++2e-. (202) 

13_ __ Manganic hydroxide (no mineral name) :

Mn+2 +3H2O=Mn(OH) 3+3H++e~. (203)

(190)

(191)

For the hydrolysis reactions the equilibrium constants 

were calculated as a function of temperature if data 

were available. For calcite the function used is a 

least squares function fitted to the measurements of 

Larson and Buswell (1942) and is:

In XCm=27.8459347-8.257873 InT (204)

where K.C(T) is the equilibrium constant of calcite in 

the form

(205)

For the other hydrolysis reactions for which the standard state enthalpy (A-fiT°) only is known, the equation:

In Km =ln

where

(206)

K(T) is the appropriate equilibrium constant in the 

form consistent with the hydrolysis reactions 

given, and

^298.15 is the equilibrium constant at 25°C.

The tacit assumption that ACP=0 is used. For the 

azurite and malachite reactions not even AH° is known, 

so that the equilibrium constant is assumed independent of temperature or

In tf(r,=ln 

which is the same as assuming

(207)

The calculations for the temperature dependence of 

solubility are, in decreasing order of reliability:

1. From experimental data over a temperature range.

2. From experimental data including AH° at one 

temperature.

3. From solubility data at one temperature with no 

A#° data.

The equilibrium constants obtained by computation 

were combined with the activity product (AP) values 

from the observed composition of the water to give

AP (208)

The chemical potential existing because of the differences between actual and equilibrium states hence can 

be calculated for the hydrolysis reactions. Although, as 

pointed out in the theoretical discussion, there is no 

thermodynamic rigor in assigning departures from 

equilibrium to any single ion, it is a helpful index for 

those used to compositional variables. The convention 

used in this paper is consistent for all solids. The state 

of the reaction is expressed as a ratio of the actual 

activity of the metal cation divided by the activity of 

the metal cation at equilibrium. For example, for the 

reaction involving solid Cu2S

Cu2S+2H+=2Cu+ +H2S(aq),

(«Cu«) actual(«H2S(aq))actual

(209)

actual

and

K= (211)
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS

If it is assumed that

(aH2S(aq))actuaI (aH2S(aq))eq (212)

and 

then

and

/ \ _ / \ 

V aH+ /actual V^HVeqj

AP = (aCu+) 2actual 

K ((Xr.»+Y»n

\K J ~

If the assumption is made that

(TCu+) a c tua 1 = (TCu+) eq j

then

(213)

(214)

(215)

(216)

(217) \KJ ~

where CR is the cation ratio.

It is thus possible to arrive at a description of the state 

of a reaction in terms of concentration ratios or activity 

ratios in terms of single ions. The description is entirely 

arbitrary, however convenient it may seem to be. A 

rigorous comparison can be made, as has been shown, as

(218)

The data analysis for reactions involving electron 

transfer is only slightly more complicated than that 

for simple hydrolysis reactions. For example, for the 

reaction

Fe°=Fe+2+2<r, 

the Nernst law relation is

(219)

(220)

For solutions at temperatures other than 25° C, the 

temperature variation of E( T ° must be calculated. 

The function used is an integrated form of the GibbsHelmholtz equation and is

(221) "' 298.15 

implicit in which is the assumption 

A<7n=0. (222)

Data on the temperature dependence of E° values are 

sorely lacking.

D19

The chemical analysis and field study provide 

measured oxidation potentials (Ehm), T, and mFe+2.

Calculation of the individual ion activity coefficients 

such as 7Fe+2 make the Nernst equation determinate 

for two conditions, the actual state and the state for 

equilibrium. For example, from the measured oxidation 

potential the aFe+2 at equilibrium with iron metal 

may be calaculated as

In (223)

- In

The («Fe«)eq may be calculated from

From the measured mFe+2 the oxidation potential that 

should be measured if the solution were in equilibrium 

with Fe° may be calculated as

(224)

(225)

(226)

(227)

If

then

(TFe+2)eq= (TFe+2) actual,

which is in the same form as the CR for the hydrolysis 

reaction. The ratio of the activities, of course, would 

be numerically the same and be

actual (7Fe+2) actual_ '- (228)

The rigorous relation developed in the section on theory

is

R=rcg (EhTC-Ehm). (229)

All the above ways of describing the states of the 

reactions studied have been used in the program 

given in the appendix.

RESULTS

For a completely rigorous treatment of solute species 

and the related apparent behavior of solid phases occurring in natural systems, it seems necessary to show 

the following:

1. The aqueous phase is supersaturated with a solid 

phase and the solid phase is precipitating.

2. The aqueous phase is supersaturated with a solid 

phase and the solid phase is not precipitating.
D20 HYDROLOGY OF AQUIFER SYSTEMS

3. The aqueous phase is unsaturated with a solid phase 

and the solid phase is dissolving.

4. The aqueous phase is unsaturated with a solid phase 

and the solid phase is not dissolving.

5. An equilibrium exists between the aqueous phase 

and the solid phase.

If the information listed were available, then plausible 

reaction mechanisms could be postulated if sufficiently 

detailed information were available on the aqueous 

phase. If the time dependence of the precipitation or 

solution reactions, coupled with the concentrations (or 

activities) of the aqueous species were known, then 

kinetic interpretations could be made. Unfortunately, 

such information is not currently available.

Suppose that a solid phase is present in the natural 

system and that the aqueous phase is unsaturated with 

that solid. The only sure test of dissolution of the solid 

phase is by an artificial introduction of a known mass 

of that phase and by a measurement of the mass in 

time, assuming that the properties of the aqueous 

phase remain constant. In the present study, the only 

solid phase introduced into the wells (except for the 

corrosion probes) is iron metal, which is of slight 

geologic significance. Tests for the behavior of other 

solids with which the aqueous phase is possibly unsaturated are empty, in that their presence has not been 

established, and it cannot be proven that they do dissolve or do not dissolve.

The only tests available with present data relate to 

degree of departure from equilibrium of the solutions 

sampled at the wellhead with respect to appropriate 

solid phases, and a comparison with solids observed 

on well casing or screen in one well. Geologically, the 

nature of the substrate on which deposits are formed 

is probably of importance, but an assessment of the 

importance of the substrate cannot be made at this 

time. A further precaution is that, locally, solutions 

may be supersaturated or unsaturated, but the mixture 

of locally derived solutions as sampled r t the wellhead 

may be quite different in its properties from each of 

the individual solutions.

In the extreme, the characterization of the apparent 

behavior of solid phases can be made only on the 

grounds of relative supersaturations, or departures 

from equilibrium. Presumably, if a phase is precipitating 

locally from a solution, perhaps not represented by the 

solution sampled at the wellhead, then broad limits for 

the behavior of possible solids may be inferred. At 

least the properties of an aqueous solution at the 

wellhead may be determined; and, in terms of the bulk 

or integrated sample, the behavior of various solids 

may be studied.

Specimens of solid materials obtained from Shadman 

well 34 located in West Pakistan were subjected to 

optical, X-ray, and chemical tests. In 1964 solids were 

obtained from a mild-steel well screen that had been 

removed from the well and stored in air for less than a 

month before samples were obtained. The samples 

collected in 1964 were from three types of deposits: 

deposits filling the slots of the well screen; deposits 

on the outside of the well screen (on the aquifer side 

of the screen); and deposits on the inside wall of the 

well screen.

As shown in figures 2 and 3, the material found filling 

the slots was not homogeneous. The layers or zones 

were roughly symmetrical about central zone 3. 

Neither zones 2 nor 4 were in contact with the mildsteel screen, these zones being physically separated from 

the steel by zones 1 and 5. A summary of the phases 

found is presented in table 1. The pattern may have 

been influenced by catalytic effects of primary deposits.

The zones in contact with the steel (zones 1 and 5) 

are composed largely of silt-sized material with a few 

fine sand-sized grains which, upon optical examination, 

appear to be quartz and white mica. By X-ray diffracFIGURE 2. Diagrammatic sketch, encrustation plug, corroded steel casing slot, 

Shadman well 34, West Pakistan.

FIGURE 3. Encrustation plug, steel casing slot, Shadman well 34, West Pakistan.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D21

TABLE 1. Identifications of solid phases found in slot filling of 

the mild-steel well casing removed from Shadman well 34, West 

Pakistan

Zone Phases identified 

land 5... Siderite, Mn3O4 (spinel), Cu(OH) 2 , hausmannite,

magnetite(?), maghemite(?), and detrital(?) quartz

and white mica.

2 and 4___ Cu(OH) 2 , mackinawite, and detrital(?) quartz. 

3________ Calcite, siderite, mackinawite, detrital(?) quartz,

mica, and plagioclase(?) feldspar.

tion zones 1 and 5 (in contact with the mild steel) were 

found to consist chiefly of approximately equal amounts 

of siderite (FeCO3) and a mixture of very fine grained 

cubic Mn3O4 (spinel structure) and Cu(OH) 2 . The 

largest siderite diffraction peaks are apparently displaced from the positions expected for siderite to 

smaller unit cell spacings. Possibly the apparent shift 

in the positions of the peaks may be due to the substitution of Mn+2 for Fe+2 in the siderite.

Two magnetic separation methods were applied to 

materials from zones 1 and 5 (the zones adjacent to 

the mild-steel surfaces), but both magnetic separates 

were apparently identical from X-ray diffraction 

studies. X-ray diffractograms of the two magnetic 

separates showed only siderite, even with strong pulse 

height discrimination. The two apparently identical 

magnetic separates were combined to make a single 

magnetic fraction and photographed using iron Xradiation. The results of the iron X-ray photography 

are tabulated in table 2. A study of the film exposed by 

iron radiation showed siderite as the dominant phase 

with presumably lesser amounts (lighter lines) of 

Cu(OH) 2 and both forms of Mn3O4 . The strongest 

diffraction lines of both the isometric Mn3O4 (spinel 

structure) and the tetragonal Mn3O4 (hausmannite) 

were found. At least one iron oxide and possibly both 

magnetite (Fe304) and maghemite (Fe2O3) are present. 

A phase intermediate between magnetite and maghemite, such as the phase described by Harrison and 

Peterson (1965), also is a possibility.

Zones 2 and 4 lying between innermost zone 3 of the 

slot filling and zones 1 and 5 in contact with the mild 

steel also were examined. Zones 2 and 4 were composed 

of a dull, metallic gray material that was quite brittle. 

There was noticeable gradation between zones 1 and 2 

and between zones 5 and 4. Both inner zones 2 and 4 

were made of botryoidal masses coated with silt-sized 

quartz. Both the inner zones (2 and 4) had relatively 

more or perhaps more coarsely crystalline Cu(OH)2 

than the outer zones (1 and 5). Both the inner zones 

(2 and 4) contained mackinawite (tetragonal FeS) 

but no carbonate phase was detected.

Innermost zone 3, found in the middle of the filled 

slots, also was botryoidal in texture with silt-sized 

quartz. Upon crushing some of the botryoidal masses 

of the innermost zone, it was found that some contained 

black massive material, but others contained blood-red 

material with a boxwork structure. The material of 

the innermost zone was too fine grained to permit 

physical separation of the botyroidal masses for a 

comparative X-ray study. X-ray investigation of the 

bulk material of the innermost zone yielded rather 

poorly resolved diffractograms; therefore some identifications were questionable. The material was found to 

be mostly quartz and calcite with siderite and mackinawite. Minor amounts of a phase which gave a diffractogram peak at 10 A (angstroms) may have been 

mica. Apparently a feldspar was present also, possibly 

plagioclase, but a definite identification was not possible. 

This sequence suggests that catalytic surface effects 

as well as water composition may have influenced the 

nature of the deposit. Hem (1964) found such effects 

in his study of manganese. Localized corrosion processes 

also may have contributed to the structure by producing products not predictable on the basis of this 

type of analysis; these products, in turn, may have

TABLE 2. A comparison of the composition in weight percent by spectrographic analysis of materials found on the well screen of Shadman

well 3^, West Pakistan 

[Slot-filling zones shown in figure 2. Spectrographic analysis by Pauline Dunton. Materials separated by Roger Wolff and Pauline Dunton. Minerals identified by Blair Jones

Zones 1 and 5, next to mild 

steel

Element

Fe. .........

Mn.... . ...

Co .......

Cu... .......

Ni.. ........

Si. ._._.....

Wolff

34

.1

.5 

.03 

.05

.7

.3 

4

Dunton

48 

Nd

.5 

.03 

.1 

1.0

.3

Nd

Minerals

(spinel) . 

Cu(OH) 2 .

Hausmannite. 

Magnetite

Maghemite

Slot filling

Zones 2 and 4

Wolff Dunton Minerals

......... 44 Cu(OH)2 .

wite.

_..__... .007 ..............

........ .05 ..............

......... .03 ...__..._...__

........ Nd ..............

Zones 3, innermost zone

Wolff

16 

5

.1 

.007 

.003 

.03

.005 

18

Dunton

27 

Nd

.1

.003 

.0007 

.05

.005

Nd

Minerals

Siderite-....

Mackinawite. 

Mica(?)

Feldspar

Crust from outside of screen

Wolff Dunton Minerals

.5 .__..__.._ Cu(OH) 2

(spinel).

.07 .......................

.5 .......................

.3 .......................

3 .......................

Crust from inside of screen

Wolff Dunton

. 32 . .___.___..

.1 ..........

.1 .._..__.._

. .007 .__..__...

. .01 ...__.._..

.1

. .03 _........

. 14 ........_.

Minerals

Cu(OH) 2 . Mackinawite. 

Siderite.

Mn(OH) 2

1 Analyses by Eaulin&Dunlon using X-ray fluorescence. 

324-262 O-69 4
D22 HYDROLOGY OF AQUIFER SYSTEMS

catalyzed precipitation of compounds found in the 

deposit.

Material also was obtained from inside the well 

screen removed from Shadman well 34. This sample was 

flaky in appearance and consisted of massive metallic 

material coated by granular material on the side exposed to the water within the well screen. The granular 

material could not be separated from the massive 

metallic material owing to the fineness of grain and 

thinness of the granular coating. X-ray diffractometer 

study showed Cu(OH) 2 as the most abundant phase, 

with very small amounts of (or extremely fine-grained) 

mackinawite, siderite, and possibly Mn(OH) 2 .

The phases identified in the study of materials 

collected in 1964 from the screen of Shadman well 34 

are summarized in table 1, together with available 

chemical data from the same well. Comparisons of the 

reported compositions of samples prepared by Roger 

Wolff and Pauline Dunton show that the analytical 

data are not absolute in nature, but show relative 

abundances of the several elements reported in the 

samples. The chemical analyses do not accurately 

reflect the relative proportions of the solids as determined by X-ray diffraction. The various grain sizes 

mentioned in the descriptions of the samples would 

lead one to expect the poor agreement shown in table 

2. The presence of quartz (Si not determined) and 

amorphous materials such as Fe(OH) 3 also would 

complicate relation of chemical composition to apparent 

relative amounts of materials found by X-ray study. 

The chemical data do provide a test for the X-ray 

data, however, in that all the phase identifications 

appear to be reasonable. All samples in which Cubearing phases were found by X-ray study did have 

appreciable Cu as shown by chemical analysis. All 

the samples in which Mn-containing phases were found 

by X-ray study did contain Mn as shown by chemical 

analysis. No further interpretation of the data in table 

2 seems warranted.

In addition to the materials described thus far, all of 

which were collected in 1964, a sample was scraped off 

the inside of a pump column installed in Shadman well 

34 before the 1965 field season. Both the well screen 

sampled in 1964 and the pump column sampled in 1965 

were of mild steel. However, the well screen had been 

stored in air prior to sampling, whereas the pump 

column sample was collected in 1965 immediately after 

removing it from the well. An X-ray study of the pump 

column sample showed magnetite apparently to be the 

most abundant phase, with quartz and a small amount 

of another phase giving a diffraction peak at 10 A 

(possibly a mica). A surface film of the same sample 

exposed by iron X-radiation revealed evidence of the 

metastable polymorphs of Fe3S4, smythite (rhombohedral) and greigite (cubic). A systematic study of the 

film showed that mackinawite; pyrrhotite, Fei_xS; 

valeriite, Cu2Fe4S7 (?); pyrite, FeS2 ; copper hydroxide, 

Cu(OH) 2 ; manganese hydroxide, Mn(OH) 2 ; manganese 

spinel, Mn3O4 (isometric); and hausmannite, Mn3O4 

(tetragonal), were not detectable by the X-ray technique used, if indeed they were present at all.

The results of the mineralogic study of the solids 

found upon the mild-steel well screen, well casing, and 

pump column of Shadman well 34 give tentative 

identifications of possible occurring phases. Presumably 

the phases identified have been deposited from the 

water flowing through or standing in, or immediately 

outside of, the well casing and screen. Even if the 

existence of each suggested phase is accepted, there is 

no way of telling whether the phases found are primary 

precipitates formed directly in place by precipitation 

from a true solution, or whether suspended particulate 

matter had deposited as a sludge of encrustant on the 

various surfaces. Possibly the iron-bearing phases 

identified are related to corrosion of the well casing 

and would not have been formed on an iron-free substrate in contact with the same water. Catalytic effects 

of primary precipitates on further precipitation already 

have been mentioned as a possibility. There also is the 

possibility that certain precipitating solids were swept 

away, and thus not detected.

In spite of the uncertainty of the origins of the 

solids tentatively identified, they must be considered 

in any reasonably complete study of corrosion and 

encrusting properties of the water. The data for composition of water samples were analyzed to determine 

the states of reaction (supersaturation, equilibrium, 

and unsaturation) with respect to most of the oxides, 

hydroxides, carbonates, sulfides, and sulfates of the 

metal cations other than the alkali metal cations. The 

reactions used are summarized in the section on "Data 

analysis." Extreme values of the AJU/J and CR are 

given in table 3, along with the identification of the 

wells yielding the extreme values. Shadman well 34, 

the well from which the solids were obtained for 

detailed examination, is not listed in table 3. Water of 

Shadman well 34 is not as far from equilibrium as 

some of the others sampled in spite of the rich suite 

of exotic phases identified such as Mn(OH) 2 and 

Cu(OH) 2 .

Both positive and negative values of AMR are given 

for supersaturation. The reason is that the redox 

reactions were all written to yield electrons on the 

right-hand side of the equation. Sometimes the solid 

appears on the left side of the reaction (reactant) and 

sometimes on the right side of the reaction (product). 

For supersaturated states, the sign AJUR will be + if the 

solid is on the left side of the reaction and if the solid
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D23

TABLE 3. Ranges of numerical results of data analysis for possible reactions of waters and solids 

[Reaction numbers are the same as in text and appendixes; Ss, supersaturated; Un, unsaturated]

Maximum values of AMR and OR, well water in 

which founa, state of reaction

Minimum value* of AMR and OR, well water in 

which found, state of reaction

0

1

2 

3

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

«11

512

13

Cuprite.-...-..--,..--.--.......

Azurite __ -.........-..-.._...-

Siderite.. .................... ...

Calcite.--. -_-._._._--_..._-.

Bornitei- ...................

Iron __ --.-..--.

Ferric hydroxide or "limonite"...

Bixbyite... ......................

Pyrtte (H2S reaction) ..........

Copper _ --..._. .... ... .

Pyrite (SO4 reaction)... ......

... CuzO

... CuO

... Cu(OH)s

... CU3(C03 )2(OH) 2 

... Cu2 (C03)(OH)2

... CuS

... MnCOs

... Fe(OH) 2

... MgCOs

... CaMs(CO3) 2

... CaCOs

FeS

.. Cu5Fe&4

... Mn(OH)..

... CaS04 -2H2O

... Fe

... Fe3 04

.. Fe(OH) 3 

.. HjS-SOr2

__ FeS2

.. Cu

.. Fe2O3

.. Mn(OH) 3

Well identification

Sangla Hill 2 ». .

.....do .......... 

... __do - __.-

.....dor .........

.....do.............

Mona 83 »_______..

_..._do ..........

Shahkot251'- -

Khaipur K12'..i. 

...._do....._._.....

Daloriz.. .........

... ..do... ...,-... _.

 do -- 

Dalori 2.. ......_..

.... .do..... ....__..

.....do... .......

> West Pakistan. 

« Nigeria. 

3 Egypt.

State of AMR 

reaction (kcal)

Ss 

Ss 

Ss 

Ss 

Ss 

Ss 

Ss 

Ss 

Un 

Ss 

Ss 

Ss 

Ss

Un 

Un 

Un 

Un 

Ss 

Un

Un 

Un 

Uii

Ss 

Ss 

Ss 

Ss

Un

8.43 

3.25 

1.48 

9.75 

7.56 

26.2 

36.7 

.632 

-3.36 

1.60 

.53 

2.06 

.83

-6.92 

-.221 

-. 0147 

-13.6 

-7.20 

5.62

_ qi fu

35.0 

35.2 

31.3 

-24.0 

9.48 

-4.09 

26.2

28.2

OR

1.04X103 

2.54X102 

1.25X10» 

2.46X102 

6.32X102 

2.15X10" 

2.22X10" 

2.85X100 

3.82X10-3 

1.42X101 

2.44X100 

3.18X101 

4.03X100

7.25X10-6 

6.82X10-» 

9.76X10-1 

1.75X10-10 

5.30X101 

9.19X10-5

7.2X10-26 

4.80X10-9 

5.76X10-12 

7.84X1016 

6.54X106 

2.94X101 

6.21X1018

9. 58X10-21

Well identification

Sangla Hill 21.... .

. .do -----

...--do-. -------

.....do. -------

Sangla Hill 21 .. 

Rashda3,_. .......

Mut» --~-

Rashda '_-.----

Muf . ------

Rashda 3 -. --------

. .do... .... -----

...-do -----

Sangla Hill 2 i ..

Mona 113 i-. . --

. Sangla Hill 21. ..

...-do ---------

.....do.... ... ......

_____do --------

__._ -do... -_-_--.-

.-..do -------

.....do ..... ---.

.....do -_.-_---.-

Sangla Hill 2 »...-.

State of AMR 

reaction (kcal)

Un 

Un 

Un 

Un 

Un 

Ss 

Ss 

Un 

Un 

Un 

Un 

Un 

Un

Un 

Un 

Un 

Un

Ss 

Ss

Un 

Un 

Ss 

Ss 

Un 

Ss 

Un

Un

-4.09 

-7.11 

-8.98 

-25.3 

-16.1 

20.5 

22.8 

-1.94 

-6.12 

-.47 

-3.49 

-5.48 

-2.68

-10.3 

-4.98 

-4.89 

-48.6 

-37.3 

-5.00 

.- -129

1.11 

.96 

-2.72 

-44.2 

-12.3 

-35.4 -214

7.86

CR

3.06X10-2 

9.09X10-6 

4.27X10-' 

5.30X10-5 

6.54X10-5 

2.65X10" 

2.87X108 

4.18X10-2 

4.38X10-5 

4.61X10-1 

3.30X10-3 

1.25X10-1 

1.23X10-2

4.69X10-8 

3.18X10-1 

3.66X10-1 

1.09X10-36 

1.59X109 

3.32X10'

1.49X10-1 

5.79X10-1 

1.01X101 

5.41X1032 

7.92X10-W 

1.28X1013 

3.21X10-159

1.52X10-6

i No G° data available. 

5 Used for distributing copper species.

NOTE. See "Appendix 2" for detailed chemical data of wells listed.

is on the right. The state of the reaction is given to 

make the meaning of the AJUR values unequivocal.

Several regularities of behavior may be found in 

the data presented in table 3. The simple carbonates, 

such as FeCO3 and CaCO3 , are relatively well behaved 

in that the maximum departures from equilibrium on 

the supersaturated side of equilibrium are only 1.6 and 

0.83 kcal for siderite and calcite, respectively, and both 

have been found as solid phases. In terms of compositions of the solutions, maximum supersaturation (CR) 

is only 14. and 4.0, respectively. The inference drawn 

is that both phases may precipitate so rapidly that the 

solubilities of siderite and calcite are effective controls 

on the compositions of the ground waters in comparison to the apparent extreme departures from equilibrium of the other phases studied. Departure from 

equilibrium on the unsaturated side of equilibrium 

( 0.47 kcal for siderite and 2.68 kcal for calcite) 

may only indicate the lack of contact of the solid 

phases with the water, a condition due either to the 

complete absence of the carbonates from the aquifer(s) 

or at least to the absence of the carbonates along the 

flow paths of the waters withdrawn.

The simple oxides and hydroxides, including those 

of copper, iron, and manganese, apparently do not 

generally operate as effectively as the simple carbonates 

in controlling ground-water compositions. CU(OH) 2 ,

a notable exception, has only 1.48 kcal as a maximum 

chemical potential for reaction, a value representing 

supersaturation of only a factor (CR) of 12.5. The 

anhydrous copper oxides, cuprite and tenorite, and 

the anhydrous iron oxides, magnetite and hematite, 

apparently react slowly enough so that very large 

departures from equilibrium may occur, as shown in 

table 3.

The largest observed departures from equilibrium 

involve sulfides. The departures from equilibrium range 

from at least +20 kcal on the positive side to as large 

a negative potential as 214 kcal. Although the 

reactions are probably very complicated in detail, the 

general inference may be drawn that sulfides do not 

react readily.

Table 4, drawn from table 3, summarizes the phases 

with which the aqueous solutions studied were found 

to be consistently supersaturated. Although the data 

are fragmentary and inconclusive, several tentative 

inferences may be drawn. The simple oxides listed 

apparently do not precipitate rapidly, as the departures 

from equilibrium (apparent supersaturations) range 

from 2.72 kcal to 35.4 kcal. In contrast, the 

simple carbonates (CaCO3 , FeCO3 , MnCO3) depart 

from equilibrium by only 0.63 to 1.60 kcal as maximum 

supersaturations. As the carbonates become more 

complex and hydrated, supersaturated solutions appar-
D24 HYDROLOGY OF AQUIFER SYSTEMS

TABLE 4. A/JR for waters supersaturated with respect to solids 

that might precipitate from the well water as sampled at the 

wellhead

[All values are in kilocalories]

A/UR (max) A/UR (min)

Cu2 0____ ____________________

CuO____________-____________

Mn2 03 _______________________

Fe203 -----__--_-________-____

CaC03 -__ ____________________

FeC03 -_______--_________-___

MnCOs- -------------------- .

CaMg(C03) 2 ___ _______________

Cu2C03 (OH) 2 _ ________________

Cu3 (C03 ) 2 (OH) 2 __-____________

Cu(OH) 2 _ ____________________

Fe(OH),_--_-.._. _ _._._

Cu_--________-_--____-______

CuS_________________________

Cu,S... _-____._..__..__._.._

FeS2 (H2S reaction) ___________

FeS2 (S04 reaction) ____________

Fe304 -__--__---_--___-_____-_

________ 8.43 _.

________ 3. 25 _.

________ -4.09

________ . 83 _.

________ 1. 60 _.

________ . 63 __

________ 2. 06 _.

________ 7. 56 _.

________ 9. 75 _.

________ 1. 48 _.

________ 9. 48 _.

________ 26. 2

________ 36.7

________ - 24. 0

________ 26. 2 _.

________ ' - 7. 2

-2. 72

-35. 4

-5. 00

20. 5

22. 8

-44. 2

-37. 3

ently deviate by as much as 9.75 kcal from equilibrium. 

The only carbonates found to precipitate are FeCO3 

and CaCO3 .

The simple sulfides considered here are quite different 

from the other solids. Although examined only in terms 

of reactions involving precipitation from aqueous 

phases containing sulfide (except for pyrite, in which 

both sulfide and sulfate reactions were considered), 

the sulfides studied departed from equilibrium with 

the coexisting aqueous phase markedly more than did 

the complex carbonates, the simple carbonates, and 

the oxides.

From the work of Barnes, Stuart, and Fisher (1964) 

it may be concluded that apparently pyrite dissolved 

into some aqueous solutions (including mine water 

containing H2S, at pH of 5.4 or less) rapidly enough to 

come to saturation. Such is not the case in the sulfidecontaining solutions at higher pH's as reported on here. 

Not only do sulfides not precipitate readily from 

sulfide-containing solutions but apparently the presence 

of sulfide species at pH values of 7.0 or more may 

inhibit the solution of the sulfide-containing phases if 

they be present.

The small amount of data on the apparent behavior 

of the solid phases is summarized in table 5, which 

gives the nature of the departures from equilibrium of

TABLE 5. States of reaction including all well waters and summary 

of phases found in samples from Shadman well 34, West Pakistan

Super- Unsaturated Both super- Phase was

Solid name saturated for all waters saturation found in

for all waters tested andunsatu- mineral

tested ration found analysis

CuzO, cuprite--..---------------------------------------- Yes......... No.

CuO,tenorite---_ -------------------------------- Yes.-..-..- No.

Cu(OH)., copper hydroxide---.-.-..--.----------------- Yes......... Yes(?).

Cu3 (C03)2(OH)2, azurite - ---- -- -- Yes.--..... No.

Cu2 (C03)(OH)2, malachite----.-----. ------------- Yes..-. . No.

CuS, covellite- .-.....-- Yes..................................... No.

CujS, chalcocite.............. Yes..... ............................. No.

MnCOs, rhodochrosite..-.-.---.--..--.----------- Yes......... No.

Fe(OH)2, ferrous h>droxide-._-... ..... Yes..................... No.

FeCOs, siderite...... ....... -.---- -. - Yes......... Yes.

MgCOs, magnesite...._-_ --.-- - ------ --------- Yes.... ... No.

CaMg(C03 )2, dolomite.................................... Yes..... No.

CaCOs.calcite---... -.-..- -- ---- Yes........ Yes.

Mn(OH)j, manganous _ _-.__._._. Yes....____.__ _......... Yes(?).

hydroxide. 

CaSO< anhydrite__....... ..... ...... Yes...... ............... No.

CaSO4-2H2 0, gypsum.-...-..-.--...-.. Yes..-..----..-..... No.

Fe, iron metal....----.--.--------- Yes_...................... Yes (well

casing). 

Fes04, magnetite.--.-------- Yes......................... .......... Yes.

Fe(OH) 3 , ferric hydroxide..-- .-.--...----.--- Yes........ Yes.

MnOs.pyrolusite.......................... Yes....................... No.

MrsOi, hausmannite.-.--..---- --.- -- Yes....................... Yes(?).

MrnOs, bixbyite ...........................v.......... Yes........ No.

FeSz, pyrite (H2S reaction) . Yes__...................... ......---.. No.

Cu, copper metal-.. .................. .............. Yes.. ... No.

Fe203 , hematite... ,......... Yes. ..____.__ .......-........-.--... No.

FeS2 , pvrite(S04 reaction).-.......-..-.-.........----... Yes......... No.

Mn(OH)s, manganic --__-....... Yes....._-.-------- No.

hydroxide.

the solids presented in table 3. Also presented in table 5 

is the list of solids which were found on substrates in 

Shadman well 34. It is unfortunate that samples of 

encrustants were not available from wells other than 

Shadman well 34. Because the water from Shadman 

well 34 does not represent the extreme value for the 

departure from equilibrium for any solid, it would be 

expected that more solids than those listed may be 

forming on substrates on other wells. In any event, 

Shadman well 34 water, although it is supersaturated 

with several solids, is only precipitating one stable 

phase, calcite. Siderite, ferric hydroxide, and magnetite 

are metastable relative to (more soluble than) hematite. 

Cu(OH) 2 is metastable relative to (more soluble than) 

any other copper phase considered.

Table 6 gives the detailed chemistry of Shadman well 

34. Not only is Cu(OH) 2 metastable with respect to 

the other copper-bearing phases, but the bulk discharge 

of the well is unsaturated with Cu(OH) 2 . The water 

obtained from Shadman well 34 is unsaturated 

with both hausmannite (tentatively identified) and 

Mn(OH) 2 .

TABLE 6. Results of chemical analysis and data analysis, Shadman well 34, West Pakistan

[Extracted from computer program (see "Appendix 2"). Field Eh, pH, Fe+2 , HCO3 , by F. E. Clarke, USAID, and West Pakistani scientists, March 1965; other chemical data

by laboratories of the U.S. Geological Survey, May 1965]

A. Intrinsic thermodynamic properties of water general characteristics

Oxidation- Temperature 

pH reduction (°C) 

potential (volt)

Partial 

Ionic strength pressure, CO2 

(atmosphere)

Aqueous CO2 

(molality)

Aqueous COs 

(ppm)

Standard 

potential

Fe3 S4

Log activity

of S O4~2 at 

equilibrium 

with H2S

Log activity

of iron in 

equilibrium 

with pyrite at

measured SO4 -

7.49 0. 0870 28. 00 0. 01089 0. 0116517 0. 000368 16. 19 0. 739 40. 4757 61. 4646
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS

B. Intrinsic thermodynamic properties of water ionic data

D25

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

Solid phase

CU2O

CUO

CU(OH2

AZURIT

MALACH

CUS

CU2S

MNCO3

FE(OH2

FECO3

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

Ion Concentration (ppm) Activity coefficient Molality Activity molal scale

CA 62.000 0.665516 1.5469@-03 1.0295@-03

MG 27.000 .680260 1. 1106@-03 7. 5547@-04

NA 61.000 .897684 2. 6534@-03 2. 3819@-03

K 3.100 .894677 7. 9280@-05 7. 0930@-05

CL 23.000 .894677 6.4875@-04 5. 8042@-04

SO4 45.000 .649373 4.6845@-04 3.0420@-04

HCO3 356.680 .897684 5.8456@-03 5. 2475 @- 03

FE 2 .400 .665516 7. 1624@-06 4. 7667@-06

FES .000 .429915 .0000@ + 00 .0000@+00

MN 2 .117 .665516 2. 1272@-06 1.4157@-06

GUI .036 .894677 5. 7035@-07 5. 1028 @- 07

CU 2 .004 .665516 5. 9737@-08 3. 9756@-08

HS .388 .896202 1. 1743@-05 1.0524@-05

H2S .100 1.000000 2. 9285@-06 2. 9285@-06

CU2OH2 .000 .693776 4. 9218@-11 3.4146@-11

CUTOT . 040

H2STOT . 500

C. Thermodynamic state of water with respect to coexisting solid phases undergoing hydrolysis reactions

Equilibrium Cation at Cation at

Activity product constant at Activity product/ Cation, actual/ equilibrium equilibrium

observed equilibrium constant cation, equilibrium (molality) (ppm)

temperature

2. 4866@ + 02 1.9691@-02 1. 2628@ + 04 1. 1238® + 02 6. 8230@-09* 4. 3353@-04

3. 7967® + 07 5. 9293® + 07 6.4033® -01 6. 4033® -01 9. 3291® -08 5. 9277® -03

3. 7967@ + 07 1.2311@+09 3. 0839@-02 3. 0839@-02 1.9371® 06 1.2308© 01

3. 8920@-18 1.0836® 18 3. 5916@ + 00 1.5314© + 00 3. 9007@-08 2. 4785@-03

1.2156@-05 1.6113® 06 7. 5441@ + 00 2. 7467@ + 00 2. 1749@-08 1.3819® 03

1.1118@ + 02 9. 1162®- 16 1.2196® + 17 1.2196© + 17 4.8979@-25 3. 1122@-20

7. 2821@-04 2. 2282@-28 3.2682@ + 24 1.8078® + 12 3. 1549@-19 2. 0046@-14

1.1401® 11 1.4281® 11 7. 9836@-01 7. 9836@-01 2. 6644@-06 1.4638® 01

4. 5522@ + 09 1. 3113@ + 13 3. 4715@-04 3. 4715@-04 2.0632® 02 1. 1522@ + 03

3. 8389@-ll 2. 0247@-11 1.8960@ + 00 1.8960@ + 00 3. 7777@-06 2. 1097@-01

6. 0842@-09 1.1100®- 08 5. 4810® -01 5. 4810@-01 2. 0262@-03 4. 9261@ + 01

5. 0444@-17 1.0000® -17 5. 0444@ + 00 5. 0444@+00 3. 0666@-04 1.2291® +01

8. 2910@-09 4. 2276@-09 1.9612@ + 00 1.9612@ + 00 7. 8876@-04 3. 1614@ + 01

1.3331® +04

1.4822® + 06 _______________ _ ____ _ __________________________________________

7. 8599® 01 _- _ _

1.3520® + 09 1.3859® + 15 9. 7548® -07 9. 7548® -07 2. 1807® + 00 1. 1980® + 05

3. 1317@-07 3. 4675® 05 9. 0315@-03 9. 0315@-03 1.7128@-01 6. 8649@ + 03

3. 1317@-07 2. 4319@-05 1.2877© -02 1.2877® 02 1.2013® 01 4. 8146@ + 03

Actual

chemical

potential

(k cal)

5. 65170

-.26678

-2.08204

. 76519

1. 20935

23. 54499

33. 78096

- . 13477

-4.76720

. 38286

-.35985

. 96848

. 40309

-8. 28292

-2.81698

-2.60467

D. Thermodynamic state of water with respect to coexisting solid phases undergoing oxidation-reduction reactions

Standard state Calculated

potential at oxidation-reduction Cation at Cation at

Solid phase observed potential at Cation, actual/ equilibrium equilibrium

0

1

2

3

4

5

6

7

8

9

10

11

12

13

FE MET

FE304

FE(OH3

H2S

MN02

MN304

MN203

PY H2S

CU MET

FE203

PY SO4

CUDIST

CUDIST

MN(OH3

temperature observed cation, equilibrium (molality) (ppm)

(volts) temperature

(volts)

-0.4398 -0.5989 1. 1097® -23 6. 4541® + 17 3. 6044® + 22

.9763 -.3370 5. 3715@ + 04 1. 3334® 10 7. 4467® -06

1.0548 .0301 8. 9623@ + 00 7. 9917® -07 4. 4631® -02

.3028 -.2416 1. 0174© 44 . 0000® + 00 . 0000® + 00

1.2270 .5066 9. 0480® 15 2. 3510@ + 08 1.2916®+ 13

1.8166 .5505 6. 7375@-06 3. 1572@-01 1. 7345®+ 04

1.4406 .4474 9. 3150@-07 2. 2836® + 00 1.2546© + 05

 . 1409 -. 5464 1. 5798® + 21 4. 5338® -27 2. 5320® -22

.3370 .1159 9. 2846@ + 00 6. 4340® -09 4. 0882® -04

.7242 -.3005 3. 0548® + 06 2. 3447® -12 1. 3094® -07

.3662 -.1981 .0000@+00 . 0000® + 00 . 0000® + 00

1.9242 .9310 7. 5138® 15 2. 8310@ + 08 1. 5553®+ 13

Actual

chemical

potential

(kcal)

-31. 631911

- 19. 554358

 1. 312443

-60. 622113

19. 352011

21. 379154

16. 621050

-29. 211877

1. 333586

- 17. 872735

-92. 032368

19. 463210
D26 HYDROLOGY OF AQUIFER SYSTEMS

Two alternative interpretations are obvious if the 

data are correct. Either some of the solids are indeed 

much less soluble than data in the literature indicate, 

or there are local conditions within the aquifer-well 

system which are not represented by the water discharged from the well. The second alternative is much 

more likely. The appearance of the well screen as 

shown in figure 4 is not uniform. Heavily encrusted 

and bare metal areas are apparent. Because detailed 

knowledge of the local properties of the water in the 

aquifer and in the intake areas is lacking, more specific 

interpretation of the data at hand does not seem 

warranted.

The chemical data do give the bulk properties of 

the water from the well, and it is the mixture of incompatible waters that gives rise to the troublesome 

encrustations such as were described from Shadman 

well 34. Detailed information on microenvironmental 

conditions within the intake (screen) and aquifer should 

be sought to aid in reaching an understanding of local 

corrosion attack or fouling of well screens and other

parts of the well installation. This will require remote 

sensing equipment not yet perfected. The bulk properties of the water discharging from the well are equally 

important, since they shed light on corrosion problems 

above the intake, and possibly on the screen. As stated 

earlier, a test of the applicability of the chemical data 

analysis to corrosion problems may be illustrated by 

the comparison of predictions based upon the chemical 

characteristics -of the water with the observed corrosive 

properties. Regardless of the uncertainties, any high 

order correlations between bulk water properties and 

corrosion and encrustation behavior are useful.

Corrosion test probes were introduced into nine wells. 

Mild (plain carbon) steel, the material most often used 

in the well construction, was one of the materials tested 

in the nine wells. Curves showing the corrosion probe 

results of nine wells (Dalori and Ngala, Nigeria; Kharga 

1, Nasser 1, and Nasser 3, Egypt; and Shadman 27, 

Shadman 47, Shahkot 251, and Shahkot 252, West 

Pakistan) are given in figures 5 through 13. The corrosion effect (metal penetration or metal loss), as indiFIGUKE 4. Encrusted slotted casing, Shadman well 34, West Pakistan.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D27

cated by the varying slopes in the corrosion curves in 

the plots for some of the wells, is not a simple function 

of time. In these cases it is not known whether there 

were intermittent periods of more severe attack because 

of variations in water quality, intermittent formation 

and loss of protective film, or periodic occurrence of 

localized effects, such as concentration cell corrosion. 

Sampling of a localized corrosion phenomenon, such as 

pitting corrosion, by the relatively small and specifically

700

Average corrosion rate, 

0.028 inch penetration per year

Maximum corrosion rate, 

0.12 inch penetration per year

30 40 50 60 

TIME, IN DAYS

FIGURE 5. Corrosion curve, mild steel, Dalori well, Nigeria.

900

Average corrosion rate, 

0.075 inch penetration per year

Maximum corrosion rate, 

0.13 inch penetration per year

20 30 40 

TIME, IN DAYS

50 60 70

FIGURE 6. Corrosion curve, mild steel, Ngala well, Nigeria.

located corrosion probe element is likely to be misleading without other evidence of metal damage.

Whatever the source of changes in corrosion rates, 

average corrosion represents the accumulated effects 

to whatever extent the probes represent the actual well. 

Because of the stated uncertainties, the solubilities

1000

Average corrosion rate, 

0.039 inch penetration per year

Maximum corrosion rate, 

0.22 inch penetration per year

C5 

Z ^

Q o

UJ v IT A

UJZ

(/) x

2" £?o -" 

o

z ^

a o

40 50 60 

TIME, IN DAYS 

FIGURE 7. Corrosion curve, mild steel, Kharga well 1, Egypt.

90 100

700

600

500

400

300

200

100

0

Average corrosion rate, 

0.017 inch penetration per year

Maximum corrosion rate, 

0.08 inch penetration per year

0 10 20 30 40 50 60 70 80 90 100 110 120 130

TIME, IN DAYS 

FIGURE 8. Corrosion curve, mild steel, Nasser well 1, Egypt.

800 

700 

600 

500 

400 

300 

200 - 

100 - 

0

Average corrosion rate, 

0.0022 inch penetration per year

Maximum corrosion rate, 

0.00365 inch penetration per year

0 20 40 60 80 100 120 140 160

TIME, IN DAYS

FIGURE 9. Corrosion curve, mild steel, Nasser well 3, Egypt.
D28 HYDROLOGY OF AQUIFER SYSTEMS

140

120

fK? 100

2 u

80

60

Average corrosion rate, 

0.0007 inch penetration per year

Maximum corrosion rate, 

0.002 inch penetration per year

0 10 20

TIME, IN DAYS

FIGURE 10. Corrosion curve, mild steel, Shadman well 27, West Pakistan. 

180

30

160

Q o 140

< "-1

2 120

z 100

80

60

40

Average corrosion rate, 

0.015 inch penetration per year

Maximum corrosion rate, 

0.021 inch penetration per year

0 10 20 30 

TIME, IN DAYS

FIGURE 11. Corrosion curve, mild steel, Shadman well 47, West Pakistan.

of possible reaction products are compared with both 

average corrosion rates and maximum corrosion rates 

as determined from the corrosion curves. Table 7 shows 

these comparisons in terms of Iogi0 CR.

TABLE 7. Possible behaviors of solid phases capable of protecting 

iron from corrosion

Value of logio C R State of reaction Result

>0_____________ Supersaturation___ Protection; encrustation; catalytic 

coprecipitation. 

Uncertain. 

._ No protection; 

corrosion.

Equilibrium _ 

Unsaturation_ _ _ _.

CORROSION AND ENCRUSTATION OF WELLS

The well waters examined are all unsaturated with 

respect to iron metal as shown in table 3. As a consequence, there is a potential to dissolve iron metal 

(corrode) into all the well waters reported here. Iron

C3

Z 

~ ">

120

Q o

cc x 100

cc = o ^ 

o

80

60

40

Average corrosion rate, 

0.0058 inch penetration per year

Maximum corrosion rate, 

0.0093 inch penetration per year,

10 20 30 

TIME, IN DAYS

FIGURE 12. Corrosion curve, mild steel, Shahkot well 251, West Pakistan.

160

< 2 14°

120

" <

cc & 100

LiJ h

o"-

00 i

si

cc _ o ^ 

o

80

60

40

Average corrosion rate, 

0.004 inch penetration per year

Maximum corrosion rate, 

0.011 inch penetration per year

10 20 

TIME, IN DAYS

30 40

FIGURE 13. Corrosion curve, mild steel, Shahkot well 252, West Pakistan.

metal is the most soluble phase considered; every other 

iron-bearing phase tested in the data analysis is less 

soluble than iron metal. Not only is there a potential 

to dissolve iron metal, there is also the possibility of 

precipitation of the iron dissolved from the metal in 

other iron-bearing phases (corrosion products). Whether 

or not some of the iron-bearing phases found precipitating are in whole or in part corrosion products is moot 

because for all iron-bearing phases identified in Shadman well 34, potentials have been found to cause 

precipitation from the bulk waters studied even if 

corrosion of iron parts were not involved. There is a 

possibility for corrosive attack on iron by all the 

waters studied and there is evidence of it in the damage 

observed on corrosion probes and well parts. Consideration also needs to be given to the possibility of protective action by some of the solids, including corrosion 

products, which precipitate from the waters.

The comparison of reaction states of possibly protective solid phases and the average corrosion rates of 

mild steel are given in figures 14 through 20. For only 

two of the solids tested, CaCO3 (calcite) and Fe(OH) 3 

(limonite), was a consistent relation found between the 

state of the reaction and corrosion rate (figs. 15, 16, 

21, and 22). All solutions found supersaturated with one
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D29

Shadman 27 

/ Nasser 3 

7V Shahkot 251

Shadman 

47

Moderate 

corrosion

r> asser 1

Dalori

Khargall 

 I ENCRUST

Severe 

corrosion

CORRODE

Ngala'

Extreme 

corrosion

0.01 002 0.03 0.04 0.05 0.06 0.07 0.08

AVERAGE CORROSION RATE, 

IN INCH PENETRATION PER YEAR

FIGURE 14. Average corrosion rates plotted against reaction states, FeCOs. 

2

+ 1

-1

3 -

i

Shadman 27 

/ Shahkot 25 V. -Sh

Shahkot

-Nasser 3 

Nasser 1

Moderate

corrosion

i i

> 

adman 47

251

Dalori

 

Kharga

Severe

corrosion

i

i i 

ENCRUST

CORRODE

Ngala^ -

Extreme

corrosion

i

0.01 0.02 0.03 0.04 0.05 0.06 0.07

AVERAGE CORROSION RATE, 

IN INCH PENETRATION PER YEAR

0.08

FIGURE 15. Average corrosion rates plotted against reaction states, CaCOs.

were also supersaturated with the other. There is no 

way of telling from present results, therefore, which of 

the two is effective in reducing corrosion rates, or 

whether both Fe(OH) 3 and CaCO3 are effective. 

Certainly the long and rather successful role of CaCO3 

in reducing corrosion in water systems (see Langlier, 

1946) indicates that CaCO3 at slight supersaturation 

is likely to be a corrosion inhibitor in the wells studied. 

The role of Fe(OH) 3 is not known, but its ubiquitous 

occurrence in tubercular corrosion indicates Fe(OH) 3 is 

not an effective corrosion inhibitor. All the other phases 

considered (figs. 14, and 17 through 20), including 

FeCO3 , Fe3O4 , iron metal, Mn3O4 , and Cu(OH) 2 seem 

to give little, if any, corrosion protection to mild steel 

No regular relation is found in the plots made.

e o

Shahkot

- Shadman 27

*Sh

Nasser 3

_ Nasser 1_

_

Moderate

corrosion

i i 

251

adman 47

Kharga 1_

Dalori

Severe

corrosion

J

 ! !

-

ENCRUST

CORRODE

Ngala^

Extreme

corrosion

I I

3 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.(

AVERAGE CORROSION RATE, 

IN INCH PENETRATION PER YEAR

FIGURE 16. Average corrosion rates plotted against reaction states, Fe(OH)s.

The reaction states of the solids are compared with 

maximum corrosion rates in figures 21 through 27. No 

adjustment is made for the fact that equivalent corrosion damage may result from the general metal loss over 

a period of time as compared with intermittent severe 

attack during recurring periods of relatively short 

duration; nor does the analysis consider the wellestablished fact that severe localized attack may be 

more damaging than general corrosion because of 

extreme effects on susceptible parts. Neglecting these 

factors, exactly the same inferences may be drawn 

whether average or maximum corrosion rates are 

considered. CaCO3 and Fe(OH) 3 (figs. 21 and 22) are 

the only phases that have consistent behavior. All the 

other solids (figs. 23 through 27) apparently are 

ineffective in giving protection against corrosion attack.

Such limitations as inability to collect reaction 

products immediately at the point of their formation; 

uncertainty about pertinent products lost from the 

metal surfaces with the flowing water; possible surface 

catalytic effects; deposition of reaction products that 

would not be predicted on the basis of water chemistry; 

and collection of corrosion data from one metal surface 

and deposits from another are recognized. Nevertheless,
D30

fa

+1

-i

1 

-Shahkot 2

Shadman 27 

Sh

" 

Nasser 3

Nasser 1

Moderate

corrosion

i

i i 

51

adman 47

Kharga

Dalori

ENCRUST

CORRODE

Severe

corrosion

i

i

-

1

Ngala^

Extreme

corrosion

i

HYDROLOGY OF AQUIFER SYSTEMS

+ 1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

AVERAGE CORROSION RATE, 

IN INCH PENETRATION PER YEAR

FIGURE 17. Average corrosion rates plotted against reaction states, FesOi.

the graphical data in figures 21 and 27 contain strong 

evidence that there is a high degree of correlation 

between corrosion rates in deep water wells and saturation with CaCO3 and Fe(OH) 3 . This indicates the need 

for more careful studies in natural systems, particularly 

studies of microenvironments located as closely as 

possible to the points at which corrosion is occurring. 

Such work may develop this type of analysis into a 

more useful tool for predicting the behavior of natural 

ground-water systems in terms of encrustation and 

corrosion.

The behavior of the solids considered thus far has 

been discussed in terms of corrosion and corrosion 

inhibition. Of equal importance to the operator of a 

water well is the problem of encrustation or fouling of 

well screen and casing surfaces. Whether or not corrosion inhibition results, serious losses of well screen 

transmissibility may result from accumulations of 

various solids. The observations made on Shadman well 

34 show that Fe(OH) 3 , CaCO3 , FeCO3 , Mn3O4 , Fe3O4, 

FeS (both forms), Fe3S4 , Cu(OH) 2 (?) and Mn(OH) 2 (?) 

all may form more or less troublesome deposits. In the 

wells reported here, the well yield apparently remains 

relatively constant until a major part of the screen is 

plugged. Periodic specific capacity observations in such

o

-i

 

Moderate

corrosion

 r i 

ENCRUST

CORRODE

Severe

corrosion

 i I

Extreme

corrosion

9

10

11

12

T5 13

I

«^j 14

E

3

E 15

3

cr

(D

+<D 16

fa

o

3 17

18

19

20

21

22

23

24

Of.

-

-

Nasser 3 

* 

"Shadman 2

Sh

Shahkot

Dalori

Masser 1

Kharga 1*

7

adman 47

251

-

-

"

"

-

-

-

-

_

Ngala^

-

-

-

-

i i

0.01

AVERAGE CORROSION RATE, 

IN INCH PENETRATION PER YEAR

FIGURE 18. Average corrosion rates plotted against reaction states, iron metal.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D31

T 1

0

-1

2

3

4

5

6 

7

8

9

10

1 1

-

-

-

Shahkot

_

Shadman 27

 s

Nasser 3

 9

Nasser 1

Moderate 

corrosion

i

ENCRUST

CORRODE

251

ladman 47

Kharga 1

Dalori

Severe 

corrosion

! 1

-

-

-

-

Ngala^

-

-

Extreme 

corrosion

i i

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

AVERAGE CORROSION RATE, 

IN INCH PENETRATION PER YEAR

FIGURE 19. Average corrosion rates plotted against reaction states, MnsO-i.

cases do not give sufficient early warning of encrustation or fouling problems. By the time the yield is 

obviously affected as indicated by conventional capacity tests such extensive and impermeable deposits 

may have formed as to make physical or chemical 

cleaning impracticable or at best, only partly effective 

in restoring expected performance. Much more study 

of the reaction rates will be needed before reliable 

predictions can be made of the probability of encrustation and the extent of encrustation at any point in time 

after start of operation. The nature and extent of encrustation varies locally even in the same well as shown 

in figure 4.

Chemical cleaning processes for water-well screens 

have not yet been perfected. However, from the type 

of data and data analysis reported here, predictions 

can be made of the mineralogic nature of encrustants

T I

0

-1

2

3

4

6

7

8

9

in

st-

-

~ Nasser 3

Moderate 

corrosion

ENCRUST

CORRODE

adman 27

Dalori

Severe 

corrosion

j i

-

-

-

"

Extreme 

corrosion

i i

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 

AVERAGE CORROSION RATE, IN INCH PENETRATION PER YEAR

FIGURE 20. Average corrosion rates plotted against reaction states, Cu(OH)2.

likely to form and the best chemical cleaning solution 

for removing them with minimum damage to well 

parts. Well-screen materials should be chosen on the 

basis of resistance to attack by chemical cleaning solutions thought to be required, as well as their corrosion 

resistance to the natural environment.

If, as the results of this study seem to show, corrosion 

problems may be separated from encrustation problems 

on the basis of chemical equilibrium studies, more 

effective design may be possible. If, for a particular 

well location, corrosion is expected to be relatively 

moderate but fouling of the screen is predicted, construction materials should be chosen to resist whatever 

corrosion is expected to result from periodic chemical 

or other type of cleaning; conversely, if the environment is known to be corrosive to steel, a more corrosion-resistant construction material should be 

selected. Fortunately, materials now are available, some 

at little more than the cost of milcl steel, which will 

resist corrosion by either the aqueous environment or 

chemical descaling solutions. Stainless steel and rein-
D32 HYDROLOGY OF AQUIFER SYSTEMS

£.

O

U +1

CO

T o

.a

t - 1

CM

"as 2

~S

M 3

J

4

i 

Shadma

i i i i i i i i i i i i i i i i i i 

i 27

/ Shah'kot 251 

J / wShadman 47

A i 0 FNf~*RI 1 Q~T 9 -mm 

 

r tiNUKUbi Sh

-_ Nasser

Moderate

corrosion

i

)hkot252 CORRODE

Dalori

3 ^Nasser 1 Ngala , 

 * Kharga 1

-

Severe Extreme

corrosion corrosion

ii i i i i i i i i i i i i i i i

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14' 0.15 0.16 0.17 0.18 0.19 020 021 02

MAXIMUM CORROSION RATE, IN INCH PENETRATION PER YEAR 

FIGURE 21. Maximum corrosion rates plotted against reaction states, CaCOs.

d

2

+ 1 

0

-1 

2

3

4

5 

6

7

 1 

*Shar

~ Shadma

1 1

- 

Nasser C

"

-

Moderate 

corrosion

i

 1 1 | | 1 1 1 1 1 1 1 "T" 1 1 1 1 II

kot 251

. 27 

*Shadman 47 ENCRUST

CORRODE 

Kharga 1-

: 

-Ngala 

Nasser 1 

-

_ Dalori

"

Severe Extreme 

corrosion corrosion

ii i i ill II J I I 1 I 

MAXIMUM CORROSION RATE, IN INCH PENETRATION PER YEAR 

FIGURE 22. Maximum corrosion rates plotted against reaction states, Fe(OH)s.

+ 1

-1

 i 

-Shadmar 

/ Nasser 

l^^Shaf

-

Moderate

corrosion

i

 i i 

27 

3

ikot 251

m 

Shadman 47

Severe

corrosion

I I

 i i i i i i r i i i i i i iii 

Dalori

ENCRUST Kharga 1^

*Nasserl Ngala CORRODE

-

Extreme

corrosion

1 | | ! 1 1 1 1 1 1 1 1 1 1 i 1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 

MAXIMUM CORROSION RATE, IN INCH PENETRATION PER YEAR

FIGURE 23. Maximum corrosion rates plotted against reaction states, FeCOs.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D33

+1

__ 1

Shahkot 251

Shadrric n 27 

Shadman 47

Nasser

Moderate 

corrosion

Severe 

corrosion

i i i i i i i i i i i i

Kharga 1

Nasser 1

Dalori

K1 . Ngala

ENCRUST

CORRODE

Extreme 

corrosion

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 

MAXIMUM CORROSION RATE, IN INCH PENETRATION PER YEAR

FIGURE 24. Maximum corrosion rates plotted against reaction states, FesOi.

forced plastics are examples. The fact that such relatively inert materials have been found to reduce 

mineral encrustation as well as corrosion (for example, 

in plastic wells of West Pakistan) supports the suggestion earlier in this paper that catalytic effects of corroding surfaces have a marked bearing on encrustation 

processes.

SUMMARY

The properties of a number of ground-water samples 

have been determined by direct measurement in the 

field of unstable properties such as pH, Eh, and the 

concentrations of HCO3~, dissolved oxygen, and iron 

in the well-water samples. The field determinations 

have been supplemented by laboratory analyses of 

specially treated samples, such as precipitation of sulfides for H2S and acidification for Ca+2 and Mn+2. More 

stable constituents, such as Mg+2, Na+ , K+ , Cl~, SO4~2 , 

and copper, were determined in the laboratory on untreated water samples. The data thus obtained should 

give reliable information on the properties of the 

water as it comes from the well, with a minimum of 

uncertainties.

Appropriate thermodynamic and physical chemical 

arguments were used to analyze the observed data. All 

the data were analyzed for the conditions found in the 

field. There was no attempt to reduce the observations 

to any artificial standard set of conditions. The results

of the data analysis, then, give the properties of the 

water under field conditions and do not involve any 

assumption as to how the waters should behave. The 

results of the data analysis should be of interest to the 

geochemist, because the results show the behavior of a 

number of geologically important phases in the mixture 

of natural solutions represented by the discharge of a 

well.

Data were also obtained on the corrosion resistance 

of mild steel in a number of wells by means of wire 

probes. The comparison of physical chemical behavior 

of various solids leads to an understanding of the conditions under which either corrosion attack or mineral 

encrustation of the well screen leads to troublesome 

problems in the withdrawal of ground waters.

Quantitative considerations show that in all 39 wells 

studied in Egypt, Nigeria, and Pakistan, the waters all 

were unsaturated with (potentially corrosive to) mild 

steel (iron metal). The only phases that appear from 

these observations to inhibit corrosion are calcite, 

CaCOg, and "limonite," Fe(OH) 3 . Calcite has long been 

known as a relatively effective corrosion inhibitor, if 

properly controlled; thus the results in respect to this 

mineral are not surprising. It was not possible to show 

from the results of this study that Fe(OH) 3 alone is an 

effective corrosion inhibiting phase, and further work 

in this area is needed to determine the effect of the
D34 HYDROLOGY OF AQUIFER SYSTEMS

ENCRUST

CORRODE

-1

2

9

10

11

12

 a

4-> 

0)

S 13

I

I"

.0

= 15

3 

CTa) 

¥ 16

0)

fe 

f 0* 17

) 

I

18

19

20

21

22

Moderate 

corrosion

Severe 

corrosion

23 h

24k

25

Nasser

^Shadman 27

.Shadman 47

Sha'hkot 251

* I i

Extreme 

corrosion

Dalori

Nasser1

Kharga 1

Ngala

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 

MAXIMUM CORROSION RATE, IN INCH PENETRATION PER YEAR

FIGURE 25. Maximum corrosion rates plotted against reaction states, iron metal.

solubility of Fe(OH) 3 on the corrosiveness of ground 

water on mild steel. None of the other 28 solids considered appears to affect corrosion.

Despite the failure of all but two of the solids to 

inhibit corrosion, a number of solids apparently are 

capable of causing troublesome encrustations on well 

screens: calcite; limonite; magnetite, Fe3O4 ; siderite,

FeCO3 ; hausmannite, Mn3O4 (tetragonal); a manganese 

spinel, Mn3O4 (isometric); greigite, Fe3S4 ; mackinawite, 

FeS (tetragonal); smythite, Fe3S4 (rhombohedral); 

copper hydroxide, Cu(OH) 2 ; and manganese hydroxide, 

Mn(OH) 2 . All were at least tentatively identified in the 

crusts studied and thus are potentially troublesome 

encrustants.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D35

-r i 

0

-1

2

3

4

5

6 

7

8

9

10

11 

(

 i 

-

-

-

Sha

-

Shadm;

Nasser

-

-

Moderate 

corrosion

 i i 

nkot 251

n 27 

Shadman 47

3

Severe 

corrosion

i

ii iii i i i i i ii 

ENCRUST

CORRODE

-

-

-

-

-

Ngala Kharga 1

Nasser 1

Dalori

-

Extreme 

corrosion

i i i i i i i i i i i

) 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.2

MAXIMUM CORROSION RATE, IN INCH PENETRATION PER YEAR 

FIGURE 26. Maximum corrosion rates plotted against reaction states, MnsCh.

Of geochemical interest is the observation that only 

three solids of the 29 considered exhibited behaviors 

even approximately predictable from equilibrium 

models. Calcite apparently precipitates from solutions 

only slightly supersaturated, and calcite is a stable 

phase in the waters studied. Both siderite and limonite, 

as illustrated by Fe(OH) 3 , may also precipitate from 

solutions only slightly supersaturated with the appropriate solid phase, but neither siderite nor limonite was 

a stable solid in any of the waters sampled.

CONCLUSIONS

The results of this study show that equilibrium 

considerations are useful in establishing a reference 

for the actual properties and probable effects of naturally occurring ground-water solutions. The detailed 

physical chemical calculations necessary, when performed on reliable data on the properties of such 

natural aqueous solutions, are useful in understanding

the nature and predicting behaviors of such solutions 

in water wells and other environments.

The practical results of the study are that the corrosiveness of natural waters upon mild steel may be 

predicted on the basis of rapid and inexpensive field 

measurements coupled with laboratory analyses made 

on appropriately treated water samples. The same 

data yield useful information on potential encrustation 

problems that may occur in water wells.

Knowledge of the corroding and encrusting potentials of the ground water simplifies selection of materials 

and types of construction of wells to minimize the 

adverse effects stemming from the nature of the water 

being handled.

Further work is required to establish certain microenvironmental processes within water wells. Local 

conditions not accurately represented by the bulk 

discharge from the well may cause problems not 

otherwise anticipated.
D36 HYDROLOGY OF AQUIFER SYSTEMS

+ 1

-1

- Nasser 3

7 -

9 -

10

Moderate 

corrosion

k Shadman 47

Severe 

corrosion

ENCRUST

CORRODE

Dalori

Extreme 

corrosion

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 

MAXIMUM CORROSION RATE, IN INCH PENETRATION PER YEAR

FIGUKE 27. Maximum corrosion rates plotted against reaction states, Cu(OH)2.

0.11 0.12

REFERENCES

Akerlof, G. C., and Oshry, H. I., 1950, The dielectric constant 

of water at high temperatures and in equilibrium with 

its vapor: Am. Chem. Soc. Jour., v. 72, p. 2844-2847.

Bass Becking, L. G. M., Kaplan, I. R., and Moore, D., 5960, 

Limits of the natural environment in terms of pH and 

oxidation-reduction potentials: Jour. Geol., v. 68, no. 3, 

p. 243-284.

Back, William, 1963, Preliminary results of calcium carbonate 

saturation of ground water in central Florida: Internat. 

Assoc. Sci. Hydrology Bull., v. 8, no. 3, p. 43-51.

Back, William, and Barnes, Ivan, 1961, Equipment for field 

measurement of electrochemical potentials, -in Short papers 

in the geologic and hydrologic sciences: U.S. Geol. Survey 

Prof. Paper 424-C, p. C366-C368.

 1965, Relation of electrochemical potentials and iron 

content to ground-water flow patterns: U.S. Geol. Survey 

Prof. Paper 498-C, 16 p.

Barnes, Ivan, 1964, Field determinations of pH and alkalinity: 

U.S. Geol. Survey Water-Supply Paper 1535-H, 17 p.

 1965, Geochemistry of Birch Creek, Inyo County, 

California, a travertine depositing creek in an arid climate: 

Geochim. et Cosmochim. Acta, v. 29, p. 85-112.

Barnes, Ivan, and Back, William, 1964a, Geochemistry of ironrich ground water of southern Maryland: Jour. Geol., 

v. 72, no. 4, p. 435-447.

 1964b, Dolomite solubility in ground water, in Short

papers in geology and hydrology: U.S. Geol. Survey Prof.

Paper 475-D, p. D179-D180. 

Barnes, Ivan, and Clarke, F. E., 1964, Geochemistry of ground

water in mine drainage problems: U.S. Geol. Survey Prof.

Paper 473-A, 6 p.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D37

 1967, Chemical properties of ground water and their 

corrosion and encrustation effects on wells: U.S. Geol. 

Survey open-file rept.

Barnes, Ivan, Stuart, W. T., and Fisher, D. W., 1964, Field 

investigation of mine waters in the northern anthracite 

field, Pennsylvania: U.S. Geol. Survey Prof. Paper 473-B, 

8 p.

Clarke, F. E., 1963, Appraisal of corrosion characteristics of 

Western Desert well waters, Egypt: U.S. Geological Survey 

open-file rept.

Clarke, F. E., and Barnes, Ivan, 1964, Preliminary evaluation 

of corrosion and encrustation mechanisms in tube wells of 

the Indus Plains, West Pakistan: U.S. Geol. Survey openfile rept.

 1965, Preliminary study of water well corrosion, Chad 

Basin, Nigeria: U.S. Geol. Survey open-file rept.

Denbigh, Kenneth, 1955, The principles of chemical equilibrium: 

Cambridge, The University Press, 491 p.

Garrels, R. M., 1960, Mineral equilibria: New York, Harper & 

Brothers, 254 p.

Germanov, A. I., Volkov, G. A., Lisitsin, A. K., and Serebrennikov, V. S., 1959, Investigation of the oxidation-reduction 

potential of ground waters: Geokhimiya, 1959, no. 3, p. 

322-329.

Guggenheim, E. A., 1950, Thermodynamics: New York, Interscience Publishers, Inc., 412 p.

Harned, H. S., and Owen, B. B., 1958, The physical chemistry 

of electrolytic solutions [3d ed.]: New York, Reinhold, 

803 p.

Harrison, C. G. A., and Peterson, M. N. A., 1965, A magnetic 

mineral from the Indian Ocean: Am. Mineralogist, v. 50, 

p. 704-712.

Hem, J. D., 1959, Study and interpretation of the chemical 

characteristics of natural water: U.S. Geol. Survey WaterSupply Paper 1473, 269 p.

 1960a, Some chemical relationships among sulfur species 

and dissolved ferrous iron: U.S. Geol. Survey Water-Supply 

Paper 1459-C, 17 p.

 1960b, Restraints on dissolved ferrous iron imposed by 

bicarbonate, redox potential and pH: U.S. Geol. Survey 

Water-Supply Paper 1459-B, 23 p.

 1960c, Chemical equilibrium diagrams for ground-water 

systems: Internat. Assoc. of Sci. Hydrology Bull., v. 5, 

no. 19, p. 45-53.

 1961a, Stability-field diagrams as aids in iron chemistry 

studies: Am. Water Works Assoc. Jour., v. 53, p. 211-228.

 1961b, Calculation and use of ion activity, U.S. Geol. 

Survey Water-Supply Paper 1535-C, 17 p.

1963a, Chemical equilibria and rates of manganese oxidation: U.S. Geol. Survey Water-Supply Paper 1667-A, 64 p.

 1963b, Chemical equilibria affecting the behavior of 

manganese in natural water: Internat. Assoc. of Sci. Hydrology Bull., v. 8, no. 3, p. 30-37.

 1963c, Some aspects of chemical equilibrium in ground 

water: Ground Water, v. 1, no. 3.

 1963d, Increased oxidation rate of manganese ions in 

contact with feldspar grains, in Short papers in geology and 

hydrology: U.S. Geol. Survey Prof. Paper 475-C, p. 

C216-C217.

 1963e, Manganese complexes with bicarbonate and 

sulfate in natural water: Jour. Chem. and Eng. Data, v. 8, 

p. 99-101.

 1964, Deposition and solution of manganese oxides:

U.S. Geol. Survey Water-Supply Paper 1667-B, 42 p. 

Hem, J. D., and Cropper, W. H., 1959, Survey of ferrous-ferric

chemical equilibria and redox potentials: U.S. Geol. Survey

Water-Supply Paper 1459-A, 31 p. 

Himmelblau, D. M., and Loy, H. L., 1961, The first ionization

constant of hydrogen sulfide in water: Jour. Phys. Chemistry,

v. 65, no. 2, p. 264-267. 

Keenan, J. H., and Keys, Frederick, 1936, Thermodynamic

properties of steam: New York, John Wiley and Sons, Inc.,

39 p. 

Kielland, Jacob, 1937, Individual activity coefficients of ions

in aqueous solutions: Am. Chem. Soc. Jour., v. 59, p.

1675-1678. 

Langlier, W. F., 1946, Chemical equilibria in water treatment:

Am. Water Works Assoc. Jour., v. 38, no. 2, p. 169-178. 

Larson, T. E., and Buswell, A. M., 1942, Calcium carbonate

saturation index and alkalinity interpretations: Am. Water

Works Assoc. Jour., v. 34, no. 11, p. 1667-1684. 

Latimer, W. M., 1952, The oxidation states of the elements and

their potentials in aqueous solutions [2 ed.]: New York,

Prentice-Hall, Inc., 392 p. 

Rainwater, F. H., and Thatcher, L. L., 1960, Methods for

collection and analysis of water samples: U.S. Geol.

Survey Water-Supply Paper 1454, 301 p. 

Roberson, C. E., Feth, J. H., Seaber, P. R., and Anderson,

Peter, 1963, Differences between field and laboratory determinations of pH, alkalinity, and specific conductance of

natural water, in Short papers in geology and hydrology:

U.S. Geol. Survey Prof. Paper 475-C, p. C212-C215. 

Robinson, R. A., and Stokes, R. H., 1959, Electrolyte solutions:

London, Butterworths, 559 p. 

Solomin, G. A., 1965, Methods of determining Eh and pH in

sedimentary rocks; authorized translation from the Russian

by Paul Porter Sutton: New York, Consultants Bureau.

56 p. 

Swartzendruber, Dale, and Olson, Tamlin C., 1963, Rate of

change as determined graphically with an equilateral

glass prism: Soil Sci. Soc. Am. Proc., v. 27, no. 1, p. 108-110. 

U.S. National Bureau Standards, 1963, New values for the

physical constants recommended by NAS-NRC: U.S.

Natl. Bur. Standards Tech. News Bull., v. 47, no. 10, p.

175-177. 

Wright, R. H., and Maas, O., 1932, The electrical conductivity

of aqueous solutions of hydrogen sulfide and the state of

the dissolved gas: Canadian Jour. Research, v. 6, p. 588-

594.

APPENDIX 1

DIGITAL COMPUTER PROGRAM FOR CONSTITUENT 

ANALYSIS

The listing of the computer program is in ALGOL 60 (extended ALGOL for the B5500). Some translation may be 

necessary if individual compilers cannot accept this version of 

ALGOL 60.

The construction of the program is not for efficient use of 

computation time but for a logical flow of the chemical arguments. 

The chemical arguments are sufficiently involved that a segregation of types of arguments is not possible^ For example, the 

distribution of copper species involves oxidation potentials. The
D38 HYDROLOGY OF AQUIFER SYSTEMS

distribution of the copper species is necessary for considerations 

of mass-action reactions of copper species not involving oxidation. Similarly, the distribution of manganese species involves 

only mass-action reactions but the distribution must be known 

before oxidation reactions involving manganese species may be 

considered. Mass-action and oxidation reactions are both necessary in the assignment of species. As far as possible, however, 

the mass-action and oxidation reactions are separated.

The program is open ended in that other species and reactions 

involve only extensions of arrays already included. If the program 

is greatly extended, the allowable block size may be exceeded.

Three nested blocks are in the listed program and provide for 

some increase in each.

The exponential nature of some arguments leads to the 

extensive use of write statements. If an error in data punching 

is made, the exponential overflow error is quickly found to be 

after the last write statement. It is urged that write statements 

be used before and after each logarithmic assignment statement 

or exponentiation.

All the reactions listed are the same in sequence as the reactions 

given in the data analysis and results. The identifiers used are 

in the following table.

Identifier (ALGOL program) Algebraic notations (data analysis) Significance

MI______________________ m____________________________ Molality.

PPM________-.___________ ppm_________________________ Parts per million parts.

GFW____________________ GFW________________________ Gram formula weight.

MEQ--_._______________________________________________ Milliequivalents per liter.

LOGGAMMA____________ log >-,________________________ Logio activity coefficient.

DHA_____________________ a0 ___________________________ Effective distance of nearest approach (Deby^-Hiickel).

GAMMA_________________ y_ ___________________________ Activity coefficient.

ALFA.___________________ «____________________________ Activity (molal).

AP_______________________ AP'__________________________ Activity product.

LOGEAP_______________ In (AP)______________________ Natural logarithm of the activity product.

EHTC___________________ EhTC______________________ Eh calculated from the composition and temperature of the solution.

CREEL __________________ CR___ _______________________ Cation ratio; cation (actual)/cation (eq) based on Eh measurements.

MCATEQ________________ raeq __________________________ Molality of cation at equilibrium with the solids involving oxidation reactions, all other properties of the solution held constant.

PPMCATEQ.-__________._ ppmeq___ _____________________ Parts per million of cation in equilibrium with solids involving

oxidation reactions, all other properties of the solution held 

constant.

LOGEKTO_______________ lnj£25°c----------------------- Natural logarithm of the equilibrium constants at 25°C.

CR______________________ a actuai/«e Q ; m ac t U aiMeq; The ratio of the actual cation concentration or activity to the

ppm actuai/ppm eq . equilibrim concentration or activity of the cation in equilibrium

with the solid phase undergoing mass-action reactions, all other 

properties of the solutions held constant.

DELMU_________________ A/iR________________________ The actual chemical potential found for hydrolysis reactions.

DELMUEH______________ A/IR__________________________ The actual chemical potentials found for oxidation reactions.

N________________________ n_-_--____-_-_____________.-_ Number of electrons in oxidation reactions.

Z________________________ z____________________________ Ionic charge.

ID, PAGE1, PAGE2, None________________________ Printout arrays.

PAGES.

!________________________ None________________________ Array member.

FLAGl, FLAG2, FLAG3___ None________________________ Identifiers for punching errors indicating options not selected.

MU____________________ r 1 __________________________ Ionic strength.

MUHALF________________ r 1 /2 __________________________ Square root of the ionic strength.

T________________________ T____________________________ Temperature, degrees Kelvin.

TEMP_ ______ ____________ i_ ___________________________ Temperature, degrees centigrade.

D________________________ D__________________________ Dielectric constant.

DTHALF________________ (DT) 1 -/2 _______________________ Square root of the temperature (°K) times the dielectric constant.

DT3HALF_______________ (DT) 3 /2 _______________________ Cube of the square root of the temperature (°K) times the dielectric

constant.

A._______________________ A*dwl ^(DT)-3 '2 .^ _____________ See "Data analysis."

B________________________ B*(d,,,)i/»(Z>:r)-»/»______________ See "Data analysis."

K2HCO3-________________ KHC03 ----------------------- Equilibrium constant for the dissociation of HCO3 .

i Both chemical potentials and ionic strengths are commonly designated 'V'; upper case gamma (r) has been used for ionic strength in algebraic notation. The authors 

regret the inconsistency.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D39

Identifier (ALGOL program) Algebraic notations (data analysis) Significance

F___-._____-___-_---_---_- g--__---___-___.________-_____ Volt equivalent per gram mole.

EHM____________________ Ehm.________________________ Measured Eh oxidation potential.

R_______-_______-_____-__ R- ----_---_______---________ Gas constant.

SUMl, SUM2, DIFF, SUM_ None________________________ Used in copper species distribution.

ALFACO3___-___________- aco^2 .----------------------- Activity (molal) of COr2 .

LOGALFACO3 ___________ Iog10aco3~2 --_____--_--________ Base 10 logarithm of the activity (molal) of COr2 .

DUM____________________ None________________________ RT/$ or $/RT used for efficient coding.

LOGKIH2CO3__ _______.--- log10Kn2 co3------------------- Base 10 logarithm of the equilibrium constant for the dissociation

of H2C03 .

MCO2AQ_________________ mco,(.«>~- ------------- Molality of CO2(aq) .

LOGPCO2___.____________ logioPcoz ------------------- Base 10 logarithm of the partial pressure of CO2 ( g) in equilibrium

with the solution.

PCO2____________________ PCo2 -.----------------------- Partial pressure of C02 ( g) in atmospheres that would be in equilibrium with the solution.

PPMCO2AQ___________-._ ppmc o2 (aq) --- - --- - Parts per million of CO2 (aq) .

PH______________________ PH__._______________________ PH.

EOFE3S4.-_-____-___.--- -E°Fe3S4 -_-------_-----------_- The standard oxidation potential calculated from the properties of

the solution assuming the solution in equilibrium with greigite 

for which no AG° values are available. AG° data so obtained are 

about 52 kcal.

C________________________ logioe_-______________________ Base 10 logarithm of e, the base of natural logarithms.

E_---_-_-________________ In 10_______________________ Natural logarithm of 10.

LNKHS__________________ In _fH2 8(aq) ------------------- Natural logarithm of the equilibrium constant for the dissociation

Of H2S(aq).

KlH2CO3__-____________- Ks^Oi --------------------- Equilibrium constant for the dissociation of H2 CO3 .

LOGMI13---___--________ logi0mH2 s___-____---____-_-__ Base 10 logarithm of the molality of H2S (aq).

POW____________________ None._______________________ Exponents used for ease of coding exponentiation.

LOGMSO4_ ______________ logi0TO 8 04(eq)------------------ Base 10 logarithm of the activity of SO*-2 (molal) at equilibrium

with H2S(aq) at the measured Eh, pH, and other actual properties 

of the solution.

DENS___________________ d_,____________________________ Density of water.

DELT___________________ 374.11 J(°C)_________________ A term from Keenan and Keys (1936) used in calculating the density of water.

LOGACTFEPYSO4-______ logioaFe+2eq_-_-_------ --_ Base 10 logarithm of the activity (molal) of Fe+2 in equilibrium with

pyrite at the pH, Eh, and S(X~2 activity found in the solution.

G, H, J, DIFI, D1F2______ None__________________._____ Used in copper species distribution.

DENSHALF____________ du,1 /2 _________________________ Square root of the density of water.

In addition to the listing and glossary, "Appendix 1" also 

contains a test case (p. D47) with the actual printout (p. 

D42-D46) from the test case. The input data are exactly 

the data given in the printout with the following exceptions:

MN 2_______ The printed Mn+2 data are not the Mn+2 input

data. Within the program the total Mn is 

distributed among Mn+2, MnHCO3+, and 

MnSOi0 aqueous species. The computed Mn +2 

is printed.

GUI, CU2, The distribution of the copper among Cu+1,

CU2OH2, Cu+2, and Cu2 (OH) 2+2 is computed from the

CUTOT. properties of the solutions and the total copper

(CUTOT). CUTOT is thus input data but

GUI, CU2 and CU2OH2 are computed results.

HS, H2S, The distribution of the sulfide species, H2S(aq>

H2STOT. and HS", is computed from the total aqueous

sulfide analysis (H2STOT) and the properties

of the solution. HS and H2S are computed

and H2STOT is the total sulfide input data.

SO4 __------- The sulfate concentration is high to test the

distribution of the sulfate species.

The input is on four punch cards which are reproduced on 

pages D40-D41.
D40 HYDROLOGY OF AQUIFER SYSTEMS

III 1 111 I II III III I ii 1 1 1 II 1

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Sample cards in Stanford version ALGOL 60. Shadman well 40, West Pakistan, test case at 74.54 DG C. Field Eh, pH, Fe+2, HCOs, and S by F. E. Clarke (U.S. Agency for 

International Development) and West Pakistani (Water and Soils Investigation Division) scientists, March 1964; other chemical databy U.S. Geological Survey laboratories 

July 1964.
I Z t » S 9 L 0 6 01 II II tl « SI 91 U 81 61 02 U K 

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Printout from test case on page D47

. . STANFORD B5500 ALGOL -- 07/05/66 VERSION 254/67 

BEGIN REAL ARRAY Ml»PPM*GFW*MEQCO»l6]*LOGGAMMA»DHA*GAMMA,ALFAi:o:l4]*AP*L. 

nGEAP[Oil8],EHTC»CREH,MCATEQ»PPMCATEQ!:Ot l3]»LOGEKTO,DH»EQT»DHQ*E0298,LOG. 

K,APKRAT,LOGME*ME,PPMEe*LOGEKT,KT,CR,DELMUi:Ol 18 ],DELMUEHt 01 13]; INTEGER A. 

RRAY NCO»13]»Z[0«16];ALPHA ARRAY ID COt12] » PAGE11 0«16],PAGE2[0:18]* PAGE31,

0:13];INTEGER i»FLAGi,n.AG2,FLAGS;REAL Mu»MUHALF,T*TEMP»D*DTHALF,DT3HALF,

,A»B*K2HC03*F*EHM,R,SUMl»SUM2*nlFF»SUM,FACTOR,ALFAC03»LOGALFAC03*DUM*LOG. 

KiH2C03,MC02AQ,LOGPC02*PC02*PPMCQ2AQ,PH,EOFE3S4,C,E,LNKHS*KlH2C03,LOGMl 1. 

3,POW,LOGMS04,DENS»DELT»LDGACTFEPYS04*G*H*J»DIF1*DIF2*DENSHALF;LABEL STA. 

RT*EOF,LOOP1,LOOP2*LOOP3,CQNT>FORMAT IG(13A6,/3l1),HEADF(13A6},FORM1(y3*. 

"PH"»X4,»EH MEAS",X5* f'T f'»X6» f'IQN STRENGTH PC02 ATM", X 4,"MCO? AQ",X4,"PP. 

M C02 AQ EO FE3S4"*X2»"LOGACTSQ4 EG LOG ACT FE PY SQ4 W /F6.2*FlO,4,F8, 

.2»Fl3.5*Fl4.7,Fll.6*Fl0.2*Fl2.3*2Fl4.4,//X4,"lON"*X9, ff PPM"*y8* M GAMMA''*X. 

6,"MOLALlTY»*X5»«ALPHA")»FORM2fI2*X2»A6,F12.3*F12.6,X1*2E12.4}»FORM3(/X3. 

,"PHASE H »X8, ft AP",X10,«KT",X8,« AP/K",X7," CR "»X4,"MQL CAT EQ"X1,"PP, 

MCATEQUlL"»X4,«DEL MU")»FORMA(12*X5,A6,El 1.4*5E12.4*F12.5)*FORMS(/X3,"PH. 

ASE"»X8,"EOT"*X6*f'EH T CALC CR MOL CATEQUIL PPM C ATEQUIL", X4*". 

PEL MU")*FORM6CI2,Xl»A6*Fll,4,Fl5,4,Xl*3El2.4*F12,6),ERRFMlC f'REDUcTlON C. 

ANNOT 'V'PROCEDE CUlc"*El 1. 4 , " CU2»",E 11»4*" CU20H2s",E 11 .4/ ) ,ERRflRl. 

(' CONCENTRATION UNITS NOT SPECIFIED* FLAG1 IS MI SSl NG") *ERROR2( "FLAG? MI. 

SSING* EHM NOT SPEC IF IED") * ERROR3("FL AG3 IS MISSING. DO YOU WANT CALCUL.A. 

TED EH VALUES?");DEFINE IUP = FQR I«-OSTEP 1UNTIDULIST ERR1 ( MI [ 10 ]* Ml [ 11].

*MIC14]);FILL GFW[*]WITH 40.08, 2/4, 312, 22. 9898*39.102, 35. 453*96t06l6, 61.0. 

1732,55,847*55.847,54.938,63.54*63.54,33.07197,34.07994,161.09474,63.54*. 

34.07994;FILL DHA[*]WiTH 6*8,4»3,3,4,4,6*9,6,3*6,3.5*0*10;FILL Z[*lWITH . 

2, 2, 1,1, 1,2, 1*2*3, 2,1, 2*1*1*2, 2* i; FILL N[*1V«ITH 2,2,1,8,2*2,2*2,2,2,14,1.

*2*i;FILL E0298[*]WITH»0.^^*0.981353,1.056808,0.303339,1.228968,1.820468. 

, 1.443408,-0.1400694,0.337*0.7278838,0.366683,O.i53,0.46656,1.885082;plL. 

L OHOC*]WITH-21.0,68.368*28.95l*65.768,65.73fl,101.768,79.45l,-2.72,l5.39, 

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6,21.1P5R08,-41.36621,"13,33847*-34.92704*-64,2*955,-2^.9548,30,5717126,.

*2^.545i52*-18,214731,.39.14395*0,0,0.0,0.0*0.0, 35.2541*.10.19803*-10,62.

OI^;FILL DHOJWITH-3.677*-i5.827,-is.144*0.0,0.0*17.59*34.4,-1.03,-21.83.

4,-4.63,-6.04,0,0,0.0,0.0,0.0,0.0*-23.134*-4.25,-0.2<u;c«-2.30258509;F4.23.

,0603;R«-0.00198719;E«-O.A3429448iFILL PAGEH * ]WI TH"C A '^"Mr, "*"NA .

"»"« "*"CL ",«S04 ","HCC3 »,"FE 2 ft » w FE 3 "*"MN 2 W »"CU 1.

"»"cU 2 "*"HS ","H2S "*"CU2DH2"*"CUToT "*"H2STOT";FILL PAGE2f*3W.

ITH"CU?0 "» f'CUO "»"CUCOH2"»"A7URlT"*"MALACHt', ff CUS "*"CU2S ","MNC03.

"»"FECOH2ff »"FEC03 ","MGC03 ", "DOLCM I", "c AC03 ","FES M , "CUFES2 ft *"BORN I.

T«* N MN(OH2 f'*"ANHYDR"* w r,YPSUM M ;FlLL P AGF.3 t * 3 W ITH"FE MET"*"FE3n4 M *"FECOH3.

","H2S "*"MN02 "*"MN304 "*"MN203 ","PY H2S"*"CU MET tf *"FE203 ","PY 504,

","CUDlST"»"CUOIST ff ,"MN(OH3 ff ;START:READ(CARDFIL/IG,IUP 12DO I DC II *Jt. AG 1* .

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(pRlNFlL,ERROR2)^READ(CARDFlL)>REAC(CARnFlD;Gn TO START END;IF FLAG3=OT. 

HEN BEGIN READ(CARDFlLi'READ(CARDFlL);WRlTE(PRlNFIL,ERROR3);r,0 TO START .

FND;IF FLAGI = ITHEN IUP 1600 Mi[ii*-ppMti]/<iooo.oxGFwtn)ELSE IF FLAGi=2T.

H£N BEGIN IUP 16DO PPMH3*MEOtl3xGFWCl]/Zf I3;IUP 1600 M I [ U «-MEQ t 13/(1000. 

. 0 X ZC13 j; END; MU* 0. 0; DELf«-( 3 74, H-TEMP);nENS«-( 1.0+0.1 3424 89xDTLT*( 1/3 5-0.. 

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3xDELT*4);DENSHALF«-SQRT(OENS)MUP 9DO MU«-MU*Ml CI ]xZ[ I ]*2; MU+MU/2; MUHALF +.

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GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D43

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D46 HYDROLOGY OF AQUIFER SYSTEMS

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GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS

SHADMAN WELL 40, WEST PAKISTAN, TEST CASE AT 74-54 DG 0^'

INTRINSIC THERMODYMMIC PROPERTIES OF WATER

General Characteristics 

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S4 LOGACTS04 EQ LOG ACT FE PY S04

7-55 0.0465 74.54 0.02645 o.oi64487 0.000231 10.18 0.703 40.3922 62.1199

Ionic Data

D47

ION 

0 CA 

1 MG 

2 NA 

3 K 

4 CL 

5 S04 

6 HC03

7 FE 2 

8 FE 3 

9 MN 2 

10 CU 1 

11 CU 2 

12 HS 

13 H2S 

14 CU20H2 

15 CUTOT 

16 H2STOT

THERMODYNAMIC STATE OF WATER

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

PHASE

CU20

cuo

CU( OH2

AZURIT

MALACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

THERMODYMMIC STATE

0

1

2

3

4

5

6

7

8

9

10

11

12

PHASE

FE MET

FE304

FE(OH3

H2S

MN02

MN304

MN203

AP

0.0000@+00

0.00000+00

0.0000@+00

0.0000@+00

0.00000+00

0.00000+00

0.00000+00

0.00000+00

6.o44i@+09

4.74100-11

5. 6632®- 09

2.73850-17

4. 8357®- 09

2.70050+03

0.00000+00

O.OOOOO+OO

0.0000@+00

2-3579@-06

2. 3 579®- 06

PPM GAMMA MOLALITY ALPHA 

36.600 0.536246 9.l3l7@-o4 4.8969@-o4 

24.800 0.562206 1.0201®- 03 5-7349@-04 

56.100 0.843898 2.4402@-03 2.05930-03

o.ooo 0.837220 o.ooooo+oo o.ooooo+oo

12.600 0.837220 3-55400-04 2.9755O-04 

912.000 0.507178 9.49390-03 4. 81 51®- 03 

266.000 0.843898 4.3594@-03 3.6789@-03 

0.500 0.536246 8.95300-06 4.80100-06 

o.ooo 0.286965 o.ooooo+oo o.ooooo+oo 

o.ooo 0.536246 o.ooooo+oo o.ooooo+oo 

o.ooo 0.837220 o.ooooo+oo o.oooo@+oo 

o.ooo 0.536246 o.ooooo+oo o.oooo@+oo 

0.179 0.84062Q 5.42180-06 4.55770-06 

0.015 1.000000 4.46800-07 4.46800-07 

o.ooo 0.585506 o.ooooo+oo o.ooooo+oo

0.000 

0.200

WITH RESPECT TO COEXISTING SOLID PHASES UNDERGOING HYDROLYSIS REACTIONS

8

1

4

1

l

4

4

l

9

7

2

1

1

7

1

2

OF WATER WITH

EOT

0.4375

0.8981

1.0238

0.2945

1.1964

1.7563

1-3970

PY H2S -0.1535

CU MET

FE203

PY S04

CUDIST

CUDIST

0.3375

o. 6671 0.3585

EH

-0

-0

-0

-0

-99

-99

-99

-0

-99

-0

-0

KT

.65180-03

.72050+06

. 1623JO+07

.08360-18

.61130-06

.6601®- 14

.8904®- 2 5

.1342®- 11

. 9286O+10

.1885®- 12

.8751®- 09

.00000-17

.2909@-09

.84620+12

.34030-05

.30280-05

RESPECT TO

T CALC

.6209

.6350

.1719

.3218

.9000

.9000

.9000

 5738

.9000

.5286

.2858

AP/K

0.00000+00

0.00000+00

0.0000@+00

0.00000+00

0.0000@+00

o.ooooo+oo

0 . 0000@+00

0.00000+00

6.08760-02

6.5953@+00

1.9697@+00

2.73850+00

3 . 746o@+oo

0.00000+00

1-7 592®- 01

1.0239®- 01

COEXISTING

CR

4. 4870®- 20

3.85080+06

1.46470+03

1.95180-43

0.00000+00

0.00000+00

0 . 00000+00

9.5639^17

0.00000+00

2.16990+08

0.0000@+00

CR

0.0000@+00

0.0000@+00

0.00000+00

0.0000@+00

0.00000+00

o.ooooo+oo

0.0000@+00

0.00000+00

6.08760-02

6. 5953@+00

l.9697@+oo

2.73850+00

3.746o@+oo

o.ooooo+oo

1-7592®- 01

1.02390-01

MOL CAT EQ

4.

2.

6.

3-

2.

1.

3-

2.

1.

1.

5-

3-

2.

1.

5-

8.

8887®- 09

54860-09

1652®- 09

8 539®- 08

12300-08

54500-22

5219@-17

l4l9@-o6

4707®- 04

3575@-06

17870-04

3345®- 04

4377@-o4

1622®- 02

19080-03

91830-03

PPMCATEQUIL

3-

l.

3-

2.

1.

9-

2.

1.

8.

7-

1.

1.

9-

6.

2.

3-

10630-04

6194®- 04

9174®- 03

5588@-03

34900-03

8l68@-l8

23780-12

1767®- 01

2134@+00

58l2@- 02

2590@+oi

33650+01

7703@+00

3851@+02

08050+02

5744@+02

DEL MU

99.99999

99-99999

99-99999

99.99999

99-99999

99.99999

99.99999

99-99999

-1.93390

1-30337

0.46840

0.69608

0.91253

99-99999

-1.20067

-1.57^62

SOLIDS UNDERGOING OXIDATION-REDUCTION REACTIONS

MOLCATEQUIL

1.9953®+!^

2.32500-12

6.11260-09

0.00000+00

2.5344@+03

4.56400-04

1.56910-03

9.36130-24

6.81320-09

4.i26i@-i4

0 . 00000+00

PPM CATEQUIL

1.

1.

3-

0.

i.

2.

8.

5-

4.

2.

0.

1143@+19

2984®- 07

4l37@-o4

0000@+00

3923@+o8

5074@+oi

6201@+01

22800-19

3291®- o4

30430-09

0000@+00

DEL MU

-30.

-31-

-5-

-67.

-99-

-99-

-99-

-28.

-99-

-26.

-107.

782008

432083

036579

949305

900000

900000

900000

606504

900000

525900

292127

13 MN(OH3 2.5315 -99.9000 o.oooo@+oo 4.36690+13 2.399i@+i8 -99.900000

-'Test case at 74.5^ DG C. Field Eh, pH,

March 1964; other chemical data by USGS Laboratories.

HC03 , by Clarke, USAID and West Pakistani (WASID) Scientists,
D48 HYDROLOGY OF AQUIFER SYSTEMS

APPENDIX 2

COMPUTER ANALYSIS, GROUND-WATER DATA, 

EGYPT, NIGERIA, AND WEST PAKISTAN

The amount of information generated by the data analysis is 

too great to embody in the text. The extracted information summarized in the section on "Results" does not provide enough of 

a description to compare the ground waters reported in the text 

to other ground waters. The data that are reported here in 

"Appendix 2" (p. D50-D58) give a complete description of 

some of the waters sampled. For complete data, see Barnes and 

Clarke (1967).

With few exceptions the differences that may be especially 

noteworthy between the waters reported here and more generally available reports on ground-water properties is that the 

data here reported are reasonably complete and certain particularly pertinent data represent water under field conditions.

The results of the data analysis are reported in three groups of 

information, all groups headed by a line of identification of the 

sample. The column headings are all capital letters, but correspond as closely as possible to notation used in the text. The 

PH and EH represent the results of field measurements of pH 

and platinum electrode potential reading (Eh) respectively. 

The temperature is in degrees centigrade. The ionic strength is 

on the molal scale and provides a quick test for the reliability of 

the activity coefficients. The computed -Pco, m atmospheres, 

the molality, and parts per million of CO2 (ftq) are given.

Some calculations may not be made because of insufficient 

data. In such cases dummy printout is substituted. For example, 

if no H2S(aq) or iron data are available, then no E° for the Fe3S4 

reaction can be calculated. To avoid confusion, the E° for the 

Fe3S4 reaction is assigned a value of 99.999 if it cannot be 

calculated. Similarly, the Iogi0as o4-2 (molal scale) in equilibrium 

with the H2S(aq) at the pH and Eh measured cannot be calculated 

if H2S(aq> data are not available. In such a case an impossible 

value of 0.0000 is assigned. The entire loglc aFe+2 (molal) in 

equilibrium with pyrite at the Eh and pH measured at the activity of S04~~2 found is also given, and clearly shows that pyrite 

is not in equilibrium with the solutions studied.

The description of the sample composition lists the identity 

(0, 1, and so forth) of the species in the computations. The 

chemical identity of the species (ION) is also given. The concentration of the species in parts per million (PPM), the activity 

coefficients (GAMMA), the concentration in molal units 

(MOLALITY) and the activity of the species in molality 

(ALPHA) are given.

The mass-action reactions are identified (0, 1, and so forth) 

in the same array sequence as in the program and the text of 

the paper, and identified by the name of the appropriate solid. 

The computed activity products (AP), and equilibrium constants at the field temperature (KT) and their ratios give a 

quick test for the relation of the actual properties of the solutions 

to the equilibrium properties. The ratio of the metal cation as it 

actually is in solution to the metal cation at equilibrium with the 

appropriate solid (all other properties held constant) and the 

concentrations (both parts per million and molality) of the metal 

cation at equilibrium with the solid are given for the convenience 

of the readers more .accustomed to compositional variables. 

The A/.R (DEL MU) values in kcal give the direction of the 

departures from equilibrium by their signs and give the extent, 

by the magnitude of the A/XR values. Where insufficient data 

are available to compute the various parameters, standard 

dummy values are inserted. They are as follows:

Dummy value if

computation 

Heading cannot be made

AP__-__--_____-___________--___-__-___-- 0.0000 @ + 00

AP/K__-_-__-----_--------_--_----------_- 0.0000 @ + 00

CR__--_----_---------_---------,---------- 0.0000 @ + 00

MOL CAT EQ_______....___.___..____.._. 0.0000 @ +00

PPMCATEQUIL _-__-_--_----__--_-___- 0.0000 @ + 00

DEL MU_____--_---__-_-__----_---------- 99.99999

Oxidation reactions are listed in the same numerical sequence 

as in the program and text. The identification of the solid under 

consideration is also given. The oxidation of H2S(aq) to SOt~2 

is identified as H2S, and the copper ion oxidation reactions used 

in the distribution of copper species are identified as CUDIST. 

The standard oxidation potential at the temperature of the 

solution in the field (EOT) is given along with the Eh calculation 

from the solution properties and compositions under the field 

conditions. The ratio of the actual metal cation to the metal 

cation at equilibrium with the appropriate solid and the concentration of the metal cation at equilibrium with the solid both 

in molality (MOL CATEQUIL) and parts per million (PPM) 

are given for the convenience of readers more accustomed to 

concentrations as operational variables. The values of _v*R 

(DEL MU) give the direction of the departures from equilibrium 

by their signs and give the extent, by the magnitude of the A^R 

values. Because necessary data may be missing, some variables 

cannot be computed in some cases. Dummy values are substituted and are chosen to be readily noticed and then disregarded. The dummy values are:

Heading Dummy values 

EH T CALC_.---------------------------- -99.9000

CR_-_---_-_------------------------------ 0.0000 @ + 00

MOL CATEQUIL __---__---------------- 0.0000 @ +00

PPM CATEQUIL -___.--_-____---------- 0.0000 @ +00

DEL MU__.__ _ ---- - - -- - -- -99.900000

KEY TO COMPUTER PROGRAM COLUMN HEADINGS

Column headings Definition

ALPHA-___________---_- Activity molal scale.

AP____________________ Activity product.

AP/K-__.--____---_---_- Activity product/equilibrium

constant. 

CR__----_-------------- Cation, actual/cation at

equilibrium. 

DEL MU_-------------- Actual chemical potential.

EH MEAS-------------- Oxidation-reduction potential,

volt. 

EH T CALC_______----- Calculated oxidation-reduction

potential at observed

temperature. 

EO FE3S4_____________ Standard potential, Fe3S4 .

EOT.__________--------- Standard state potential at

observed temperature. 

GAMMA_______---_----_ Activity coefficient.

ION________-_ - Ion.

ION STRENGTH------- Ionic strength.

KT_______--_----------- Equilibrium constant at observed

temperature. 

LOG ACT FE PY SO4__ Log activity of iron in equilibrium

with pyrite at the measured

SO4 , Eh, and pH.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D49

Column headings Definition 

LOGACTSO4 EQ________ Log activity of SO4 at equilibrium

with H2S at the measured pH

and Eh. 

MCO2 AQ_____________ Molality aqueous CO2 .

MOLALITY.____________ Molality.

MOL CAT EQ

MOL CATEQUILj

PCO2 ATM _____________ Partial pressure of CO2 in

atmospheres.

Column headings Definition

Molality of cation at equilibrium.

pH.

PHASE---______._------ Solid phase.

PPM _ _________________ Concentrations in parts per

million. 

PPMCATEQUIL_________ Parts per million of cation at

equilibrium. 

PPM CO2 AQ_ __________ Aqueous CO2 , ppm.

T_ _______-__-_-_--__---_ Temperature, degrees centigrade.
D50 HYDROLOGY OF AQUIFER SYSTEMS

KHARGAWELL 1.

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

General Characteristics

PH "" EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S4 LOGACTS04 EQ LOG ACT FE PY S04 

6.91 -0.0034 38.00 0.00361 0.0156605 0.000392 17.23 0.729 25.0952 35.1668

Ionic Data

ION PPM GAMMA MOIALITY ALPHA 

0 CA 14.000 0.773233 3.4930@-04 2. 7009@- 04 

1 MG 4.900 0.780074 2.0155@-04 1.5722@- Oit2 NA 22.000 0.935515 9-5695@-o4 8.9524@-o4 

3 K 27.000 0.934348 6.9050@-04 6.4517@-04 

4 CL 34.000 0.934348 9.5902®- Ok 8. 9606®- Ok

5 SOk 12.000 0.765956 1.2492@-04 9. 5683@-05 

6 HC03 104.000 0.935515 l.7044@-03 1.5945®- 03 

7 FE 2 2.600 0.773233 4.6556@-05 3.5998@-05 

8 FE 3 0.000 0.577287 0.0000@+00 0.0000@+00 

9 MN 2 0.273 0.773233 4.9775@-o6 3.8487@-06 

10 CU 1 0.000 0.934348 0.0000@+00 0.0000@+00 

11 CU 2 0.000 0.773233 0.0000@+00 0.0000@+00 

12 HS 1.224 0.93^937 3-7007®- 05 3.4600@-05 

13 H2S 0.939 1.000000 2.7547@-05 2-7547@-05 

14 CU20H2 0.000 0.786517 0.0000@+00 0.0000@+00 

15 CUTOT 0.000 

16 H2STOT 2.200

THERMODYNAMIC STATE OF WATER WITH RESPECT TO COEXISTING SOLID PHASES UNDERGOING HYDROLYSIS REACTIONS

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MALACH

cus

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

AP

0.0000@+00

0.0000@K>0

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

o.oooo@+oo

2. 9229®- 12

2.3784@+09

2. 7338®- 11

1.1940@-10

2. 4491@- 20

2. 0512®- 10

6. 5517@+04

0.0000@+00

o.oooo@+oo

2.5428@+08

2.5843®- 08

2.5843®- 08

THERMODYNAMIC STATE OF WATER

0

1

2

3

4

5

6

7

8

9

10

11

12

13

PHASE

FE MET

FE304

FE(OH3

H2S

MN02

MN304

MN203

PY H2S

CU MET

FE203

PY S04

CUDIST

CUDIST

MN(OH3

EOT

-0.4393

0.9595

1.0481

0.3010

1.2204

1.8036

1.4312

-0.1436

0.3371

0.7119

0.3645

2.0547

KT

1.6l63@- 02

2.5345@+07

5-4590@+o8

1.0836®- 18

1.6113®- 06

2.3445@-l5

1.4133®- 27

1.3 512®- 11

4.0597@+12

1.5790®- 11

8. 0256®- 09

1.0000®- 17

3. 2283®- 09

4.0014@+14

2. 7600®- 05

2.4003@-05

WITH RESPECT

EH T CALC

-0.5765

-0.3355

0.0426

-0.2281

0.5343

0.5986

0.4856

-0.5782

-99.9000

-0.2936

-0.1781

1.1091

AP/K

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@K>0

0.0000@+00

0.0000@+00

0.0000@+00

2. 1631®- 91

5.8586@-o4

1.7313@+00

1.4877®- 02

2. 4491®- 03

6. 3537®- 02

6.3548®-07

9- 3636®- 04

1.0767®- 03

TO COEXISTING

CR

2. 7226®- 19

3.8519@+03

V 7977®- 01

7. 6854®- 30

3. 8195®- 18

3.l624@- 07

1.1996@-0"8

4.1509@+l8

o.oooo@+oo

5.0l63@+04

2.4517@-4o

9. 5627®- 19

CR

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

2. l631@- 01

5. 8586®- 04

1.7313@+00

1.4877®- 02

2. 4491®- 03

6. 3 537®- 02

6. 35^8®- 07

9. 3636®- 04

1.0767®- 03

MOL CAT EQ

2. 0228®- 08

4. 9611®- 07

1.0686@-05

3- 9^75®- 07

2. 3176®- 07

1.6660®- 24

9. 4312®- 19

2. 3010®- 05

7. 9466®- 02

2. 6890®- 05

1-3 5^7®- 02

1.4263®- 01

5. 4976®- 03

7.8326@+00

3- 7304®- 01

3. 2442®- 01

PPMCATEQUTL

l.2853@-03

3- 1523®- 02

6. 7897®- 01

2. 5083®- 02

1.4726®- 02

1.0586®- 19

5-9926@-l4

1.264l@4-00

4.4379@+03

1.5017@+00

3.2936@+02

5.7l64@+03

2.2034@+02

4.3031@+05

1.495l@+o4

1.3003@+04

DEL MU

99-99999

99-99999

99-99999

99.99999

99-99999

99.99999

99.99999

-0.94669

-4.60191

0.339^0

-2.60190 -3.71745

-1.70421

-8.82294

-4.31196

-4.22562

SOLIDS UNDERGOING OXIDATION- REDUCTION REACTIONS

MOL CATEQUIL

1.7100@+14

1.2087®- 08

2. 5898®- 04

0.0000@+00

1.3032@+12

1.574o@+01

4.1492®+02

1.12l6@~23

1.2031®- 11

9. 2809®- 10

0.0000@+00

5.2051@fl2

PPM CATEQUIL

9.5496@+l8

6. 7500®- 04

l.4463@+0l

0.0000@+00

7.1593@+l6

8.6470@+05

2.2795@+07

6. 2637®- 19

7.6447@-07

5. 1831®- 05

0.0000@+00

2.8596@+17

DEL MU

-26.432246

-15.315482

1.061123

-41.452017

24.799154

27.763398

22.555188

-26.507891

-99.900000

-13.384497

-56.396163

25.655448

-/Field Eh, pH, HC03 , by Clarke, USAID, and Egyptian Scientists (EGDDO), June 1962; S Data by EGDDO; 

other chemical data "by USGS Laboratories, July 1965.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS

RASSER WELL 1,

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

General Characteristics

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3Sk LOGACTSO^ EQ LOG ACT FE PY SCh 

6.70 -0.0210 31.00 0.01012 0.0188927 0.00055l| 2^.37 0.660 19.6137 23-7373

Ionic Data

D51

THERMODYNAMIC

0

1

2

3

k

5

6

7

8

9

10

11

12

13

Ik

15

16IT

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MAIACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

THERMODYNAMIC

0

1

2

3

k

5

6

7

8

9

10

11

12

13

-'Field Eh

PHASE

FEMET

FE30^

FE(OH3

H2S

MN02

MN30lt

MN203

PY H2S

CU MET

FE203

PY SOk

CUDIST

'CUDIST

MN(OH3

, pH, H

ION 

0 CA 

1 MG 

2 NA 

3 K 

k CL 

5 SOlj6 HC03

T FE 2 

8 FE 3 

9 MW 2 

10 CU 1 

11 CU 2 

12 HS 

13 H2S 

111- CU20H2 

15 CUTOT 

16 H2STOT

PPM

3k. ooo 

28.000 

36.000 

38.000 

116.000 

111.000 

89.500 

lu 200 

0.000 

O.klk 

0.000 

0.000 

0.685 

0.99^ 

0.000 

0.000

1.700

GAMMA 

0.672359 

0.686^76 

0.900286 

0.897142 

0.897142 

0.65693!^ 

0.900286

0.672359 

o. 1^38311

0.672359 

0.897142 

0.672359 

0.898881^ 

1.000000 

0.699^2

MOLALITY 

8.k%30@-0k 

1.1517®- 03 

1.5659®- 03 

9.7l82@-0li3. 2719®- 03 

1.15558-03 

1 4668®- 03 

7- 5205®- 05 

o.ooco@+oo 

7- 5378®- 06

0.0000®+ 00 

0.0000@+00 

2. 0719®- 05 

2.9l6l<@-05 

0.0000@+00

ALPHA 

5.7036@-0lt 

7.906l@-0lt 

1 4098®- 03 

8. 7215®- 0^ 

2.9361*@-03 

7.5909@-0lt 

1.3205®- 03 

5. 0565®- 05 

0.0000®+00

5.0681®- 06

0.0000®+00 

0.0000®+00 

l.862l*@-05 

2.9l6tt@-05 

0.0000@+00

STATE OF WATER WITH RESPECT TO COEXISTING SOLID PHASES UNDERGOING HYDROLYSIS REACTIONS

AP

0.0000@+00

0.0000@+00

0.0000®+00

0.0000®+ 00

0.0000@+00

0.0000@+00

0.0000@+00

l.T592@- 12

1.2701@+09

1.7552@- 11

2. 7143®- 10

5 4332®- 20

1.9798®- 10

3.70^3®K&

0.0000®+00

0.0000@+00

1.2731@K)8

k. 3296®- 07

k. 3296®- 07

STATE OF WATER

EOT

-04397

0.9713

1.0528

0.3023

1.2250

1.8127

14378

-O.llUT

0.3371

0.7205

0.3657

1.963lt

C03 , by Clarke,

KT

1.8533®- 02

1^5679§+07

9.5920@+o8

1.0836®- 18

l.6ll3@- 06

1.2182®- 15

3. 9280@- 28

l.lKAo@-ll

9.1501@+12

1.8760®- 11

1.00^9®- 08

i.oooo®- 17

3.895^-09

94659®KlA 3. 2330®- 05

2 4222®- 05

WITH RESPECT

EH T CALC

-0.5693

-0.2572

0.0990

-0.1925

0.5761

0.67^6

0.5^3

-0-5^71

-99.9000

-0.2333

-O.lUlS

1.0699

AP/K

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

1.2530®- 01

1.388l@-0li9-356o@-Ol

2. 7310®- 02

5- 1^332®- 03

5-082l*@-02

1.3^9@_07

1.3392®- 02

1.7875@- 02

TO COEXISTING

CR

6. 7^3 5@- 19

lK0701@+02

1.0266®- 02

l.Qk7k@-23

1.6339®- 20

2. 0699®- 08

1^.3008®- 10

2.7130@+17

0.0000@+00

3.2908@+03

9. 2 589®- 29

8.lkL08@-l9

CR

0.0000@+00

0.0000@+00

0.0000®+ 00

0.0000@+00

0.0000®+00

0.0000®+ 00

0.0000@+00

1.2 530®- 01

1.3881®- o^

9- 3 56o@- 01

2. 7310®- 02

5 4332®- 03

5-082lt@-02

1-3^9®- 07

1-3392®- 02

1.7875@- 02

MOL CAT EQ

1^.0399®- 08

2. 70^7@- 06

5- 6795@- 05

1.0561®- 06

6. 3937®- 07

24733@-2lt

8. 1591*®- 19

6. 0159®- 05

5 4178®- 01

8.0382@-05

k. 2171®- 02

1.5613®- 01

1.6691®- 02

5.6ol^8@+0l

6. 3314®- 02

k. 7^58®- 02

PPMCATEQUIL

2.5670@-03

1.7186®- 01

3.6087@+00

6. 7106®- 02

k. 0626®- 02

1.5715@- 19

5-18^5®-!!)-

3.3050@+oo

3.0257@+0lt

li-489l@+00

1.0253@+03

6.2578@+03

6.6897@+02

3.0793®+o6

2.5388@+03

l.902l@+03

DEL MU

99.99999

99-99999

99-99999

99-99999

99-99999

99-99999

99-99999

-1.255^3

-5.36873

-0.0^023

-2.17623

-3.15220

-1.80081

-9.56306

-2.6069!^

-2432^2

SOLIDS UNDERGOING OXIDATION- REDUCTION REACTIONS

MOL CATEQUIL

1.1152®+!^

1.8^78®- 07

7-3255@-03

0.0000@+00

li-.6l35@+llt

3.61^17@+02

l-7527@+0^

2. 7720®- 22

2. 02 52@- 12

2. 2853®- 08

0.0000@+00

8.9621@+12

USAID, and Egyptian Scientists (EGDDO),

PPM CATEQUIL

6.2282@+l8

1.0319®- 02

1^.0911@+02

0.0000®+00

2.53lt6@+l9

2.0007@+07

9.6288@+o8

1.5lt8l@- 17

1.2868®- 07

1.2763®- 03

0.0000®+ 00

1^.9236@+17

June 1962; S

DEL MU

-25.289^16

-10.895652

2.767593

-31.638969

27.538000

32.082550

26.071275

-2^.262778

-99.900000

-9.790332

-39.015180

25.15587^

Data by EGDDO;

other chemical data by USGS Laboratories, July 1965.
D52 HYDROLOGY OF AQUIFER SYSTEMS

NASSER WELL 3, EGYPT^'

INTRINSIC THERMODYMMIC PROPERTIES OF WATER

General Characteristics

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S^ LOGACTSO^ EQ LOG ACT YE PY 

6.89 -0.0282 37.00 0.00*420 0.01699114 0.00014314 19.11 0.614! 21.11493 28-9905

Ionic Data

ION 

0 CA 

1 MG 

2 NA 

3 K 

14 CL 

5 30*4 

6 HC03 

7 FE 2 

8 FE 3 

9 MN 2 

10 CU 1 

11 CU 2 

12 HS 

13 H2S 

1*4 CU20H2 

15 CUTOT 

16 H2STOT

PPM 

18.000 

11.000 

0.000 

27.000 

59.000 

11.000 

110.000 

2.100 

0.000

0.282 

0.050

0.000 

OA86 

0.399 

0.000

0.050 

0.900

GAMMA 

0.7599^ 

0.767601 

0.93H53 

0.929819 

0.929819 

0.751769 

0.931153 

0.7599^ 

0.557^29 

0 . 7599^^ 

0.929819 

0.7599!^ 

0.930^93 

1.000000 0.77^787

MOIALITY

^.^910®- ok

k.52kj@-0k 

0.0000@+00 

6.9050@-0^ 

l.66^2@-03 

i.i^5i@-o^ 

1.8028®- 03 

3- 7603©- 05 

0.0000@+00 

5. 1356©- 06 

7- 8651©- 07 

1.0562©- 09 

l.Vf03@- 05 

1.1705©- 05 

2. 6890®- 15

ALPHA

3.^129@-0^ 

3. Vno©- o^

0.0000@+00 

6.k20b@-0k 

l.5^7i»@-03 

8. 6085©- 05 

1.6787©- 03 

2. 8576®- 05 

0.0000@+00 

3. 9028®- 06 

7- 3131©- 07 

8. 0267©- 10 

1.368l@- 05 

1.1705©- 05 

2.083^-15

THERMODYNAMIC STATE OF WATER WITH RESPECT TO COEXISTING SOLID PHASES UNDERGOING HYDROLYSIS REACTIONS

0

1

2

3

1*

5

6

7

8

9

10

11

12

13

ll*

15

16

17

18

PHASE

CU20

CUO

CU(OH2

AZURIT

M/VLACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

AP

3.2226^-01

k. 8366@+Ol4

l4.8366@+0l4

1.76148®- 26

2. 9216®- 11

5. 6613©- 01

3.772i@-oi4

2.9370©- 12

1.7219@+09

2. 1505@- 11

2. 6136®- 10

6.7128@-20

2. 56814©- 10

2.0155@+0l4

I.ll4l0@+0l4

1.6235®- 03

2.3517®K>8

2. 9380©- 08

2. 9380©- 08

THERMODYNAMIC STATE OF WATER

0

1

2

3

l*

5

6

7

8

9

10

11

12

PHASE

FE MET

FE3Q14

FE(OH3

H2S

MN02

MN3014

MN203

PY H2S

CU MET

FE203

PY SOk

CUDIST

CUDIST

EOT

-O.V39^

0.9612

1.01488

0.3012

1.2211

1.80149

1.14322

-0.11433

0.3371

0.7132

0.36147

KT

1.61475©- 02

2.7525@+07

5.90?6@+o8

1.0836®- 18

1.6113©- 06

2. 1390@- 15

l.l8l2@-27

1.3585©- 11

I4.5l492@+12

1.6176®- 11

8. 28214©- 09

1.0000®- 17

3. 3152©- 09

l4.5lM4@+ll4

2.8218®- 05

2. 14033©- 05

WITH RESPECT

EH T CALC

-0.5792

-0.3155

0.05614

-0.2222

0-539^

0.6081

0.^929

-0.5^81

0.0573

-0.2793

-0.1756

AP/K

i.956o@K>3

1.7572©- 03

8. 1871©- 05

1.6286®- 08

l.8l 32@- 05

2.6^67©+!^

3.l931)@*-23

2. 1620®- 01

3.7850@-0^

1.329i)@+00

3. 1556®- 02

6. 7128®- 03

7- 7^73©- 02

5. 2092©- 07

1.0tL2@- 03

1.2225©- 03

TO COEXISTING

CR

1.2^01©- 18

1.2932@+03

^.2239®- 02

6. 1037©- 26

3. 5720®- 19

1.2798®- 07

3.1^0^0©- 09

7.8^01@+l6

5.9850@+02

1.20l8@+0^

2. 9208@- 3^

CR

1^227@+01

1.7572©- 03

8. 1871©- 05

2. 53^8©- 03

1^.2581©- 03

2.6^67©+!^

5.6510©+!!

2. 1620®- 01

3. 7850®- o^

I.329i4@+oo

3. 1556®- 02

6. 7128®- 03

7- 7Vf3@- 02

5. 2092©- 07

1.0Ul2@-03

1.2225©- 03

MOL CAT EQ

2. 1759®- 08

6. 0110®- 07

1.2901©- 05

1^.1670®- 07

2.i^805@-07

3.9908@-2i^

1.3918®- 18

2.375^05

9- 93^7©- 02

2. 8285©- 05

1.1*338®- 02

6. 6902©- 02

5. 7969®- 03

9.8588@+00

MiS^oi

3- 6737©- 01

PPMCATEQUIL

1.3826®- 03

3.8i9*«g-02

8.i97l«g-oi

2.6i^77@-02

1.576l@- 02

2. 53 58@- 19

8.8^35©-!^

1.3050@+00

5.5^82@+03

i.5796@+oo

3A858@+02

2.68li4@+03

2.323i)@+02

5.^l62@+05

l.7288@+0^

lA72i4@+0^

DEL MU

U. 67108

-3-91013

-5.80005

-11. 0529i*.

-6.72918

20.1*.6856

33-35703

-0.914397

-^.85638

0.17550

-2.13008

-3.081403

-1.57651

-8.91710

-14.23270

-^.13376

SOLIDS UNDERGOING OXIDATION-REDUCTION REACTIONS

MOL CATEQUIL

3.0323@+13

2. 9076®- 08

8.902i4©-0ij.

0.0000@+00

1.V377@+13

^.0128@+01

l.5087@+03

^.7962©- 22

1.76^8®- 12

3. 1289®- 09

0.0000@+00

PPM CATEQUIL

I.693i4@+i8

1.6238®- 03

^ 9717@+01

O.OOOC@+00

7-8987@+l7

2.20^5@+o6

8.2885@+07

2. 6785©- 17

1.1213©- 07

1.7Vfl«g-0^

0.0000@+00

DEL MU

-25Al28li^

-13.2^821^

1.950375

-35-78U061

26.1799^3

29.3^6808

2^.035^3

-23.976272

3.9^1190

-11.58010^

-14.7.591868

13 MN(OH3 1.10214 1.2088@+13 6.6lHl@+l7 26.073059

-'Field Eh, pH, HCOg , by Clarke, USAID, and Egyptian Scientists (EGDDO), June 1962; S Data by EGDDO; 

other chemical data "by USGS Laboratories, July 1965.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS D53

DALORI WELL, NIGERIA-^/

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

General Characteristics

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S4 LOGACTS04 EQ LOG ACT FE PY S04 

7.29 -0.2671 31.00 0.00567 0.0104106 0.000305 13.44 -99-999 0.0000 -22.!

Ionic Data

ION PPM GAMMA MOIALITY ALPHA 

0 CA Ik. 000 0.733457 3. 4930®- 04 2.5620@-04 

1 MG 6.800 0.742919 2.7970@-04 2.0779@-04 

2 NA 76.000 0.922203 3- 3058®- 03 3.0486®- 03 

3 K 14.000 0-920482 3. 5804®- 04 3. 2957®- 04 

4 CL 10.000 0.920482 2.8206@-04 2. 5963®- 04 

5 S04 29.000 0.723279 3. 0189®- 04 2.1835®- 04 

6 HC03 187.500 0.922203 3. 0729®- 03 2. 8338®- 03 

7 FE 2 7-000 0.733^57 l.2534@-04 9-l933@-05 

8 FE 3 0.000 0.519398 0.0000@+00 0.0000@+00 

9 MN 2 1.024 0.733457 1.8631@-05 1.3665@-05 

10 CU 1 0.040 0.920482 6. 2952@- 07 5. 7947®- 07 

11 CU 2 0.000 0.733457 8.4928@-l4 6. 229l@- Ik 

12 HS 0.000 0.921352 0.0000@+00 0.0000@+00 

13 H2S 0.000 1.000000 0.0000@+00 0.0000@KX> 

Ik CU20H2 0.000 0.751737 6.2143®- 23 k. 6715®- 23 

15 CUTOT 0.040 

16 H2STOT 0.000

THERMODYNAMIC STATE OF WATER WITH RESPECT TO COEXISTING SOLID PHASES UNDERGOING REACTIONS

0

1

2

3

4

5

6

7

8

9

10

11

12

13Ik15

16

17

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MAIACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

THERMO DYNAMIC STATE

0

1

2

3

4

5

6

7

8

9

10

11

12

13

FE MET

FE304

FE(OH3

H2S

MN02

MN304

MN203

PY H2S

CU MET

FE203

PY SOk

CUDIST

CUDIST

MN(OH3

AP

1.2766@+02

2.3682@+01

2.3682@+01

7- 7173®- 37

4.2751®- 18

0.0000@+00

0.0000@+00 3. 9600®- 11

3.4952@+lO

2. 6642®- 10

6.02l8@-10

k. 4709®- 19

7. 4245®- 10

0.0000@+00

0.0000@+00

0.0000@+00

5.1952@+09

5-594l@- 08

5. 5941®- 08

1.

k.

9-

1.

1.

1.

3-

1.

9-

1.

1.

1.

3-

9-

3-

2.

KT

8533®- 02

5679@+07

59202*08

0836®- 18

6113®- 06

2l82@-15

9280®- 28

4o4o@-n

1501@+12

8760®- 11

0049@-08

oooo@- 17

89514®- 09

4659@+l4

2330®- 05

4222@-05

OF WATER WITH RESPECT TO

EOT

-0.^397

0.9713

1.0528

0.3023

1.2250

1.8127

1.^378

-0. Ila7

0.3371

0.7205

0.3657

1.963^

EH

-0.

-0.

-0.

-99.

0.

0.

0.

-99-

-0.

-0.

-0.

0.

T CALC

5615

4232

0235

9000

4919

4932

4115

9000

O6l4

3558

1861

9371

6.

5-

2.

7-

2.

0.

0.

2.

3.

1.

5-

4.

1.

5-

1.

2.

AP/K

8882@+03

1845@-07

4690®- 08

1217®- 19

6532®- 12

0000@+00

0000@+00

8205@+00

8199®- 03

4202@+01

9926®- 02

4709®- 02

9060®- 01

4883§-06

7303®- 03

3095®- 03

CR

8.2995@+01

5.1845@-07

2. 4690®- 08

8. 9302®- 07

1.62 89®- 06

0.0000@+00

0.0000@+00

2.8205@+00

3- 8l99@- 03

1.4202@+01

5- 9926®- 02

4. 4709®- 02

1.9060®- 01

5- 4883®- 06

1-7303®- 03

2. 3095®- 03

MOL CAT EQ

9. 5192®- 09

1.638l@- 07

3. 4398®- 06

9. 5102®- 08

5. 2139®- 08

0.0000@+00

0.0000@+00

6. 6055®- 06

3.28l3@- 02

8. 8259®- 06

4. 6674®- 03

7.8128®- 03

1.8327®- 03

3-3946@+00

2. 0187®- 01

1.5124®- 01

PPMCATEQUIL

6.

1.

2.

6.

3-

0.

0.

3-

1.

4.

1.

3-

7-

1.

8.

6.

0485®- 04

0409@-02

1857®- 01

0428@-03

3129®- 03

0000@+00

0000@+00

6289®- 01

8325@+03

9290®- 01

1347@+02

I3l4@+02

3453@+Ol

8649@+05

0910@+03

O6l8@+03

DEL MU

5-34164

-8.74747

-10.58762

-25.25643

-16.11107

99-99999

99-99999

0.62673

-3.36515

1-60375

-1.70124

-1.87829

-1.00188

-7.32132

-3.84380

-3.66928

COEXISTING SOLIDS UNDERGOING OXIDATION- REDUCTION REACTIONS

1.

5-

9-

0.

7-

3-

5-

0.

6.

2.

6.

1.

CR

7538®- 10

2975@+01

1896S-05

0000@+00

0549®- 26

9952®- 09

7090®- 12

0000@+00

5438@+o6

9457@+Ol

1978@+18

1165®- 20

MOL CATEQUIL

7-l469@+05

2. 366l@- 06

l-364o@+00

0.0000@+00

2.64o8@+20

4.6632@+03

3.2633@+o6

0.0000@+00

1.2978®- 20

4. 2551®- 06

0.0000@+00

l.6687@+l 5

PPM CATEQUIL DEL MU

3.9913@+10

l.32l4@-0l

7.6l73@+0^

0.0000@+00

l.4508@+25

2.56l9@+o8

l.7928@+ll

0.0000®- 00

8.2465@-l6

2. 3763®- 01

0.0000@+00

9.l674@+!9

-13-

-7-

5-

-99-

35-

35-

31-

-99-

9-

-4.

26!

27-

577810

198348

618032

900000

004286

065348

295818

900000

485839

089453

153855

768145

i/Field Eh, pH, Fes , HC03 , "by Clarke, USAID, and Nigerian Scientists, Fet>. 1965; remaining determinations 

"by USGS Laboratories, May 1965.
D54 HYDROLOGY OF AQUIFER SYSTEMS

NGAIA, NIGERIA^/

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

General Characteristics 

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S4 LOGACTS04 EQ LOG ACT FE PY S04

6.70 0.0274 40.00 0.00987 0.0874851 0.00209^ 92.14 -99-999 O.OOO'o 37. f

Ionic Data

ION PPM GAMMA

o CA 8.000 0.671086

1 MG 4.100 0.685152 

2 NA 176.000 0.899872 

3 K 9.000 0.897039 

4 CL 34.000 0.897039 

5 S04 83.000 0.655728 

6 HC03 360.000 0.899872 

7 FE 2 0.300 0.671086 

8 FE 3 0.000 0.436400 

9 MN 2 0.416 0.671086

10 cu i o.ooo 0.897039

11 CU 2 0.000 0.671086 

12 HS 0.000 0.898476 

13 H2S 0.000 1.000000 

14 CU20H2 0.000 0.698079 

15 CUTOT 0.000 

16 H2STOT 0.000

THERMODYNAMIC STATE OF WATER WITH RESPECT TO COEXISTING

0

1

2

3

4

5

6

7

8

9

10

ll

12

13

14

15

16

17

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MAIACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

THERMODYNAMIC STATE

0

1

2

3

4

5

6

7

8

9

10 '

11

12

13

PHASE

FE MET

FE304

FE(OH3

H2S

MN02

MN304

MN203

PY H2S

CU MET

FE203

PY S04

CUDIST

CUDIST

MN(OH3

0

0

0

0

0

0

0

8

9

5

1

3

2

0

0

0

1

7

7

AP

.00000+00

.00000+00

. ooooe+00

.00000+00

.00000+00

.00000+00

.00000+00

.1474®- 12

.0552@+07

.7780®- 12

.8520@-10

.9760®- 20

.14690-10

. 0000@+00

. 0000@+00

.0000@+00

.27690+08

.5891®- 08

.5891®- 08

KT

1.5560@-02

2.1522O+07

4.6686@+o8

1.08360-18

1.61130-06

2.8ll6@-l5

2.0l62@-27

1.33690-11

3.2401O+12

1.5053®- ll

7.54020-09

1.0000®- 17

3.06200-09

3.1510@+14

2.64l4@-05

2.39420-05

OF WATER WITH RESPECT TO

-0

0

1

0

1

1

1

-0

0

0

0

2

EOT

.4392

.9561

.0468

 3007

.2191

.8010

.4294

.1441

 3372

.7095

.3642

.0808

EH T CALC

-0.6083

-0.2018

0.1361

-99.9000

0.5509

0.6292

0.5093

-99.9000

-99.9000

-0.2013

-o1. 161*6

1.1608

0.

0.

0.

0.

0.

AP/K

00000+00

0000@+00

00000+00

0000@+00

00000+00

o.ooooo+oo

0.

6.

2.

3-

2.

3-

7-

4.

2.

3-

0000®+ 00

09420-01

7948©- 05

83850-01

456l@- 02

9760®- 03

01160-02

0522@-07

8731@- 03

16980-03

MOIALITY ALPHA 

1.99600-04 1.3395®- 04 

1.6864@-o4 1.1 554®- 04 

7.65560-03 6.88900-03 

2 . 3017®- 04 2 . 0647@- 04 

9 . 59020- 04 8 . 6028®- 04 

8 . 64030- 04 5 . 6657©- 04 

5.90000-03 5-30920-03 

5.37180-06 3.60500-06 

0 . 0000@+00 0 . 0000@+00 

7 5747®- 06 5 . 0832®- 06 

0.0000@+00 0.0000@+00 

0 . 0000@+00 0 . 0000@+00 

0 . 00000+00 0 . 00000+00 

0.0000@+00 0.0000@+00 

0 . 00000+00 0 . 0000@+00

SOLID PHASES UNDERGOING HYDROLYSIS REACTIONS

CR

0.0000@+00

0.0000@+00

0.00000+00

0.00000+00

0.00000+00

0.0000@+00

0.0000@+00

6.09420-01

2.79480-05

3.83850-01

2. 4 56l@- 02

3. 9760®- 03

7.01l6@- 02

4.05220-07

2. 8731®- 03

3.16980-03

MOL CAT EQ

3.70880-08

1.27680-06

2. 7695®- 05

3- 8159®- 07

2. 98ll@- 07

0.0000@+00

0.00000+00

1.24290-05

1.9221@-01

i-3995@-05

6.86620-03

5. 0201®- 02

2. 8467®- 03

1.86930+01

6.94720-02

6.29700-02

PPMCATEQUIL

2

8

1

2

1

0

0

 6

i

7

1

2

1

1

2

2

.35660-03

.11260-02

. 75980+00

.4246®- 02

.8942@- 02

.00000+00

. 00000+00

.8284®- 01

. 0734@+04

.81560-01

. 66930+02

.01200+03

.l4lO@+02

. 02690+06

. 7844@+03

. 52380+03

DEL MU

99-99999

99.99999

99-99999

99.99999

99-99999

99-99999

99-99999

-0.30820

-6.52501

-0.59587

-2.30664

-3-43979

-1.65385

-9-15965

-3-64197

-3.58082

COEXISTING SOLIDS UNDERGOING OXIDATION-REDUCTION REACTIONS

3-

2.

1.

0.

1.

3.

1.

0.

0.

4.

5-

5-

CR

44950-21

87870+02

78320-02

00000+00

4ll7@-17

4969@-07

75420-08

0000@+00

00000+00

78820+03

60220-44

7539®- 19

MOL CATEQUIL

1.5573@+15

1.8661®- 08

3.01240-04

0.0000@+00

5.3657@+ll

2.l66ie+01

4.31800+02

0.00000+00

1.5956®- 10

1.1219®- 09

0.0000@+00

1.31640+13

PPM CATEQUIL

8. 69690+19

1.04210-03

1.6823O+01

0.00000+00

2.94780+16

1 . 190OO+06

2.37220+07

0.00000+00

1.01380-05

6.2654@-05

0.00000+00

7.23220+17

-29

-10

2

-99

24

27

22

-99

-99

-10

-61

26

DEL MU

. 320721

. 571474

. 505873

.900000

.145042

. 754121

. 227182

. 900000

. 900000

. 546777

.976060

.136479

-/Field Eh, pH, Fe8 , HCOa , by Clarke, USAID, and Nigerian Scientists, Feb. 1965; remaining determinations 

by USGS Laboratories, May 1965.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS

SHADMAN WELL 27, WEST PAKISTAIji'

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

General Characteristics

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S4 LOGACTSOU EQ LOG ACT FE PY Sdk 

7.69 0.0580 28.00 0.00693 0.0051+1+15 0.000172 7-57 0.759 38.7765 58.5980

Ionic Data

D55

ION 

0 CA 

1 MG 

2 MA 

3 K 

h CL 

5 S0l+ 

6 HC03 

7 FE 2 

8 IE 3 

9 MN 2 

10 CU 1 

11 CU 2 

12 HS 

13 H2S 

ll+ CU20H2 

15 CUTOT 

16 H2STOT

PPM 

1+2.000

16.000 

35.000 

5.000 

13.000 

18.000 

259.100

0.220 

0.000

0.099

0.000 

0.000

0.920 

0.152

0.000 

0.000 

1.100

GAMMA 

0.714253 

0.725125 

0.915505 

0.9131+6!+ 

0.9131+61+ 

0.7021+96 

0.915505 

0.711+253 

0.1+92971+ 

0.711+253 

0.9131+61+ 

0.711+253 

0.911+1+97 

1.000000

0.735208

MOLALITY 

1.01+79©- 03 

6.58ii@-ol+ 

1.522!+®- 03

1.2787@-0l+ 

3.6668@-ol+ 

i.8738@-ol+ 

l+. 2l+63@- 03 

3- 9393®- 06

0.0000@+00

I.8o68@-o6 

o.oooo@+oo 

o.oooo@+oo

2. 7812®- 05

l+.l+655@-o6 

o.oooo@+oo

ALPHA 

7. 1+81+7®- Ol+ 

l+.7721@-0l+ 

1.3938®- 03 

l.i68i@-ol+ 

3.3l+95@-ol+ 

l.3l63@-ol+ 

3- 8875®- 03 

2. 8137®- 06

0.0000@+00

1.2905®- 06

0.0000@+00 

0.0000@+00

2.5l+3i+@-05 

1+. 1+655®- 06

0.0000@+00

THERMODYNAMIC STATE OF WATER WITH RESPECT TO COEXISTING SOLID PHASES UNDERGOING HYDROLYSIS REACTIONS

0

1

2

3

1+

5

6

7

8

9

10

11

12

13

il+

15

16

IT

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MAIACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

AWHYDR

GYPSUM

AP

0.0000@H-00

0.0000@H-00

0.0000@H-00

0.0000@+00

0.0000@H-00

0.0000@H-00

0.0000@+00

1.2203®- 11

6.7l+95@+09

2.66o6@-ii

1+. 5126®- 09

3.1938®- 17

7. 0776®- 09

3.oii+o@+oi+

0.0000@+00

0.0000@+00

3-0957@+09

9. 8523®- 08

9. 8523®- 08

THERMODYNAMIC STATE OF WATER

0

1

2

3

1+

5

6

7

8

9

10

11

12

PHASE

FE MET

FE301+

FE(OH3

H2S

MN02

MN301+

MN203

PY H2S

CU MET

FE203

PY SOU

CUDIST

CUDIST

EOT -0.1+398

0.9763

1.051+8

0.3028

1.2270 1.8166

1.41+06

-0.11+09

0.3370

0.721+2

0.3662

KT

1.9691®- 02

5-9293@+07

1.2311@+09

1.0836®- 18

1.6113®- 06

9. 1162®- 16

2. 2282®- 28

1.1+281®- 11

1.3H3@+13

2.021+7®- 11

1.1100®- 08

1.0000®- 17

4. 2276®- 09

1.38593*15

3. 1+675®- 05

2.1+319@-05

WITH RESPECT

EH T CALC

-0.6057 -0.361+3

0.0079

-0.2606

0.1+839

0.5063

0.1+139

-0.571+1+

-99.9000

-0.3227

-0.2158

AP/K

0.0000@+00

o.oooos+oo

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

8. 51+51®- 01

5.ll+72@-Ol+

i.3ii+i@+oo

i+. 0652®- 01

3.1938@+00

1.67l+l@+00

2. 2336®- 06

2. 81+1 3®- 03

1+.0513@-03

TO COEXISTING

CR

6.1218®- 23

5.l399@+ol+

6.8893@+oo

2. 2023®- 1+3

5.5686@-l5

9. 9 561®- 06

1.1058®- 06

i.l+639@+2i

0.0000@+00

2.3l+82@+o6

0.0000@+00

CR

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000®+ 00

0.0000@+00

8. 5l+5l@- 01

5.ll+72@-0*+

i.3ii+i@+oo

i+. 0652®- 01

3.1938@+00

1.67iH@+00

2. 2336®- 06

2.81+13®- 03

1+. 05130-03

MOL CAT EQ

i+. 0113®- 09

3.1+606®- 08

7.l85l+@-07

2. 1+023®- 08

1.1800®- 08

1.19150-25

1.5789©- 19

2.111+1+®- 06

7- 6533®- 03

2. 9978®- 06

1.6189©- 03

3.2811®- oi+

6.2593@-oi+

8. 0890®- 01

3.6881®- 01

2. 5866®- 01

PPMCATEQUIL

2.5l+88@-ol+

2. 1988®- 03

1+. 5656®- 02

1.5265®- 03

7.1+977@-Ol+

7. 5708@- 21

1.0032@-ll+

I.l6i6@-oi

l+.27l+2@+02

1.671+2®- 01

3.9359@+Ol

1.3151@+01

2-5087@+01

IK l+l+39@K>l+

l.l+782@+Ol+

1.0367@+Ql+

DEL MU

99.99999 99.99999 99.99999 99.99999

99.99999

99.99999

99-99999

-0.091+09

-!+. 531^9

0.1631+5

-0.53869

0.691+94

0.30839

-7.78712

-3.50908

-3.29677

SOLIDS UNDERGOING OXIDATION- REDUCTION REACTIONS

MOL CATEQUIL

6.i+3l+9@+i6

7. 661+3®- 11

5. 7l8l@- 07

0.0000@+00

3.2l+i+6@+o8

I.8i47@-oi

i.6339@+oo

2. 6910®- 27

6.1+il+S®- 10

1.6776®- 12

0.0000@+00

PPM CATEQUIL

3-5937@+2l

1+. 2803®- 06

3-i93i+@-02

0.0000@+00

1.7825@+13

9. 96980+0 3

8.9764@+ol+

1.5029®- 22

1+. 0760®- 05

9. 3689©- 08

0.0000@+00

DEL MU

-30.609901

-19.1+75216 -1.155013

-58.781938

19.61+2506

20.678052

16.1+1571+6

-29.166275

-99.900000

-17.557876

-88.397619

13 MN(OH3 1.921+2 8.9197@-15 2.0256@+08 1.1128@+13 19.360559

i/Field Eh, pH, Fe^ , HC03 , S, ty Clarke, USAID, and W. 

chemical data "by USGS Laboratories, May 1965.

Pakistani (WASID) Scientists, March 1965; other
D56

SHADMAN WELL 4?, WEST

HYDROLOGY OF AQUIFER SYSTEMS

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

General Characteristics

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S4 LOGACTS04 EQ LOG ACT FE PY S04 

7.50 0.0815 27-00 0.01033 0.011530*4- 0.000373 16.44 0.738 39-9759 59.8760

Ionic Data

ION 

0 CA 

1 MG 

2 HA 

3 K 

4 CL 

5 S04 

6 HC03 

7 FE 2 

8 FE 3 

9 MN 2 

10 CU 1 

11 CU 2 

12 HS 

13 H2S 

14 CU20H2 

15 CUTOT 

16 H2STOT

THERMODYNAMIC STATE OF WATER

0

1

2

3

4

5

6

7

8

9

10

11

12

13lit

15

16

17

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MALACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

AP

4.3529@+03

1.3069@+08

I.3069@+o8

1.5403®- 16

1.14-189®- (A

6.9521@+02

2. 3155@- 02

1.7159®- 11

2.4059@K>9

1.9985®- 11

4. 2191®- 09

3. 113%- 17

7.3793@- 09

l.2798@K)4

8.8972®+o6

4.770l@+03

2.0657@K>9

3- 3987®- 07

3. 3937®- 07

PPM 

53-000

18.000 

77-000 

3-14-00 

22.000 

56.000 

365.500 

O.200 

0.000 

0.169 

O.H4-8 

0.012 

0.697 

0.181 

0.000 

0.160 

0.900

GAMMA 

0.671814 

0.686045 

0.900053 

0.897182 

0.897182 

0.656256 

0.900053 

0.67l8l4 

0.1(-37770 

0.67l8ll4. 

0.897182 

0.671814 

0.898638 

1.000000 

0.699108

MOLALITY 

1.3224®- 03 

7.4038@-o4 

3- 3493®- 03 

8.6952@-05 

6.2054@-o4 

5. 8296®- 04 

5.9901©- 03 

3. 5812®- 06

0.0000@+00

3. 0748®- 06 

2. 3255®- 06 

1.9454®- 07

2. 1089@- 05'

5. 3193®- 06 

5. 1083®- 10

WITH RESPECT TO COEXISTING SOLID PHASES

KT

2. 0098®- 02

6.4754@+07

1.3394@+09

1.0836®- 18

1.6ll3@- 06

8. 2659®- 16

1.8399®- 28

1.4383®- 11

1.4808@+13

2. 0776®- 11

1.114.80®- 08

i.oooo®- 17

14-. 314.52®- 09

I.576l4@+l5

3.5505@-05

2.4352@-05

THERMODYNAMIC STATE OF WATER WITH RESPECT TO

0

1

2

3

4

5

6

7

8

9

10

11

12

PHASE

FE MET

FE304

FE(OH3

H2S

MN02

MN304

MK203

PY H2S

CU MET

FE203

PY S04

CUDIST

CUDIST

EOT

-0.4399

0.9780

1.0555

0.3030

1.2277

1.8179

1.14-14-15

-0.114-06

0.3370

0.7254

0.3664

EH T CALC

-0.6072

-0.3068

0.0501

-0.2*40.6

0.5036

0.5390

0.1(-lt-01

-0.5525

0.1320

-0.2800

-0.1971

AP/K

2.l658@+05

2.oi83@+oo

9- 7576®- 02

1.4215@-H32

8.8057@+0l

8.4106@+17

1.2585@+26

1.1947@+00

1.6214.8®- 04

9. 6191®- 01

3- 6752®- 01

3.1134@+00

1. 6983^+00

1.31014®- 06

9-5722®- 03

1.39 56@- 02

COEXISTING

CR

7. 4560®- 2*4.

2.2202@+04

3.3728@+00

k. 014.14-0®- 414.

6. 7103®- 15

7. 5670®- 06

9. 514.44®- 07

1.9574@+2l

4.9753@+01

1.1737@+06

0.0000@+00

CR

4.6538@+02

2.0l83@+00

9. 7576®- 02

5.2i89@+oo

9.3838®+00

8.4lo6@+l7

1.1218@+13

1.1947@+00

l.6248@-o4

9.6l9l@-0l

3-6753§-Ol

3.1134@+00

l.6983@+00

1.3104@-06

9. 5722®- 03

1.3956®- 02

ALPHA

8. 8838®- 04 

5.0793@-o4 

3.oi46@-03 

7.8012®- 05 

5.5674@-o4 

3. 8257®- 04 

5.3914®- 03 

2.4059®- 06

0.0000@fOO

2. 0657®- 06 

2.0864®- 06 

1.3069®- 07 

1.8952®- 05 

5- 3193©- 06 

3. 5713©- 10

UNDERGOING HYDROLYSIS REACTIONS

MOL CAT EQ

6.6731@-09

9. 6386®- 08

1.9937®- 06

3.7276@-O8

2. 0731®- 08

2. 3130®- 2 5

2. 0729®- 19

2. 5738®- 06

2.204l@-02

3. 7230®- 06

2.0145®- 03

4.2472@-04

7-7865@-o4

2-3465@+00

1.38l4@- 01

9. 4750®- 02

PPMCATEQUIL

4.24oi@-o4

6. 1244®- 03

1.2668®- 01

2.3685@-03

1.3173®- 03

1.4697©- 20

I.3l7l@-l4

I.4i4o@-oi

1.2309@+03

2. 0792®- 01

4.8977@+Ol

l.7023@+0l

3.1208@+01

l.289l@K>5

5.5368@+03

3-7976@+03

DEL MU

7- 32813

0.41889

-1.38807

2.95664

2.67100

24.61857

35-84644

0.10610

-5.20423

-0.02316

-o. 59706

O.67744

0.31589

-8.07938

-2.77295

-2-54804

SOLIDS UNDERGOING OXIDATION- REDUCTION REACTIONS

MOL CATEQUIL

4.8031@+17

1.61 30®- 10

I.o6i8@-o6

0.0000@+00

4.'5822@+o8

4.0635@-01

3.22l6@+00

1.8296®- 27

3.910U§-09

3- 0512®- 12

0.0000@+00

PPM CATEQUIL

2.6824@+22

9.008l@- 06

5. 9298®- 02

0.0000@+00

2.5174@+13

2.2324@+o4

1. 7699@+05

1.0218®- 22

2.4845@-o4

1.7O40@-07

0.0000@+00

DEL MU

-31.764095

-17.908467

-0.725160

-59-597702

19.466036

21.100385

16.536834

-29.242711

2.330471

-16.672280

-89.952712

13 MN(OH3 1.9112 0.9097 1.2425@-l4 2.4748@+08 1.3596@+13 19.098585

-'Field Eh, pH Feg, HC03 , S, Tsy Clarke, USAID, and W. Pakistani (WASID) Scientists, March 1964; 

other chemical data "by USGS Laboratories, July 1964.
GROUND WATER, CORROSION AND ENCRUSTATION EFFECTS ON WELLS

SHAHKOT WELL 251, WEST PAKI STAIR

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

D57

General Characteristics

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AG 

3.12 0.1185 21.00 0.001*65 0.0009029 0.000031* 1.52

Ionic Data

EO FE3S1* LOGACTSQl* EQ LOG ACT FE PY SO** 

0.832 1*9.7868 77.201*5

ION PPM GAMMA MOIALITY ALPHA 

0 CA 27.000 0.756080 6.73650-01* 5.0931*0-0!* 

1 MG 10.000 0.761*131* 1*. 11 320-01* 3.11*300-0!*

2 NA 19.000 0.929816 8.26i*5@-oi* 7.681*50-01*

3 K 1*.300 0.9281*01 1.09970-01* 1. 02100- Ql* 

1* CL 6.800 0.9281*01 1.9180®- Ol* 1.78070-01* 

5 SOil- 1*2.000 0.7l*7l*6l 1*. 37220-01* 3.26800-0!*

6 HC03 125.600 0.929816 2.0581*0-03 1.91^0®- 03 

7 FE 2 0.220 0.756080 3-9393@-o6 2.9785@-o6 

8 FE 3 0.000 0.552103 0.00000+00 0.00000+00 

9 MN 2 0.105 0.756080 1.9077®- 06 1. M*2l*©-06 

10 CU 1 0.000 0.9281*01 0.00000+00 0.00000+00

11 cu 2 o.ooo 0.756080 o.ooooo+oo o.ooooo+oo

12 HS 0.1*51 0.929116 1.3627@-05 1.266l@-05 

13 H2S 0.036 1.000000 1.0l*l*60-06 l,0l*l*60-06 

ll* CU20H2 0.000 0.771677 0.0000@+00 0.00000+00 

15 CUTOT 0.000 

16 H2STOT 0. 500

THERMODYNAMIC STATE OF WATER WITH RESPECT TO COEXISTING SOLID PHASES UNDERGOING HYDROLYSIS REACTIONS

0

1

2

3

l*

5

6

7

8

9

10

11

12

13

ll*

15

16

17

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MAIACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

OTFES2

BORNIT

MN{OH2

ANHYDR

GYPSUM

THERMODYNAMIC

0

1

2

3

1*

5

6

7

8

9

10

11

12

13

PHASE

FE MET

FE304

FE(OH3

H2S

MN02

MN30J4-

MN203

PY H2S

CU MET

FE203

PY SOk

CUDIST

CUDIST

MN(OH3

AP

0.0000@+00

0.0000@+00

0.0000®+00

0.0000@+00

o.oooc@+oo

0.0000@+00

0.0000@fOO

1.561fO@-ll

5.176o®+lO

3. 2296®- 11

3.^08K§-09

1.8822®- 17

5. 5229®- 09

5Ao67@K>4

0.0000@+00

0. 0000@+00

2.5065@4-10

1.66^5@-07

1.66^5®- 07

STATE OF WATER

EOT

-0.4^02

0.9881

1.0595

o. 30*4.1

1.2316

1.8256

1 All-72

-0.1390

0, 3370

0.7328

0.3673

1.8329

KT

2. 2791@- 02

1.1125@K>8

2.2if8l@+09

1.0836®- 18

1.6ll3@- 06

^.5296®- 16

5.67te@-29

1.1*878®- 11

3-12li-3®+13

2.U34o@-ll

lAlll«g-08

1.0000®- 17

5- I33l*@-09

3-V773®+15

14-.1059@-*O5

2.1*556@-05

WITH RESPECT

EH T CALC

-0.6015

-0.1*239

-0.0398

-0.2702

0.1*51*2

0.1*1*12

0.3662

-0.5765

-99-9000

-0.3665

-0.2261*

0.7520

AP/K

0.0000@+00

0.0000@+00

0.0000@+00

0.0000®fOO

o.oooc@+oo

0.0000@+00

0.0000@+00

1.0512@+00

1.6567®- 03

i.3269@+oo

2.1*ll*7@- 01

1.8822@+00

l.0759@+00

7. 2083®- 06

1*. 051*0®- 03

6.7781*@-03

TO COEXISTING

CR

2.1365@-25

1.5675OK>6

5.15900+02

0.0000@+00

3.11*900-12

2.05910-Ql*

5.69650-05

6.52510+23

0.00000+00

2.0392O+08

0.00000+00

1.1*0280-11

CR

0.00000+00

0.00000+00

0.00000+00

0.00000+00

0.0000@+00

0.0000@+00

o.oooc@+oo

1.05120+00

1.6567®- 03

1.32690+00

2.Ul^7©-01

1.88220+00

1.07590+00

7. 2083®- 06

1*. 051*0®- 03

6.7781*0-03

MOL CAT EQ

1.511*70-09

8A6730-09

1.71100-07

1.07060-08

3.86760-09

3.30020-26

6. 0221®- 20

1.8ll*7©-06

2.37780-03

2.96890-06

1.703li®-03

3.5790@-0l*

6.26150-01*

2.61*650-01

1.6617®- 01

9.93820-02

PPMCATEQUIL

9.62l*l©-05

5.380l@-oi*

1.08720-02

6.80250-01* 2.14.5750-01*

2.09700-21

3.8261*0-15

9.96960-02

1.32790+02

1.65800-01

1*. 11*130+01

1.14.31*50+01

2. 5096@+01

1.1*5390+01*

6.66020+03

3.98320+03

DEL MU

99-99999

99-99999

99-99999

99-99999

99-99999

99-99999

99.99999

0.02921

-3.71*285

0.16533

-0.83065

0.36971

0.01*275

-6.92126

-3.21975

-2.91926

SOLIDS UNDERGOING OXIDATION- REDUCTION REACTIONS

MOL CATEQUIL

1.81*380+19

2. 5131®- 12

7.6358®-09

0. 00000+00

6.058l@+05

9.261*1*0-03

3.3^890-02

6.03720-30

1*. 32l*7@- 08

1.93180-1!*

0.00000+00

l-3599@+05

PPM CATEQUIL

1.0297O+21*

1.1*0350-07

1*. 261*1*®- Ol*

0.00000+00

3.3282O+10

5.0897O+02

1.83980+03

3.37160-25

2. 71*790- 03

1.07880-09

0.00000+00

7 . 1*711©+09

DEL MU

-33-205739

-25.O15882

-3.651063

-71.703800

15.1*8121*0

ll*. 885119

11.1*25736

-32.053969

-99-900000

-22.368750

-111.35361*9

ll*. 607935

-'Field Eh, pH, Feig, HCOg , S, ty Clarke, USAID, and W. 

chemical data "by USGS Laboratories, May 1965.

Pakistani (WASID) Scientists, March 1965; other
D58 HYDROLOGY OF AQUIFER SYSTEMS

SHAHKOT WELL 252, WEST PAKISTAN^'

INTRINSIC THERMODYNAMIC PROPERTIES OF WATER

General Characteristics

PH EH MEAS T ION STRENGTH PC02 ATM MC02 AQ PPM C02 AQ EO FE3S4 LOGACTSC4 EQ LOG ACT YE PY SO** 

3.12 0.3392 22.00 0.00l*ll* 0.0008992 0.000033 1.1*7 -99-999 0.0000 130.51*29

Ionic Data

0

1 

2 

3

1*

5 

6 

7 

8

9

10

11

12

13 

il*

15 

16

ION 

CA 

MG 

NA 

K 

CL 

SOl* 

HC03 

FE 2 

FE 3 

MN 2 

CU 1 

CU 2 

HS 

H2S 

CU20H2 

CUTOT 

H2STOT

THERMODYNAMIC STATE

0

1

2

3

1*

5

6

7

8

9

10

11

12

13

il*

15

16

17

18

PHASE

CU20

CUO

CU(OH2

AZURIT

MAIACH

CUS

CU2S

MNC03

FE(OH2

FEC03

MGC03

DOLOMI

CAC03

FES

CUFES2

BORNIT

MN(OH2

ANHYDR

GYPSUM

0

0

0

0

0

0

0

0

0

0

3

1

5

0

0

0

0

1

1

THERMODYNAMIC STATE

0

1

2

3

1*

5

6

7

8

9

10

11

12

PHASE

FE MET

FE301*

FE(OH3

H2S

MN02

MN301*

MN203

PY H2S

CU MET

FE203

PY SOl*

CUDIST

CUDIST

-0

0

1

0

1

1

1

-0

0

0

0

OF WATER

AP

.0000@+00

. 0000@+00

. 0000@+00

.0000@+00

,0000@+00

.0000@+00

.0000@K>0

.0000@t-00

. 0000@+00

. 0000@+00

.0521®- 09

.7807®- 17

.83M«g-09

. 0000@+00

.0000@+00

. 0000@+00

. 0000@+00

.18 38®- 07

.l838@-07

PPM 

28.000

8.800 

15.000 

3.800 

3.800

28.000

123.000

0.000 

0.000 

0.000 

0.000 

0.000 

0.000 

0.000 

0.000 

0.000 

0.000

GAMMA 

0.7661*01* 

0.773797 

0.933235 

0.931957 

0.931957 

0.758515 

0-933235 

0.7661*11* 

0.567350 

0.7661*11* 

0.931957 

0.7661*11* 

0.932602 

1.000000

0.780738

MOIALITY

6.986o@-ol* 

3.6l96@-0l* 

6.52i*6@-ol* 

9. 7182©- 05

1.07l8@-0l* 

2.9il*8@-ol*

2.0158@-03 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00

WITH RESPECT TO COEXISTING SOLID PHASES

2

1

2

1

1

5

6

1

2

2

1

1

1*

3

1*

2

OF WATER WITH

EOT

.1*1*02

.9861*

.0588

 3039

.2309

.821*1*

.1)462

 1393

 3370

.7316

.3672

EH

-99

-99

-99

-99

-99

-99

-99

-99

-99

-99

-99

KT

.2310®- 02

.Oi50@+o8

.0592@+09

.0836©- 18

.6113®- 06

.0157®- 16

.9262©- 29

.1*789®- 11

 7529@+l3

.3696®- 11

.3628®- 08

.0000®- 17

.9916®- 09

.oi*io@+i5

.oo6o@-05

/i*5e2@-05

RESPECT TO

T CALC

.9000

.9000

.9000

 9000

.9000

 9000

.9000

.9000

.9000

.9000

 9000

AP/K

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

2.2395@-01

1.7807@+00

I.i688@+oo

0.0000^-00

2.951*90-03

l*.827l«g-03

COEXISTING

CR

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0 . 0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.0000@+00

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

2.

1.

1.

0.

2. 1*.

CR

0000@+00

0000@+00

0000@+00

0000@+00

0000@+00

0000@+00

0000@+00

0000@+00

0000@+00

0000@+00

2395@-oi

7807@+00

i688@+oo

0000@+00

95^9®- 03

827**®- 03

ALPHA 

5.35i+l@-0l* 

2.8008@-0l*

6.o890@-ol* 

9.0569@-05 

9. 9891®- 05

2.2109@-0l* 

l.88l2@-03 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@+00 

0.0000@K)0 

0.0000@+00

UNDERGOING HYDROLYSIS REACTIONS

MOL CAT EQ

l.l*78l«g-09

7. 6211®- 09

1.5l*6l@- 07

i.o 527®- 08

3.8o6l@- 09

0.0000@+00

0.0000@+00

1.7708@- 06

2. 0676®- 03

2. 8373®- 06

1.6l62@- 03

3.923l@-0l*

5.9769@-Ol*

2. 2832®- 01

2.361*2®- 01

1.1*1*72®- 01

PPMCATEQUIL

9-3939@-05

l*.8l*2l*@-ol*

9.82l*l@- 03

6.6887@-Ol*

2.kl8b@-0k

0.0000@+00

0.0000@+00

9. 7285®- 02

1.15^3@+02

1.581*5®- 01

3.929l*@+0l

1.572l*@+01

2-3955@+Ol

i.25l*l*@+oi*

9.1*757@+03

5-8003©+03

DEL MU

99.99999

99.99999

99.99999

99.99999

99.99999

99.99999

99.99999

99.99999

99.99999

99.99999

-0.87765

0.3381*5

0.09151

99.99999

-^.1*1617

-3-12828

SOLIDS UNDERGOING OXIDATION- REDUCTION REACTIONS

MOLCATEQUIL

5-

6.

1.

0.

i.

2.

1*.

0.

1.

2.

0.

3700@+26

71*98®- 15

1030®- 12

0000@+00

22l*6@-02

3328®- 05

5l+l*8@- 06

0000@+00

5553§+00

8515®- 18

0000@+00

PPMCATEQUIL

2.9990@+3l

3. 7696®- 10

6.l6oi@-o8

0.0000@+00

6.7275@+02

1.28l6@+00

2. 1*968®- 01

0.0000@+00

9.8822@+Ol*

1.5925®- 13

0.0000@+00

DEL MU

-99-900000

-99-900000

-99.900000

-99.900000

-99-900000

-99-900000

-99-900000

-99.900000

-99-900000

-99.900000

-99-900000

13 MN(OH3 1.81*59 -99.9000 1.1*028®-11 3.0377@K>1 1.6688@+06 -99-900000

Field Eh. pH, Feg , HCOg , S, by Clarke, USAID, and ¥., Pakistani (WASID) Scientists, March 1965; other 

chemical data by USGS Laboratories, May 1965.

U.S. GOVERNMENT PRINTING OFFICE : l»69 O 324-262