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THE URANIUM WEATHERING RATE AS AN INDICATOR

OF URANIUM MOBILITY IN CONTAMINATED SOIL

presented by

Richard A. Sturn

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M-S- degree in Geological Sciences

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THE URANIUM WEATHERING RATE As AN INDICATOR OF URANIUM
MOBILITY IN CONTAMINATED SOIL
By

Richard A. Sturn

A THESIS
Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Geological Sciences

1997

ABSTRACT

THE URANIUM WEATHERING RATE AS AN INDICATOR OF URANIUM
MOBILITY IN CONTAMINATED SOIL

By

Richard A. Stum

The goals of this study were to determine the rate of uranium weathering in contaminated
soil from the Femald Environmental Project (FEMP) site near Cincinnati Ohio and to
estimate from this rate the maximum solution-phase U concentrations expected during
typical leaching events at the site. Uranium release rates were measured in four
experiments with different soil-to-solution ratios and ﬂow rates using a mixed-ﬂow
reactor and a pH 7.4 1.67 mM CaClz inﬂuent solution. The experimental uranium
weathering rate, 0.20 i 0.01 pg U h'1 g"soil, was independent of the steady-state uranium
concentration over the range in these experiments, 0.038 to 0.235 ppm U, and applied to a
relatively small labile fraction of the total soil uranium. Qualitative calculations based on
this rate predict that the uranium concentrations of the soil solution should be about 1

ppm during leaching events, far above that typical of natural waters.

 

TABLE OF CONTENTS

LIST OF TABLES .............................................................................................................. iv
LIST OF FIGURES ............................................................................................................. v
INTRODUCTION ............................................................................................................... 1
MATERIALS AND METHODS ......................................................................................... 5
Soils ......................................................................................................................... 5
Measurement of Uranium Release Rates ................................................................. 6
Chemical Analyses .................................................................................................. 8
RESULTS ............................................................................................................................ 9
Steady-State Effluent Concentrations ...................................................................... 9
Uranium Speciation ............................................................................................... 11
Uranium Release Rates .......................................................................................... 12
DISCUSSION .................................................................................................................... 13
CONCLUSIONS ............................................................................................................... 16
APPENDIX ........................................................................................................................ 17
LIST OF REFERENCES ................................................................................................... 21

LIST OF TABLES

Table 1. Common uranium (V I) minerals and their solubility products ...................... - ........ 2
Table 2. Equilibria for some important U(VI) complexes in solution ................................. 3
Table 3. Experimental conditions for mixted-ﬂow reactor experiments. ............................ 8

Table 4. Steady-state solution compositions of the eﬁ'luent, and calculated U release rate

Table 5. Uranium Speciation and saturation state of the steady-state eﬂ'luent ................... 12
Table 6. Analytical results. ................................................................................................ 17

iv

LIST OF FIGURES

Figure 1. Schematic of the mixed-ﬂow reactor ................................................................... 7
Figure 2. Time-dependence of efﬂuent uranium concentrations. ........................................ 9

Figure 3. Time-dependence of efﬂuent solution concentrations of Ca, alkalinity and Mg..10

INTRODUCTION

Soils containing inorganic contaminants such as uranium are potential sources of
groundwater contamination. The contaminant phases present in the soil and the rate at
which they weather largely control contaminant mobility and the aqueous concentration
of the contaminant entering the shallow groundwater system. Thus, an estimate of a
contaminant's weathering rate can provide a measure of mobility that is useful for risk
assessment and remediation decisions.

Uranium-contaminated soil is a potential source of groundwater contamination at
the Femald Environmental Management Project, located approximately 30 miles
northwest of Cincinnati, Ohio. The F emald Environmental Management Project (FEMP)
was previously called the Feed Materials Production Center at Femald, Ohio, which from
1954 to 1989 produced various uranium and thorium products for the US. weapons
complex. As a consequence of the metallurgical and chemical processes that occurred at
FEMP, approximately 2,000,000 m3 of soil was contaminated with uranium. The
uranium-contaminated soil overlies approximately 50 feet of glacial till that caps a
regional buried-valley aquifer (Sminchak et. al., 1996). Though composed predominantly
of low permeability clay and silt, the till contains interconnected sand and gravel lenses
that provide potential migration pathways into this important groundwater resource
(Sminchak et. al., 1996).

Uranium, which was released through efﬂuent leaks, solid product spills, and by
deposition of airborne particulates from plant incinerators, exists mainly as discreet
uranium-rich particles rather than sorbed on clays or organic matter (Francis et al., 1993;
Lee and Marsh, 1992). X Ray absorption spectroscopy indicates that uranium is mostly
hexavalent, but large (>10 um) U(IV)-bearing phases, presumably uraninite (U02), are
also present (Bertsch et al., 1994). The following uranium-bearing phases have been

identiﬁed in FEMP soils by a combination of SEM-EDS and analytical electron
I

2

microscopy: uranyl phosphate minerals, uranyl silicates, uranium (IV) oxides
(presumably uraninite), a calcium uranium (V I) oxide, and uranium associated with
amorphous iron oxides (Buck et al. 1993, Lee and Marsh, 1992).

Many U(VI) phases are soluble in oxidizing, carbonate-rich environments such as
surface soils at FEMP (Table 1). Of the U(VI) minerals identiﬁed in FEMP soil, the
uranyl phosphate minerals are the least soluble, followed by uranyl silicates. The
solubility of U(V I) phases increases in the presence of carbonate and other oxygen-
containing ligands, which form strong complexes with the uranyl ion (Table 2). Anionic
uranyl carbonate complexes are the most abundant form of aqueous U(VI) with
concentrations typically several orders of magnitude greater than that of the free uranyl
ion. Uranyl complexes are predominately anionic, which minimizes uranyl ion sorption

by negatively charged clays and organic matter.

Table 1. Common uranium (V I) minerals and their solubility products.

 

 

 

 

 

 

 

 

 

 

 

 

Mineral Name Formula Log (K522 ‘
carnotite K2(U02)2a04)20 I -3 H20 -5 6.9
tyuyarnunite Ca(UOz)2(VO4)207-l IHzO -53.41
K-autunite K2(UOz)2(PO4)208-12H20 -48.099
autunite Ca(UOz)2(PO4)208-12H20 43.927
uranophane C3£U02)2(Si03)2(0H)2'5H20 “17-490
rutherfordite U02C03 -14.434
haweeite C3(U 02)2(8160 l 5) -6.329

schoepite UOz(OH)20HzO -4.724

soddite (U02)(Si04)02H20 -0.512

 

Solubility products for tyuyarnunite and caronite are from Langmuir (1978);
all others are from the MINTEQA2 database (U .8. EPA; CREAM 1991)

3

Table 2. Equilibria for some important U(V I) complexes in solution.

Reaction Reference
2U02 + 30H' +C03' Oz )2 Maya, 1982

1982
1992
1980
1979
1992
+CH '=U CH COO 1953
+ O + . ' 1980
+H U 0 + . ' 1980
3U +5H O + 1980

 

In contrast to the high solubility and mobility of U(VI) in carbonate-rich
environments, U(IV) minerals such as uraninite, which may persist in oxidizing
environments, are highly insoluble. At circumneutral to acidic pH, groundwater at
equilibrium with uraninite typically contains less than 0.01 ppb (Langmuir, 1979).

Since uranium exits mainly as discrete U-rich particles in FEMP soil, uranium
release will occur largely by dissolution of these U-bearing phases. If dissolution rates
and surface areas of each uranium mineral are known, a composite weathering rate could
be derived by summing the individual dissolution rates. Several workers have used this
approach for silicate minerals to model watershed response to acid deposition (Sverdrup,
1989, Sverdrup and Warfvinge 1993) and to calculate the composition of weathering
solutions (Made and Fritz, 1989, 1990). However, since this soil contains a mixture of
crystalline and noncrystalline uranium phases with a range of particle sizes, it is not

possible to measure the surface area of each phase. Also, uraninite is the only uranium

4
mineral for which an empirical dissolution rate has been determined (Grandstaﬁ‘, 1976;

Bruno et al., 1991). An alternative approach is to measure the overall uranium
weathering rate directly from a soil sample.

Mixed-ﬂow reactors, which consist of a well-stirred reaction vessel through which
solution ﬂows at a constant rate, are suitable for measuring the net rate of uranium release
from FEMP soil. They have been used to measure the dissolution kinetics of silicate
minerals (Chou and Wollast, 1985; Mast and Drever 1987; Dove and Crerar, 1990), of
uranium oxides (Bruno et al., 1991), and of mineral mixtures (Swoboda-Colberge and
Drever, 1993). The primary advantage of mixed-ﬂow reactors over batch systems is that
they allow calculation of reaction rates directly from the steady-state mass balance
condition of the eﬁluent rather than ﬁtting concentration vs. time data to an assumed rate
law (Dove and Crerar, 1990). The steady-state mass balance condition for the uranium

concentration of the effluent is

[UlssQ/M = [UIInQ/M + R (1)

where Q is the solution ﬂux through the system (gm.l1 h"); M is the soil mass contained in
the reaction vessel (gson); [U]ss and [U];n are the steady-state and inﬂuent uranium
concentrations (pg U g"so.n), and R is the uranium release rate (pg U g'lson h").

The goals of this study are to determine the rate of uranium weathering in
contaminated soil at F EMP and to estimate from this rate uranium mobility in FEMP soil.

The uranium weathering rate is measured from a soil sample with a mixed-ﬂow reactor.

5
In this study, all uranium phases are regarded collectively as a bulk soil property. Thus, it

is not necessary to estimate surface areas of each U-bearing solid phase.

MATERIALS AND METHODS
Soils

The soil used in this study was a homogenized mixture of highly contaminated
(>1200 pg U g") soil from the incinerator area at FEMP and uncontaminated background
soil. The total soil uranium concentration of < 2-mm diluted soil (hereaﬁer "soil”)
determined by microwave digestion/ICP-MS (465 i 12 pg U g") and by gamma
spectroscopy (475 i 55 pg U g") were very close to the average soil U concentration (500
pg U g") of soils at the FEMP site (Francis et al., 1993).

The soil contained 2.3 i 0.1 % CaCO3, 1.7 :t 0.1 % organic carbon, 16 i l g Feocg
kg", and 1.9 i 0.1 g A1DCB kg" [DCB = extractable by dithionite-citrate-bicarbonate
(Jackson et al., 1986)]. Mineralogical and grain size analyses were not performed
speciﬁcally for this soil, but these characteristics are known for FEMP soils in general
(Elless et al., 1993). Soils at FEMP are ﬁne-grained (275% silt and clay). Quartz is the
most abundant mineral on a per-mass basis with lesser amounts of calcite, dolomite, and,
in the clay fraction, kaolinite, illite, vermiculite, and chlorite. Carbonate gravels, which
were added to the soils during construction and erosion-control activities prior to 1989,

constitute 20% to 30% of the total mass of surface soils at the site.

Measurement of Uranium Release Rates

The rate of uranium release from F EMP soils was determined using a mixed-ﬂow
reactor (Figure. 1). Depending on the experiment, 125-mL or 50-mL Erlenmeyer ﬂasks
were used as the reaction vessel. A variable-speed, multi—channel, peristaltic pump was
used to maintain a constant solution ﬂux in and out of the reaction vessel. The soil was
kept in suspension with a magnetic stir bar. Because most mixed-ﬂow reactors are
designed for material with grain-sizes much coarser than FEMP soils, the major design
challenge in these experiments was to keep the ﬁne silt and clay in the reactor. The best
approach was to use a stainless steel, 2-pm-pore-size HPLC pumpcinlet ﬁlter to ﬁlter the
efﬂuent solution. The ﬁlter was connected to the output line and submerged in the
reaction vessel. Eﬁluent solutions drawn through the ﬁlter contained no visible clay,
though they could have contained <2-pm colloids.

Four uranium weathering experiments with different ﬂow rates and soil-to-
solution ratios (Table 3) were performed to determine the uranium weathering rate of the
soil as a function of effluent uranium concentration. The feed solution for all
experiments was a pH 7.4 solution of 1.67 mM CaClz. For each experiment, the desired
soil and solution masses were added to the reaction vessel. The feed solution was then
continuously pumped through the reactor. Experiments lasted 50 to 120 h. A 10 to 30-
mL sample of efﬂuent was collected at least once every four residence times. Steady-

state uranium concentrations were determined by plotting the uranium concentration of

 

 

 

feed solution

 

 

 

 

 

 

C II ) 4,
peristaltic pump ‘
J I! . I. f
- , r.»

 

outflow

 

 

 

reaction vessel and stir plate

Figure 1. Schematic diagram of the mixed-ﬂow reactor.

Table 3. Experimental conditions for mixed-ﬂow reactor experiments.

 

 

 

 

 

 

Soil Mass Solution Mass Flow Rate Q/M Residence Time
8 g g If1 gsotn 1‘" 345061 11
10.40 104 .00 9.46 0.90 1 1.0
4.94 47.32 6.60 1.32 7.2
5.00 50.41 10.30 2.06 4.9
4.90 100.01 23.23 4.73 4.3

 

 

the efﬂuent as a function of residence time and averaging the U concentrations of samples
from the plateau region of the graph (see Figure 2). Uranium release rates for each
experiment were calculated from the steady—state uranium concentration using Eq. 1.

Chemical Analyses

The uranium concentration of each efﬂuent sample was determined by ICP-MS.
For ICP-MS analysis of uranium, samples were diluted in 1% HN03 and spiked with
20S’Bi as an internal standard. The pH, alkalinity and major cation concentrations of
effluent solutions were also determined to verify that the solution composition was
similar in all experiments. Solution pH was measured with a semi-micro glass
combination electrode. Alkalinity was measured by acid titration. The concentrations of
Ca and Mg in selected samples were measured by atomic absorption spectroscopy, Na by
atomic emission spectroscopy, and Fe, Al, and Si by directly coupled plasma-atomic

emission spectroscopy.

RESULTS

Steady-State Effluent Concentrations

The uranium concentration of the reactor efﬂuents increased rapidly to a

maximum value and then decreased to steady-state, with the greatest peak concentrations
in the experiments with the lowest Q/M values (Figure 2) and longest residence tirrIes.
For the lowest Q/M, about 3% of the total soil U was released during the 8 residence
times prior to steady state, whereas much less than 1% of soil U was released prior to

steady state at the highest Q/M. The steady-state concentrations ranged from 0.038 to

0.235 pg U g'l (Table 4) and generally decreased with Q/M (gm... h‘I gl ,0" ).

 

0.8 -'
0.7 -’

0.6 -«

ppm U

0.0 -

0.5 -.
0.4 -»
0.3 -'
02 -’
0.1 4'

 

 

 

Figure 2. Time-dependence of effluent uranium concentrations.

Residence Times

cm -0.00
am - 132
x cm .200
+005 «.73

10

Calcium

w-s
”—
70-
004 x
50...
40—1
30....
20—
10-
o—

 

an
t
0
1H8
3

ppm Ca

 

 

 

I
0 10 20

Residence Times

Magnesium

 

8 —
O
7 “ O
6 -‘ O
5 'i go X Q/M: 091)
a: Q/M-‘ 1.32

3_ + £ + Q.’M=2.06
0 o Q/va;

ppmMo

 

 

 

o-
.a
O
8

Residence Times

Alkalinity
go ..

 

70-0”

eo-i 4?.

350+ u x

840- or it xx
++max4+§nxxn x
m—

8,0-

10-4

 

 

0

 

I
0 10 20

Residence Times

Figure 3. Time-dependence of efﬂuent solution concentrations of Ca, alkalinity, and Mg.

The time-dependence of alkalinity, Ca, and Mg in efﬂuent solutions is shown in

Figure 3; steady-state concentrations are summarized in Table 4. Efﬂuent pH in all four

experiments attained a steady-state value of 7.8 within two residence times (not shown).

Alkalinity attained steady-state (36 mg HCO3 L") prior to or at approximately the same

time as uranium. The steady-state concentrations of Ca approached those of the input

solution within a few residence times. The efﬂuent Mg concentrations were initially high

but than decreased to steady-state values (near 1 ppm Mg) after 8 to 10 residence times,

similar to the time-dependence of U concentrations. Silica concentrations were measured

only for the experiment with Q/M of 1.32, which had a steady-state silica concentration of

approximately 12 ppm (Appendix 1). Iron and aluminum were below detection limits for

all samples, as expected for the high solution pH.

Table 4. Steady-state efﬂuent solution compositions, and calculated U release rate (R).

 

 

 

 

 

 

 

Q/M U pH Alkalinity Na Ca Mg R
ggm h" g" .on) (ppm) (iLHCOs'U') (ppm) (ppm) (ppm) his U 0'2".”-
0.90 0.235 7.8 36.6 8 76.3 1.5 0.21
1.32 0.155 7.8 36.6 7 69 0.9 0.20
2.06 0.106 7.8 36.6 7.5 65.6 0.7 0.21
4.73 0.038 7.8 36.6 6.6 64.7 0.7 0.18

 

 

Uranium Speciation

Geochemical modeling results indicate that in all experiments the steady-state

effluent was undersaturated with respect to common uranyl oxides, hydroxides, and

rutherfordite, UOzCO3, and that >99% of the total dissolved uranium was uranyl

12
carbonate complexes (Table 5). Modeling results for the experiment with Q/M =

show that efﬂuent was also undersaturated with respect to uranophane,

1.32

Ca(UOz)2(SiOgOH)2, (Log IAP/K,p =-3.89) and that aqueous concentration of U-silica

complexes (2x10 "5 M kg") was a minor portion of the total dissolved uranium. The

saturation state of the effluent with respect to uranyl phosphate minerals was also

investigated by assuming a total dissolved phosphate concentration of 0.1 ppm P04. In

all cases the steady-state efﬂuent was undersaturated with respect to autunite (Log

IAP/Ksp decreased from-3.98 to -6.48 with increasing Q/M), other autunite group

minerals, and (U02)2(PO4)2. Thus, it is likely that the solution residence times in

these

experiments were suﬁiciently rapid to ensure that the efﬂuent remained undersaturated

with respect to pure, crystalline uranium minerals in FEMP soil.

Table 5. Uranium Speciation and saturation state of the steady-state efﬂuent.

 

 

 

 

 

Q/M % U [U022Im] log log log log log

(gnu. h’| bound M kg'l lAP/Ksp lAP/Ksp IAP/Ksp lAP/Ksp IAP/Ksp
g" rail) to C03 UO,(OH)2 Jummite rutherfordite U03 schoepite
0.90 99.8 3.5mml2 -l .53 -6.39 -293 -3.70 4.39
1.32 99.9 2.2mm"2 -1.72 -6.58 -3.16 -3.87 -l .58
2.06 99.9 1.4mm"2 -1.90 -6.76 -3.30 -4.08 -l .77
4.73 99.9 5.53x10'” -221 -751 -374 .451 -221

 

 

the solution compositions listed in Table 4.

Uranium Release Rates

Saturation indices were calculated with MINTEQA2 V. 3.10 (CREM, US EPA 1990) at

Since the pH, alkalinity and the concentrations of the major cations were nearly

identical in all experiments, the net uranium release rate of the soil for each experiment

 

13
can be compared as a function of [U]ss, independent of these other solution parameters.

Although the steady-state uranium concentration of these experiments varies by a factor
of~ 6, from 0.038 to 0.235 ttg U g", the uranium release rates calculated with Eq. 1 for
each Q/M are independent of uranium concentration (Table 2). The average net
experimental uranium weathering rate in FEMP soil at the solution composition these

experiments (R) is 0.20 a .01 pg U h" g" ,0...

DISCUSSION

The soil used in this study had a total uranium concentration near 470 pg U g ",0“,
which is comparable to the average soil U concentration at F EMP. Thus, although the
soil was a mixture of contaminated soil and uncontaminated soil, the results of this study
should be applicable to the FEMP site. The fraction of total soil uranium released during
these experiments, 8%, 4% 6%, 2% in order of decreasing Q/M, consisted of a labile
fraction of the total soil uranium. The high uranium concentrations during the period
prior to steady-state may be due mainly to rapid dissolution of very ﬁne grained and/or
amorphous uranium phases, possibly uranyl carbonates, oxides, and/or hydroxides. Once
these dissolved, the efﬂuent uranium concentration decreased to a steady state value
controlled by a less reactive uranium phase(s). However, the uranium concentration
decreased slightly after an initial steady state period in two of the experiments (Q/M of

2.06 and 4.73), indicating that U phase(s) controlling [U]ss had dissolved completely.

14

Thus, it is likely that a new steady-state concentration corresponding to a more inert
uranium mineral(s) would have been obtained for all Q/M values if the experiments had
lasted longer. The uranium weathering rate measured here applies to a relatively small
labile fraction of the total soil uranium rather than the bulk of U contamination.

Laboratory-derived weathering rates typically are one to three orders of magnitude
greater than mineral weathering rates derived from elemental mass balances of
watersheds because all the mineral surface area interacts with the inﬂuent solution in the
mixed ﬂow reactor, whereas only a small portion of the mineral surface area interacts
directly with adjective water in the soil proﬁle (V elbel 1993, Swoboda-Colberge and
Drever, 1993). Thus, to correct for partial soil-solution contact in the soil proﬁle, it is
reasonable to assume that 10% of the soil interacts directly with advective water. Thus,
the uranium weathering rate in the ﬁeld should be about 10% that measured in the mixed-
ﬂow reactor, or 0.02 pg U h'l g'I so“,

Uranium contamination at F EMP mainly occurs in the upper 10-15 cm of the soil
proﬁle and leaches from this upper layer to the underlying soil horizons and ultimately to
groundwater. Assuming saturated or nearly saturated conditions during main leaching
events, the time-dependent uranium concentration of the soil solution during leaching,

[U]L, can be calculated from the following expression:

[U]t = 0.1Rt0,‘l (2)

where the factor of 0.1 corrects the laboratory-derived weathering rate R for partial soil-

solution contact in the ﬁeld, [U]. represents pg U g",ot.mon aﬁer 1 hours of soil-solution

15
contact, and 08 is the gravimetric water content of the soil, g H20 g ",0". The

concentrations predicted by Equation 2 are considered maximum estimates because it
does not account for many of the complex chemical and physical processes meaning in
the soil proﬁle. Saturation water content for FEMP soil is about 0.38 g H20 g",on. The
hydraulic conductivity as a function of water content is unknown for these soils, but a
range from 0.5 to 2 cm hr'l is a reasonable estimate for near-saturated conditions.
Assuming piston ﬂow, the corresponding solution residence time in the upper 10 cm of
the proﬁle is 5 to 20 hr. Assuming that the solution pH and alkalinity the ﬁeld are similar
to those in the efﬂuent solutions from the mixed-ﬂow reactors, and that the U weathering
rate is independent of U concentration as it was in the mixed-ﬂow reactors, the uranium
concentration in the soil solution will range from 0.26 to 1.1 ppm U, which corresponds
to much less than 1% of soil U. If the factor of 0.1 is not used to correct for the fact that
bulk water contacts only a fraction of the soil, then the U concentration of the soil
solution will range from 2.6 to 11 ppm U. Although it is not known whether the
experimental weathering rate is valid at total dissolved uranium concentrations greater
than 0.235 ppm, ), the free [U022+] will remain very low at high total dissolved [U]
because of the relatively high alkalinity of the soil solution (Table 4), so the U weathering
rate is likely valid at high total dissolved [U]. The uranium concentrations predicted by
this model are similar to uranium concentrations of shallow groundwater (1 to 12 ppm U)
measured at FEMP, (Cunnane, 1995), even though the simple model used here greatly

oversirnpliﬁes the complex chemical and hydraulic process that occur in the ﬁeld.

16

CONCLUSIONS

The experimental uranium weathering rate, which applies to a relatively small
labile fraction of the total soil uranium, was 0.20 a: 0.01 pg U h" 84.0“ and was
independent of steady-state uranium concentration. Simple qualitative calculations based
on this rate predict that the uranium concentrations of the soil solution are at ppm levels
during leaching events. These results indicate FEMP soil contains a relatively labile and
therefore mobile fraction of soil uranium that is capable of producing soil solutions with
uranium concentrations far above those of typical natural waters, 0.01 ppm U (Langmuir,
1979)

APPENDIX

17

APPENDIX

ANALYTICAL RESULTS

Table 6. Analtical results

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Q/M=O.90”2
TIME U Ca Mg Na K pH Alkalinity
(H) (ppb) (ppm) (ppm) (ppm) (ppm) (mchoa'L")
3.28 82 90.3 7.5 13.3 2.0 7.9 73.3
6.91. 630 87.8 6.9 14.1 nd 7.9 nd
12.8 709 nd 6.3 nd nd 7.9 nd
17.55 736 nd 5.5 nd nd 7.8 nd
18.65 662 73.4 4.7 19.8 0.9 7.8 61.9
26.05 604 nd 4.5 nd 0.5 7.8 nd
31.58 432 nd 2.9 nd nd 7.8 nd
36.70 404 nd 2.8 nd nd 7.8 42.7
51.75 416 nd 2.6 nd nd 7.8 nd
67.70 328 79.8 2 8.5 0.5 7.8 nd
72.70 291 nd 1 .9 nd nd 7.8 nd
82.46 233 77.3 1.7 8.5 nd 7.8 36.6
89.91 236 75.3 1.3 7.5 nd 7.8 36.6

 

 

ppb.

nd = not determined

Iron and aluminum concentrations in all experiemtns were below the detection limit, ~ 8

 

Table 6 (con'td).

/M=1.32

 

TIME U Ca Mg Si Na K pH Alkalinity

 

 

 

 

 

 

 

 

 

(H) (ppm) (ppm) (ppm) (ppm) (9me (ppm) (mgHCOa'L")
11.5 253 81.8 4.9 3.9 6.6 0.4 7.9 61.0
22.5 278 79.3 3.1 3.0 6.6 nd 7.9 54.9
28.48 284 66.5 2.6 19.0 7.5 0.9 7.8 48.8
46.63 227 nd 1.7 15.0 ad nd 7.8 42.7
52.43 200 nd ad ' nd nd nd 7.8 36.6
58.10 159 67.0 1.2 19.9 7.5 0.2 7.8 36.6
69.06 178 nd 1.2 ad 7.5 ad 7.8 36.6
92.55 157 ad 0.9 12.7 6.6 0.9 7.8 36.6
102.4 157 ad 0.9 12.8 6.6 ad 7.8 36.6

 

 

118.2 148 71.4 0.8 12.0 nd 0.9 7.8 36.6

 

 

Table 6 (con'td).

l9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

QIM=2.06

TIME U Ca Mg Na K pH Alkalinity
(H) (ppb) (ppm) (ppm) (ppm) (ppm) (mchoa‘U)
7.25 250 78.3 5.3 7.5 nd 7.8 67.1
16.00 263 nd 3.3 nd 0.2 7.8 54.9
19.31 231 63.8 2.2 7.5 1.4 7.8 42.7
28.28 187 nd 1.3 nd 110 7.8 48.8
41.50 148 71.4 1.14 5.6 2.1 7.8 42.7
46.43 137 nd 1.0 110 nd 7.8 42.7
49.86 130 67.1 1.0 6.5 2.4 7.8 36.6
67.59 110 61.9 0.8 7.5 2.9 7.8 36.6
71.44 103 nd 0.7 nd 110 7.8 36.6
74.98 100 68.0 0.7 7.5 nd 7.8 36.6
79.12 98 nd 0.7 nd nd 7.8 36.6
93.31 67 62.4 0.5 6.5 nd 7.8 36.6

 

 

20

Table 6 (con'td).

 

 

 

 

 

 

 

 

 

 

/M = 4.73

TIME U Ca Mg Na K pH Alkalinity

(H) (PPb) (ppm) (PPm) (ppm) (ppm) (mgHCOa’ L4)
4.77 76 72.9 3.6 nd 2.0 7.9 54.9
15.88 55 72.4 1.6 6.6 1.4 7.9 42.7
19.72 52 68.1 1.2 6.6 nd 7.8 36.6
23.63 41 64.8 1.2 6.6 0.6 7.8 36.6
30.67 39 nd 0.9 11d 0.5 7.8 36.6
36.05 39 64.2 0.7 6.6 110 7.8 36.6
49.60 34 65.2 0.6 6.6 0.3 7.8 36.6

51.3 28 68.1 0.6 6.6 nd 7.8 36.6

 

 

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