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Measurement of Groundwater and Contaminant Flux in Fractured Rock Media with a Passive Flux Meter: An Evaluation of Sorptive Materials with Alcohol Tracers

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Title:
Measurement of Groundwater and Contaminant Flux in Fractured Rock Media with a Passive Flux Meter: An Evaluation of Sorptive Materials with Alcohol Tracers
Series Title:
Journal of Undergraduate Research
Creator:
Ishii, Stephanie
Newman, Mark
Place of Publication:
Gainesville, Fla.
Publisher:
University of Florida
Publication Date:
Language:
English

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Subjects / Keywords:
Journal of Undergraduate Research
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serial ( sobekcm )

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Abstract:
Groundwater hydrologists must accurately estimate water and contaminant fluxes in aquifers in order to predict risk, regulation compliance, and contaminant attenuation. A new direct method for the simultaneous measurement of cumulative groundwater and contaminant flux in fractured rock aquifers through the use of a fractured rock passive flux meter (FRPFM) is under development. This paper identifies a sorptive material and a range of resident alcohol tracers that can be used in combination as part of the FRPFM to quantify the aforementioned fluxes. When exposed to groundwater flow, the resident alcohol tracers are eluted from the fabric at rates relative to the magnitude of the groundwater flux. In order to quantify the groundwater flux based on the removal of tracers, the partition coefficient for each tracer between water and the sorptive material must be known. This paper presents sorption isotherm curves from several laboratory experiments. These curves contribute to the determination of the final partition coefficient, KD, for each tracer when exposed to water and the selected sorptive material AC Felt 1300.

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Measurement of Groundwater and Contaminant Flux in Fractured

Rock Media with a Passive Flux Meter: An Evaluation of Sorptive

Materials with Alcohol Tracers


Stephanie Ishii


College of Engineering, University of Florida


Groundwater hydrologists must accurately estimate water and contaminant fluxes in aquifers in order to predict risk, regulation
compliance, and contaminant attenuation. A new direct method for the simultaneous measurement of cumulative groundwater and
contaminant flux in fractured rock aquifers through the use of a fractured rock passive flux meter (FRPFM) is under development.
This paper identifies a sorptive material and a range of resident alcohol tracers that can be used in combination as part of the FRPFM
to quantify the aforementioned fluxes. When exposed to groundwater flow, the resident alcohol tracers are eluted from the fabric at
rates relative to the magnitude of the groundwater flux. In order to quantify the groundwater flux based on the removal of tracers, the
partition coefficient for each tracer between water and the sorptive material must be known. This paper presents sorption isotherm
curves from several laboratory experiments. These curves contribute to the determination of the final partition coefficient, KD, for each
tracer when exposed to water and the selected sorptive material AC Felt 1300.


Introduction

Groundwater is withdrawn from aquifers for municipal,
agricultural, and industrial purposes. Eventually,
groundwater becomes naturally incorporated in surface
water due to discharge at locations such as springs and
seeps. Should this groundwater become contaminated, it
poses a threat to human and environmental health via direct
consumption and indirect pathl\ a s such as vapor intrusion
[1].
Because groundwater is ubiquitous, it is therefore
necessary for groundwater hydrologists to accurately
estimate water and contaminant fluxes in aquifers. Truthful
measurements of water and contaminant mass fluxes are of
great significance due to the fact that they lend themselves
to the prediction of risk, regulation compliance, and
contaminant attenuation. Despite the importance of these
measurements, accurate estimations of subsurface
contaminant mass flows are difficult. Many methodologies
represent short-term evaluations that reflect aquifer
conditions at one instant in time and not long-term trends.
These measurements do not account for variability in
concentrations and flow rates over a period of time [2].
In response to this dilemma, the passive flux meter
(PFM) was introduced. This new method is a simultaneous
direct in situ point measurement of time-averaged water
and contaminant fluxes in porous media [3]. However, the
hydrology of a porous media aquifer is extremely different
than that of a fractured rock aquifer. Hence, the latter
remains a field in which minimal research has been
published. This research contributes to the expansion of the
PFM from porous media to fractured rock aquifers.


The Passive Flux Meter
As used in porous media, the PFM is a self-contained
permeable cylinder that is inserted into a well or boring.
The meter can remain in the ground for a time period
ranging from days to months. While in the borehole, the
meter passively intercepts groundwater flow without
retaining it. As shown in Figure 1, the groundwater flow
first comes into contact with a thin, non-reactive layer of
permeable material that functions as a boundary layer.
After passing the external layer, the water is intercepted by
packed granular activated carbon. The granular activated
carbon serves two purposes: to retain various organic
contaminants from the groundwater flowing through the
meter and to release non-toxic 'resident tracers' at rates
proportional to the amount of water flowing through the
meter. The resident tracers are known amounts of various
alcohols that the granular activated carbon is pretreated
with prior to deployment. Each tracer is water soluble, but
to a different degree. The short-chain alcohols have a
stronger tendency to exist in the aqueous phase, and thus
are released first when exposed to water flow. The long-
chain alcohols are more strongly sorbed to the granular
activated carbon and require a larger amount of
groundwater flow to be released [4].
Once the period of deployment is complete, the meters
are carefully removed from the ground and the granular
activated carbon is placed in an extraction solution to
quantify the remaining amount of each tracer. Then a
secondary extraction is performed to quantify the
intercepted contaminants. Contaminant mass is used to
determine the cumulative contaminant flux during the
given time period, and the residual resident tracer mass is


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010





STEPHANIE ISHII


Groundwater
Flow
_ Direction
*-*------*
w


r L

I
Permeable i
Flux Meter
Sorbent
Boundary
sy


Figure 1: Cross-sectional illustration of a passive flux meter
(PFM) of radius r [3]

used to determine the cumulative water flux based on
predetermined sorption and desorption behavior [3].

Fractured Rock Passive Flux Meter
Although this new technology has already confirmed
its worth in porous media, the hydrology of a fractured
rock aquifer is decidedly more complex. Unlike in porous
media, the groundwater flow is highly heterogeneous [2].
These complex hydrogeologic conditions result in difficult
characterization of groundwater flow and contamination;
however, these measurements are essential to evaluating
contaminant risk, regulation compliance, and attenuation.
With some modification, the porous media PFM may
be able to be extended to fractured rock. The ability to
obtain cumulative fluxes in fractured rock aquifers under
ambient closed-hole conditions would accomplish
estimating contaminant mass discharge from source zones
with much greater ease. In turn, assessment of long-term
risk, evaluation of remedial performance, and regulatory
compliance could be done with an increased level of
accuracy and promptness. Significant cost savings can be
realized with a cumulative measurement by eliminating the
need to take numerous concentration samples over time
and recognizing when a fractured rock site poses little off-
site risk due to its own natural attenuation [2].
This paper addresses one modification to the original
PFM. In lieu of the loose granular activated carbon, an
activated carbon impregnated fabric will be used. The
fabric will be designed such that it intercepts contaminants
as groundwater flow passes through it and releases the
alcohol tracers it has been pre-saturated with at rates
proportional to groundwater flow. The purpose of this
paper is to evaluate the feasibility of various sorptive
fabrics and tracers that could be used in combination to
measure water flux at sites consisting of fractured rock


media. In order to realize this objective, a relationship
regarding sorptive capacity must be established between
the fabric and its tracers. This relationship is given by the
partition coefficient, KD. Equations describing the
correlation between the partition coefficient, residual tracer
amounts, and their corresponding groundwater flux are
given elsewhere [2], [3].

Definition of Flux
For the purposes of this paper, flux shall be defined as
the flow rate per unit area. Thus, a mass flux would have SI
units ofkg/(m2s) [5].

Materials & Methodology

The primary objective is to determine a sorptive media
that may be used in combination with a range of alcohol
tracers to indicate the magnitude and direction of
groundwater flow in a given fracture. This fabric, when
pretreated with the alcohol tracers and exposed to
groundwater flow, should gradually elute the tracers from
itself. The rate at which elution occurs for each tracer is
dependent upon the magnitude of the groundwater flow.
Once the meter is removed from the ground, a residual
tracer distribution can be generated, as shown in Figure 2.


Uniformly
Distributed
/ Tracers


Tracers have been
washed away

SZ


-------o
qTr s


Tracers Remaining


Figure 2: A cross-sectional illustration of the residual tracer
distribution on the sorptive material after being exposed to
groundwater flow qo. The cross-section is for the case of a
perpendicular intersection of borehole and fracture plane [2].

Activated Carbon Impregnated Fabrics
The first materials to be identified for this study were
an assortment of possible activated carbon impregnated
fabrics. Nine different fabrics, as shown in Figure 3, were
collected as possible sorptive materials.
The fabrics were separated into two main categories:
activated carbon (AC) felt and cloth. The fabrics char-
acterized as AC felts are thicker (thicknesses were approx-
imately 3mm) and have more structural integrity, while the
cloths are thin and very flexible. Some of the clothes (BET
1000, BET 1300, and BET 1500) were thin enough for
light to shine through. Table 1 presents the commercial
name for each fabric as well as the labels that are used to
refer to each fabric for the remainder of this paper.


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010





MEASUREMENT OF GROUNDWATER AND CONTAMINANT FLUX IN FRACTURED ROCK MEDIA WITH A PASSIVE FLUX METER


AC FELT


CLOTH


Figure 3: Nine activated carbon impregnated fabrics chosen for
testing and separated into activated carbon (AC) felt and cloth
categories. Fabrics characterized as felts are thicker and have
more structural integrity.


Resident Alcohol Tracers
In order to choose appropriate tracers for the PFM, the
octanol-water partition coefficients and carbon chain
lengths of several alcohols were analyzed. The tendency
for a tracer to remain sorbed to a fabric increases with both
the chain length and the octanol-water partition coefficient,
Kow. The Kow value is the ratio of a chemical's
concentration in octanol and in water at equilibrium and at
a constant temperature [6]. Hence, a low Kow value denotes
a chemical's increased tendency to exist in the aqueous
phase. These values must differ for each tracer so that each
tracer has a different affinity for water and is therefore
released from the fabric at various rates. These various
rates can then be used as an indication of the magnitude of
groundwater flow passing through the fabric. For example,
a strong flux of groundwater may result in the removal of
2-butanol, 1-butanol, 3-pentanol, and 1-pentanol, while a
weak flux of groundwater may only result in the partial
removal of 2-butanol; 1-heptanol, which has the highest
sorption affinity, will exhibit the lowest rate of elution.
Table 2 displays the Kow values for the range of alcohol
tracers used as well as their molecular weight as an
indicator of chain length.


Table 1: The commercial names of the nine activated carbon
impregnated fabrics chosen for testing. The labels given for each
fabric are used throughout this paper in lieu of their commercial
name.

Fabric Type Commercial Name Label
AC Felt AmeriAsia BET AC Felt 1000
1000 felt
AC Felt AmeriAsia BET AC Felt 1300
1300 felt
AC Felt AmeriAsia BET AC Felt 1500
1500 felt
AC Felt Polyorgs Activated Polyorgs
Carbon Fabric
Cloth Calgon Carbon FM 10
Zorflex cloth
FM 10
Cloth Calgon Carbon FM 100
Zorflex cloth
FM 100
Cloth AmeriAsia MY- BET 1000
QW-011, BET
1000 cloth
Cloth AmeriAsia MY- BET 1300
QW-013, BET
1300 cloth
Cloth AmeriAsia MY- BET 1500
QW-015, BET
1500 cloth

Table 2: Alcohols used as resident tracers with their
corresponding octanol-water partition coefficients and molecular
weights. Increasing property values indicate increasing
tendencies to sorb and remain sorbed to the fabric.

Chemical CAS Log( Kow) Molecular
Name Number Weights
2-butanol 78-92-2 0.6 74.1
1-butanol 71-36-3 0.9 74.1
3-pentanol 584-02-1 1.21 88.2
1-pentanol 71-41-0 1.40 88.2
1-hexanol 111-27-3 2.03 102.2
2,4- dimethyl- 600-36-2 2.31 116.203
3-pentanol
(DMP)
1-heptanol 111-70-6 2.34-2.62 116.2


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010
3





STEPHANIE ISHII


Preliminary Tests
As a preliminary test, eight of the nine fabrics were
tested for usability. BET 1500 was automatically
eliminated based on its thinness. Sorption isotherm curves,
as described later in this paper and elsewhere [7], were
generated for each fabric. Alcohol tracer solution was
prepared consisting of tracer concentrations ranging from
800ppm (2-butanol) to 600ppm (1-heptanol), which was
used to treat incrementally increasing amounts of fabric
(varying number of square centimeter pieces), as shown in
Figure 4. Based on these results, the nine fabrics were
reduced to three: Polyorgs, FM 100, and AC Felt 1300.


Figure 4: Varying amounts of activated carbon fabrics (square
centimeter pieces) being treated with constant concentrations of
alcohol tracers for the first preliminary test.

These three fabrics were tested in a similar fashion, but
in lieu of varying amounts of fabric, each vial contained a
constant amount of fabric and various dilutions of the
alcohol tracer solution. The original solution included
tracer concentrations ranging from 150ppm (2-butanol) to
1000ppm (1-heptanol). Dilutions ranged from 100%
original alcohol tracer solution to 5% tracer solution with
95% water. From these results, AC Felt 1300 was deemed
the most viable.

Tests for Felt 1300
For the previous batch test concerning AC Felt 1300,
Polyorgs, and FM 100, in which AC Felt 1300 was deemed
the most plausible, a tracer mixture was made according to
the measurements presented in the second column of Table
3. Each tracer was individually pipetted into one glass
bottle. Once all tracers had been deposited, the glass bottle
was tightly sealed with a screw cap and Teflon septum.
The mixture was allowed to equilibrate for 45 minutes to
an hour while being shaken every ten minutes. After all the
tracers had been thoroughly combined, 4.4mL of tracer
mixture and a magnetic stir bar were added to 1L of water


in a 1L volumetric flask to obtain the concentrations
presented in column 3 of Table 3. A glass stopper was
placed into the flask and wrapped with Teflon tape in order
to ensure minimal volatilization of tracers. The solution
was placed on a stir plate and allowed to mix until all
alcohol ganglia had disappeared and the tracers were
thoroughly dissolved.

Table 3: Tracers and their corresponding volumetric contribution
to the pure alcohol mixture and their final concentration in the
tracer solution, which consisted of the mixture and water.

Volumetric Concentration in
Contribution to
Alcohol Tracer r Tracer Solution
Tracer Mixture
(mL) (ppm)
2-butanol 1.3 150
1-butanol 1.8 200
3-pentanol 1.8 200
1-pentanol 3.1 350
1-hexanol 7.0 800
2,4-DMP 7.0 800
1-heptanol 8.8 1000
Total 30.8 3500

Ten 40mL Environmental Protection Agency (EPA)
glass vials with plastic caps and Teflon septa were labeled
and their empty weights recorded. AC Felt 1300 was cut
into one square centimeter pieces, six of which were placed
into each vial; the weights were again recorded to deduce
the exact weight of fabric in each vial. Specific amounts of
water were then transferred into each vial with a
volumetric pipette according to the vial's corresponding
dilution factor. After the water had been added, the
remaining fraction of the 40mL volume was filled with
alcohol solution via volumetric pipette. Water was first
pipetted into each vial to avoid volatilization of alcohol
tracers. Table 4 provides the dilution information for each
vial. Once filled with water and solution, the vial weights
were recorded.
The vials were then placed on a rotator (see Figure 5)
set at 20rpm for 48 hours to fully expose all areas of the
fabric to the alcohol tracers. After the rotation period, the
vials were removed from the rotator and allowed to settle
for 24 hours. It is important to note that during this time,
the vials were not refrigerated, as sorption behavior is
heavily influenced by changes in temperature [8]. Samples
of the resulting aqueous solution were transferred into 2mL
auto sample vials with disposable glass pipettes for
analysis using a gas chromatograph (GC). The GC
analyzed the samples for the remaining concentration of
tracers in the aqueous solution. Due to conservation of
mass, the difference between the original concentration and
the remaining concentration for each tracer was assumed to
have sorbed onto the AC Felt 1300.


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 | Spring 2010





MEASUREMENT OF GROUNDWATER AND CONTAMINANT FLUX IN FRACTURED ROCK MEDIA WITH A PASSIVE FLUX METER


Table 4: The volume of water and alcohol solution in each vial
depending on its designated dilution. Vials included 0%, 20%,
40%, 60%, 70%, 80%, 90%, and 95% dilutions.

Vial # Water Volume (mL) Solution Volume (mL)
1 0 40
2 8 32
3 16 24
4 16 24
5 24 16
6 28 12
7 28 12
8 32 8
9 36 4
10 38 2


Table 5: Tracers and their corresponding volumetric contribution
to the pure alcohol mixture and their final concentration in the
tracer solution for the first batch experiment concerning AC Felt
1300 only.

Volumetric
Volume Concentration
Contribution to
in Tracer
Alcohol Tracer Tracer Mixture
(mL) Solution (ppm)
(mL)
2-butanol 5.0 125
1-butanol 5.0 125
3-pentanol 5.0 125
1-pentanol 8.3 200
1-hexanol 25.0 620
2,4-DMP 25.0 620
1-heptanol 33.3 830
Total 106.6 2645


Figure 5: 40mL EPA glass vials on the rotator to ensure
complete exposure of fabric to the alcohol tracers.


AC Felt was selected as the best option after analyzing
the results from this batch experiment with three fabrics,
and a batch experiment with just AC Felt 1300 ensued with
two modifications. Initial alcohol tracer concentrations
were reduced, and the felt was cut into 2cm x 6cm strips
instead of the square centimeter pieces; then two strips
were deposited into each vial. One consecutive piece of
fabric more closely mimics field conditions by reducing
layering of fabric and the length of exposed edges. Similar
to Table 3, the new tracer mixture and solution recipes are
given in Table 5. At first glance, these concentrations may
not seem significantly reduced, but it is important to note
that the first batch test was done with a total of 6cm2 of


fabric per vial while the second batch test was done with
12cm2 of fabric per vial. Save these two modifications, the
methodology for the first batch test using only AC Felt
1300 was identical to the methodology utilized during the
batch test for AC Felt 1300, Polyorgs, and FM 100.
As shown in the Results & Discussion section, the
consequential sorption isotherm curves for AC Felt 1300
followed an obvious trend for the three longest-chain
alcohols, yet the four shorter-chain tracers showed
unpredictability. In response to this dilemma, a second
batch test was conducted for AC Felt 1300 in which the
fabric strips were exposed to one solution containing 2-
butanol and 1-butanol, and different fabric strips were
exposed to a solution containing 3-pentanol and 1-
pentanol.
Two different alcohol tracer solutions were made. The
first solution consisted of 0.lmL of 2-butanol and 1-
butanol in 0.5L of water (160ppm each). The second
solution included 0.lmL of 3-pentanol and 1-pentanol in
0.5L of water (160ppm each). A set often 40mL EPA glass
vials was allocated to each solution. As shown in Figure 6,
one 2cm x 6cm strip of fabric was placed in each vial along
with increasingly diluted alcohol tracer solution. The
weight of each vial was taken before and after the addition
of fabric. Once again, the vials were rotated for 48 hours
and then allowed to settle for 24 hours. Disposable glass
pipettes were used to deliver the resulting aqueous solution
from the 40mL EPA vials to 2mL auto injection GC vials.
The 2mL samples were analyzed by the GC to determine
the equilibrium concentration of tracers in the aqueous
phase. With these data, a fourth set of sorption isotherm
curves was created.


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010
5





STEPHANIE ISHII


Figure 6: 40mL EPA glass vial containing one 2 cm x 6 cm strip
of fabric and a solution with known alcohol tracer
concentrations.


Results & Discussion

The sorption isotherms constructed from the
preliminary test data are shown in Figure 7 (a-g). As with
all sorption isotherm curves displayed in this paper, the
independent variable represents the equilibrium
concentration of tracer remaining in the aqueous phase
after being exposed to a sorptive material, and the
dependent variable is the mass of tracer sorbed per unit
mass of material. The partition coefficient, KD, is estimated
as the slope of the initial linear portion of the curve.
Preliminary test data confirm that the alcohol tracers
with higher Kow values and longer-chain lengths are more
readily sorbed by all of the sorptive materials. These data
also show that when the aqueous equilibrium concentration
is high, the amount of sorbed tracer per sorbent tends to
decrease. If the aqueous concentration of tracer is high, a
tracer's affinity for the sorbed phase may be overwhelmed
by its affinity for itself and the strong sorption affinities of
the other longer-chained alcohols. From these data, it was
determined that a subsequent batch test had to be
conducted with lower initial concentrations of tracers.
Additionally, the eight sorptive materials from the first
preliminary test were reduced to three choices: AC Felt
1300, Polyorgs, and FM 100. These fabrics were selected
based on their trend-like sorption behavior with most of the
tracers. These fabrics were also chosen due to physical


characteristics, including structural integrity and a
substantial thickness. BET 1000, BET 1300, and BET 1500
all had thicknesses of approximately 1 mm. In order to
intercept contaminants and elute tracers, water must flow
through the fabric. If the fabric is too thin, groundwater
streamlines may bypass the fabric by flowing around it in
the borehole. FM 10 was eliminated due to excessive
fraying during testing procedures. AC Felt 1000 and AC
Felt 1500 both possessed desirable thicknesses, but during
testing procedures they displayed physical degradation. If
Figure 4 is given a closer look, suspended particles of
activated carbon that have been divorced from AC Felt
1500 can be seen. On the contrary, Figure 6 is a close-up of
a vial containing AC Felt 1300 and there is a significant
decrease in the amount of suspended carbon.
Figure 8 (a-g) presents the sorption isotherms for AC
Felt 1300, Polyorgs, and FM 100. For this batch test, the
initial concentration of each tracer was reduced in order to
avoid high aqueous equilibrium concentrations that would
conflict with the normal partitioning of tracers on fabric.
These data show that all three fabrics result in trend-like
sorption behavior, but AC Felt 1300 was chosen as the
superior sorptive material because it had the highest
sorption capacity.
The results for a subsequent batch experiment
concerning only AC Felt 1300 are presented in Figure 9 (a-
g). The initial tracer concentrations were again reduced in
an effort to focus on the initial linear portion of the
sorption isotherm. It was during this batch experiment that
the square centimeter pieces of fabric were replaced with
two 2cm x 6cm pieces of fabric to more closely mimic
field conditions. Graphs e, f, and g in Figure 9 include the
initial linear portion of each sorption curve from which the
partition coefficient is derived as well as a progression
toward maximum capacity. Graphs a, b, c, and d have less
defined trends, and instead of asymptotically approaching
maximum capacity, these sorption curves appear to be
returning to zero. On their own, the short-chain alcohols
have a low affinity for sorption onto the solid phase, and
this affinity decreases even more when undergoing
competition. In the presence of long-chain alcohols (i.e. 1-
heptanol), which have a high tendency to sorb to the solid
phase, the true partitioning of 1-butanol, 2-butanol, 3-
pentanol, and 1-pentanol between water, and the AC Felt
1300 becomes impossible to determine. In response to this
dilemma, a second batch test was conducted for AC Felt
1300 in which the fabric strips were exposed to one
solution containing 2-butanol and 1-butanol and different
fabric strips were exposed to a solution containing 3-
pentanol and 1-pentanol. Figure 10 displays the sorption
curves for the four short-chained tracers when separated.
The behavior showed a much higher level of predictability,
and the curves appear to be approaching maximum
capacity.


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010





MEASUREMENT OF GROUNDWATER AND CONTAMINANT FLUX IN FRACTURED ROCK MEDIA WITH A PASSIVE FLUX METER

Conclusion

Thus far, these data have shown that AC Felt 1300 can
be feasibly used in a FRPFM with regard to the sorption of
the seven aforementioned alcohol tracers. As shown in
graphs e, f, and g in Figure 9 and graphs a, b, c, and d in
Figure 10, there is an initial linear relationship for each
tracer between its existence in either the aqueous or sorbed
phase. The slope of the linear portion of each sorption
isotherm represents the partition coefficient, KD Further
research is needed to more clearly define KD via additional
batch experiments at different initial tracer concentrations
as well as tests involving actual water flow.
Once the partition coefficient for each tracer is
determined, tests must be conducted with surrogate
contaminants to evaluate their sorption behavior when
exposed to AC Felt 1300. These results would allow AC
Felt 1300 to serve as an indicator of water flux by means of
tracer elution and as an indicator of contaminant flux
through contaminant sorption.

Acknowledgments

I would like to extend my sincerest gratitude to my
mentors, Dr. Mark Newman and Dr. Jaehyun Cho, for
sharing their extensive knowledge and skills with me. You
both have shown me the importance of thinking big while
taking baby steps and the necessity in treating obstacles as
creative opportunities. Thank you for introducing me to the
world of research as mentors and friends.




























University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010






STEPHANIE ISHII


a. 2-butanol

35
* BET 1000
30 - M BET1300
25 AC FELT 1000

20 - AC FELT 1300
15 x AC FELT 1500
= � FM 10
+ +,+ +FM100

5 - FOLYORGS
0 "

-5
Equ. Conc., mg/L



b. 1-butanol

50
40 BET 1000
40 BET 1300

30 AC FELT 1000
AC FELT 1300
I 20 * ---------------
Sx AC FELT 1500
10- * FM10
"w *+ FM 100
S0 - FOLYORGS

-10
Equ. Conc., mg/L



c. 3-pentanol

35
30 BET 1000
25 - BET 1300
20 -B
S.15 - ACFELT1000
10 - AC FELT 1300
"5.S x ACFELT1500
S5 - *FMO--
S0 FM 10p
- + _______+___ FM100
"5 t I� j- , 'a� , " 1t F,,
S - -FOLYORGS
H 10
-15
Equ. Conc., mg/L



d. 1-pentanol


35
30 * * *BET 100
25 - BET 1300
20 t
.U _ ACFELT 1000
15 *
f � - AC FELT 1300
1 10 -- -----
5 x AC FELT 1500
* FM10
0 di + FM 100
S "5 t' J j ij i, I'l, a , t + FMl.
S10 - FOLYORGS

-15
Equ. Conc., mglL


e. 1-hexanol

100

80 - z * BET 1000
* *BET 1300
S60 - AC FELT 1000
' c40 . AC FELT 1300
40 - ------
S -' x AC FELT 1500
20-- * FM 10
+ FM 100
0 - FOLYORGS

-20
Equ. Conc., mg/L



f. 2,4-DMP


90
80 �- BET 100
70 - BET1300
60 - ACFELT 1000
50 AC FELT 1300
S40 - - - x AC FELT 1500
t 30 . - FM10
S20 + FM 100
S10 - IFOLYORGS
0 l
0 200 400 600 800
Equ. Conc., mg/L



g. 1-heptanol

* 300
* BET 1000
250 , * BET 1300

200 - AC FELT 1000
1, * AC FELT 1300
S150--*---
1 * * * x AC FELT 1500
100 -' -- FM10

I - FOLYORGS

0 100 200 300 400 500 600
Equ. Conc., mg/L




Figure 7: Sorption isotherm curves from the preliminary
test data concerning all nine fabric choices. Each graph
represents a different tracer, going from shortest-chain
alcohol (highest aqueous solubility) to longest-chain
alcohol (highest tendency to sorb).


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010

8





MEASUREMENT OF GROUNDWATER AND CONTAMINANT FLUX IN FRACTURED ROCK MEDIA WITH A PASSIVE FLUX METER


a. 2-butanol

3

25 -

2
SAC Felt 1300
1 5 - * Polyorgs
1 FM 100

05
0 --
0 5 ---- i---- i---- ----
o 0
0 50 100 150 200
Equ. Conc., mg/L


b. 1-butanol


r
B 5

S* AC Felt 1300
S3 -- Polyorgs
S* FM 100

1

SO
0 50 100 150 200 250
Equ. Conc., mg/L


c. 3-pentanol

8
7 -
6
5 - * AC Felt 1300
4 -- - m Polyorgs
3 - FM 100
22
1
0

0 50 100 150 200 250
Equ. Conc., mg/L


d. 1-pentanol

20
18
16 *
14
12 * *AC Felt 1300
10 Polyorgs
8 FM 100
6
4I

I 0
0 100 200 300 400
Equ. Conc., mg/L


e. 1-hexanol

80
70
60
50 - AC Felt 1300
40 - m Polyorgs
S30 (- FM 100
S20
10 1

0 100 200 300 400 500 600
Equ. Conc., mg/L


f. 2,4-DMP

80-
70 -
60
50 * AC Felt 1300
S40 - Polyorgs
t 30 - FM 100
2 20
1 10 ,I
10
olI
0 200 400 600 800
Equ. Conc., mg/L


g. 1-heptanol

1180
160
140 -
S120 * AC Felt 1300
100 -*
SPolyorgs
S 80 * �
�l __--60--------- m FM 100
40 f-
4 20
20

0 100 200 300 400
Equ. Conc., mg/L




Figure 8: Sorption isotherm curves from the second
preliminary test data concerning three fabric choices.
Each graph represents a different tracer, going from
shortest chain alcohol (highest aqueous solubility) to
longest chain alcohol (highest tendency to sorb). AC Felt
1300 shows the highest sorption affinity for the alcohol
tracers and was therefore chosen as the most viable
option.


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010






STEPHANIE ISHII


a. 2-butanol

2
18 -
1 6 - ,
S14
1 2 -
S1 AC Felt 1300
I 08 1
06
0 04 *
1 02
0
0 50 100 150
Equ. Conc., mg/L


b. 1-butanol

4 ,
5 35
3 3 -
1 25 * p
S15AC Felt 1300
1 5
Q 1
i 05
0 I
0 50 100 150
Equ. Conc., mg/L


c. 3-pentanol

6 -

5 - p

4 *

3 * * AC Felt 1300


I 1

0 0
0 20 40 60 80 100 120
Equ. Conc., mg/L


d. 1-pentanol

16 |
14 -
S12 -

8 AC Felt 1300
� 6 ----------------
S4
! 2
6 0
0 50 100 150 200

Equ. Conc., mg/L


e. 1-hexanol

80

70
60
S50
S40 - AC Felt 1300
S30'
*20
010
0
0 50 100 150 200 250 300
Equ. Conc., mg/L


f. 2,4-DMP

t80
70 -
60
5 50
40 I AC Felt 1300
S30 -
220
110
0

0 50 100 150 200 250
Equ. Conc., mg/L


g. 1-heptanol

160
140 -
, 120 -

S8*
100 o
* 80 ,* *AC Felt 1300
60 -
40
S20
20

0 20 40 60 80
Equ. Conc., mg/L


Figure 9: Sorption isotherm curves from the first batch
test data concerning only AC Felt 1300. Each graph
represents a different tracer, going from shortest chain
alcohol (highest aqueous solubility) to longest chain
alcohol (highest tendency to sorb). Tracers represented
by graphs a-d show more unpredictability, while tracers
represented by graphs e-g demonstrate clear trends.


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010
10





MEASUREMENT OF GROUNDWATER AND CONTAMINANT FLUX IN FRACTURED ROCK MEDIA WITH A PASSIVE FLUX METER


a. 3-pentanol

30 0

25 0
20 0

150 - I IAC Felt 1300

100
S50

00
00 50 100 150 200
Equ. Conc., mg/L


b. 1-pentanol

300 -

250
' 20 0

S150 ACFelt 1300

100 -
t 50
N
S00
00 20 40 60 80 100
Equ. Conc., mg/L


c. 2-butanol

l 25 0

200 -
15' *



50









250
H r *










200

150 I 1

100

50

00
00 100 200 30 0 40 500
Equ. Conc., mg/L
S 250-----
al 200 -----





S 5 0 ---------------



Equ. Cone., mg/L


Figure 10: Sorption isotherm curves from the second
batch test data concerning only AC Felt 1300. Each
graph represents a different tracer that previously
showed inconsistent sorption behavior. For this batch
test, AC Felt 1300 was treated with one solution
containing just 2-butanol and 1-butanol, and in separate
vials it was treated with a solution containing just 3-
pentanol and 1-pentanol.


University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010





STEPHANIE ISHII

REFERENCES

[1] Department of Health and Human Services, Agency for
Toxic Substances and Disease Registry. "Evaluation of
Environmental Contamination, Exposure Pathways, and the
Public Health Implications." Retrieved March 15, 2009,
from ATSDR Web site:


[2] Hatfield, K. "Demonstration and Validation of a Fractured
Rock Passive Flux Meter (FRPFM)." Research Proposal
prepared for the Department of Defense.

[3] Hatfield, K., Annable, M., Cho, J., Rao, P., & Klammler, H.
(2i" '-4. "A direct passive method for measuring water and
contaminant fluxes in porous media." Journal of
Contaminant Hydrology, vol. 75, pp. 155-181.

[4] Weber, W., McGinley, P., & Katz, L. (1990). "Sorption
phenomena in subsurface systems concepts, models and
effects on contaminant fate and transport." Water Resources,
vol. 25 (no. 5), pp. 499-528.

[5] Stauffer, P. (2006). "Flux flummoxed: A proposal for
consistent usage." Ground Water Technical Commentary,
vol. 44 (no. 2), pp. 125-128.

[6] U.S. Geological Survey. (2008). "Octanol-Water Partition
Coefficient (Kow)." Retrieved February 4, 2009, from USGS
Web site:


[7] Brandsgaard, J., Granada, B., Myers, A., & Van Hoosen.
"Bioremediation: Sorption Isotherm." Retrieved February 4,
2009, from D. Woodrow Wilson National Fellowship
Foundation Web site:
/isotherm.htm>

[8] Chern, J. & Wu, C.. (2001). "Desorption of dye from
activated carbon beds: effects of temperature, pH, and
alcohol." Water Research, vol. 35 (no. 17), pp. 4159-4165.





















University of Florida I Journal of Undergraduate Research I Volume 10, Issue 2 I Spring 2010




Full Text

PAGE 1

University of Florida | Journal of Under graduate Research | Volume 10, Issue 2 | Spring 2010 1 Measurement of Groundwater and Contaminant Flux in Fractured Rock Media with a Passive Flux Meter: An Evaluation of Sorptive Materials with Alcohol Tracers Stephanie Ishii College of Engineering, University of Florida Groundwater hydrologists must accurately estimate water and contaminant fluxes in aquifers in order to predict risk, regulati on compliance, and contaminant attenuation. A new direct method for the simultaneous measuremen t of cumulative groundwater and contaminant flux in fractured rock aquifers through the use of a fractured rock passive flux meter (FRPFM) is under developme nt. This paper identifies a sorptive material and a range of resident alcohol tracers that can be u sed in combination as part of the FRPFM to quantify the aforementioned fluxes. When exposed to groundwater flow, the resident alcohol tracers are eluted from the fab ric at rates relative to the magnitude of the groundwater flux. In order to quantify the gr oundwater flux based on the removal of tracers, the partition coefficient for each tracer between water and the sorptive material must be known. This paper presents sorption iso therm curves from several laboratory experiments. These curves contribute to th e determination of the final partition coefficient, K D , for each tracer when exposed to water and the selected sorptive material AC Felt 1300. Introduction Groundwater is withdrawn from aquifers for municipal, agricultural, and industrial purposes. Eventually, groundwater becomes naturally incorporated in surface water due to discharge at locations such as springs and seeps. Should this groundwater become con taminated, it poses a threat to human and environmental health via direct consumption and indirect pathways such as vapor intrusion [1]. Because groundwater is ubiquitous, it is therefore necessary for groundwater hydrologists to accurately estimate water and contaminant fluxes in aquifers. Truthful measurements of water and contaminant mass fluxes are of great significance due to the fact that they lend themselves to the prediction of risk, regulation compliance, and contaminant attenuation. Despite the im portance of these measurements, accurate estimations of subsurface contaminant mass flows are difficult. Many methodologies represent short term evaluations that reflect aquifer conditions at one instant in time and not long term trends. These measurements do not account for variability in concentrations and flow rates over a period of time [2 ]. In response to this dilemma, the passive flux meter (PFM) was introduced. This new method is a simultaneous direct in situ point measurement of time averaged water and contaminant fluxes in porous media [3 ]. However, the hydrology of a porous media aquifer is extremely different than that of a fractured rock aquifer. Hence, the latter remains a field in which minimal research has been published. This research contri butes to the expansion of the PFM from porous media to fractured rock aquifers. The Passive Flux Meter As used in porous media, the PFM is a self contained permeable cylinder that is inserted into a well or boring. The meter can remain in the ground for a time period ranging from days to months. While in the borehole, the meter passively intercepts groundwater flow without retaining it. As shown in Figure 1, the groundwater flow first comes into contact with a thin, non reactive layer of permeable material that functions as a boundary layer. After passing the external layer, the water is intercepted by packed granular activated carbon. The granular activated carbon serves two purposes: to retain various organic contaminants from the groundwater flowing thro ugh the meter and to release non proportional to the amount of water flowing through the meter. The resident tracers are known amounts of various alcohols that the granular activated carbon is pretreated with prior to depl oyment. Each tracer is water soluble, but to a different degree. The short chain alcohols have a stronger tendency to exist in the aqueous phase, and thus are released first when exposed to water flow. The long chain alcohols are more strongly sorbed to th e granular activated carbon and require a larger amount of groundwater flow to be released [4]. Once the period of deployment is complete, the meters are carefully removed from the ground and the granular activated carbon is placed in an extraction solutio n to quantify the remaining amount of each tracer. Then a secondary extraction is performed to quantify the intercepted contaminants. Contaminant mass is used to determine the cumulative contaminant flux during the given time period, and the residual resid ent tracer mass is

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S TEPHANIE I SHII University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 2 Figure 1: Cross sectional illustration of a passive flux meter (PFM) of radius r [3] used to determine the cumulative water flux based on predetermined sorption and desorption behavior [3]. Fractured Rock Passive Flux Meter Although this new technology has already confirmed its worth in porous media, the hydrology of a fractured rock aquifer is decidedly more complex. Unlike in porous media, the groundwater flow is highly heterogeneous [ 2]. These complex hydrogeologic condit ions result in difficult characterization of groundwater flow and contamination; however, these measurements are essential to evaluating contaminant risk, regulation compliance, and attenuation. With some modification, the porous media PFM may be able to be extended to fractured rock. The ability to obtain cumulative fluxes in fractured rock aquifers under ambient closed hole conditions would accomplish estimating contaminant mass discharge from source zones with much greater ease. In turn, assessment of l ong term risk, evaluation of remedial performance, and regulatory compliance could be done with an increased level of accuracy and promptness. Significant cost savings can be realized with a cumulative measurement by eliminating the need to take numerous c oncentration samples over time and recognizing when a fractured rock site poses little off site risk due to its own natural attenuation [2]. This paper addresses one modification to the original PFM. In lieu of the loose granular activated carbon, an activ ated carbon impregnated fabric will be used. The fabric will be designed such that it intercepts contaminants as groundwater flow passes through it and releases the alcohol tracers it has been pre saturated with at rates proportional to groundwater flow. T he purpose of this paper is to evaluate the feasibility of various sorptive fabrics and tracers that could be used in combination to measure water flux at sites consisting of fractured rock media. In order to realize this objective, a relationship regardin g sorptive capacity must be established between the fabric and its tracers. This relationship is given by the partition coefficient, K D . Equations describing the correlation between the partition coefficient, residual tracer amounts, and their correspondin g groundwater flux are given elsewhere [ 2], [3 ]. Definition of Flux For the purposes of this paper, flux shall be defined as the flow rate per unit area. Thus, a mass flux would have SI units of kg/(m 2 s) [5]. Materials & Methodology The primary objective is to determine a sorptive media that may be used in combination with a range of alcohol tracers to indicate the magnitude and direction of groundwater flow in a given fracture. This fabric, when pretreated with the alcohol tracers an d exposed to groundwater flow, should gradually elute the tracers from itself. The rate at which elution occurs for each tracer is dependent upon the magnitude of the groundwater flow. Once the meter is removed from the ground, a residual tracer distributi on can be generated, as shown in Figure 2. Figure 2: A cross sectional illustration of the residual tracer distribution on the sorptive material after being exposed to groundwater flow qo. The cross section is for the case of a perpendicular intersection of borehole and fracture plane [2]. Activated Carbon Impregnated Fabrics The first materials to be identified for this study were an assortment of possible activated carbon impregnated fabrics. Nine different fabrics, as shown in Figure 3, were collected as possible sorptive materials. The fabrics were separated into two main categories: activated carbon (AC) felt and cloth. The fabrics char acterized as AC felts are thicker (thicknesses were approx imately 3mm) and have more structural integrity, while the cloths are thin and very flexible. Some of the clothes (BET 1000, BET 1300, and BET 1500) were thin enough for light to shine through. Table 1 presents the commercial name for each fabric as well as the labels that are used to refer to each fabric for the remainder of this paper.

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M EASUREMENT OF G ROUNDWATER AND C ONTAMINANT F LUX IN F RACTURED R OCK M EDIA WITH A P ASSIVE F LUX M ETER University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 3 Figure 3: Nine activated carbon impregnated fabrics chosen for testing and separated into activated carbon (AC) felt and cloth categories. Fabrics characterized as felts are thicker and have more structural integrity. Resident Alcohol Tracers In order to choose appropriate tracers for the PFM, the octanol water partition coefficients and carbon chain lengths of several alcohols were analyzed. The tendency for a tracer to remain sorbed to a fabric increases with both the chain length and the octanol water partition coefficient, K ow . The K ow concentration in octanol and in water at equilibrium and at a constant temperature [6] . Hence, a low K ow value denotes y to exist in the aqueous phase. These values must differ for each tracer so that each tracer has a different affinity for water and is therefore released from the fabric at various rates. These various rates can then be used as an indication of the magnit ude of groundwater flow passing through the fabric. For example, a strong flux of groundwater may result in the removal of 2 butanol, 1 butanol, 3 pentanol, and 1 pentanol, while a weak flux of groundwater may only result in the partial removal of 2 butano l; 1 heptanol, which has the highest sorption affinity, will exhibit the lowest rate of elution. Table 2 displays the K ow values for the range of alcohol tracers used as well as their molecular weight as an indicator of chain length. Table 1: The commer cial names of the nine activated carbon impregnated fabrics chosen for testing. The labels given for each fabric are used throughout this paper in lieu of their commercial name. Fabric Type Commercial Name Label AC Felt AmeriAsia BET 1000 felt AC Felt 1000 AC Felt AmeriAsia BET 1300 felt AC Felt 1300 AC Felt AmeriAsia BET 1500 felt AC Felt 1500 AC Felt Polyorgs Activated Carbon Fabric Polyorgs Cloth Calgon Carbon Zorflex cloth FM 10 FM 10 Cloth Calgon Carbon Zorflex cloth FM 100 FM 100 Cloth AmeriAsia MY QW 011, BET 1000 cloth BET 1000 Cloth AmeriAsia MY QW 013, BET 1300 cloth BET 1300 Cloth AmeriAsia MY QW 015, BET 1500 cloth BET 1500 Table 2: Alcohols used as resident tracers with their corresponding octanol water partition coefficients and molecular weights. Increasing property values indicate increasing tendencies to sorb and remain sorbed to the fabric. Chemical Name CAS Number Log( K ow ) Molecular Weights 2 butanol 78 92 2 0.6 74.1 1 butanol 71 36 3 0.9 74.1 3 pentanol 584 02 1 1.21 88.2 1 pentanol 71 41 0 1.40 88.2 1 hexanol 111 27 3 2.03 102.2 2,4 dimethyl 3 pentanol (DMP) 600 36 2 2.31 116.203 1 heptanol 111 70 6 2.34 2.62 116.2

PAGE 4

S TEPHANIE I SHII University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 4 Preliminary Tests As a preliminary test, eight of the nine fabrics were tested for usability. BET 1500 was automatically eliminated based on its thinness. Sorption isotherm curves, as described later in this paper and elsewhere [7], were generated for each fabric. Alcohol tracer solution was prepared consisting of tracer concentrations ranging from 800ppm (2 butanol) to 600ppm (1 heptanol), which was used to treat incrementally increasing amounts of fabric (varying number of square centimeter pieces ), as shown in Figure 4. Based on these results, the nine fabrics were reduced to three: Polyorgs, FM 100, and AC Felt 1300. Figure 4: Varying amounts of activated carbon fabrics (square centimeter pieces) being treated with constant concentrations of alcohol tracers for the first preliminary test. These three fabrics were tested in a similar fashion, but in lieu of varying amounts of fabric, each vial contained a constant amount of fabric and various dilutions of the alcohol tracer solution. The original solution included tracer concentrations rangi ng from 150ppm (2 butanol) to 1000ppm (1 heptanol). Dilutions ranged from 100% original alcohol tracer solution to 5% tracer solution with 95% water. From these results, AC Felt 1300 was deemed the most viable. Tests for Felt 1300 For the previous batch test concerning AC Felt 1300, Polyorgs, and FM 100, in which AC Felt 1300 was deemed the most plausible, a tracer mixture was made according to the measurements presented in the second column of Table 3. Each tracer was individually pipetted into one glass bottle. Once all tracers had been deposited, the glass bottle was tightly sealed with a screw cap and Teflon septum. The mixture was allowed to equilibrate for 45 minutes to an hour while being shaken every ten minutes. After all the tracers had been thor oughly combined, 4.4mL of tracer mixture and a magnetic stir bar were added to 1L of water in a 1L volumetric flask to obtain the concentrations presented in column 3 of Table 3. A glass stopper was placed into the flask and wrapped with Teflon tape in ord er to ensure minimal volatilization of tracers. The solution was placed on a stir plate and allowed to mix until all alcohol ganglia had disappeared and the tracers were thoroughly dissolved. Table 3: Tracers and their corresponding volumetric contributio n to the pure alcohol mixture and their final concentration in the tracer solution, which consisted of the mixture and water. Alcohol Tracer Volumetric Contribution to Tracer Mixture (mL) Concentration in Tracer Solution (ppm) 2 butanol 1.3 150 1 butanol 1.8 200 3 pentanol 1.8 200 1 pentanol 3.1 350 1 hexanol 7.0 800 2,4 DMP 7.0 800 1 heptanol 8.8 1000 Total 30.8 3500 Ten 40mL Environmental Protection Agency (EPA) glass vials with plastic caps and Teflon septa were labeled and their empty weights recorded. AC Felt 1300 was cut into one square centimeter pieces, six of which were placed into each vial; the weights were again recorded to deduce the exact weight of fabric in each vial. Specific amounts of water were then transferred into each vial with a dilution factor. After the water had been added, the remaining fraction of the 40mL volume was filled with alcohol solution via volumetric pipette. Water was first pipetted into each via l to avoid volatilization of alcohol tracers. Table 4 provides the dilution information for each vial. Once filled with water and solution, the vial weights were recorded. The vials were then placed on a rotator (see Figure 5) set at 20rpm for 48 hours to fully expose all areas of the fabric to the alcohol tracers. After the rotation period, the vials were removed from the rotator and allowed to settle for 24 hours. It is important to note that during this time, the vials were not refrigerated, as sorption behavior is heavily influenced by changes in temperature [8]. Samples of the resulting aqueous solution were transferred into 2mL auto sample vials with disposable glass pipettes for analysis using a gas chromatograph (GC). The GC analyzed the samples for the remaining concentration of tracers in the aqueous solution. Due to conservation of mass, the difference between the original concentration and the remaining concentration for each tracer was assumed to have sorbed onto the AC Felt 1300.

PAGE 5

M EASUREMENT OF G ROUNDWATER AND C ONTAMINANT F LUX IN F RACTURED R OCK M EDIA WITH A P ASSIVE F LUX M ETER University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 5 Table 4: The vo lume of water and alcohol solution in each vial depending on its designated dilution. Vials included 0%, 20%, 40%, 60%, 70%, 80%, 90%, and 95% dilutions. Vial # Water Volume (mL) Solution Volume (mL) 1 0 40 2 8 32 3 16 24 4 16 24 5 24 16 6 28 12 7 28 12 8 32 8 9 36 4 10 38 2 Figure 5: 40mL EPA glass vials on the rotator to ensure complete exposure of fabric to the alcohol tracers. AC Felt was selected as the best option after analyzing the results from this batch experiment with three fabrics, and a batch experiment with just AC Felt 1300 ensued with two modifications. Initial alcohol tracer concentrations were reduced, and the felt was cut into 2cm x 6cm strips instead of the square centimeter pieces; then two strips were deposited in to each vial. One consecutive piece of fabric more closely mimics field conditions by reducing layering of fabric and the length of exposed edges. Similar to Table 3, the new tracer mixture and solution recipes are given in Table 5. At first glance, these concentrations may not seem significantly reduced, but it is important to note that the first batch test was done with a total of 6cm 2 of Table 5: Tracers and their corresponding volumetric contribution to the pure alcohol mixture and their final concentr ation in the tracer solution for the first batch experiment concerning AC Felt 1300 only. Alcohol Tracer Volumetric Contribution to Tracer Mixture (mL) Concentration in Tracer Solution (ppm) 2 butanol 5.0 125 1 butanol 5.0 125 3 pentanol 5.0 125 1 pentanol 8.3 200 1 hexanol 25.0 620 2,4 DMP 25.0 620 1 heptanol 33.3 830 Total 106.6 2645 fabric per vial while the second batch test was done with 12cm 2 of fabric per vial. Save these two modifications, the methodology for the first batch test using only AC Felt 1300 was identical to the methodology utilized during the batch test for AC Felt 1300, Polyorgs, and FM 100. As shown in the Results & Discussion section, the consequential sorption isotherm curves for AC Felt 1300 followed an obvious trend for the three longest chain alcohols, yet the four shorter chain tracers showed unpredictability. In response to this dilemma, a second batch test was conducted for AC Felt 1300 in which the fabric strips were exposed to one solution containing 2 butanol and 1 butanol, and different fabric strips were exposed to a solution containing 3 pentanol and 1 pentanol. Two different alcohol tracer solutions were made. The first solution consisted of 0.1mL of 2 butanol and 1 butanol in 0.5L of water (160ppm each). The second solution included 0.1mL of 3 pentanol and 1 pentanol in 0.5L of water (160ppm each). A set of ten 40mL EPA glass vials was allocated to each solution. As shown in Figure 6, one 2cm x 6cm strip of fabric was placed in each vial along with increasingly diluted alcohol tracer solution. The weight of each vial was taken before and after the addition of fabric. Once again, the vials were rotated for 48 hours and then allowed to settle for 24 hours. Disposable glass pipettes were used to deliver the resulting aqueous solution from the 40mL EPA vials to 2mL auto injection GC vials. The 2mL samples were analyzed by the GC to determine the equilibrium concentratio n of tracers in the aqueous phase. With these data, a fourth set of sorption isotherm curves was created.

PAGE 6

S TEPHANIE I SHII University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 6 Figure 6: 40mL EPA glass vial containing one 2 cm x 6 cm strip of fabric and a solution with known alcohol tracer concentrations. Results & Discussion The sorption isotherms constructed from the preliminary test data are shown in Figure 7 (a g). As with all sorption isotherm curves displayed in this paper, the independent variable represents the equilibrium concentration of tracer remaining i n the aqueous phase after being exposed to a sorptive material, and the dependent variable is the mass of tracer sorbed per unit mass of material. The partition coefficient, K D , is estimated as the slope of the initial linear portion of the curve. Prelimi nary test data confirm that the alcohol tracers with higher K ow values and longer chain lengths are more readily sorbed by all of the sorptive materials. These data also show that when the aqueous equilibrium concentration is high, the amount of sorbed tra cer per sorbent tends to decrease. If the aqueous concentration of tracer is high, a by its affinity for itself and the strong sorption affinities of the other longer chained alcohols. From these da ta, it was determined that a subsequent batch test had to be conducted with lower initial concentrations of tracers. Additionally, the eight sorptive materials from the first preliminary test were reduced to three choices: AC Felt 1300, Polyorgs, and FM 10 0. These fabrics were selected based on their trend like sorption behavior with most of the tracers. These fabrics were also chosen due to physical characteristics, including structural integrity and a substantial thickness. BET 1000, BET 1300, and BET 15 00 all had thicknesses of approximately 1 mm. In order to intercept contaminants and elute tracers, water must flow through the fabric. If the fabric is too thin, groundwater streamlines may bypass the fabric by flowing around it in the borehole. FM 10 was eliminated due to excessive fraying during testing procedures. AC Felt 1000 and AC Felt 1500 both possessed desirable thicknesses, but during testing procedures they displayed physical degradation. If Figure 4 is given a closer look, suspended particles o f activated carbon that have been divorced from AC Felt 1500 can be seen. On the contrary, Figure 6 is a close up of a vial containing AC Felt 1300 and there is a significant decrease in the amount of suspended carbon. Figure 8 (a g) presents the sorptio n isotherms for AC Felt 1300, Polyorgs, and FM 100. For this batch test, the initial concentration of each tracer was reduced in order to avoid high aqueous equilibrium concentrations that would conflict with the normal partitioning of tracers on fabric. T hese data show that all three fabrics result in trend like sorption behavior, but AC Felt 1300 was chosen as the superior sorptive material because it had the highest sorption capacity. The results for a subsequent batch experiment concerning only AC Felt 1300 are presented in Figure 9 (a g). The initial tracer concentrations were again reduced in an effort to focus on the initial linear portion of the sorption isotherm. It was during this batch experiment that the square centimeter pieces of fabric were r eplaced with two 2cm x 6cm pieces of fabric to more closely mimic field conditions. Graphs e, f, and g in Figure 9 include the initial linear portion of each sorption curve from which the partition coefficient is derived as well as a progression toward max imum capacity. Graphs a, b, c, and d have less defined trends, and instead of asymptotically approaching maximum capacity, these sorption curves appear to be returning to zero. On their own, the short chain alcohols have a low affinity for sorption onto th e solid phase, and this affinity decreases even more when undergoing competition. In the presence of long chain alcohols (i.e. 1 heptanol), which have a high tendency to sorb to the solid phase, the true partitioning of 1 butanol, 2 butanol, 3 pentanol, an d 1 pentanol between water, and the AC Felt 1300 becomes impossible to determine. In response to this dilemma, a second batch test was conducted for AC Felt 1300 in which the fabric strips were exposed to one solution containing 2 butanol and 1 butanol and different fabric strips were exposed to a solution containing 3 pentanol and 1 pentanol. Figure 10 displays the sorption curves for the four short chained tracers when separated. The behavior showed a much higher level of predictability, and the curves ap pear to be approaching maximum capacity.

PAGE 7

M EASUREMENT OF G ROUNDWATER AND C ONTAMINANT F LUX IN F RACTURED R OCK M EDIA WITH A P ASSIVE F LUX M ETER University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 7 Conclusion Thus far, these data have shown that AC Felt 1300 can be feasibly used in a FRPFM with regard to the sorption of the seven aforementioned alcohol tracers. As shown in graphs e, f, and g in Figure 9 and graphs a, b, c, and d in Figure 10, there is an initial linear relationship for each tracer between its existence in either the aqueous or sorbed phase. The slope of the linear portion of each sorption isotherm represents the partition coefficient, K D. Fur ther research is needed to more clearly define K D via additional batch experiments at different initial tracer concentrations as well as tests involving actual water flow. Once the partition coefficient for each tracer is determined, tests must be conduct ed with surrogate contaminants to evaluate their sorption behavior when exposed to AC Felt 1300. These results would allow AC Felt 1300 to serve as an indicator of water flux by means of tracer elution and as an indicator of contaminant flux through contam inant sorption. Acknowledgments I would like to extend my sincerest gratitude to my mentors, Dr. Mark Newman and Dr. Jaehyun Cho, for sharing their extensive knowledge and skills with me. You both have shown me the importance of thinking big while taking baby steps and the necessity in t reating obstacles as creative opportunities. Thank you for introducing me to the world of research as mentors and friends.

PAGE 8

S TEPHANIE I SHII University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 8 Figure 7: Sorption isotherm curves from the preliminary test data concerning all nine fabric choices. Each graph represents a different tracer, going from shortest chain alcohol (highest aqueous solubility) to longest chain alcohol (highest tendency to sorb).

PAGE 9

M EASUREMENT OF G ROUNDWATER AND C ONTAMINANT F LUX IN F RACTURED R OCK M EDIA WITH A P ASSIVE F LUX M ETER University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 9 Figure 8: Sorption isotherm curves from the second preliminary test data concerning three fabric choices. Each graph represents a different tracer, going from shortest chain alcohol (highest aqueous solubility) to longest chain alcohol (highest tendency to sorb). AC Felt 1300 shows the highest sorption affinity for the alcohol tracers and was therefore chosen as the most viable option.

PAGE 10

S TEPHANIE I SHII University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 10 Figure 9: Sorption isotherm curves from the first batch test data concerning only AC Felt 1300. Each graph represents a different tracer, going from shortest chain alcohol (highest aqueous solubility) to longest chain alcohol (highest tendency to sorb). Tracers rep resented by graphs a d show more unpredictability, while tracers represented by graphs e g demonstrate clear trends.

PAGE 11

M EASUREMENT OF G ROUNDWATER AND C ONTAMINANT F LUX IN F RACTURED R OCK M EDIA WITH A P ASSIVE F LUX M ETER University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 11 Figure 10: Sorption isotherm curves from the second batch test data concerning only AC Felt 1300. Each graph represents a different tracer that previously showed inconsistent sorption behavior. For this batch test, AC Felt 1300 was treated with one solution containi ng just 2 butanol and 1 butanol, and in separate vials it was treated with a solution containing just 3 pentanol and 1 pentanol.

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S TEPHANIE I SHII University of Florida | Journal of Undergraduate Research | Volume 10, Issue 2 | Spring 2010 12 REFERENCES [1] Department of Health and Human Services, Agency for ion of Environmental Contamination, Exposure Pathways, and the from ATSDR Web site: [2] tured Research Proposal prepared for the Department of Defense. [3] Hatfield, K., Annable, M., Cho, J., Rao, P., & Klammler, H. Journal of Contaminant Hydrology, vol. 75, pp. 155 181. [4] phenomena in subsurface systems concepts, models and Water Resources, vol. 25 (no. 5), pp. 499 5 28. [5] Ground Water Technical Commentary, vol. 44 (no. 2), pp. 125 128. [6] Water Partition Coefficient (K ow , from USGS Web site: [7] Brandsgaard, J., Granada, B., Myers, A., & Van Hoosen. 2009, from D. Woodrow Wilson National Fellowship Foundation Web site: [8] activated carbon beds: effects of temperature, pH, and Water Research, vol. 35 (no. 17), pp. 4159 4165.