United States
Environmental Protection
Agency
National Exposure
Research Laboratory
Las Vegas, NV 89193-3478
Research and Development
EPA/600/S-97/004
July 1997
&EPA Summary Report
Determination of Pollutant
Distribution and Movement by
Controlled Laboratory
Experiments
David K. Kreamer, David E. James and Katrina E. Varner
The goal of this project was to di-
rectly observe and evaluate the sub-
surface movement and distribution of
selected volatile organic compounds,
particularly components of petroleum
fuels, through controlled laboratory ex-
periments. Sand tank, column, and
batch-type laboratory experiments were
employed to measure the effect of spe-
cific variables associated with under-
ground contamination events. The sand
tank experiments were carried out to
characterize leak sources and contami-
nant movement. Leak rate, petroleum
type, soil type, temperature, and back-
fill configuration were examined to de-
termine which materials and methods
produced results that had the best ap-
plication to field and regulatory situa-
tions. The spatial and temporal propa-
gation of leaking fluids was measured
and recorded by several methods in-
cluding gas chromatography and time-
lapse photography. The spatial and tem-
poral measurements of vapor concen-
trations were mathematically modeled
using two-dimensional inverse meth-
ods. Diffusion parameters of Effective
Diffusion Coefficient, De, and Sorption-
corrected Porosity, A*, were deter-
mined, with De for gasoline generally
ranging from approximately 0.0024 cm2/
sec for clay to 4.4 cnWsec for pea
gravel. Calculated diffusion parameters
were used to predict three-dimensional
propagation of vapors, and results were
compared with field and laboratory val-
ues. Additionally, the sand tanks were
used to measure the distribution of light
non-aqueous phase liquids around the
water table during conditions of verti-
cal water table movement. Some of the
results from the research indicate that
the distribution of hydrocarbons in
these situations is more extreme than
previously recognized, and that en-
trapped diesel fuel in sands ranged
from 33 to 67 liters/cubic meter. Di-
mensional analysis as well as color-
density dye studies were also per-
formed on the physical modeling.
In other work, plastic columns
equipped with fiber optic sensors were
used to measure diffusion parameters
from gasoline and diesel sources. One-
dimensional mathematical modeling
was applied to observed concentration
values to calculate diffusion param-
eters. The data were compared with
the findings of other researchers, and
the reproducibility of results was evalu-
ated. Generally, experimental reproduc-
ibility was quite good, and the fiber
optic probes showed a large dynamic
range to maximum responses of 22,000
to 35,000 ppmv for gasoline and 43,000
to 62,000 ppmv for diesel fuel. Field
operation of fiber optic devices was
also evaluated.
Sorption studies of selected organic
compounds on various soils were car-
ried out in enclosed steel chambers.
The chambers allowed measurement of
sorption in soil media configured to
simulate actual field conditions. Soil
moisture content, temperature, soil
type, vapor pressure, and soil organic
content were incrementally varied.
Moisture content of an unsaturated soil
was generally the most important vari-
able affecting sorption in vadose zone
materials. Partitioning coefficients were
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found to be relatively independent of
the degree of saturation when gravi-
metric water contents exceeded 2-5%.
These findings correlate well with sorp-
tion-corrected porosity values obtained
from inverse mathematical modeling of
physical sand tank and column mod-
els. While some compounds displayed
sorption fitting a Freundlich isotherm,
dry soils typically exhibited nonlinear
isotherms and finite sorption kinetics.
Hydrogen-bonding compounds also
displayed nonlinear isotherms and fi-
nite sorption and desorption kinetics
in the presence of water. A recalcitrant
fraction was observed to be resistant
to desportion, especially with certain
compounds in clays.
Goals and Objectives of the
Research
The goal of this project was to directly
observe and evaluate the subsurface
movement and distribution of selected
volatile organic compounds, particularly
components of petroleum fuels, through
controlled laboratory experiments. Sand
tank, column, and batch-type laboratory
experiments were used to measure the
effect of specific variables associated with
underground contamination events. Many
of the studies centered on gaseous mi-
gration, and the variables examined in-
cluded moisture content, soil type/grain
size, leak rate, temperature, and vapor
densities.
Objectives included: 1) establishing a
visual record through time-lapse photog-
raphy of the movement of organic liquids
through unsaturated porous media, 2) aug-
mentation of this visual record with quan-
titative measurements of vapor concen-
tration and migration, 3) observation of
effect of the water table on the distribution
of non-aqueous phase liquids, and 4) the
quantitation of sorptive partitioning of the
gaseous phase organics onto and into
porous material and water. This work pro-
vided a video which has been extensively
used for educational purposes, publica-
tions in refereed journals, publications in
conference proceedings, and several
master's theses.
Research Approach
There were three components of the
research approach: sand tank experiments,
column experiments, and batch-type sorp-
tion experiments. As the work progressed,
the research approach underwent review,
at times partial revision, and augmenta-
tion to optimize results.
Sand tank experiments were carried out
to characterize leak sources and contami-
nant movement. Experiments were first
performed to vary the tank filling proce-
dure to allow the best reproducibility pos-
sible in the experimentation. Leak rate,
petroleum type, soil type, temperature, and
backfill configuration were examined to
determine which materials and methods
produced results that had the best appli-
cation to field and regulatory situations. In
another aspect of experimentation, it was
quickly discovered that the sand tank en-
vironment was inadequate to simulate va-
por extraction remediation; gaseous ad-
vection on the small sand tank scale suf-
fered boundary interferences which were
too severe to proceed using the smaller
volume tanks proposed in this work.
In vadose zone leak simulations per-
formed in the sand tanks, liquid and vapor
measurements were made. The spatial
and temporal propagation of leaking fluids
was measured and recorded by several
methods including gas chromatography
and time lapse photography. Contour maps
of the distribution of leaked fluids were
constructed. The spatial and temporal
measurements of vapor concentrations
were mathematically modeled using two-
dimensional inverse methods. Diffusion
parameters of Effective Diffusion Coeffi-
cient, De, and Sorption-corrected Porosity,
A*, were determined. Calculated diffusion
parameters were used to predict three-
dimensional propagation of vapors, and
results were compared with field and labo-
ratory values. Additionally, the sand tanks
were used to measure the distribution of
light non-aqueous phase liquids around
the water table during conditions of verti-
cal water table movement.
Column experiments took on several
forms. Experiments were performed to
measure the flux of organic compounds
across the water table. A glass column
equipped with side ports was used to de-
termine the feasibility of this approach.
Additionally, plastic columns equipped with
fiber optic sensors were used to measure
diffusion parameters from gasoline and
diesel sources. One-dimensional math-
ematical modeling was applied to observed
concentration values to calculate diffusion
parameters. The data were compared with
the findings of other researchers. The re-
producibility of results was evaluated.
Sorption studies of selected organic
compounds on various soils were carried
out. Experiments in enclosed steel cham-
bers were conducted. The chambers al-
lowed measurement of sorption in soil
media configured to simulate actual field
conditions. Soil moisture content, tempera-
ture, soil type, vapor pressure, and soil
organic content could be controlled and
incrementally varied.
Summation of Individual Areas
of Research
Sand Tank Experiments
Through controlled laboratory experi-
ments, the effect of specific variables as-
sociated with underground contamination
events was examined with time-lapse pho-
tography and quantitative measurements
of vapor concentration and migration. The
research approach had several subcom-
ponent activities. Initial sand tank experi-
ments examined the tank filling procedure
with the objective to allow the best repro-
ducibility possible in the experimentation.
Although several procedures were used,
the most reproducible filling technique in-
volved the gravity release of soil into a
tank through a overhead funnel equipped
with sieves. This methodology is visually
shown in a short video (available from
authors), and is described in James et al.
(1996a).
Another subcomponent of the sand tank
activities involved the measurement of liq-
uid and gaseous propagation from a pe-
troleum hydrocarbon leak. The goal of this
endeavor was to characterize leak propa-
gation, hopefully in a way amenable to
mathematical modeling. This undertaking
was successful. The spatial and temporal
propagation of leaking fluids was mea-
sured and recorded by the methods dis-
cussed previously. Contour maps (in re-
gards to the distribution of leaked fluids)
were constructed. Time-lapse movement
of liquid migration is shown in the video
tape. The spatial and temporal measure-
ments of vapor concentrations were math-
ematically modeled to determine values
of coefficients and porosity. For example,
De for gasoline was generally found to
range from approximately 0.0024 cm2/sec
for clay to 4.4 cm2/sec for pea gravel.
Calculated diffusion parameters were used
to predict three-dimensional propagation
of vapors, and results were compared with
field and laboratory values. Mathematical
modeling of gaseous movement is de-
tailed in Chaganti (1990), Johnson and
Kreamer (1994), Kreamer et al. (1996),
and Squire (1996). Calculated gaseous
diffusion parameters showed conformance
to the few values available in the litera-
ture. Optimal leak rates, petroleum types,
soil types, temperatures, and backfill con-
figuration were examined to determine
those procedures allowing efficient and
safe experimental techniques, while re-
taining applicability to real field and regu-
latory situations.
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In another aspect of experimentation,
the sand tanks were used to measure the
distribution of light non-aqueous phase liq-
uids (LNAPLs) around the water table dur-
ing conditions of vertical water table move-
ment. This aspect of research is shown in
the video, and is reported in James et al.
(1996a, 1996b), Rajagopalan (1995), and
Sabapathi (1993). Results indicated that
the distribution of hydrocarbons in these
situations is more excessive than previ-
ously recognized, and that entrapped die-
sel fuel in sands ranged from 33 to 67
liters/cubic meter. Dimensional analysis
and color-density dye studies were also
performed on the physical modeling.
Column Studies
Column studies were undertaken to
measure the flux of organic compounds
across the water table and capillary fringe,
and to determine diffusion parameters from
gasoline and diesel sources. A glass col-
umn equipped with side ports was used to
determine the feasibility of vertical flux
measurements. This line of experimenta-
tion was basically unsuccessful. Slow dif-
fusion in the aqueous phase (approxi-
mately 5 orders of magnitude slower than
gaseous diffusion), coupled with advec-
tion created by withdrawal of water and
vapor during sampling, created results with
little reproducibility. Spacing of the side
ports was also too wide, and the perturba-
tion of the soil column created by syringe
sample withdrawal appeared to be largely
responsible for the lack of reproducible
results. To gain some understanding of
hydrocarbon movement and distribution
near the water table, studies of vertical
LNAPL distribution around moving water
tables were initiated in sand tanks as de-
scribed earlier (James etal., 1996a, 1996b;
Rajagopalan, 1995; Sabapathi, 1993).
Additionally, plastic columns equipped
with fiber optic sensors were used to mea-
sure diffusion parameters from gasoline
and diesel sources (Kreamer et al., 1996).
One-dimensional mathematical modeling
was applied to observed concentration
values to calculate diffusion parameters.
The data were compared with the findings
of other researchers and the reproducibil-
ity of results was evaluated. Generally,
experimental reproducibility was quite
good, and the fiber optic probes showed a
large dynamic range to maximum re-
sponses of 22,000 to 35,000 ppmv for
gasoline and 43,000 to 62,000 ppmv for
diesel fuel. Field operation of fiber optic
devices was also evaluated (Kreamer et
al., 1996).
Sorption Batch Testing
Sorption studies of selected organic
compounds on various soils were carried
out in enclosed steel chambers (Fairley,
1993; Houston and Kreamer, 1989; Oja
and Kreamer, 1992; Kreamer et al., 1994;
Schmeltzer, 1993; Steinberg et al., 1994;
Steinberg and Kreamer, 1992, 1993). The
chambers allowed measurement of sorp-
tion in soil media configured to simulate
actual field conditions. Soil moisture con-
tent, temperature, soil type, vapor pres-
sure, and soil organic content could be
controlled and incrementally varied.
Moisture content of an unsaturated soil
was generally the most important variable
affecting sorption in vadose zone materi-
als. Partitioning coefficients were found to
be relatively independent of the degree of
saturation when gravimetric water content
exceeded 2 to 5%. These findings corre-
late well with sorption-corrected porosity
values obtained from inverse mathemati-
cal modeling of physical sand tank and
column models. While some compounds
displayed sorption fitting a Freundlich iso-
therm, dry soils typically exhibited nonlin-
ear isotherms and finite sorption kinetics.
Hydrogen-bonding compounds also dis-
played nonlinear isotherms and finite sorp-
tion and desorption kinetics in the pres-
ence of water. A recalcitrant fraction was
observed to be resistant to desorption,
especially with certain compounds in clays.
Research Accomplishments
This research has contributed to many
publications, reports, master's theses, a
widely distributed video, and provided sup-
porting information for many workshops
and conferences.
Publications
Houston, S.L., Kreamer, O.K. and R.
Marwig, 1989. A Batch-Type Testing
Method for Determination of Adsorp-
tion of Gaseous Compounds on Par-
tially Saturated Soils. Geotechnical
Testing Journal, ASTM, March 1989,
p.3-10.
Houston, S.L. and O.K. Kreamer, 1989.
Effect of Temperature on the Potential
for Gaseous Adsorption by Partially
Saturated Soils, Engineering Geology
and Geotechnical Engineering, Watters
(ed.) p.357-361. A.A. Balkema/
Rotterdam/Brook, Hardbound, ISBN 90
6191 8782.
James, D. E, Kreamer, O.K., Sabapathi,
J. and V. Rajagopalan, 1996a. Effects
of Vertical Water Table Fluctuations on
LNAPL Distribution in Porous Media,
1. Effects of Varying Water Table Rise
Rates in Initially Dry Sand. J. of Con-
taminant Hydrology. Accepted 1995 for
Publication in 1996.
James, D. E, Kreamer, O.K., Rajagopalan,
V. and S.K. Steinberg, 1996b. Effects
of Vertical Water Table Fluctuations on
LNAPL Distribution in Porous Media,
2. Effects of Varying Grain Size in Ini-
tially Moist Sands. J. of Contaminant
Hydrology. Accepted 1995 for Publica-
tion in 1996.
Johnson, T.E. and O.K. Kreamer, 1994.
Physical and Mathematical Modeling of
Diesel Fuel Liquid and Vapor Move-
ment in Porous Media. Ground Water,
Vol. 32, No. 4., p. 551-560.
Kreamer, O.K., Brown, C. and D. Sloop,
1996. Report on the Suitability of
PetroSenseฎ Probes for Leak Detec-
tion at Contaminated Sites. Las Vegas,
NV, March 1996.
Kreamer, O.K., Oja K.J., Steinberg, S.M.,
and H. Phillips, 1994. Vapor Adsorp-
tion of a Solvent on Quartz Sands of
Varying Grain Size. Journal of Environ-
mental Engineering, ASCE, Vol. 120,
No. 2, p. 348-358.
Kreamer, O.K., Starr, K., Cogent, S.,
Johnson, T. and H.A. Phillips, 1990.
Gasoline Vapor Compound Ratios as
a Tool to Locate Subsurface Fuel
Leaks; from Minimizing Risk to the Hy-
drologic Environment, Selected Papers
from the American Institute of Hydrol-
ogy Conference, Las Vegas, Nevada,
March 13-15, 1990, p.243-249.
Soft bound.
Kreamer, O.K. and K.J. Stetzenbach, 1990.
Development of a Standard, Pure-Com-
pound Base Gasoline Mixture for Use
as a Reference in Field and Laboratory
Experiments. Ground Water Monitor-
ing Review, Spring 1990, p. 135-145.
Oja, K.J. and O.K. Kreamer, 1992. (In-
vited Paper). The Effect of Moisture on
Adsorption of Trichloroethylene Vapor
on Natural Soils. Proceedings of the
U. S. Environmental Protection Agency
and National Center for Ground Water
Research Symposium on Soil Venting,
April 29 - May 1, 1991, Houston, TX, p
13-28. Softbound.
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Steinberg, S.M., Fairley, J. and O.K.
Kreamer, 1994. Slow Desorption of
Toluene from Several Ion-Exchanged
Montmorillonites. J.Soil Contamination
3(3):249-264.
Steinberg, S.M. and O.K. Kreamer, 1992.
Determination of Sorption Isotherms for
Volatile Organic Compounds on Soil
using Gas Chromatography. Structure,
Bonding, and Kinetics at Mineral Sur-
faces Symposium, American Chemical
Society, April 5-10, 1992, San Fran-
cisco.
Steinberg, S.M. and O.K. Kreamer, 1993.
Persistence of Several Volatile Organic
Compounds in a Low Organic Carbon,
Calcareous Soil from Southern Nevada.
Proceedings of the National Sympo-
sium on Measuring and Interpreting
VOCs in Soils: State of the Art and
Research Needs. U.S. Environmental
Protection Agency, Jan. 12-14, Las Ve-
gas, NV.
Steinberg, S.M. and O.K. Kreamer, 1994.
Determination of Sorption Isotherms for
Volatile Organic Compounds on Un-
saturated Calcareous Soil from South-
ern Nevada Using Inverse Chromatog-
raphy. Environmental Science and
Technology. Vol. 27, No. 5, 883-888.
Videos
Two short videos were produced: Physi-
cal Modeling of Subsurface Fuel Migra-
tion by Controlled Laboratory Tests (10
mins) and Effects of Vertical Water Table
Fluctuations on LNAPL Distribution (14
mins). These videos have been shown at
approximately 65 conferences and work-
shops. On request, they have been dis-
tributed to approximately 700 people.
Theses
Master's theses supported are:
a) from the University of Nevada, Las
Vegas:
Fairley, J., 1993. Desportion Hysteresis
in Five Ion Exchanged Montmorillo-
nites. Master of Science Thesis. Water
Resources, Department of Geo-
science, UNLV.
Rajagopalan, V., 1995. Influence of Grain
Size of a Porous Medium on the
Movement of Diesel Fuel Due to
Water Table Fluctuations. Master of
Science thesis. Water Resources, De-
partment of Geoscience, UNLV.
Sabapathi, J., 1993. Effect of Water
Table Fluctuations on Petroleum
Contamination Distribution. Master of
Science Thesis. Water Resources,
Department of Geoscience, UNLV.
Schmeltzer, J., 1993. Effects of Soil
Moisture, Soil Carbonate and Organic
Matter Content on Vapor Phase Sorp-
tion of Volatile Organic Compounds
Using Inverse Gas Chromatography.
Master of Science Thesis. Water Re-
sources, Department of Geoscience,
UNLV.
Squire, J., 1996. Effect of Unsaturated
Zone Soil Moisture Content on Vapor
Phase Pollutant Propagation in Con-
trolled Laboratory Experiments. Mas-
ter of Science Thesis. Water Re-
sources, Department of Geoscience,
UNLV.
Starr, K., 1993. Sand Tank Modeling
of Hydrocarbon Migration Design,
Construction, and Testing. Master of
Science Thesis. Water Resources,
Department of Geoscience, UNLV.
b) from Arizona State University
Chaganti, S., 1990. Vapor Transport
Modeling in Simulated Leaking Un-
derground Storage Tank Environ-
ments. Master of Science Thesis. De-
partment of Civil Engineering, ASU.
Johnson, T., 1991. Modeling Diesel
Vapor Transport In a Simulated Un-
derground Environment. Master of
Science Thesis. Department of Civil
Engineering, ASU.
Instruction/Technology
Transfer
Conferences, lecture series, training,
and workshops where information from
this research has been presented include:
Superfund University Training Insti-
tute (SUTI) - approximately 6 courses,
U.S. EPA
DNAPL National Workshop Series -
10 courses, U.S. EPA
Monitoring Well Design National Se-
ries - 10 courses, U.S. EPA
Landfills RCRA Subtitle D National
and International Series -15 courses,
U.S. EPA
U.S. Bureau of Land Management
Hazardous Waste Training - 5
courses. U.S. BLM
Pesticide Managers Training, UC
Davis Extension - 5 courses, U.S.
EPA
National Educational courses - 25
courses, National Ground Water As-
sociation and Environmental Educa-
tion Enterprises
Many National and International Con-
ferences
Project Conclusions and
Recommendations
This work supports the contention that
vapor monitoring around underground stor-
age tanks is beneficial to leak detection
efforts. Problems with the even, radially
outward propagation of gases can exist.
For example, this research has shown
that dry materials tend to sorb vapors,
and a recalcitrant fraction, resistant to de-
sorption, can be formed. Organic materi-
als in soils tested did not demonstrate
sorptive capacities that would make them
effective barriers to vapor migration. Fiber
optic probes showed some promise as
monitoring devices in varying degrees of
vapor saturation.
In sand tank models, colorimetric analy-
sis of dyes, added to leaked fuels, showed
correlation to measured hydrocarbon con-
centrations, but the disparity is generally
too great between dye color and hydro-
carbon concentration to rely on for quanti-
tative work in scientific studies. In experi-
ments run with air-dried porous material
overlying a LNAPL pool floating on a wa-
ter table, unexpected isolation of product
occurred in situations where the water
table was raised. The distribution of en-
trapped hydrocarbon was observed to be
much more irregular than similar situa-
tions where the vadose zone was origi-
nally moist. This suggests the potential for
unusual hydrocarbon entrapment when the
water table rises in conditions where va-
por extraction (enhanced volatilization)
techniques have been conducted in an
overlying vadose zone. This situation may
occur with remediation techniques that in-
volve the combination of dewatering and
vapor extraction. Little is known about the
physics of interfacial interactions in soils
of varying moisture content, and a recom-
mendation from this work is that this be
investigated further.
Acknowledgments
The Principal Investigators, David K.
Kreamer and David E. James, would like
to extend our appreciation to our students,
without whose efforts the research would
not be complete. We also extend our grati-
tude to the University of Nevada, LV for
funding distribution of the research vid-
eos.
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Environmental Protection Agency
Center for Environmental Research Information (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
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