PA/600/A-96/078
U.S. Environmental
Protection Agency (EPA)
USAF Armstrong Laboratory,
Environics Directorate (AL/EQ)
USAF Center for Environmental
Excellence (AFC EE)
Symposium on Natural Attenuation of
Chlorinated Organics in Ground Water
The Hyatt Regency Dallas
Dallas, TX
September 11-13, 1996
Logistical Fact Sheet
A block of rooms is being held for symposium attendees an the Hyatt Regency Dallas for
September 10-13, 1996. The rase is $84/night single occupancy or $ 100/night double occupancy,
plus 13% tax. Reservations and payments must be made on an individual basis. Government
employees must present a valid government identification or tax exempt certificate « be exempt
from federal axes. Please make your room reservations by calling the hotel direcdy and
referencing the "Natural Attenuation Symposium." Reservations must be made by August 9,
1996. After this dan, reservations will be accepted on a space* and rate-available basis only.
Accessibility From Dallas/Fart Worth International Airport (I-35E) South: Take the International Parkway
by Car South and follow signs to 183 East. 183 East will merge with I-35E South. Continue on I-35E to
the Commerce EastfReunion Boulevard exit At the bottom of the exit, look for the Reunion
Boulevard/Reunion Arena exit sign. Stay right to Reunion Boulevard and at the stop sign, turn left
onto Reunion Boulevard. Follow Reunion Boulevard to the right until you reach the second light.
Turn left at the light onto Hotel Drive. This will lead you to the front entrance of the Hyatt
Regency Dallas.
From Waco (1-35E) North; Follow I-3SE North. As you approach downtown, stay in the right-
hand lane. Take the Commerce East/Reunion Boulevard exit. At the bottom of the exit ramp,
turn right onto Reunion Boulevard. Follow Reunion Boulevard to the right At the traffic light
turn left onto Hotel Drive. This will lead you to the front entrance of the Hyatt Regency Dallas.
From Fort Worth (1-30) East: Follow 1-30 East As you approach downtown, stay in the right-
hand lane. Take the Industrial Boulevard exit At the bottom of the exit ramp, turn left ones
Industrial Boulevard. At the first light turn right onto Reunion Boulevard. Follow Reunion
Boulevard to the right At the traffic light turn left onto Hotel Drive. This will lead you to the
front entrance of the Hyatt Regency Dallas.
Registration Eastern Research Group, Inc.
Information 110 Hartwel] Avenue
Lexington, MA 02173-3134
617-674-7374
Hotel Hyatt Regency Dallas
Arrangements 300 Reunion Boulevard
Dallas, TX 75207-4498
. . 800-233-1234
or 214-651-1234
@ Printed on Recycled Pacer

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Case Study: Natural Attenuation of a Trichloroethene Plume
at Picatinny Arsenal, New Jersey
Thomas E. Imbrigiotta and Theodore A. Ehlke
U.S. Geological Survey, West Trenton, New Jersey
Barbara H. Wilson and John T. Wilson
U.S. Environmental Protection Agency, Ada, Oklahoma
INTRODUCTION
Past efforts to clean up aquifers contaminated with chlorinated solvents typically have
relied on engineered remediation systems that were cosdy to build and operate. Recently,
environmental regulatory agencies have begun to give serious consideration to the use of natural
attenuation as a more cost-effective remediation option. The successful use of natural
attenuation to remediate chlorinated-solvent contamination sites depends on understanding the
processes that control the transport and fate of these compounds in the ground-water system. To
this end, the U.S. Geological Survey, as part of its Toxic Substances Hydrology Program, has
been conducting an interdisciplinary research study of ground-water contamination by
chlorinated solvents at Picatinny Arsenal, New Jersey. The objectives of the study are to (1)
identify and quantify the physical, chemical, and biological processes that affect the transport
and fate of chlorinated solvents, particularly trichloroethene (TCE), in the subsurface; (2)
determine the relative importance of these processes at the site; and (3) develop predictive
models of chlorinated-solvent transport that may have transfer value to other solvent-
contaminated sites in similar hydrogeologic environments. This paper reports on the results of
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work done to identify and quantify the natural processes that introduce and remove TCE to and
from the plume at Picatinny Arsenal and to determine which natural TCE-attenuation
mechanisms are the most important on a plume-wide basis.
GEOHYDROLOGY
Picatinny Arsenal is a weapons research-and-development facility located in a narrow gla-
ciated valley in north-central New Jersey (fig. 1). The site is underlain by a 15- to 20-m (meter) -
thick unconfined aquifer consisting primarily of fine to coarse sand with some gravel and discon-
tinuous layers of silt and clay. Ground water flows from the sides of the valley toward the center,
where it discharges to Green Pond Brook. Within the unconfined aquifer, flow is generally hori-
zontal, with some downward flow near the valley walls and upward flow near Green Pond Brook.
Estimated ground-water-flow velocities range from 0.3 to 1.0 m/d (meters per day) at the site on
the basis of hydraulic conductivities that range from 15 to 90 m/d, gradients that range from 1.5
to 3.0 m/ 500 m, and an average porosity of 0.3 (1-4).
GROUND-WATER CONTAMINATION
Ground water at Picatinny Arsenal was contaminated over a period of 30 years as a result
of activities associated with metal-plating and degreasing operations in Building 24 (5-6). The
areal and vertical extent of TCE contamination at the site, determined on the basis of data from
October and November 1991, is shown in figure 1. A really, the plume, as defined by the 10-p.g/L
(micrograms per liter) line, extends about 500 m from Building 24 to Green Pond Brook and is
approximately 250 m wide where it enters the brook. Vertically, TCE contamination is found at
shallow depths near the source, over the entire 15-20-m thickness of the unconfined aquifer in the
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plume center, and at shallow depths as it discharges upward to the brook (figure IB), Whereas
TCE concentrations greater than 1,000 ^ig/L are found in the source area, the TCE concentrations
are highest (>10,000 |ig/L) near the base of the aquifer midway between the source and discharge.
GEOCHEMISTRY OF THE PLUME
Determination of the pH and redox conditions present in a plume is essential to predicting
the types of natural biological interactions that may take place in the aquifer. Results of water-
quality analyses indicate that the pH of ground water in the plume is near-neutral (6.5-7.5) and
concentrations of both dissolved oxygen (< 0.5 mg/L (milligrams per liter)) and nitrate (< 1 mg/L)
are very low. Concentrations of iron(II) are greater than 1 mg/L in some areas of the plume,
whereas sulfate and carbon dioxide are consistently plentiful (> 40 mg/L and > 100 mg/L as
bicarbonate, respectively) as potential terminal electron acceptors. In addition, sulfide odor was
noted in water from many wells within the plume and methane was present at concentrations
ranging from 1 to 85 (ig/L. These findings indicate the plume is primarily anaerobic and contains
a variety of reducing redox environments controlled in different areas by iron(III) reduction, sul-
fate reduction, and methanogenesis. Under these conditions, reductive dechlorination of TCE can
take place if sufficient electron donors are available. Dissolved organic carbon (DOC), consisting
primarily of humic and fulvic acids, may fulfill the electron-donor requirement in this system.
Concentrations of DOC are highest immediately downgradient from the source area (5-14 mg/L)
and also are elevated near the discharge point (1-2 mg/L).
The presence of cis-1,2-dichloroethene (cisDCE) and vinyl chloride (VC), TCE break-
down products, in 75 percent of the wells sampled in and around the plume indicates that reduc-
tive dechlorination of TCE is taking place in the aquifer. Because neither of these compounds
was used in Building 24, they are believed to originate from the biologically mediated breakdown
3

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of TCE. Further evidence for reductive dechlorination of TCE is the similarity among the distri-
butions of TCE, cisDCE, and VC in the aquifer, although the concentrations of cisDCE and VC
are highest in the downgradient portion of the plume near the discharge point.
TRICHLOROETHENE MASS DISTRIBUTION
The mass of TCE dissolved in the ground water in the plume was estimated on the basis
of results of six synoptic samplings during 1987-91. By using a plume volume of 2.3 x 106 m3
(cubic meters), a porosity of 0.3, and the assumption that each well represents a finite volume of
the aquifer, the average mass of TCE dissolved in the plume was determined to be 1,000 ± 200
kg (kilograms) (7). This estimate did not show a consistent increasing or decreasing trend over
the six samplings, which implies that the plume was essentially at steady-state. Most of the
dissolved TCE mass (57%) is present in the ground water near the base of the unconfined
aquifer, where TCE concentrations are greater than 10,000 |ig/L.
The mass of sorbed TCE within the plume was estimated from methanol-extraction
analyses of sediments from six sites along the centerline of the plume (8). The ratio of the
masses of sorbed TCE to dissolved TCE per unit volume of aquifer ranged from 3:1 to 4:1 at
these six sites. Therefore, 3,000 to 4,000 kg of TCE are calculated to be sorbed to aquifer
sediments within the plume. A sorbed mass of 3,500 kg of TCE was used in all calculations.
TRICHLOROETHENE MASS-FLUX ESTIMATES
The major naturally occurring processes that affect the input or removal of TCE to or
from the plume were identified and studied independently as part of the Toxic Substances
Hydrology Program project at Picatinny Arsenal (9-10). The TCE-removal processes
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considered include advective transport, lateral dispersion, anaerobic biotransformation,
diffusion-driven volatilization, advection-driven volatilization, and sorption. The TCE-input
processes evaluated include desorption, infiltration, and dissolution. Each of these processes is
described briefly below and a TCE mass-flux estimate is made for each on the basis of the
results of research conducted in the Picatinny Arsenal plume.
Removal-Process Flux Estimates
Advective transport is the process by which dissolved TCE is removed from the plume
in ground water that is discharging to Green Pond Brook. The mass flux of TCE was calculated
by using an advective flux rate of 800 liters per meter squared per week (based on modeling
analyses (4,11)), a median ground-water TCE concentration of 1,200 (ig/L, and a cross-sectional
area of 980 m~ where the aquifer discharges to the brook. On the basis of these values,
approximately 50 kg/yr (kilograms per year) of TCE are removed from the plume by discharge
to Green Pond Brook.
Lateral dispersion is the process that causes plume spreading by transport of TCE out of
the side boundaries of the plume where the concentration is 10 jug/L (figure 1). By using Fick's
Law, the lateral TCE-concentration gradient, and the estimated area of the sides of the plume, it
was calculated that less than 1 kg/yr of TCE is lost from the plume by this mechanism.
Anaerobic biotransformation is the the biologically mediated process of reductive
dechlorination whereby TCE undergoes the sequential replacement of the chlorine atoms on the
molecule with hydrogen atoms to form cisDCE, VC, and ethene as breakdown products (12-
13). Biotransformation rate constants were determined in laboratory batch microcosm studies of
core samples from five sites along the centerline of the plume (14-15). The first-order TCE-
degradation rate constants obtained in these studies range from -0.004/wk (per week) to -0.035/
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wk, with a median of -0.007/wk. If this latter rate constant is applied to the 1,000 kg of TCE
dissolved in the plume, then about 360 kg/yr of TCE are removed from the plume by the
naturally occurring anaerobic biotransformation.
Volatilization is the loss of TCE from ground water into the soil gas of the unsaturated
zone across the water table. Volatilization is driven by diffusive and advective mechanisms.
The rate of loss of TCE in diffusion-driven volatilization is determined by the TCE gradient in
the soil gas of the unsaturated zone. Diffusion-driven volatilization was estimated by using
Fick's Law, field-measured unsaturated-zone soil-gas TCE gradients, bulk diffusion coefficients
from the literature for sites with similar soils, and the area of the plume. Removal of TCE from
the plume by diffusion-driven volatilization is calculated to be less than 1 kg/yr over the area of
the plume (7,16). In advection-driven volatilization the rate of loss of TCE is controlled by
pressure and temperature changes in the unsaturated-zone soil gas. Advection-driven
volatilization was investigated by using a prototype vertical-flux-measuring device at Picatinny
Arsenal (16). On the basis of flux measurements made with the device at eight sites and the area
of the plume, the TCE removed from the plume by advection-driven volatilization is calculated
to be approximately 50 kg/yr.
Sorption is the partitioning of TCE from the ground water into the organic-carbon
fraction of the aquifer sediments. Field partition coefficients measured at several locations
within the plume (8) indicate that more TCE was sorbed to aquifer organic materials at all sites
than would be predicted if the sorbed TCE concentrations were in equilibrium with the ground-
water TCE concentrations. Therefore, desorption processes rather than sorption processes most
likely predominate. Removal of TCE by sorption is estimated to be less than 1 kg/yr.
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Input-Process Flux Estimates
Desorption is the process by which TCE partitions out of the organic phase on the
contaminated sediments back into the ground water in response to concentration gradients. This
process at Picatinny Arsenal was characterized as having two parts: an initial rapid phase of
desorption in which 0 to 10 percent of the TCE is released and a second, slower phase of
desorption in which most of the TCE is released over a longer period of rime (8). First-order
desorption rate constants ranging from -0.003/wk to -0.015/wk were measured in flow-through
column experiments. Because these experiments were conducted with clean water, the
desorption rates obtained probably are higher than in situ desorption rates. For this reason, the
smaller of the desorption rate constants (-0.003/wk) and the total amount of TCE estimated to be
sorbed to the plume sediments (3,500 kg) were used to calculate that 550 kg/yr of TCE are being
input to the plume by means of desorption.
Infiltration, the process by which TCE in the soil gas or on the unsaturated-zone soil is
dissolved by percolating recharge to the ground water, was studied with laboratory soil columns,
field infiltration experiments, and multi-phase solute-transport modeling (17). Because the
concentrations of TCE in the soil gas generally are low over most of the plume, and because
infiltration occurs only during recharge events rather than continuously throughout the year, it
was estimated that the input of TCE to the plume by this process is less than 1 kg/yr.
Dissolution is the process by which dense nonaqueous phase liquid (DNAPL) TCE
dissolves into the ground water. The presence of DNAPL TCE at Picatinny Arsenal at the base
of the unconfmed aquifer midway between the source and the brook has been suspected because
concentrations of TCE in ground water at this location are much higher than those immediately
upgradient. Concentrations of TCE in deep wells in this area consistently exceed 2% of
saturation, which is one indication of DNAPL presence (18). DNAPL TCE has not been
7

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confirmed by measurement or observation of free-phase TCE in any water or soil sample from
the arsenal. Consequently, the mass of DNAPL TCE that is input by dissolution cannot be
calculated directly but can only be estimated by the difference between the sum of the mass
removed by all removal processes and the sum of the mass introduced by all other input
processes.
MASS-BALANCE ANALYSIS
The estimated mass balance for the TCE plume at Pieatinny Arsenal is shown in figure
2. All inputs are represented with open arrows; all outputs are represented with solid arrows.
Approximately 460 kg/yr of dissolved TCE are estimated to be removed from the plume
by natural processes. Of this, 360 kg/yr, or 78% of the TCE removed annually, is removed as a
result of anaerobic biotransformation. This is by far the most important TCE removal process
operating in the Pieatinny Arsenal plume. Removal by advective transport to Green Pond Brook
and advection-driven volatilization are each estimated at 50 kg/yr. Therefore, each of these
processes is responsible for the removal of about 11% of the total TCE removed annually from
the plume. Lateral dispersion, diffusion-driven volatilization, and sorption are all of minor
importance when compared to these major processes.
The finding that natural anaerobic biotransformation is the principal mechanism for
removal of TCE from the plume at Pieatinny Arsenal is significant. Anaerobic
biotransformation has been reported to be a major natural removal process for TCE at only a
few sites (19), and this conclusion has not previously been reached by quantifying and
comparing the magnitude of all other removal processes occurring at a site. This result is likely
to have great transfer value to other sites with similar geochemistry, hydrology, and geology.
The process of desorption is the most important input mechanism evaluated at Pieatinny
8

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Arsenal; it accounts for the introduction of an estimated 550 kg/yr of TCE. Input by infiltration
is very small in comparison (<1 kg/yr). Because the sum of the inputs is larger than the sum of
the outputs, dissolution of DNAPL TCE in the system cannot be estimated.
The fact that long-term desorption is a significant continuing source of TCE to the
aquifer may explain why the TCE concentrations are still relatively high in the source area
(>1,000 ug/L) 13 years after the use of TCE was discontinued at the site. This finding is
significant because it shows that desorption can be an important input mechanism even at sites
where the sediment organic content is low (<0.5%),
Because the mass of TCE in the plume was at steady-state during these studies, the
sources of TCE ideally should equal the sinks of TCE. Although the estimated inputs do not
equal the estimated outputs in the mass balance, they are of the same order of magnitude.
Additional study of the individual processes would be necessary to refine the mass balance
further. Because confidence in the output-process mass-flux estimates is high and the TCE-
desorption rate constants used probably were on the high side, the desorption mass-flux estimate
may be higher than the actual value.
FIELD-SCALE ESTIMATE OF NATURAL ATTENUATION RATE
The natural attenuation rate of TCE at Picatinny Arsenal was calculated from field data
and compared to the anaerobic-biotransformation rates calculated in the laboratory microcosm
studies. If first-order kinetics are assumed, the decrease in TCE concentrations from the source
area to the discharge area (1,900 jig/L to 760 (ig/L), the time of travel for TCE between these
two points in the plume (3.1 yr), and the distance between these two sites (470 m), the field-
scale natural-attenuation rate constant is calculated to be -0.006/wk. This field-calculated rate
constant is nearly identical to the median rate constant of -0.007/wk determined in the laboratory
9

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microcosm experiments. That both methods yield rate constants of similar magnitude confirms
that most of the natural attenuation that occurs in the Picatinny Arsenal plume is due to
anaerobic biotransformation. In addition, it indicates that the methods used to make these
estimates and measurements are valid.
COMPARISON OF NATURAL ATTENUATION PROCESSES TO PUMP-AND-TREAT
REMEDIATION
A pump-and-treat system was installed as an interim remediation measure in the
Picatinny Arsenal TCE plume as an interim remediation measure in September 1992. It consists
of a set of five withdrawal wells from which an average of 440,000 L/d are pumped to a
treatment system equipped with stripping towers and granulated activated-carbon filters. On the
basis of average pumpage values and ground-water TCE concentrations in each withdrawal well
during 1995, the pump-and-treat system is currently removing about 70 kg/yr of TCE at a cost
of $700,000/yr. This is about one-fifth the amount of TCE being removed from the plume each
year by anaerobic biotransformation. It is just slightly more than the mass of TCE being
removed by each of the processes of advective transport and advection-driven volatilization.
CONCLUSIONS
The relative importance of all naturally occurring processes that introduce or remove
TCE to or from a contamination plume at Picatinny Arsenal, New Jersey, was determined.
Anaerobic biotransformation is the most important process for TCE removal from the plume by
almost an order of magnitude over advective transport and advection-driven volatilization.
Anaerobic biotransformation accounts for an estimated 78% of the total mass of TCE removed
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from the plume annually. Other removal processes-lateral dispersion, diffusion-driven
volatilization, and sorption-are minor in comparison. Desorption is the most significant TCE
input process evaluated. A mass-balance analysis shows that the removal of TCE from the
plume by natural attenuation processes is of the same order of magnitude as the input of TCE to
the plume. The natural-attenuation rate constant calculated from field TCE concentrations and
time-of-travel data is in close agreement with anaerobic-biotransformation rate constants
measured in laboratory microcosm studies.
Anaerobic biotransformation removes approximately five times the mass of TCE
removed by an interim pump-and-treat remediation system operating at the Picatinny Arsenal
site. The pump-and-treat system removes just slightly more mass per year than each of the
processes of advective transport to the Green Pond Brook and advection-driven volatilization.
REFERENCES
1.	Martin, M. 1989. Preliminary results of a study to simulate trichloroethylene movement in ground water at
Picatinny Arsenal, New Jersey. U.S. Geological Survey Toxic Substances Hydrology Program-Proceedings of
the technical meeting, Phoenix, Ariz., September 26-30,1988, G.E. Mallard and S.E. Ragone, eds. U.S.
Geological Survey Water-Resources Investigations Report 88-4220. pp. 377-383.
2.	Martin, M. 1991. Simulation of reactive multispecies transport in two dimensional ground-water-flow
systems. U.S. Geological Survey Toxic Substances Hydrology Program-Proceedings of the technical meeting,
Monterey, Calif., March 11-15,1991, G.E. Mallard and D.A. Aronson, eds. U.S. Geological Survey Water-
Resources Investigations Report 91-4034. pp. 698-703.
3.	Martin, M. 1995. Simulation of transport, desorption, volatilization, and microbial degradation of
trichloroethylene in ground water at Picatinny Arsenal, New Jersey. U.S. Geological Survey Toxic Substances
11

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Hydrology Program-Proceedings of the technical meeting, Colorado Springs, Colo., September 20-24,1993,
D.W. Morganwalp and D.A. Aronson, eds. U.S. Geological Survey Water-Resources Investigations Report 94-
4015.
4.	Voronin, L.M. 1991. Simulation of ground-water flow at Picatinny Arsenal, New Jersey. U.S. Geological
Survey Toxic Substances Hydrology Program-Proceedings of the technical meeting, Monterey, Calif., March
11-15,1991, G.E. Mallard and DA. Aronson, eds. U.S. Geological Survey Water-Resources Investigations
Report 91-4034. pp. 713-720.
5.	Sargent, B.P., T. V. Fusillo, D.A. Storck, and J.A. Smith. 1990. Ground-water contamination in the area of
Building 24, Picatinny Arsenal, New Jersey. U.S. Geological Survey Water-Resources Investigations Report
90-4057, p. 94.
6.	Benioff, P.A., M.H. Bhattacharyya, C. Biang, S.Y. Chiu, S. Miller, T. Patton, D. Pearl, A. Yonk, and C.R.
Yuen. 1990. Remedial investigation concept plan for Picatinny Arsenal, Volume 2: Descriptions of and
sampling plans for remedial investigation sites. Argonne National Laboratory, Environmental Assessment and
Information Sciences Division, Argonne, 111. pp. 22-1 - 22-24.
7.	Irnbrigiotta, T.E., T.A. Ehlke, M. Martin, D. Koller, and J.A. Smith. 1995. Chemical and biological processes
affecting the fate and transport of trichloroethylene in the subsurface at Picatinny Arsenal, New Jersey. Hydro-
logical Science and Technology 1 l(l-4):26-50.
8.	Koller, D., TJE. Irnbrigiotta, A.L. Baehr, and J.A, Smith. 1995. Desorption of trichloroethylene from aquifer
sediments at Picatinny Arsenal, New Jersey. U.S. Geological Survey Toxic Substances Hydrology Program-
Proceedings of the technical meeting, Colorado Springs, Colo., September 20-24,1993, D.W. Morganwalp and
D.A. Aronson, eds. U.S. Geological Survey Water-Resources Investigations Report 94-4015.
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9.	Imbrigiotta, TJ2. and M. Martin. 1991. Overview of research activities on the movement and fate of
chlorinated solvents in ground water at Picatinny Arsenal, New Jersey. U.S. Geological Survey Toxic
Substances Hydrology Program-Proceedings of the technical meeting, Monterey, Calif., March 11-15,1991,
G.E. Mallard and D.A. Aronson, eds. U.S. Geological Survey Water-Resources Investigations Report 914034,
pp. 673-680.
10.	Imbrigioua, TJE., and M. Martin. 1995. Overview of research activities on the transport and fate of
chlorinated solvents in ground water at Picatinny Arsenal, New Jersey, 1991-93. U.S. Geological Survey
Toxic Substances Hydrology Program-Proceedings of the technical meeting, Colorado Springs, Colo.,
September 20-24,1993, D.W. Morganwalp and D.A. Aronson, eds. U.S. Geological Survey Water-Resources
Investigations Report 94-4015.
11.	Martin, M., and T.E. Imbrigioua. 1994. Contamination of ground water with trichloroethylene at the Building
24 site at Picatinny Arsenal, New Jersey. U.S. Environmental Protection Agency Symposium on Intrinsic
Bioremediation of Ground Water, Denver, Colo., August 30-September 1,1994. EPA/540/R-94/515. pp. 143-
153.
12.	Parsons, FZ., P.R. Wood, and J. DeMarco. 1984. Transformations of tetrachloroethene and trichloroethene in
microcosms and ground water. Journal of the American Water Works Association 76<2):56-59.
13.	Vogel, T.M., C.S. Criddle, and P.L. McCarty. 1987. Transformations of halogenated aliphatic compounds.
Environmental Science and Technology 21(8):722-736.
14.	Wilson, B.H., T.A. Ehlke, T.E. Imbrigioua, and J.T. Wilson. 1991. Reductive dechlorination of
trichloroethylene in anoxic aquifer material from Picatinny Arsenal, New Jersey, U.S. Geological Survey
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Toxic Substances Hydrology Program-Proceedings of the technical meeting, Monterey, Calif., March 11-15,
1991, G.E. Mallard and D.A. Aronson, eds. U.S. Geological Survey Water-Resources Investigations Report 91-
4034. pp. 704-707.
15.	Ehlke, T. A., T£. Imbrigiotta, BJH. Wilson, and J.T.Wilson. 1991. Biotransformation of cis-1,2-
dichloroethvlene in aquifer material from Picatinny Arsenal, Morris County, New Jersey. U.S. Geological
Survey Toxic Substances Hydrology Program-Proceedings of the technical meeting, Monterey, Calif., March
11-15,1991, G.E. Mallard and D.A. Aronson, eds. U.S. Geological Survey Water-Resources Investigations
Report 91-4034. pp. 689-697.
16.	Smith, J.A., A.K. Tisdale, and HJ. Cho. In press. Quantification of natural vapor fluxes of trichloroethene in
the unsaturated zone at Picatinny Arsenal, New Jersey. Environmental Science and Technology 30.
17.	Cho, H.J., P.R. Jaffe, and J.A. Smith. 1993. Simulating the volatilization of solvents in unsaturated soils
during laboratory and field infiltration experiments. Water Resources Research 29(10):3329-3342.
18.	Cohen, R.M., and J.W. Mercer. 1993. DNAPL site evaluation. Boca Raton, Florida: C.K. Smoley.
19.	Wilson, J.T., J.W. Weaver, and D.H. Kampbell. 1994. Intrinsic biorernediation of TCE in ground water at an
NPL site in St. Joseph, Michigan. U.S. Environmental Protection Agency Symposium on Intrinsic Biorernedia-
tion of Ground Water, Denver, Colo., August 30-September 1,1994. EPA/540/R-94/515. pp. 154-160.
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A.
cos He
3**r 5~amc gsoo*
2i
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ADVECTION-DRIVEN
VOLATILfTZATlON
(50 kg/yr)
ADVECT1VE
TRANSPORT TO
GREEN POND BROOK
(50 kg/yr)
DIFFUSION-DRIVEN
VOLATILIZATION
(<1 kg/yr)
Ltad surface
DESORPTiON
(550 kg/yr)
INFILTRATION
(«1 kg/yr)
SORPTION
(«1 kg/yr)
ANAEROBIC
BIOTRANSFORMATION
(360 kg/yr)
DISSOLUTION
OF DNAPL
(not astimatad)
Estim*ted top of confininf anit
NOT TO SCALE
GAINS
TRICHLOROETHENE MASS-BALANCE COMPONENTS
[kg/yr, kilograms per year; <, less than]
LOSSES
DESORPTION	550 kg/yr
INFILTRATION	<1 kg/yr
DISSOLUTION OF DENSE not estimated
NONAQUEOUS PHASE LIQUID
TOTAL
550 kg/yr
ANAEROBIC BIOTRANSFORMATON 360 kg/yr
ADVECTIVE TRANSPORT TO BROOK 50 kg/yr
ADVECTION-DRIVEN VOLATILIZATION 50 kg/yr
LATERAL DISPERSION <1 kg/yr
DIFFUSION-DRIVEN VOLATILIZATION <1 kg/yr
SORPTION	<1 ka/yr
TOTAL
460 kg/yr
Figure 2. Mass-balance estimates of fluxes of naturally occurring processes that affect the fate and transport
of trlchloroethene In the ground-water system at Picatinny Arsenal, New Jersey.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
—
1. REPORT NO. 2.
EPA/6OO/A-96/078
3. REC1P
4. TITLE AND SUBTITLE
CASE STUDT;NATURAL ATTENUATION OF A TRICHLOROETHENE PLUME
AT PICATINNY ARSENAL, NEW JERSEY
S. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7, AUTHOftlSI
THOMAS E. IMBRIGIOTTA AND THEODORE A EHLKE (1)
BARBARA H. WILSON AND JOHN T. WILSON (2)
8. PERFORMING ORGANIZATION REPORT NO.
9, PERFORMING ORGANIZATION NAME ANO ADORESS
U.S. GEOLOGICAL SURVEY (1)
WEST TRENTON, NEW JERSEY
10. PROGRAM ELEMENT NO.
CBWD1A
11. CONTRACT/GRANT no.
USGS DW14935106
12. SPONSORING AGENCY NAME ANO AOORESS
U.S. ENVIRONMENTAL PROTECTION AGENCY (2)
ADA, OKLAHOMA
13. TYPE OF REPORT ANO PERlOO COVERED
ww rmPTro
14. SPONSORING AGENCY COOE
EPA/600/15
15. SUPPLEMENTARY NOTES r\ 1 ^ ^
Oral presentation to be given by Thomas E. Imbrigiotta at The
Synposium on Natural Attenuation of Chlorinated Organics in Ground Water at The Hyatt Regency
in Dallas. Texas. September 11-13. 1996.
16. ABSTRACT
This study determined the feasibility of in situ cometabloic remediation of gas-phase chlorinated ethenes at Picatinny
Arsenal, NJ. Cometabolic biotransformation of trichloroethylene (TCE) and cis-1,2-dichloroethylene (cis-DCE) was
studied in a laboratory experiment with unsaturated-zone soil cores collected within a contaminant plume near the
source. Concentrations of TCE and cis-DCE in soil, soil gas, and ground water within the plume also were quantified.
At the highest concentrations studied, TCE (3.2uM) mixed with cis-OCE (4.3uM) was degraded most rapidly (0.05jimol
CE/L/d, 0.09|imol cis-DCE/L/D) in acclimated soils with a 3-percent methane headspace. Degradation of TCE at
lesser concentrations (1.3p,M) as the only chloroethene present in fertilized, acclimated soil was much faster
(0.12|imol TCE/L/d) in the presence of 1.2 methane. Most of the unsaturated-zone TCE (>99.9 percent) near the
contaminant source was sorbed to soil. Results of soil-gas analyses indicate that the concentration of unsaturated-
zone TCE near the contaminant source was highest (Q.32n in a shallow clay layer, and decreased with depth to the
water table. This indicates that the original contamination was mostly from condensed TCE which drained from a
degreasing tank to a nearby dry well. The concentration of TCE in unsaturated-zone soil elsewhere throughout the
plume increased with depth, indicating that most unsaturated-zone TCE contamination resulted from volatilization
losses of TCE from contaminated shallow ground water.
17. KEY WOROS ANO DOCUMENT ANALYSIS
a. DESCRIPTORS
b.lOENTIFlERS/OPEN ENDED TERMS
c. COSATi Field.Croup
COMETABOLIC REMEDIATION
CHLORINATED ETHENES
C0NIAM9NANT PLUME
VOLITILIZATION LOSSES


18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS iThts Rrpnrr/
UNCLASSIFIED
21. NO. OF »*G€S
16
20. SECURITY CLASS /This pvw
UNCLASSIFIED
22. CRICE
SPa Fo*m 2220-1 (R«». 4-77) previous coition >s osiolcte
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