NATURAL ATTENUATION OF MTBE
James W. Weaver1, John T. Wilson2, Jong Soo Cho*3
Hydogeologist, US Environmental Protection Agency, Office of Development, National Exposure
Research Laboratory, 960 College Station Road Athens, Georgia 30605-2700, USA, email:
weaver.jim@epa. gov
2 Senior Microbiologist, US Environmental Protection Agency, Office of Research and Development,
National Risk Management Laboratory, P.O. Box 1198, Ada, Oklahoma 74820, USA, email:
wilson. johnt@eap. gov
*3 Presenter. Senior Director of Remedial Construction, Environmental Strategies and Application, Inc.
495 Union Avenue, Suite ID, Middlesex, New Jersey 08846, USA, email: cho@askesa.com
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ABSTRACT
Three case studies of MTBE contamination of ground water are presented. Each
study site had its own unique geochemical characteristics. At the first study site dissolved
oxygen was the dominant electron acceptor. At the second site, the dominant electron
acceptors were methanogenesis and iron reduction. At the third site, the dominant
electron acceptor was sulfate reduction. At the first site, the total mass of BTEX
compounds decreased over three rounds of sampling, indicating a net loss of mass in the
aquifer. In contrast, the MTBE data did not show a clear trend of attenuation over time.
Under methanogenic conditions at the second site, the distribution of MTBE in the plume
provided evidence of natural attenuation of MTBE in the ground water. A mass balance
analysis evaluated the rate of natural attenuation of the source area. Under sulfate
reducing conditions at the third site, there was field scale evidence of natural attenuation,
but attenuation may have resulted from physical processes such as dilution and
dispersion, and not through natural biodegradation. Although the rate of attenuation of
MTBE was not fast compared to attenuation of BTEX compounds, the rate was of
environmental significance, and it could be estimated qualitatively.
1. INTRODUCTION
Methyl tert-butyl ether (MTBE) has been added to gasoline since the 1970s.
Initially, MTBE was added as an octane-enhancing replacement for tetraethyl lead, which
was being phased out of use. Later, MTBE was used as a fuel oxygenate to decrease the
amount of carbon monoxide in automobile emissions. The 1990 Clean Air Act
amendment mandated the seasonal use of fuel oxygenates, such as MTBE, in certain
parts of the United States. This use has resulted in MTBE being released to ground water
(Squillace et al. [1]). Initial research on MTBE indicated that it was relatively recalcitrant
to biodegradation. Later, evidence began to emerge showing that MTBE was
biodegradable under certain conditions or when certain microorganisms were present.
Biodegradation under aerobic conditions was reported in several papers (Salanitro et al.
[2,3], Mo et al. [4]). Park and Cowan [5] reported aerobic biodegradation with a half-life
of MTBE about 2 days for selected microorganisms in the laboratory. Field studies of
MTBE biodegradation (Borden et al. [6], Landmeyer at al. [7]) indicated that under
certain anaerobic conditions, MTBE biodegradation with low but measurable rates
occurred. Mormile et al. [8] and Yeh and Novak [9] reported limited biodegradation
under anaerobic conditions.
The current consensus of research is that MTBE is biodegradable, but rates are
low relative to BTEX compounds (Chapelle [10]). This has shown that intrinsic
biodegradation is less efficient for MTBE than it is for BTEX compounds. Because of its
high solubility, low adsorption on soil, and very limited biodegradation rate, the sizes of
MTBE plumes in groundwater are much larger than BTEX plumes.
In this paper, we present three case studies of natural attenuation of MTBE in
ground water. The first case study was conducted at a gas station site in Long Island,
New York. The MTBE plume distribution was controlled by geochemical changes in the
aquifer caused by previous releases of BTEX compounds. Previous releases of BTEX
had depleted the oxygen in the aquifer. The plume MTBE was contained within a region
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of aquifer that had been previously depleted of oxygen, and as a consequence, no oxygen
was available for aerobic metabolism of MTBE. The MTBE could be thought to be
hiding behind the shadow of depleted dissolved oxygen. The natural attenuation of
MTBE was evidenced from decreasing MTBE mass in historical monitoring data. This
case was the work of the US EPA and New York State Department of Environmental
Quality.
The second case is the US EPA and US Coast Guard's work in the US Coast
Guard Supply Center, North Carolina. The geochemical condition was methanogenic.
The source of the plume was from the old fuel tank farm. We approached this site with
mass balance analysis. Third case is the US EPA's work at the gasoline spill site from
the service station in the US Navy base, California. Several studies on the MTBE plume
are still ongoing at the site, including active bioremediation, soil venting and air sparging,
phytoremediation, and natural attenuation. The EPA researchers are conducting a natural
attenuation study in the field and a laboratory microcosm study. The dominant
biodegradation processes for BTEX and MTBE at the site were iron reduction and
methanogenesis. A preliminary analysis of field data showed that MTBE concentrations
in the plume along the center path were declining.
2. CASE 1: SERVICE STATION IN LONG ISLAND, NEW YORK
Subsurface contamination was detected at E. Patchogue, New York when water
from a residential well became undrinkable. The drinking water was rendered
undrinkable because of high concentrations of methyl tert-buty\ ether (MTBE). Later
sampling also found high concentrations of benzene, toluene, ethyl benzene and xylene
isomers (BTEX) from locations near this well. By sampling, the State traced the
contamination back toward an abandoned service station approximately 4000 feet (1200
m) up gradient from the contaminated well. Soil borings in the area of the service station
confirmed the presence of hydrocarbon contamination. The tanks in the service station •
were probably removed in 1988, which could be the latest date that gasoline could have
been released.
. This gasoline spill was an unusual case study because of the size of the
contaminant plume and because of the relatively large amount of data available from the
site. Data from multilevel samplers and screened wells were used to delineate the extent
of BTEX and MTBE contamination. The contaminant plume was found to extend from
the suspected source down gradient toward the shoreline of Great South Bay, which is
located just south of the site (Figure 1). In 1994 and 1995, the contaminant plume was
mapped from samples taken from 26 multilevel samplers and 22 monitoring wells. Water
samples from four sampling rounds were analyzed for BTEX and MTBE. Total organic
carbon contents were determined on 11 clean core samples.
Published studies of groundwater flow on Long Island indicated that a regional •
ground water divide lies along the length of the island and to the north of the geographic
centerline (Eckhardt and Stackelberg [11]). South of the divide, flow is generally toward
the Atlantic Ocean. Buxton and Modica [12] estimated that the hydraulic conductivity of
the upper glacial aquifer is on the order of 8.1 ^l<5"'*cm/sec (230 ft/day) in the outwash
section near the southern shore, with estimated ground water velocity of 110 meters per
year (360 ft/year) or greater.
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Moments Analysis
The relatively large number of monitoring wells and multilevel samplers
generated a three-dimensional data set, which were analyzed by calculating the spatial
moments of each concentration distribution. For most of the plume, the wells crossed the
entire width of the plume. In some locations, however, monitoring wells with high
contaminant concentrations were located on the edge of the sampling network. Therefore
some of the contaminant mass was not included in the estimates given below. Because
the MTBE plume was located down-gradient of MW-30, MW-38, and MW-39, the
MTBE plume was contained within the sampling network, and the mass estimates of
MTBE were not greatly impacted by the spacing of monitoring wells.
Table 1 shows the mass estimates and the distance of the center of mass of BTEX
and MTBE from the source. Data in sampling round one were taken as the wells were
installed from July 1994 to March 1995. Data from sampling round two were taken from
April 11, 1995 to April 20, 1995 and those from sampling round three were taken from
October 10, 1995 to October 24, 1995. Since the sampling in round one was done over a
long time period, contaminants sampled up-gradient may have been transported to down-
gradient receptor wells before they were sampled.
The porosity and solids density were assumed to be 0.30 and 2.65 g/cm3,
respectively, giving a bulk density of 1.86 g/cm3. Table 1 lists estimated sorbed masses-
for each chemical. The estimated mass of BTEX compounds decreased between each
sample round. Each of these compounds was expected to undergo biodegradation in the
aquifer, but each continued to dissolve into the aquifer through October 1995. The latter
fact was established by the persistence of BTEX concentrations near the source. The
mass of MTBE, however, appeared to increase between the first two sample rounds; then
decreased between the second and third sample rounds. MTBE was not detected between
the source and a point approximately 600 m (2000 ft) down-gradient (Figure 2). Thus it
appeared that MTBE was almost entirely leached from the gasoline near the source.
MTBE and Electron Acceptors Distribution
The most interesting and unique characteristic of the MTBE plume at this site is
the fact that MTBE was distributed along the low concentration zone of dissolved
oxygen. Comparing the MTBE plume (Figure 2) and dissolved oxygen distribution
(Figure 3) reveals that the MTBE plume located where the dissolved oxygen
concentration was less than 2 mg/L. Geochemical analysis of the ground water indicated
that the ground water at the site had very low levels of nitrate, iron II, and methane.
Sulfate concentration was generally high (more than 30 mg/L) and the sulfate was not
being used as the primary electron acceptor inside the MTBE plume. At this site, the
major electron acceptor used for hydrocarbon degradation was the dissolved oxygen.
Table 1. Moment Based Mass Estimates and Center of Mass (E. Patchogue, NY)
From Weaver et al. [13]
MTBE
Sample Round 1
Mw
(kg)
268
Ms
(kg)
24
d
(m)
1387
Sample Round 2
Mw
(kg)
386
Ms
(kg)
34
d
(m)
1557
Sample Round 3
Mw
(kg)
229
Ms
(kg)
20
d
(m)
1583
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B
T
E
X
241
108
29
149
156
253
249
1041
991
230
347
222
117
65
24
95
76
152
206
663
1004
298
347
111
58
60
21
92
38
141
180
643
1061
306
326
272
Mw: Mass dissolved in ground water
Ms: Mass sorbed to the solid, estimated from Koc
d: distance of the center of mass from the suspected source
3. CASE 2: US COAST GUARD SUPPORT CENTER, ELIZABETH
CITY, NORTH CAROLINA
This study was conducted at the former fuel farm site at the US Coast Guard
Support Center, Elizabeth City, North Carolina. The following description is excerpted
from the Former Fuel Farm Work Plan, a part of the Remediation Feasibility Assessment
Work Plan prepared for the U.S. Coast Guard Support Center Elizabeth City, North
Carolina, by Parsons Engineering Science, 1996.
The Support Center is located on the southern bank of the Pasquotank River. The
former fuel farm was located south of concrete ramp used to recover seaplanes from the
river (Figure 4). Currently a plume of MTBE and fuel hydrocarbons in ground water
emanates from a source area in the location of the former fuel farm, and flows under the
concrete ramp toward the river to the North, and toward a drainage canal along the
western side of the seaplane ramp. This source area corresponds to the former location of
fuel storage tanks on the site.
The fuel farm had been in use since 1942, and originally consisted of a 50,000- '
gallons (190,000 liter) concrete underground storage tank and two steel underground
storage tanks with a volume of 12,000-gallons (45,000 liter) and 15,000-gallons (57,000
liter) respectively (Adjacent to location CPT-1 in Figure 4). The steel tanks were
apparently removed in mid 1980s. In addition to the underground storage tanks, two steel
above ground storage tanks with a capacity of 50,000 gallons (190,000 liters) were
installed in mid 1980s. There was evidence of corrosion in the transfer lines from these
tanks. They were taken out of service and removed from the site. No evidence of a
release from the pipes was discovered.
The U.S. Coast Guard began a free product recovery effort at the site in
September 1990. Eight recovery wells were arranged around the source area in a circle.
By March 1992, a total of 79,000 gallons (300,000 liters) of fuel was recovered.
Core Sampling in Source Area
In September 1996, a Geoprobe™ direct push system was used to acquire core
samples in continuous vertical profiles at seven locations in or near the source. The water
table was detected at the depth 7.0 to 8.0 feet (2.1 to 2.4 meters) below land surface. The
cores extended from the surface to a depth 12 to 16 feet (3.7 to 4.9 meters).
The cores were cut into subcores of 4 inches (10 cm) length and a plug was
acquired from each subcore **» extracted with 10 ml of methylene chloride and 5 ml of
distilled water. Those samples were shipped to the laboratory for analysis by a GC/MS.
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The cores at each sampling location extended from clean soil above the release, through
the release to clean aquifer material below the release. The quantity of Total Petroleum
Hydrocarbon (TPH) or MTBE in individual cores was summed to determine the total
amount of TPH and MTBE present at each location. The greatest quantity of TPH was •
found at locations CPT-2 and CPT-1 (Figure 4). These locations were near the location
of the original underground storage tanks. These two locations also had the greatest mass
of MTBE. The fuel release that contains MTBE is centered around locations CPT-1 and
CPT-2. With the assumed source area of 11,000 m2, the total quantity of fuel
hydrocarbons remaining in the source was estimated to be about 500,000 kg. With the
fuel density of 0.82 kg/liter, this corresponds to 620,000 liters (180,000 gallons) of fuel.
The total quantity of MTBE was estimated to be in the range of between 46 kg and 140
kg.
Geochemical Context of the MTBE Plume
The MTBE plume was contained within a plume of methane. Methane
concentrations generally exceeded 3.0 nig/liter, and often exceeded 10 mg/liter. In
general, this aquifer was strongly methanogenic. Concentrations of methane averaged 7
mg/liter, which corresponds to 9 mg/liter of hydrocarbon originally metabolized.
Approximately 6 mg of carbon dioxide would also be produced (Wiedemeier et al. [14]).
The MTBE plume and BTEX plume were contained within a region of the aquifer that is
depleted of molecular oxygen. Many regions of the aquifer had less than 0.1 mg/liter
oxygen. The background concentration of dissolved oxygen was near 3.6 mg/liter.
Ground water in the region of the aquifer that contains MTBE and BTEX compounds
was also depleted of sulfate. Sulfate concentrations were reduced from a background of
near 28 mg/liter to less than 4 mg/liter. The same regions that were depleted in molecular
oxygen and sulfate had significant accumulations of Iron II. The background
concentration of Iron II was less than 1 mg/liter. Many regions of the aquifer with
MTBE and BTEX compounds had Iron II concentrations greater than 50 mg/liter. The
pH of the plume was generally near 6.5 and below 6.0 only in the ground water that was
in direct contact with the LNAPL. Under these conditions, carbon dioxide produced
through oxidation of petroleum hydrocarbons would react with carbonate minerals in the
aquifer matrix to produce bicarbonate alkalinity in the ground water. Data showed that as
much as 200 mg/liter of alkalinity was produced by oxidation of petroleum hydrocarbons.
This corresponds to 88 mg/liter of carbon dioxide produced or 28 mg/liter of TPH
consumed. There was more than enough carbon dioxide production to account for the
depletion of oxygen and sulfate, and the production of Iron II and methane.
Calculation of Mass Transfer of MTBE from the Entire Source Area to the Plume
The mass transfer of MTBE from the source LNAPL to the ground water moving
underneath was estimated by calculating the flux of MTBE moving away from the source
across the East-West transect (A-A* in Figure 4), then comparing that flux to the total
mass of MTBE in the source area.
The average hydraulic conductivity for the site was used to calculate the Darcy's
velocity that corresponded to that gradient. Approximately 5,300 cubic meters of water
crosses the transect each year. The flux of water at each location was multiplied by the
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average concentration at each location, then summed. The amount of MTBE that moved
from the source area across the transect was 2.76 kg/year.
The lower limit on the total quantity of MTBE in the source area was 46 kg. If
this flux did not change over time, it would take at least seventeen years to remove the
MTBE from the source. If the rate of transfer of MTBE to ground water is proportional
to the amount of MTBE in the source, the instantaneous rate of transfer would be 0.06 per
year. The average concentration of MTBE at the most contaminated locations within the
transect was 1,200 |ig/liter. At this rate of attenuation of the source, it would require '
approximately sixty years for the concentration to reach 30 jag/liter.
Rate of Attenuation of MTBE along Flow Paths
The permanent monitoring wells at the site were sampled for MTBE and BTEX.
The rate of attenuation of MTBE at field scale was calculated from the concentration of
MTBE in those monitoring wells that were down gradient of the "hot-spot" location CPT-
1 (Figure 4). The water was sampled in October 1998. The average hydraulic
conductivity was 0.025 cm/sec and the hydraulic gradient was 0.00157. With an effective
porosity of 0.25, the calculated seepage velocity was 50 meters per year. Table 2 lists the
apparent attenuation of MTBE to the travel time from the source.
TABLE 2. ATTENUATION OF MTBE IN GROUND WITH TIME OF TRAVEL
FROM THE SOURCE.
Monitoring
Well
CPT-1
ESM-14
ESM-3
ESM-10
ESM-11
Distance from
CPT-1
(feet)
0
330
450
590
790
Distance from
CPT-1
(meters)
0
101
137
180
241
MTBE
(jag/liter)
1740
383
9.73
3.9
2
Travel Time
(years)
0.0
2.0 '
2.8
3.6
4.9
The apparent first-order rate of attenuation of MTBE at field scale was estimated
by a linear regression of the natural logarithm of the concentration of MTBE against time
of travel from the source. The rate of attenuation of MTBE was 1.54 +/- 1.02 per year at
95% confidence, where the confidence interval reflects variation in spatial distribution of
MTBE, and does not reflect uncertainty in the estimate of the seepage velocity.
4. CASE 3: NAVAL CONSTRUCTION BATTALION CENTER,
PORT HUENEME, CALIFORNIA
The records of the U.S. Navy Construction Battalion Center (CBC), Port
Hueneme, California indicate that approximately 11,000 gallons (42,000 liters) of leaded
and unleaded petroleum products were released from underground storage tank lines of a
gasoline station between September 1984 and March 1985. Most of the dissolved BTEX
compound plumes have been delineated using conventional site characterization methods.
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The measured benzene portion of the plume extended no further than 1080 feet (330
meters) down-gradient of the source, while MTBE at a concentration of 16000 (ig/liter
was identified in a well located approximated 1500 feet or 457 meters from the source.
Analysis of samples from ground water monitoring wells in 1997-1998 indicated that the
MTBE plume had traveled over 4000 feet (1200 m) of the aquifer from the source. The
plume was at least 400 feet (120 m) wide. About 75% of the surface area occupied by
the soluble plume only contained MTBE. The BTEX compounds of the spilled gasoline
have been attenuated within the remaining residual phase nearer the source (Figure 5).
The site is mostly covered with asphalt, buildings, and concrete pads. Below the
surface, there was a layer of fine-grained silty sand to a depth of 7 feet (2.1 m). Below
this low permeable layer, began the upper aquifer consisting of a sand and gravel
sequence that extended to the clay layer located at 25 feet (7.5 m) below ground surface.
The water table ranged from 8.5 to 12 feet (2.6 to 3.7 m) below ground surface.
Hydraulic conductivity ranged from 0.3 to 1.4 x 10"3 m/second. The ground water flow
was in the direction of southwest at a Darcy velocity 80 to 120 feet (24 to 36 m) per year.
With an assumed porosity of 0.3, this corresponds to a seepage velocity of 270 to 400 feet
per year.
Core Sampling the Source Area
In July 1999, the Geoprobe™ direct push system was used to acquire core samples
in continuous vertical profiles at seven locations in or near the source area (locations at
CBC-10, CBC-15, CBC-19, and near air-sparging site). The water table was 9.0 to 10.0
feet below land surface (2.7 to 3.0 meters below land surface) at the time of sampling.
The cores extended from the surface to a depth of 15 feet (4.5 m). The cores at each
sampling location extended from clean soil above the release, through the release to clean
aquifer material below the release. The greatest quantity of aromatic hydrocarbon
compounds and MTBE was found at locations near the point of the original leak, near
monitoring wells CBC-10 and CBC-19. These two locations also had the greatest mass
of MTBE, and the highest concentration of MTBE in the residual fuel at the depth of 10
feet (3 m) where the water table located. At CBC-10, the highest concentration of TPH
was 6,000 mg/kg, and the highest concentration of MTBE was 20 mg/kg. At CBC-19,
the highest concentration of TPH was 1,100 mg/kg, and the highest concentration of
MTBE was 30 mg/kg. The total quantity of fuel hydrocarbons remaining in the source
was 4.41 kg/square meter at CBC-10 and 6.89 kg/square meter at CBC-19. The total
amount of MTBE remaining was 0.0069 kg/square meter at CBC-10 and 0.023 kg/square
meter at CBC-19.
Geochemical Context of the MTBE Plume
The MTBE plume and BTEX plume were contained within a region of the aquifer
that was depleted of molecular oxygen. Many regions of the aquifer have less than
O.lmg/liter oxygen. The background concentration of dissolved oxygen was near 0.2
mg/liter. Most regions within the plume area had less than 0.1 mg/liter nitrate. Sulfate
concentrations were reduced from a background of near 8000 mg/liter to less than 0.5
mg/liter at the highly contaminated location. The pH of the plume was about 7.2 in the
ground water. The oxidation-reduction potentials were measured in the range of-110 mV
to -200 mV, which indicated strong reductive conditions in the contaminated aquifer.
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Methane concentrations did not exceed 0.3 mg/liter, except one sample acquired from the
most contaminated depth on Jun-1998 had a concentration of 3.5 mg/liter. Alkalinity was
increased from the background level 375 mg/L CaCOs to 1150 mg/L CaCO3 at the most
contaminated location. This showed that as much as 800 mg/liter of alkalinity was
produced by oxidation of petroleum hydrocarbons, which corresponded to 350 mg/liter of
carbon dioxide produced or 110 mg/liter of TPH consumed. That was more than enough
carbon dioxide production to account for the depletion of oxygen and sulfate, and
production of Iron II.
Attenuation of MTBE along Plume Path
The permanent monitoring wells at the site along the center of the MTBE plume
for two sampling occasions (June 1998 and June 1999) are depicted in Figure 6. MTBE
concentrations show a significant declination between two sampling periods (Table 3).
The MTBE attenuation rates were calculated from the MTBE concentrations in those
monitoring wells down-gradient from the source, CBC-10. The reported average ground
water flow velocity was about 30 meters per year. An overall rate of natural attenuation
was calculated by a linear regression of the natural logarithm of the concentration of
MTBE on travel time down gradient of the sources. The rate of attenuation of MTBE
was 0.76 per year for the 1998 data and 0.38 per year for the 1999 data set. At this point
the results of the laboratory microcosm study are not conclusive. It is not possible to
attribute attenuation to natural biodegradation. The attenuation seen at field scale may be
due entirely physical processes such as dilution and dispersion.
TABLE 3. ATTENUATION OF MTBE IN GROUND WATER FROM
MONITORING WELLS WITH TIME OF TRAVEL FROM THE SOURCE
Sample
CBC-10
CBC-15-CS
CBC-42
CBC-45-CD
CBC-49-CS
CBC-51
Distance
from CBC-
10 (feet)
0
350
1300
2300
3400
3800
Distance
from CBC-
10 (meters)
0
105
390
690
1020
1140
MTBE
(|ag/L), Jun-
1998
38000
5400
4800
4600
870
150
MTBE
(|ag/L), Jun-
1998
4000
1200
770
700
950
320
Travel Time
(year)
0
0.58
2.2
3.8
5.7
6.3
5. SUMMARY AND CONCLUSIONS
We have examined case studies of MTBE contamination in ground water at three
sites. Each site has own characteristics and geochemical condition, and was taken to
represent an important class of MTBE plumes. In the first case study, dissolved oxygen
was the dominant electron acceptor, while the second and third cases examined sites
where iron reduction and methanogenesis were the major biodegradation processes of
BTEX and MTBE.
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The extensive monitoring network at the Long Island site allowed the
determination of the mass and spatial moments of the contaminant distribution. Total
mass of BTEX compound decreased over the three sample rounds, indicating a net loss in
the aquifer. MTBE data do not show a clear trend. Because the release or releases which
occurred at the Long Island site occurred at unknown times and intervals, much about the
contamination at the site remains unknown. By studying the data from the geochemical
analysis, the major electron acceptor used for hydrocarbon degradation was found to be
dissolved oxygen in ground water. The unique characteristic at the site was the fact that
the MTBE plume was distributed behind a "shadow" of older spills of BTEX compounds,
where dissolved oxygen was depleted in the ground water. Comparing the MTBE plume
and dissolved oxygen distribution revealed that the MTBE plume was restricted to
regions in the aquifer that were devoid of oxygen.
The US Coast Guard site showed strong methanogenic and iron reduction
conditions. Under these anaerobic conditions, there was evidence of the attenuation of
MTBE in the distribution of the MTBE plume and in a mass balance analysis. A rate of
attenuation rate could be estimated from the field data.
The US Navy site was under sulfate reducing and iron reducing conditions. It
was only methanogenic in the area in contact with residual LNAP. The rate of natural
attenuation was much less than that from the US Coast Guard site, where methanogenic
conditions pertained throughout the plume.
After several years of study and field work at a variety of sites under different
geochemical conditions, we have collected evidence that natural attenuation of MTBE in
ground water is important is some plumes, but not in others. Even though the attenuation
of MTBE is not fast, it can be estimated and quantified at field scale. Several research
projects are ongoing to provide a better understanding of the natural attenuation processes
of MTBE in ground water.
DISCLAIMER
The study in this document has been funded wholly or in part by the United States
Environmental Protection Agency, the United States Coast Guard, the United States
Navy, and New York State Department of Environmental Protection. It has not been
subjected to Agencies' review. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
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York, Proceedings of the Conference onNon- aqueous Phase Liquids in the Subsurface Environment:
Assessment and Remediation, American Society of Civil Engineers, November 14-16, Washington, D.C.
[14] Wiedmeimer, T.D., H.S. Rifai, CJ. Newell, J.T. Wilson, 1999, Natural Attenuation of fuels and
Chlorinated Solvents in the Subsurface, John Wiley and Sons, Inc., New York, N.Y
PROTECTED UNDER INTERNATIONAL COPYRIGHT
ALL RIGHTS RESERVED
NATIONAL TECHNICAL INFORMATION SERVICE
U.S. DEPARTMENT OF COMMERCE
Heproduced from—
best available copy.
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HAGERMAN AVE. RESIDENCE
Figure 1. Service Station Site, Long Island, NY
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E. Patchugiic. NY: Sample Round I
MTBE (ppb)
B. Paichogue. NY: Sample Round 2
MTBE (ppb)
E. Paichogue. NY: Sample Round 3
MTBE (ppb)
MO NOD
E. Patchogue. NY: Sample Round 4
MTBE (ppb)
UOD «OD WUO 7010
Figure 2. MTBE Distribution in Ground Water, Long Island, I
NY
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Patehogue»NY: Sample Round 4
Dissolved Oxygen (ppm)
i n i ii 111» i n )i i n pm jilt
500 1000 1500 2000 2500
3500 4000
Distance (ft)
4500 5000 5500. 6000 6500 7000
Figure 3. Dissolved Oxygen Distribution in Ground Water
Long Island, NY
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PASQUOTANK
RIVER
Ground Water Flow
200100 0
200'
ftPPROXIMATE SCALE IN FEET
Figure 4, Fuel Tank Farm Site, US Coast Guard Supply Center, Elizabeth City
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Figure 5. BTEX and MTBE Plume, US Navy, Port Huenerae, CA
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40000
-B-Jun-98 -A-Jun-99
500 1000 1500 2000 2500
Distance from source (ft)
3000 3500
4000
Figure 6. MTBE Concentration Changes along Plume Center, US Navy
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NBMRL-ADA-00114
1 . REPORT NO .
EPA/600/A-02/010
4. TITLE AND SUBTITLE
NATURAL ATTENUATION CF MTBE
TECHNICAL REPORT DATA
2.
7. AUTHOR (S)
'"James W, Weaver, 121John T. Wilson, C31Jong Soo Cho
9. PERFORMING ORGANIZATION NAME AND ADDRESS
"•'US Environmental Protection Agency, Office of Development , National
Exposure Research Laboratory, 960 College Staty.cn Road, Athena,
Georgia 30605, USA, 121US Environmental Protection Agency, Subsurface
Protection 5 Remediation Division, Office of Research and
Development, National Risk Management Laboratory, 919 Kerr Research
Drive, Ada, Oklahoma, USA. "'Environmental Strategies and
Applications, Inc., 495 Union Avenue, Suite ID, New Jersey 08846, USA
12. SPONSORING AGENCY NAME AND ADD
U.S. EPA
Office of Research fi Development
National Risk Management Research
Subsurface Protection £ Remediatio
Ada, Oklahoma 74820
15. SUPPLEMENTARY NOTES
Project Officer: John T. Wilson
RSSS
Laboratory
n Division
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
6, PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
In-Ho«se (Task 5857)
13. TYPE OF REPORT AND PERIOD COVERED
Symposium Paper
14. SPONSORING AGENCY CODE
EPA/SOO/15
580-436-8534
16. ABSTRACT
Three cases of MTBE contamination of ground water are presented. Each case site had own characteristics and
different geochemical condition. The first case site was where dissolved oxygen was the dominant electron
acceptor, while the sites of the second and third cases ware under the anaerobic conditions where iron
reduction and methanogenesis were the major biodegradation process of BTEX and MTBE. At the first case site,
total mass of BTEX compounds decreased over the three sampling rounds, indicating a net loss in the aquifer.
MTBE data did not show a clear trend. Under then anaerobic conditions of the second and third cases, the
attenuation of MTBE could be evidenced from the MTBE plume distribution data and mass balance analysis . Through
several years of study and field works at several sites under different geochemical conditions, we could
collect evidence of the natural attenuation of MTBE in ground water . Even though the attenuation was not fast
compared to those of 3TEX compounds, it was noticeable and the rate could be estimated.
17.
A. DESCRIPTORS
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
KEY WORDS AND DOCUMENT ANALYSIS
B. IDENTIFIERS/OPEN ENDED TERMS
19, SECURITY CLASS (THIS REPORT)
UNCLASSIFIED
20. SECURITY CLASS (THIS PAGE)
UNCLASSIFIED
C. COATI FIELD, GROUP
21. NO. OF PAGES
16
22 . PRICE
EPA FORM 2220-1 (REV.4-77)
PREVIOUS EDITION IS OBSOLETE
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