THE ISRAEL WATER
AUTHORITY
The Division of Water
Quality
Ministry of National
Infrastructures,
Energy and Water
The Geological Institute
A BREAKDOWN OF FUEL COMPOUNDS IN THE GROUNDWATER IN ISRAEL
Faina Gelman1, Ravid Rosenzweig2, Zeev Ronen3
1
2
The Geological Institute
The Ben-Gurion University
This study was commissioned and financed by the Water Authority,
The Division of Water Quality
Report no. GSI/11/2014
Jerusalem, July 2014
1
Table of contents
INTRODUCTION .......................................................................................................................... 5
2. Working methods ........................................................................................................................ 7
2.1 Methods of sampling and a chemical analysis ...................................................................... 7
2.2 Biological methods ............................................................................................................... 7
3. Results and discussion ................................................................................................................ 9
3.1 The Ramatayim gas station – a general background ............................................................ 9
3.1.1 Monitoring well R-1 .................................................................................................... 10
3.1.2 Monitoring well R-2 .................................................................................................... 11
3.1.3 Monitoring well R-3 .................................................................................................... 12
3.1.4 Monitoring well R-4 .................................................................................................... 13
3.1.5 Monitoring well R-5 .................................................................................................... 14
3.1.6 Microbiological tests .................................................................................................... 15
3.1.7. Conclusions ................................................................................................................. 15
3.2 The Nir Galim gas station – a general background............................................................. 16
3.2.1 Hydrologic background ............................................................................................... 16
3.2.2 Levels and the movement of the water ........................................................................ 19
3.2.3 Monitoring well NG-1 ................................................................................................. 21
3.2.4 Monitoring well NG-2 ................................................................................................. 22
3.2.5 Monitoring well NG-3 ................................................................................................. 23
3.2.6 Monitoring well NG-4 ................................................................................................. 24
3.2.7. Monitoring well NG-5 ................................................................................................ 25
3.2.8 Monitoring well NG-6 ................................................................................................. 26
3.2.9 Microbiological tests .................................................................................................... 27
3.2.10 An evaluation of the MTBE flows
the unsaturated medium and mass balances............................................................... 29
3.2.11 Conclusions ................................................................................................................ 31
4. General summary and recommendations .................................................................................. 32
References ..................................................................................................................................... 33
Appendices .................................................................................................................................... 34
2
ABSTRACT
This report summarizes the results of the study titled "The Breakdown of Fuel Compounds in the
Groundwater of Israel" that was conducted for the Water Authority and financed by it. The main
objective of the project was to discern and assess the rate of breakdown of fuel compounds in the
groundwater of the coastal aquifer. The present study focused mainly on the investigation of the
fate of a fuel additive MTBE (methyl tertiary-butyl ether), one of the most widespread pollutants
in groundwater in the vicinity of gas stations. In order to characterize the processes occurring in
the aquifer, we used analytical chemical and classical microbiological methods and an isotopic
analysis of carbon in MTBE.
A breakdown of MTBE was discerned in two contaminated sites: Ramatayim and Nir Galim,
while in the Ramatayim site, the breakdown of MTBE occurred under aerobic conditions, and in
the Nir Galim site – under anaerobic conditions. The two processes were characterized by
different geochemical parameters: a positive redox potential and a high concentration of
dissolved oxygen in the case of the aerobic breakdown; a negative redox potential, high
concentrations of dissolved iron and manganese in the water – in the case of the anaerobic
breakdown.lu
An experiment of breakdown of MTBE that was conducted in the laboratory with microorganisms from the contaminated sites demonstrated that the breakdown of the pollutant under
anaerobic conditions is associated with a significant isotopic fractionation of carbon (εc~ - 14‰)
while the breakdown under aerobic conditions causes a relatively low fractionation (εc~ - 0.7‰).
By virtue of these findings, it is possible to reach arrive at the conclusion that breakdown of
MTBE under aerobic conditions in the contaminated sites can be detected by means of isotopic
analysis of carbon already at the initial stages of the process, while the use of isotopic analysis of
carbon for detecting breakdown of MTBE under aerobic conditions is useful only at the
advanced stages of the process (after about 70-80% of breakdown).
The attenuation rate constant of the biological breakdown of the MTBE that is calculated
according to the isotopic data measured at the contaminated sites, is within the range of 7.7-8.5 /
year for the Ramatayim site and 0.66-0.96 / year for the Nir Galim site.
3
Credits
I would like to thank the Geological Institute team: Ariel Guy, Dina Steiber, Olga Yoffe, Tami
Zilberman, and Galit Sharabi for conducting technical works and analytic tests in the project.
We thank the E. ELGRESSI Ltd and LDD Ltd company teams for their cooperation and support
in the project.
Special thanks to Guy Reshef and Sarah Elhanany for their support and assistance it the project.
4
INTRODUCTION
Land and groundwater pollution by fuel compounds is still one of the widespread problems of
groundwater pollution in Israel. The majority of pollution is a result of past activities; however,
also at the present, pollution is caused by accidents, mishaps, and leaks. According to data of the
Division of Water Quality at the Water Authority, about 140 fuel facilities were found in which
groundwater pollution was detected [Reshef et al., 2012]. Among the many ingredients of fuel,
there are aromatic compounds of the type benzene, toluene, ethylbenzene, and xylenes known as
BTEX, and a fuel additive methyl tertiary-butyl ether (MTBE). These ingredients have a high
solubility in water so that upon reaching the groundwater, these pollutants can spread to great
distances according to the flow of the water. The permitted threshold for these compounds in the
groundwater stands at a few micrograms per liter. Due to the potential hazard of these pollutants
to humans, restoration of land and groundwater where pollution is detected is required. One of
the accepted worldwide restoration approaches is a method based on natural breakdown
processes taking place at the aquifer in conjunction with monitoring and a follow-up. This
approach is preferable to active restitution, and in the majority of cases, it is also cheaper, but
requires the examination of the existence of conditions that enable a biological breakdown. For
choosing the most appropriate method, a thorough understanding is required of the geo-chemical
processes that are taking place at the polluted site. The accepted method of following-up of the
spread of the pollution through space is measuring the change in the pollutants' concentration
over distance and over time. A reduction of the pollutant's concentration through space due to
natural processes such as dispersion, dilution, adsorption, evaporation, chemical reactions, or
bacterial breakdown, constitutes a natural attenuation of the pollutant. Assuming that the kinetics
of the breakdown process are of the first order, it is possible to calculate the diminution
coefficient (k) of the pollutant over time (t):
(1)
𝐶
𝑘 = −ln (𝐶 ) /𝑡
0
C – the concentration of the pollutant at a certain time and at time zero
It is important to note that physical processes like dispersion, evaporation, dilution, and
adsorption do not cause an irreversible breakdown of the pollutant, as opposed to chemical and
biological processes. A microbial breakdown of the fuel's hydrocarbons includes a series of
chemical reactions accelerated by bacterial in the presence of various electron receivers, the main
of which being: cellular respiration under aerobic conditions, denitrification, manganese
reduction, iron reduction, sulfate reduction, and methanogenesis. The participation of electron
receivers in the breakdown depends upon their degree of availability in the aquifer and upon the
presence of the microorganisms that are able to utilize them. In order to assess the contribution
of the biodegradation process in the natural attenuation of the pollutants, it is acceptable to use
several data: the reduction of the pollutants' concentration over time and distance, detection of
the breakdown products, and a change in the concentration of the electron recipients. Although
these data are needed for the understanding of the processes, in many cases they are not
sufficient for drawing unambiguous conclusions with respect to the environmental pollutant.
Thus, for example, reduction of the pollutant's concentration in space may originate from an
adsorption or dispersion process; similarly, a change in the concentration of the electron
recipients is indicative of breakdown processes of organic matter in general so that it cannot
indicate a breakdown of specific organic compounds. In order to ascertain that a microbial
5
breakdown of individual organic compounds is taking place, it is necessary to carry out
additional measurements. One of these measurements is the testing of metabolites (intermediate
products) characteristic of certain breakdown processes. The presence of specific genes in the
micro-organisms can also indicate a potential of a microbial breakdown of an organic compound.
In recent years, there has been an increased use of isotopic ratios of carbon and hydrogen for
specific organic compounds (CSIA) for forecasting biodegradation processes. This technique is
based on the fact that in organic compounds, heavy isotopes react more slowly in biological
reactions so that isotopic fractionation occurs. Thus, with the progression of the breakdown
process, the residual fraction becomes heavier from the isotopic standpoint. It is possible to
assess quantitatively the fraction of the material that has undergone a breakdown with an
equation derived from the Riley equation:
(2)
∆𝛿13𝐶
𝑓 = 𝐶/𝐶0 = exp ( 𝜀(‰) )
- the residual fraction of the substrate
- a change in the isotopic ratio at a certain time as opposed to time zero
- the constant of isotopic enrichment in units of ‰
It is feasible to calculate the speed of a biological breakdown of the pollutant over time
(𝜆 𝑡𝑖𝑚𝑒 ) according to equation 3:
(3)
𝜆 𝑡𝑖𝑚𝑒 = −
𝑙𝑛(𝑓)
𝑡
- the residual fraction of the substrate is calculated according to the isotopic data
- time
It is feasible to calculate the speed of a biological breakdown of the pollutant over distance
(
) according to Equation 4:
(4)
𝜆𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = −
𝑙𝑛(𝑓)
𝑑
=−
𝑙𝑛(𝑓)
𝑡 𝑣
- the residual fraction of the substrate according to the isotopic data
- distance
- the speed of the movement of the groundwater
- time
A few years ago, the Division of Water Quality initiated the project of forecasting the processes
of breakdown of fuel compounds by using a CSIA analysis. In a study that was carried out by the
Geological Institute in the preceding years [Gelman and Ronen, 2009], a microbial breakdown
process of MTBE under aerobic conditions was detected at a polluted site at Ramat-Aviv. Under
anaerobic conditions, no significant breakdown processes were detected. The purpose of the
present project was to broaden the knowledge about the processes affecting the breakdown of
fuel compounds and especially MTBE in the groundwater. The study focused on polluted sites
that were located above the coastal aquifer. Among these sites, there is a site that underwent an
6
active restoration by inserting oxygen (the Ramatayim gas station) and a polluted site that did not
undergo a process of active restoration but only regular monitoring (the Nir Galim gas station).
2. Working methods
2.1 Methods of sampling and a chemical analysis
Water samplings for testing volatile organic substances, principal ions, and trace elements were
conducted with a low flow pump. The water analyses were conducted by the following methods:
A quantitative analysis of substances dissolved in fuel – (BTEX, MTBE) P&T / GC-MS
An isotopic analysis of substances dissolved in fuel (MTBE ,BTEX – P&T / GC-IRMS
An analysis of principal ions –Ion Chromatograph, ICP-OES
An analysis of trace ions – ICP-MS
2.2 Biological methods
In the majority of the sites that were tested until now, iron and manganese dissolved in water
were found, and they are a result of microbial reduction due to the breakdown of BTEX (it is
unknown if there are iron reducers and agents that breakdown MTBE). In the majority of the
sites, the disappearance of MTBE is apparent at the aerobic margins of the down in which the
concentrations of oxygen are high. From here, , it seems that it is possible to divide the sites into
a number of categories: (1) a site in which the core of the down is anaerobic (iron reduction)
without the biodegradation of BTEX and the aerobic margins of the down in which the
breakdown of BTEX and MTBE takes place, (2) a site in which the core of the down is
anaerobic (iron reduction) in which the breakdown of BTEX takes place, and the margins of the
down are aerobic in which additional breakdown of BTEX and MTBE takes place, (3) a site in
which the core of the down is anaerobic (iron reduction) in which no breakdown takes place but
there is an intermediate zone in which there is nitrate and a breakdown of BTEX, and at the
aerobic margins of the down, an additional breakdown of BTEX and MTBE takes place. From
here, apparently the research should be concentrated on the characterization of the bacteria
appropriate to these categories: aerobic iron and nitrate reducers and aerobic MTBE
breakdowners. Bio-molecular markers may be used (functional genes that encode for the
breakdown of fuel compounds). This method does not require the isolation of the bacteria from
the groundwater, and it also enables a specific identification of relevant bacteria. This is a
mandatory preliminary stage prior to using quantitative methods for the assessment of the
bacteria.
For anaerobic BTEX breaking-down bacteria, we used trackers of a functional gene that encodes
for an enzyme involved in the opening of the aromatic ring. It is important to note that this gene
is preserved (a very similar sequence) in nitrate-reducing, in iron-reducing and in sulfatereducing bacteria. In opposition, for aerobic MTBE breaking-down bacteria, we used a tracker
for M. petroleiphilum which is known to be involved in an MTBE breakdown.
7
The procedure of identifying the bacteria from the groundwater and finding the relation to the
breakdown of the pollutants will include a number of stages:
1. Sampling of the groundwater (1-5 liters)
2. Water samples of November 12, 2012, filtered with a 0.22 micrometer and
subsequently frozen to 80 degrees until the DNA was extracted. Water samples of
March 10, 2013, were centrifuged in 500 ml bottles (9500 RFC for 15 minutes); a
sludge that will be subsequently transferred to a 50 ml test-tubes repeat centrifugation
(3500 RFC for 15 minutes). Subsequently, the upper liquid was discarded, and the
precipitate was kept frozen until the phase of DNA extraction. The DNA was produced
either from samples taken directly from groundwater or from samples taken from the
experiment of enrichment of bacteria.
3. DNA extractions were carried out from biomass collected by a number of methods:
after filtration by the phenol chloroform method, after precipitation in a centrifuge and
washing with preliminary digestion of the biomass with lysosome and proteo-enzyme K
and subsequently, a DNA extraction by the phenol chloroform method and using the
DNA extraction kit according to the manufacturer's instructions, manufactured by
MoBio. The DNA concentrations were measured with a spectro-photometer
(Nanodrop).
4. Running the PCR reactions on DNA with the primers in the following table
PCR
assay
bamA-300
bamAASP1
613F
988R
Sequence (5′→ 3′)
Direction
CAGTACAAYTCCTACACVACBG
Forward
CMATGCCGATYTCCTGRC
Reverse
GTGACTGCAAGGCTGGAGCG
TCTGGTAACTTCTAGACA
Forward
Reverse
Gene
target
bamA
Primer
bamA-SP9
bamAbamA
ASP1
16S rRNA gene of M.
petroleiphilum
PM1
(Mpe_A0326a)
5. After obtaining the suitable products, a clones library was prepared and sent for
sequencing
6. The identification of the involved bacteria was based on information existing in a gene
bank.
7. A PCA analysis was conducted for testing the relation between the geochemistry of the
groundwater, the level of the pollution, the isotopic composition, and the composition
of the bacterial population.
8
3. Results and discussion
3.1 The Ramatayim gas station – a general background
Within the framework of this project we investigated the process of degradation of fuel
compounds in the groundwater in the region of the Ramatayim gas station at Hod Hasharon. In
the past, high concentrations of MTBE and low concentrations of BTEX compounds were found
in the groundwater in the area of the station. In order to prevent the spread of the pollution, the
Water Authority decided to carry out a remediation of the groundwater by means of an
electrolysis system (E. Elgressy Ltd). This treatment is based on supplying oxygen to the
groundwater by means of a reactor that is installed in the dedicated well. At the gas station, there
are 5 monitoring wells, R-1–R-5 (Figure 1). Two reactors for groundwater treatment were
installed in wells R-1 and R-4 at the beginning of 2011, and an additional reactor was installed in
wells R-2 at the beginning of 2012. According to the sampling data of the Water Authority,
before the beginning of the remediation, MTBE was the main pollutant in the groundwater at this
site, and very high concentrations of it were found in wells R-1 and R-2 (40 mg/l) and in the
region of wells R-5 (17 mg/l). At the beginning of the present project, a few months after the
activating of the reactors at wells R-1 and R-4, very high concentrations of MTBE were
measured in the monitoring well R-2.
Figure 1: A map of the monitoring wells at the Ramatayim gas station
9
The test results of the groundwater that were sampled on the site during the remediation process
are presented in Table 1.
3.1.1 Monitoring well R-1
The redox potential values and the concentrations of the oxygen dissolved in water (Figure 2 and
Table 1) that were measured in the well during the monitoring period testify of aerobic
conditions. The water was characterized by high concentrations of nitrate and sulfate and low
concentrations of dissolved manganese and iron. During the monitoring period, a significant drop
in the concentrations of MTBE was observed in conjunction with a change in the isotopic
composition of about 3‰.
(A
)
(B)
(C)
Figure 2: Monitoring well R-1.
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration and composition of MTBE
11
3.1.2 Monitoring well R-2
From the data in Table 1, it can be seen that at the beginning of the project, in the summer of
2011, at the R-2 monitoring well, there were found very high concentrations of MTBE (about 68
mg/l). A negative value of redox (-158 mV), an absence of nitrate, and low concentrations of
sulfate indicated anaerobic conditions at the well during the same period. Half a year later, a
drastic drop was observed at well R-2, of two orders of magnitude, in the concentrations of
MTBE. This drop was associated with an elevation of the nitrate and sulfate concentrations and a
drop in the concentrations of iron and manganese dissolved in the water. In the process of the
remediation process, another drop was observed in the concentrations of MTBE, and there was a
change in its isotopic composition. The changes in the chemical and geochemical parameters at
well R-2 are displayed in Figure 3.
(A
(B)
)
Figure 3: Monitoring well R-2.
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration of MTBE
11
3.1.3 Monitoring well R-3
At the beginning of the project, concentrations of MTBE of about 4 mg/l were measured at
monitoring well R-3. During the entire sampling period, negative redox potentials were
measured at this well. It should be noted that the groundwater composition at this well was very
different from the characteristic composition of coastal aquifer groundwater. For instance, twice
there were measured exceptional concentrations of nitrate in the water (600 and 1296 mg/l).
Together with this, exceptional concentrations of potassium, bicarbonate and exceptional pH
values were measured in the water. Moreover, exceptional values of δ13C for inorganic dissolved
carbon (DIC) were measured in the water that reached -40‰. These low values are not
characteristic of the isotopic composition of carbon in fuel compounds that have an isotopic
composition of about -33‰. It seems that these values stem from the decomposition of organic
matter from another source. By virtue of the chemical analyses of the water, we assume that
these exceptional concentrations stemmed from the presence of fertilizer substances. The
changes in the chemical and geochemical parameters at well R-3 are displayed in Figure 4.
(B)
(A
)
(C)
.
Figure 4: Monitoring well R-3.
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration of MTBE
12
3.1.4 Monitoring well R-4
At the beginning of the project, the concentration of MTBE in the well was about 20 mg/l. A few
months later, a slight elevation in the concentration was observed that was replaced by a
tendency to drop. According to the chemical parameters that were measured, it can be inferred
that in this region, oxygenating conditions prevail characterized by a positive redox potential,
very low concentrations of dissolved manganese and iron, and relatively high concentrations of
nitrate and sulfate. During the entire restoration period, no significant change occurred in the
concentrations of nitrate, sulfate, iron, and manganese, but a drop was observed in the
concentration of MTBE to values below the threshold of detection. Due to the low
concentrations of MTBE, it was not feasible to conduct isotopic tests of its composition. The
changes in the chemical and the geochemical parameters at well R-4 are displayed in Figure 5.
200
150
100
50
0
-50
MTBE, µg/L
(C)200
R-4
(B)200
250
NO3, SO4, mg/L
DO
ORP
Nitrate
Mn
180
160
140
120
100
80
60
40
20
0
Sulfate
Fe
50
40
30
20
10
Mn, Fe, µg/L
R-4
8
7
6
5
4
3
2
1
0
ORP, mV
DO, mg/L
(A
)
0
R-4
180
160
140
120
100
80
60
40
20
0
MTBE
Figure 5: Monitoring well R-4.
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Concentration of MTBE
13
3.1.5 Monitoring well R-5
In the beginning of the project, low concentrations of MTBE of a few milligrams per liter were
measured at the monitoring well R-5. According to chemical parameters that were measured, it
can be inferred that in this region, oxygenating conditions characterized by a positive redox
potential prevail. The concentrations of sulfate in the well were relatively stable and stood at 70
mg/ l. It should be noted that in two cases, excessive concentrations of nitrate were observed,
arising, by our evaluation, from the presence of fertilizer materials in the water; similar to well
R-3. At the end of the restoration period, the MTBE values were lower than the detection
threshold (less than 5 mg/l). Due to the low concentrations of MTBE, it was not feasible to
conduct isotopic tests. The changes in the chemical and geochemical parameters at well R-5 are
displayed in Figure 6.
(B
)
(A
)
(C)
Figure 6: Monitoring well R-5.
A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, and manganese
(C) Concentration of MTBE
14
3.1.6 Microbiological tests
Water samples that were received at the end of the rehabilitation process from drillings R-1, R-4,
and R-5 were tested. In all of the samples, it was possible to enhance with the aid of the PCR
reaction the 16s rRNA gene with the aid of general trackers. With the specific trackers, we
succeeded in confirming the presence of M. petroleiphilum in water from drillings 1 and 4, both
of which are drillings in which the water is oxygenated, and a drop in the MTBE concentration
was observed. By virtue of the literature, the isotopic enrichment constant of carbon during
MTBE degradation by this bacterium ranges between -2.0-2.4‰, and thus, it was anticipated to
obtain similar values in the process of the breakdown experiment.
In order to calculate the isotopic enrichment constant that is characteristic of aerobic breakdown
conditions in the groundwater of the contaminated site, microbial MTBE breakdown experiments
were conducted on groundwater samples from the wells that were at the site. The tests were
conducted on groundwater samples from wells R-1, R-2, and R-3, with the addition of MTBE. A
follow-up was conducted after changes in the concentrations and the isotopic composition of
MTBE over time. By virtue of the test results, the isotopic enrichment constant under aerobic
conditions was calculated to be ε = -0.7 ‰. The fact that this value is not compatible with the
value in the literature for the M. petroleiphilum bacterium suggests that breakdown processes
accelerated by other bacteria are involved, and when they break down MTBE, the enrichment
constant is smaller [Jechalke et al., 2011].
3.1.7. Conclusions
According to the results of the chemical analyses, it is possible to say that the operation of the
electro bio reactor system caused a change in the biochemical conditions on the site. The most
significant changes were observed in wells R-2 and R-3 in which the strong anaerobic conditions
became, at the end of the period, aerobic conditions. As a result from this change, a drastic drop
in the concentrations of MTBE took place associated with a change in its isotopic composition.
Assuming that the isotopic enrichment constant in the process of groundwater MTBE breakdown
equals the enrichment constant obtained from microbial experiments in the laboratory
(ε = -0.7‰), we may come to the conclusion that more than 96% of the MTBE underwent a
microbial breakdown (the calculation was made according to Equation 1). The presence of M.
petroleiphilum in the water strengthens s the assumption that this process facilitated the activity
of bacteria breaking down MTBE. It should be noted that due to the low isotopic fractionation
constant, it was possible to see the change in the isotopic composition of MTBE only after a high
degree of breakdown. On the assumption that the kinetics of the breakdown process are
compatible with a first order, it is possible to calculate the attenuation rate constant over time due
to biological breakdown (λ) of MTBE according to the isotopic data and the attenuation constant
of the first order (k) according to the changes in the concentration of the contaminant:
 For well R-2 in the period between September 24, 2011, and May 23, 2012,
(calculated by the change in the isotopic composition of MTBE; f =0.02)
15
𝜆 ~ 8.5⁄𝑦𝑒𝑎𝑟
(A first order attenuation constant is calculated
by the change of MTBE concentrations.)
𝑘 ~ 11.8⁄𝑦𝑒𝑎𝑟
 For well R-3 in the period between September 24, 2011, and May 23, 2012.
(calculated by the change in the isotopic composition of MTBE: f =0.03) 𝜆 ~ 7.7⁄𝑦𝑒𝑎𝑟
(calculated by the change of MTBE concentrations.)
𝑘 ~ 7.9⁄𝑦𝑒𝑎𝑟
It should be noted that such rates of attenuation are much higher than the natural rates of
attenuation that are known in the literature.
3.2 The Nir Galim gas station – a general background
At the Nir Galim gas station, there are 6 monitoring wells (Figure 7) that were sampled in the
period between March 2011 and September 2013. This station is not undergoing an active
remediation processes but only monitoring of the contaminants in the water and in the vicinity.
The chemical and isotopic analyses are summed up in Table 2. Most of the contamination in this
site is found in wells NG-2 and NG-3. In these wells, there were found both MTBE and BTEX
compounds. In the rest of the wells, contaminants were found in relatively low concentrations.
Figure 7: The monitoring wells map at the Nir Galim gas station
3.2.1 Hydrologic background
16
The gas station is located above the coastal aquifer, and in this region, the aquifer is
divided into two sub-aquifers by a unit of clay [Figure 8, Tolmatz, 1977]. The roof of the
clay layer constituting the floor of the upper sub-aquifer (aquifer B) is situated at a height
of about 70 meters below sea level. The level of the groundwater in this region has been
found in recent years to be at a height of between 2 to 5 meters and about 10 meters
below ground.
The direction of the flow of the groundwater in this region is southwards with a slight
eastward component (see below). The directions of the flow are influenced by the
production drilling Kibbutz Nir Galim 1, that is located 210 meters southwards from the
NG-2 drilling and to a lesser degree by the depression of the drillings field of the
Shafdan, which is located to the northeast (Figure 9). The production from this wells
amounted in recent years to an average of 1.1 MCM per year (Figure 10).
Figure 8: A geological section of the coastal aquifer along the Yossum 115 strip (Tolmatz,
1977). The study area is marked with an arrow.
17
Figure 9: A levels map of the southern coastal aquifer in the year 2011.
(The Hydrologic Service, 2013) The study area is marked.
Figure 10: The annual production from the Nir Galim 1 Kibbutz drilling (The Hydrologic
Service)
18
3.2.2 Levels and the movement of the water
Figure 11 shows the changing of the height of the level of the groundwater in the six monitoring
wells and the static height at the Nir Galim 1 Kibbutz drilling [LDD, 2013]. It is obvious that
until March 2012, there is a close connection between the level of the water at the monitoring
wells and the level of the water at the Nir Galim 1 Kibbutz production well. Subsequently, there
is a sharp rise of the level of the water at the production wells, possibly because of the reduction
of the pumping, while the reaction at the monitoring drillings was more moderate. It is possible
to see that from September 2011 to October 2013, there is a rise of about one and a half meter in
the height of the groundwater.
The magnitude and the velocity of the flow of the groundwater underneath the gas station were
calculated from the height data at the monitoring wells (except for wells NG-6 in which the level
of the wells was not measured, but was estimated by interpolation). The water level field was
adjusted to a linear function,
(5)
h  ax  by  c
In (1), h is the groundwater level that is equal to the hydraulic head, x and y are the spatial
coordinates and a, b, and c are the regression constants. The velocity of the groundwater is
obtained from Darcy's law,
(6)
v
K
h
n
v is the velocity vector, K is the hydraulic conductivity, and n is the porosity.
For the purpose of estimating the velocities, only the fields of the stationary were taken in which
the quality of the correlation to (1) was of R2 is greater than 0.7. The velocity analysis was based
on 19 sets of level measurements that were taken between October 2008 and October 2013. An
example of the heights map that was received is displayed in Figure 12. It is possible to see that
the level is high at northwest and descends in the direction of southeast.
19
Figure 11: The levels of the monitoring drills and the static elevation of the Nir Galim Kibbutz 1
drilling between the years 2008 and 2013.
The average values of the static gradient in the direction x and y that were obtained are
6.138*10-4 a =- and b =0.0013, respectively. It should be noted that while in the absolute level
of the groundwater, large changes were observed as displayed in Figure 11, the differences of the
levels between the wells remained approximately constant, and no consistent tendency over time
was observed in them. These gradients suggest a flow in the direction southeast 26º eastwards to
the south. These directions correlate well with the presence of a production well at a short
distance southwards to the gas station and the presence of the station on the western margins of
the Shafdan depression.
The groundwater velocity was calculated according to Equation (6), on the assumption that the
porosity of the aquifer is 0.3 [Shavit and Assouline, 2004] and for two values of hydraulic
conductivity 10 m/day and 20 m/day. These values represent the range of the hydraulic
conductivities that was reported for the coastal aquifer [Shavit and Assouline, 2004; Solomon
2006]. For these values, there was obtained a velocity of 0.048 m/day and 0.096 for
conductivities of 10 m/day and 20 m/day, respectively. For these velocities, the time of arrival of
a contaminant (without adsorption or deceleration) from drilling NG-2 to drilling NG-6 ranges
between 521 and 1041 days.
21
Figure 12: The maps of the levels for January 5, 2011. The origin of the coordinates was
established at the Nir Galim 1 Kibbutz drilling. The parameters obtained in the linear regression
are: a = -0.0015, b = 0.0017, and c = -2.313.
3.2.3 Monitoring well NG-1
The concentrations of MTBE and the BTEX compounds at drilling NG-1 were low during the
entire sampling period. It should be noted that in the last sampling, it was found that the
concentrations of these substances were especially low. During the entire period, oxygenating
conditions prevailed on the site with a positive redox potential and high concentrations of nitrate
and sulfate. The changes in the chemical and geochemical parameters at well NG-1 are displayed
in Figure 13.
(A
)
(B)
(C
)
Figure 13: Monitoring well NG-1
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration and composition of MTBE
21
3.2.4 Monitoring well NG-2
In this drilling, anaerobic conditions were seen during the entire period. Similarly, the redox
potential at the drilling was very negative ,and also high concentrations of dissolved iron and
manganese were observed. At the beginning of the sampling in 2011, high concentrations of
sulfate and nitrate were measured at the drilling (about 50 mg/ l). Towards the end of the
sampling period, these concentrations dropped to low values below 1 mg/ l. In this period,
changes also occurred in the concentrations of the manganese and the iron, but they remained
relatively high over the entire period of sampling. Together with this, significant changes were
observed in the concentrations of the MTBE and the BTEX compounds. It should be noted that
in March 2012, a considerable rise in the concentrations of MTBE was observed. Later in the
same year, a significant drop in the concentrations of MTBE was observed associated with a
significant change in the isotopic value of the contaminant. Concurrently with the drop, high
concentrations of TBA were found in the drilling, which is a substance known as a breakdown
product of MTBE. According to the results of the analyses of MTBE, it can be assumed that in
this region of the site, an intensive breakdown of MTBE under anaerobic conditions occurred.
The changes in the chemical and geochemical parameters at well NG-2 are displayed in Figure
14.
(A
)
(B)
(C)
Figure 14: Monitoring well NG-2.
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration and composition of MTBE
22
3.2.5 Monitoring well NG-3
This drilling showed during the entire period of sampling anaerobic conditions. At the site,
negative values of redox potential were observed, low values of nitrate and sulfate, and high
concentrations of dissolved iron and manganese. At the beginning of the project, the
concentration of MTBE at this drilling was around 3-5 mg/l. In March 2012, an elevation of the
concentrations of MTBE was observed to a value of 11 mg/l. After this elevation, during 2013, a
drop in concentrations of MTBE was observed, and it was associated with a considerable change
in its isotopic value. Similarly to well NG-2, in this well also, an elevation in the concentrations
of TBA with a drop in the concentrations of MTBE was observed. These changes testify of a
process of anaerobic breakdown of MTBE in the groundwater. The changes in the chemical and
geochemical parameters at well NG-3 are displayed in Figure 15.
(A
)
(B)
(C)
Figure 15: Monitoring well NG-3.
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration and composition of MTBE
23
3.2.6 Monitoring well NG-4
During the monitoring period between 2011 and 2013, the values of the redox potential that were
measured at this drilling changed from negative values (-4mV) to positive (60 mV). This change
of potential testifies of a change in the conditions of the water from anaerobic to aerobic. During
the entire sampling period, the concentrations of MTBE and BTEX remained very low, mostly
below the detection threshold. It can be assumed that the water at this region of the site was not
at all affected by the contamination. The changes in the chemical and geochemical parameters at
well NG-4 are displayed in Figure 16.
(B)
(A
)
(C)
Figure 16: Monitoring well NG-4
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration and composition of MTBE
24
3.2.7. Monitoring well NG-5
At the NG-5 drilling, an elevation occurred in the values of the redox potential during the entire
sampling period, and in the last sampling, they reached 169 mV. The concentrations of sulfate
remained stable during the entire period and stood at about 40 mg/l. The concentrations of nitrate
ranged between 7-19 mg /l. During the entire period, the concentrations of dissolved iron stood
at a low value of 10 mg / l, and the concentrations of the dissolved manganese stood at about 170
mg/l. In general, the concentrations of MTBE and the BTEX compounds at the site were low
during the entire period of sampling. The changes in the chemical and geochemical parameters at
well NG-5 are displayed in Figure 17.
Figure 17: Monitoring well NG-5.
(A
)
(B
)
(C
)
(A) Redox potential and dissolved oxygen (B) Concentrations of nitrate, sulfate, iron, and
manganese (C) Concentration of MTBE
25
3.2.8 Monitoring well NG-6
The values of the redox potential at this site were negative, which is evidence that at this site,
anaerobic conditions prevailed. During the entire sampling period, relatively low concentrations
of sulfate were measured with a tendency to drop over time. At the end of the sampling period,
this value stood at 4 mg/l. During the entire sampling period, the concentrations of nitrate at the
site dropped from 7 to 3 mg/l. In the sampled water, high concentrations of dissolved iron and
manganese were found. During the entire sampling period, the concentrations of MTBE and the
BTEX compounds were relatively low. These low concentrations made it impossible to
determine the isotopic composition of these substances. The changes in the chemical and
geochemical parameters at well NG-6 are displayed in Figure 18.
(A
)
(B)
(C)
Figure 18: Monitoring well NG-6.
(A) Redox potential and dissolved oxygen (B) concentrations of nitrate, sulfate, iron, and
manganese (C) Isotopic concentration and composition of MTBE
26
3.2.9 Microbiological tests
An enrichment culture
We placed enrichment cultures for bacteria that break down toluene and reduce iron as well for
aerobic bacteria that break down MTBE. The purpose was to test whether it is possible to
increase the number of bacteria that break down toluene and MTBE, which can assure their
detection by molecular methods.
Hereunder is a table that summarizes the enrichment cultures that we placed in the laboratory
from the water of the Nir Galim drillings.
Source of the
bacteria
10 ml Nir Galim 3
March 10, 2013
10 ml Nir Galim 6
March 10, 2013
10 ml Nir Galim 3
March 10, 2013
10 ml Nir Galim 6
March 10, 2013
10 ml Nir Galim 2
March 10, 2013
10 ml Nir Galim 2
March 10, 2013
Substrate  100
mg/ l
Toluene
Electrons recipient
Iron
Indication of
activity
Reduction of iron
Toluene
Iron
Reduction of iron
Control
Iron
Reduction of iron
Control
Iron
Reduction of iron
MTBE
Oxygen
Control
Oxygen
Change of color of
redox indicator
Change of color of
redox indicator
A PCR reaction
In order to identify bacteria that break down BTEX in the anaerobic groundwater, we used
specific primers for the BamA gene found in most anaerobic bacteria that break down anaerobic
substances. For the necessity of identifying this DNA segment from the DNA extract from
various wells and enrichment cultures, an optimization process of the reaction was carried out
with various fusion temperatures. A temperature of 55 degrees was found to be optimal by virtue
of the power of the band of the PCR reaction in the positive controls of Desulfococcus
multivorans (D), Azoarcus sp. (A), Thauera aromatic (T), and Geobactar metallireducns (G)
(Picture 1).
Enrichment cultures from the NG-6 drilling with toluene and iron as a source of carbon and a
recipient of electrons respectively were incubated for 10 days, during which iron reduction was
measured. As can be seen from Picture 1, even without the addition of toluene, a reduction of
iron was observed. It is possible to explain this by the fact that the water contained other organic
substances that served as a source of electrons and carbon to the bacteria. Thus, it becomes clear
that in groundwater, there are active bacteria that break down BTEX and reduce iron. This
observation is confirmed by the fact that the concentrations of toluene at this drilling are low
(104 and less than 5 micrograms per liter), and the concentrations of the iron and the manganese
are relatively high (7.4 and 5.5 mg / l for iron). In order to confirm the hypothesis that those that
27
break down BTEX are present in the culture, the BamA gene was enhanced in the PCR reaction.
The results that are displayed in Picture 2 show that the gene was enhanced, but it is possible to
see in this picture an enhancement of unspecific segments. Nevertheless, these results prove that
in the culture, there are those that break down toluene that reduce iron whose identity is still
unknown. After the success in enhancing BamA from a culture, an experiment was carried out to
enhance it from a genomic DNA originating from wells NG-2, NG-3, and NG-6. Indeed, Picture
2 shows clearly that there are in these samples replications of the gene of the bacteria that break
down BTEX. In order to identify which bacteria are involved, we intend in the future to clone the
products of the PCR and to send them for sequencing. All the findings about the reduction of
iron and the breakdown of BTEX in the water from Nir Galim show clearly that there are
bacteria in the area that are involved actively in the breakdown of these substances in an
anaerobic environment.
Figure 19: iron reduction iron-citrate substrate water drilling NG6 and without the presence of
toluene.
Out of the gel of Agarose in Picture 2, the DNA band is cut, and from it, we prepared a library of
clones that we sent for sequencing. The results of the sequencing were compared to information
from a gene bank and served as the preparation of a phylogenetic tree that describes the
relationship between the sequences that we discovered in the water from the drillings in Nir
Galim to the bacteria that are known for their ability to break down BTEX. In the next picture, it
is possible to see a classification of the sequences that were obtained from the drillings at Nir
Galim. The sequences of this test are marked as bama, while the number at the end indicates the
number of the drilling (6, 2, or 3). It is possible to see clearly that in all of the drillings, there are
representatives of bacteria that break down BTEX (a source of carbon and energy) that use
nitrate or iron or sulfate as a final recepient of electrons. It is important to note that these
sequences are of bacteria that are clearly known for their ability to break down aromatic
substances under anaerobic conditions. In comparison to the geochemical data at the drillings, it
is possible to see that there are variable dynamics of recepients of electrons over time, especially,
an attenuation of nitrate and sulfate in drilling 2, while concurrently, there is an elevation of the
concentrations of iron. In drilling 3, for example, there is a tendency for the elevation of the
concentrations of nitrate and sulfate (perhaps from the rinsing of the unsaturated section), and in
drilling 6, there is a reduction of iron concurrently with the disappearance of nitrate and sulfate.
This leads to the conclusion that it is possible that some of the processes occur simultaneously,
which is expressed by the presence of bacteria that do not necessarily represent the recipient of
electrons that are available for the oxydation of BTEX. It is interesting to note that in drillings 2,
3, and 6, the reduction of iron occurs before the disappearance of sulfate. This suggests that the
28
iron minerals in the aquifer are less available to the iron reducers, and therefore, reduction of
sulfate with BTEX as a source of energy is preferable to it.
Picture 1: A photograph of an
Agarose gel in which are run the
products of the PCR reaction to
the BamA gene that is found in
genomic DNA of enrichment
cultures of bacteria that break
down toluene iron reducers
whose origin is from drilling 6 at
Nir Galim.
(C)
Picture 2: A photograph of an
Agarose gel in which are run the
products of the PCR reaction to
the BamA gene that is found in
genomic DNA of bacteria that
were found in wells 2, 3, and 6 at
Nir Galim.
3.2.10 An evaluation of the MTBE flows from the unsaturated medium and mass balances
The quantity of MTBE in the ground underneath the tank farm was calculated from soil samples
that were taken during the drilling of the monitoring wells NG-2 and NG-3 [LDD, 2008]. Figure
19 presents the concentrations of MTBE (in mg per kg of soil) Cs as a function of the elevation
in the region of the piracy surface. The profile was estimated by a linear interpolation between
the sampling points. It can be seen that the quantity of MTBE that is beneath the drilling NG-2 is
greater and exceeds the rise of the elevation. It can be anticipated that the continuation of the
tendency of the elevation of the levels will bring about a penetration of MTBE into the
groundwater. Assuming that the profile of the concentrations at NG-2 represents the
concentrations underneath the tank farm and by neglecting the flows of MTBE from rain
(because of the asphalt) and adsorption into the soil, the quantity of MTBE that penetrated into
the groundwater from the elevation of the levels during the last two years is,
M in  Cs b hA
(7)
29
M in is the mass of MTBE that penetrated into the groundwater from the unsaturated
When
region, b is the lumpy density of the soil estimated at about 1.8 g/cm3, h is the elevation
of the level of the groundwater, and A is the surface of the tank farm, estimated at 121 m2.
The quantity of MTBE according to this calculation is estimated at 400 grams.
Subsequently, we carried out an estimation of the quantity of MTBE that was transported
with the water from the region of the tanks in the last two years. The mass of MTBE that was
transported is:
(8)
M v  CHqt
When C is the concentration of MTBE in the groundwater, H is the effective thickness of the
down, q is the flow of the water (velocity times porosity) and and t is the time period during
which the balance is performed. The calculation was based on the concentrations that were
measured at drilling NG-3, on the velocity of the flow of 0.048 m/day, and on the effective
thickness of the down of 1 meter. According to this calculation, the mass of MTBE that was
transported from the tank region in the last two years is about 800 grams – twice the quantity
that penetrated. It is possible that the actual concentration of MTBE in the soil is higher than
that measured at drilling NG-3, or that the local heterogeneity decelerates the flow
underneath the tanks.
Figure 20: The concentration of MTBE in the soil as a function of the elevation.
31
3.2.11 Conclusions
The monitoring of the Nir Galim gas station showed that in the wells in which there is a high
contamination by fuel compounds, strong anaerobic conditions develop accompanying a
reduction in nitrate and sulfate that are present in the water and a reduction of heavy metals
(manganese, iron, and occasionally arsenic) from the minerals in the soil. The chemical,
biological and isotopic results that were obtained at the Nir Galim site indicate the existence of
the process of a microbial breakdown of MTBE under anaerobic conditions. The constant of
isotopic enrichment that was obtained from the experiments of a breakdown of MTBE under
laboratory conditions is compatible with the enrichment constant that is known from the
literature for a breakdown of MTBE under conditions of methanogenesis (about -14‰ ÷ -12‰).
On the assumption that the enrichment constant in this domain is also characteristic of processes
on the terrain, it is possible to calculate that about 80% of MTBE at well NG-2 underwent a
microbial breakdown under anaerobic conditions. Signs of a breakdown of MTBE under
anaerobic conditions also exist at well NG-3. By virtue of the isotopic results, it may be
estimated that the degree of breakdown at this drilling is about 65%. The microbial tests also
showed the presence of bacteria that break down BTEX at wells NG-2 and NG-3, but no change
was detected in the isotopic composition of BTEX compounds during the entire monitoring
period. We assume that this stems from a low degree of breakdown and/or an addition of BTEX
flows from the unsaturated medium. The analysis of the flow and the mass balances at the site
showed that the time of arrival of the water from drilling NG-2 to drilling NG-6 ranges between
1.5-3 years. We suppose that the low concentrations of MTBE that was observed until now at
well NG-6 (in comparison with NG-2 and NG-3) stem from the non-arrival of the contaminated
plume center or edges in combination with degradation. The mass balance show that apparently
the quantities of MTBE underneath the tank farm are higher than those that were sampled in the
soil in drillings NG-2 and NG-3.
Assuming that the kinetics of the breakdown of MTBE at wells NG-2 and NG-3 are compatible
with the processes of the first order, it is possible to calculate the biological attenuation constant
(λ) by virtue of the isotopic data and the point attenuation coeficient (k) by virtue of the change
in the concentration of MTBE over time. If we refer to the data of the period between March 11,
2012, and October 21, 2013, we will arrive at the following results:

For the NG-2 well
(calculated by the change in the isotopic composition of MTBE; f = 0.22) 𝜆 ~ 0.96⁄𝑦𝑒𝑎𝑟
(calculated by the change in the concentration of MTBE)

k ~ 1.3 / year
For the NG-3 well
(calculated by the change in the isotopic composition of MTBE; f = 0.35) 𝜆 ~ 0.66⁄𝑦𝑒𝑎𝑟
(calculated by the change in the concentration of MTBE)
31
k ~ 1.1 / year
Assuming that the conditions suitable for the anaerobic breakdown of MTBE persist in the entire
region that are between drillings NG-2 , NG-3,and NG-6, and assuming that λav ~ 0.8 / year,
it is possible to calculate the coefficient of the breakdown of MTBE over distance according
to Equation 4:
λdistance
0.03/m (v = 26.2 m/year)
4. General summary and recommendations
The results of the project proved the existence of the microbial breakdown of MTBE in
groundwater, both under aerobic conditions and anaerobic conditions.
A breakdown of MTBE on the Ramatayim site under aerobic conditions took place as a result
of an active remediation of the site by increasing the oxygen level with EBR. Probably without
this treatment, the aerobic breakdown of MTBE on the site would not have taken place or
would have taken place very slowly, due to a lack of dissolved oxygen in the water.
The remediation of the site by using the EBR® system significantly accelerated the breakdown
process that was characterized by a high rate (the breakdown coefficient about 8 / year as
opposed to 0.7 / year for a non-accelerated anaerobic breakdown).
The results of the tests carried out at the Nir Galim site indicate the existence of a natural
process of breakdown of MTBE under anaerobic conditions. It should be emphasized that a
process of this kind is not a common process, and it was reported in the literature only for a few
contaminated sites. The biological attenuation coefficient that was calculated for MTBE at
wells 2 and 3 by virtue of the data of the isotopic analysis is about 0.8 / year. This value is
somewhat lower than the point attenuation rate constant that was calculated in the present study
based on changes in the concentration of the contaminant in the well over time. A study
published recently by the Water Quality Division of the Water Authority [Reshef and Zoravel,
2013] reports attenuation coefficients within the range between 4.02 / year and 0.15 / year, and
the median value of the attenuation coefficient calculated for MTBE is about 1 / year. The
values calculated in the present study correspond to the values calculated by Reshef and
Zoravel
It should be emphasized that anaerobic conditions in groundwater, such as a lack of oxygen
dissolved in the water, very low concentrations of nitrate and sulfate, and high concentrations
of iron and manganese dissolved in the water, are indispensable, but not an unambiguous proof
of the existence of a natural process of the breakdown of MTBE.
Given the results of the present project, we recommend:

For proving the breakdown of MTBE under anaerobic conditions, it is recommended
that the following tests be carried out at least twice a year (prior to and following the rainy
season):
1.
Testing the change in the concentration of MTBE over time
2.
Testing the change in the concentration of the breakdown product TBA over time
3.
Testing the isotopic composition of MTBE

Further monitoring of the aerobic breakdown of fuel compounds at the Nir Galim
site in order to study in depth the biogeochemical processes and the parameters affecting them.
32
It should be noted that the results of the present study are based on a survey of two
contaminated sites. Since it is possible that in any contaminated site, geochemical conditions
characteristic of it may arise, it is recommended to expand the database by surveys of other
contaminated sites.
References
Gelman P., Ronen Z., 2009, Natural breakdown of fuel compounds in groundwater in Israel.
Report GSI 02302332.
The Hydrologic Service, 2013, Development, exploitation, and the state of the water sources in
Israel until autumn 2011.
Tolmatz, I., 2006, Hydrologic Atlas of Israel – geologic sections in the coastal region – volumes
a – f, The Hydrologic Service, 1977.
LDD, 2008, Installation of wells for the monitoring and sampling of ground ater – Paz Nir
Galim, highway 41.
LDD, 2013, Periodical report of monitoring of groundwater – Paz Nir Galim, highway 41.
Solomon S., 2006, The mechanism of salinization of sloping aquifers and its effects on the
coastal aquifer, a thesis, the Technion, Haifa.
Reshef G., Gal H., Elhanani S., 2012, The activities of the Division of Water Quality at the
Water Authority in the area of prevention of fuel contaminations, summary of activities for 2012.
Reshef G., Zoravel A., 2013, Calculation of attenuation coefficients of the first order of MTBE
and benzene in groundwater in the coastal basin.
Assouline, S., and U. Shavit. "Effects of management policies, including artificial recharge, on
salinization in a sloping aquifer: The Israeli Coastal Aquifer case." Water resources research
40.4 (2004).
A guide for assessing biodegradation and source identification of organic groundwater
contaminants using CSIA. EPA 600/R-08/148. December 2008.
33
Appendices
Table 1: A synopsis of the results of the chemical and isotopic analyses of groundwater at the Ramatayim gas station
Date
Well Water depth Well depth
m
m
Temp
SpC
DO
ORP
(ms/cm)
mg/L
mV
pH
Na
K
Ca
Mg
SO4
HCO3
d13C DIC
Cl
Br-
NO3-
As
Fe
Mn
Ni
Sr
U
d13C B
Toluene
d13C T
Et B
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
‰
mg/L
mg/L
mg/L
µg/L
µg/L
µg/L
µg/L
µg/L
µg/L
MTBE d13C MTBE Benzene
µg/L
‰
µg/L
‰
µg/L
‰
µg/L
d13C EtB Xylene
‰
µg/L
d13C X
‰
10.07.2011
R1
28.84
33.7
27.23
1.0
6.87
88
6.9
106
2
75
26
75
244
-13.5
155
1.3
95
<1
<10
2
1
523
3.4
452
-28.9
<10
nd
31
nd
<10
nd
<10
nd
16.09.2011
R1
28.89
33.57
27.2
0.8
3.01
9
6.6
104
1.7
80
28
65
260
-11.6
140
2.1
92
<1
35
28
<1
483
1
114
-29.2
<10
nd
<10
nd
<10
nd
<10
nd
24.11.2011
R1
28.82
33.47
22.1
1.0
4.77
113
6.6
100
1.3
74
27
63
240
-11.8
139
3.7
98
≤1
<10
25
2
425
1
168
-28.4
10
nd
15
nd
11
nd
12
nd
24.01.2012
R1
28.9
33.34
20.7
0.6
1.54
62
7.2
102
2.4
75
28
69
244
-12.4
141
3.4
90.7
<1
125
15
4
510
0.8
89
-27
<10
nd
<10
nd
<10
nd
<10
nd
8.03.2012
R1
28.79
33.34
21
0.7
1.52
70
7.2
100
2.7
80
29
72
250
-11.9
140
3.3
105
<1
≤10
10
<1
489
0.8
104
-27.8
<10
nd
<10
nd
<10
nd
<10
nd
14.03.2012
R1
28.79
33.31
19.6
0.4
1.84
100
6.9
101
2.8
84
31
77
270
-12.0
138
2.9
84
<1
≤10
8
<1
480
1.1
42
-26.4
23
nd
<10
nd
<10
nd
<10
nd
13.05.2012
R1
28.7
33.31
20.3
0.5
3.56
95
7.1
104
1.4
82
29
82
245
-11.7
150
2
110
<1
<10
4
<1
520
1.3
10
n.d
<10
nd
<10
nd
<10
nd
<10
nd
23.05.2012
R1
28.7
33.31
23.4
0.5
4.54
62
7.0
107
1.4
85
31
80
264
-12.1
154
3
109
<1
20
68
<1
532
1
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
22.11.2012
R1
28.3
35.07
22.8
0.5
3
240
7.2
111
1.5
85
30
73
275
-12.2
145
2
95
<1
<10
24
<1
425
0.8
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
16.09.2011
R2
28.72
35.34
22.5
1.1
3.07
-158
6.4
111
2.2
114
43
22
562
-17.5
140
1.4
0.2
39
350
1350
23
732
1.5
68198
-28.6
372
-27.2
239
-26.6
1242
-27.8
787
-27.7
24.11.2011
R2
28.74
35.63
21
2.7
4.02
-229
7.5
107
83
93
42
72
1820
-17.3
138
1.5
0.1
25
90
930
18
543
2.1
55568
-28.6
143
nd
13
nd
11
nd
13
nd
24.01.2012
R2
29.9
35.62
18.1
2.9
1.8
-256
8.3
105
152
72
16.1
121
2050
-17.0
116
1.8
0.1
38
100
145
16
423
1.1
22525
-28.9
82
nd
99
nd
<10
nd
<10
nd
8.03.2012
R2
28.19
35.3
18.2
3.1
2.18
-25
8.8
99
291
49
6
130
1780
-18.0
128
1.6
36
<1
≤10
9
21
235
2.5
6555
-28.9
<10
nd
<10
nd
<10
nd
<10
nd
14.03.2012
R2
28.19
35.2
18.2
3.4
2.2
-9.5
8.8
125
3
110
38
80
407
-14.5
205
3.5
43
<1
<10
30
<1
710
2.2
420
-26.1
<10
nd
<10
nd
<10
nd
<10
nd
23.05.2012
R2
28.08
35.2
26.1
0.7
2.67
-70
6.7
139
3.4
126
45
100
444
-15.3
209
3.9
49
<1
40
155
<1
835
2.5
264
-26.2
<10
nd
<10
nd
<10
nd
<10
nd
22.11.2012
R2
28.51
34.95
23.6
0.9
2.01
201
6.9
96
4.5
73
23
67
230
-16.5
110
0.5
136
<1
100
45
<1
456
0.8
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
10.07.2011
R3
28.73
34.95
30
0.4
1.93
-41
8.9
95
406
52
21
122
1270
-37.7
171
1
1296
3
20
400
6.5
352
4.8
4423
-29.7
26
nd
74
nd
25
nd
24
nd
16.09.2011
R3
28.79
35.02
27.2
1.1
2.33
-156
6.2
120
90
82
28
22
530
-12.0
155
1.9
3
5
10500
1750
3
710
0.1
2147
-28.4
10
nd
17
nd
14
nd
17
nd
24.11.2011
R3
28.82
35.01
21.1
0.4
2.98
-180
8.8
110
294
10
2
116
4454
-18.2
148
1.8
122
12
35
10
16
710
1
4181
-28.5
16
nd
12
nd
11
nd
12
nd
24.01.2012
R3
28.8
35
18.4
0.3
0.9
-50
8.5
112
212
34
4
84
1952
-18.1
137
2.9
128
5
25
45
16
221
3.8
1160
-29
<10
nd
<10
nd
<10
nd
<10
nd
8.03.2012
R3
28.8
35
18.7
0.6
1.1
-25
8.8
110
778
12
0.4
109
1500
-14.2
138
2.8
115
12
56
25
17
225
1.4
1450
-28.3
<10
nd
<10
nd
<10
nd
<10
nd
14.03.2012
R3
28.69
35.02
19.7
0.6
2.4
-190
9.1
119
437
35
1.7
110
1060
-14.3
138
2.8
609
5
45
6
26
150
1.3
1708
-28.6
17
nd
<10
nd
<10
nd
<10
nd
13.05.2012
R3
28.58
34.99
20.1
0.5
2.6
-35
9.0
87
25
76
27
104
353
-14.6
130
2.7
75
<1
680
750
23
430
0.6
88
-26.2
<10
nd
<10
nd
<10
nd
<10
nd
23.05.2012
R3
28.58
35.02
23.8
0.5
4.13
-192
8.8
95
5.8
81
29
72
331
-13.7
134
3
34
<1
350
500
9
513
0.3
44
n.d.
<10
nd
<10
nd
<10
nd
<10
nd
22.11.2012
R3
28.53
35.04
25.3
2.8
2.2
64
8.8
98
5
81
29
76
265
-13.5
125
1.6
91
<1
250
120
8
523
0.6
35
n.d.
<10
nd
<10
nd
<10
nd
<10
nd
10.07.2011
R4
28.86
34.93
27.8
1.1
3.7
-21
6.4
99
2
95
30
136
230
-14.7
211
3.8
71
<1
20
37
3
740
0.8
18
n.d.
<10
nd
<10
nd
<10
nd
<10
nd
16.09.2011
R4
28.91
34.87
27.2
0.9
3.92
76
6.9
109
1.1
87
34
73
221
-11.3
207
3.2
80
<1
<10
13
<1
523
0.7
80
-28.1
<10
nd
<10
nd
<10
nd
<10
nd
24.11.2011
R4
28.83
34.9
24.5
0.2
4.63
148.5
6.6
110
1.3
76
30
72
195
-12.5
177
3.2
88
<1
≤10
6
2
415
0.6
38
n.d
10
nd
11
nd
10
nd
14
nd
24.01.2012
R4
28.77
35.09
25.7
0.6
1.34
61
6.8
109
1.3
82
31
74
1196
-18.0
191
3.1
86.4
<1
< 10
15
<1
623
0.8
9
n.d
<10
nd
<10
nd
<10
nd
none
nd
8.03.2012
R4
28.81
34.92
23
0.4
2.02
187
6.8
118
3.8
77
30
70
234
-14.1
177
2.8
91
<1
≤10
16
<1
430
0.3
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
14.03.2012
R4
28.7
34.92
23
0.6
2.4
120
6.8
120
1.1
76
29
68
240
-14.3
185
2.7
103
<1
<10
5
<1
523
0.6
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
23.05.2012
R4
28.7
34.92
27.4
0.6
3.57
99.9
6.8
125
0.8
82
32
78
246
-14.1
195
2.9
101
<1
<10
15
<1
625
0.8
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
22.11.2012
R4
28.6
34.85
26.5
0.6
2.07
181
7.0
105
0.7
57
22
59
200
-14.1
114
0.9
116
<1
<10
8
<1
426
0.5
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
10.07.2011
R5
28.75
31.02
26
0.7
0.94
-32
9.4
99
370
14
15
240
4150
-45.2
208
1
912
3
<10
52
19
310
5.2
113
-28.6
<10
nd
105
nd
12
nd
12
nd
16.09.2011
R5
28.76
35.02
24.9
1.0
8
298
6.5
102
6
104
34
65
325
-12.7
195
3.4
<1
4
530
250
5
611
0.8
16
n.d.
<10
nd
<10
nd
<10
nd
<10
nd
24.11.2011
R5
28.78
35.02
24.8
0.1
1.57
67.3
7.3
98
12
73
28
69
297
-12.8
165
2.7
792
≤1
15
20
3
386
1.5
63
n.d.
<10
nd
<10
nd
<10
nd
<10
nd
24.01.2012
R5
28.92
34.9
27.7
0.6
1.36
91.4
6.7
111
1.1
72
28
67
210
-14.2
170
2.8
80.4
<1
< 10
≤2
<1
523
0.7
12
n.d.
<10
nd
10
nd
none
nd
none
nd
14.03.2012
R5
28.66
35.09
23.1
1.8
1.23
39.5
9.0
99
148
41
11
70
1074
-17.4
150
2.5
251
<1
≤10
9
8
256
1.8
17
n.d.
<10
nd
<10
nd
<10
nd
<10
nd
13.05.2012
R5
28.56
35.07
25.2
0.6
1.57
52
8.7
114
22
72
26
71
280
-13.2
169
2.1
6
<1
<10
420
<1
512
1.1
23
n.d.
<10
nd
<10
nd
<10
nd
<10
nd
23.05.2012
R5
28.56
35.07
26.8
0.6
0.9
6.3
8.7
119
4.9
80
31
72
248
-15.2
182
2.9
127
<1
30
260
<1
623
0.2
58
n.d
<10
nd
<10
nd
<10
nd
<10
nd
22.11.2012
R-5
28.48
34.95
27.2
0.7
1.68
174
7.0
109
2.2
70
25
59
235
-14.6
128
1.1
145
<1
<10
45
<1
578
0.5
<5
n.d
<10
nd
<10
nd
<10
nd
<10
nd
n.d.-not determined
M- MTBE; B- benzene; T- toluene; ET- ethyl benzene; X-xylene
34
Table 2: A synopsis of the results of the chemical and isotopic analyses of groundwater at the Nir Galim gas station
Date
Well
Water depth Well depth
m
m
Temp
SpC
DO
ORP
(ms/cm)
mg/L
mV
pH
Na
K
Ca
Mg
SO4
HCO3
d13C DIC
Cl
Br-
NO3-
As
Fe
Mn
Ni
Sr
U
MTBE
Toluene
d13C T
Et B
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
‰
mg/L
mg/L
mg/L
µg/L
µg/L
µg/L
µg/L
µg/L
µg/L
µg/L
d13C M Benzene d13C B
‰
µg/L
‰
µg/L
‰
µg/L
d13C EtB Xylene
‰
µg/L
d13C X
‰
100
445
-16.0
80
0.6
44
1
10
110
1
1300
5.5
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
n.d.
06.03.2011
NG1
11.19
15.97
22.1
1.1
2.7
30
6.9
63
2.7
125
40
20.09.2011
NG1
11.27
15.83
27.2
0.7
0.8
32
6.8
59
2.7
112
36
93
380
-14.9
82
0.5
42
<1
<10
105
2
1350
4.6
<5
n.d.
28
n.d.
11
n.d.
<5
n.d.
<5
11.03.2012
NG1
10.54
15.93
26.4
0.4
2.3
30
7.0
95
3.6
205
51
137
580
-15.2
185
0.9
42
<1
<10
12
1
1780
7
222
-30.3
57
n.d.
11
n.d.
346
-28.8
145
-29
10.03.2013
NG1
10.09
16.93
24.7
1.6
4.4
62
6.9
86
3.1
181
44
128
575
-14.0
126
0.5
60
<1
<10
12
3
1600
7.6
10
n.d.
25
n.d.
32
n.d.
112
n.d.
42
n.d.
21.10.2013
NG1
9.47
15.94
27.4
1.4
5.8
112
6.6
74
2.5
147
43
100
488
-14.9
112
0.8
53
<1
<10
23
3
1500
5.8
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
06.03.2011
NG2
11.46
15.88
27.2
1.3
3.4
-41
7.0
54
1.8
104
37
46
345
-17.1
120
1
50
1
130
225
2
1030
4
1736
-31.2
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
20.09.2011
NG2
11.56
15.83
27.4
0.8
0.44
-65
6.7
64
1.9
110
40
49
360
-16.6
140
1.3
55
<1
30
230
3
1300
3.8
2517
-31.5
549
-27.3
18
n.d.
<5
n.d.
<5
n.d.
11.03.2012
NG2
10.54
15.93
29.6
0.6
5
-142
6.9
70
1
130
50
0.7
588
-15.8
126
0.8
<1
<1
5100
1400
3
1530
0.8
29713
-31.4
4232
-27.9
113
n.d.
5317
-28.8
2001
-28.9
10.03.2013
NG2
10.32
18.9
25.4
1.5
4.86
-136
6.9
75
1.8
129
52
4
603
-13.8
127
1.3
3.4
8
7400
2800
<1
1450
0.2
6636
-14.1
3729
-26.6
104
n.d.
1320
-28.9
950
-28.5
21.10.2013
NG2
10.23
18.87
27
1.4
4.99
-142
6.4
82
1.5
118
54
3
567
-16.0
163
1.8
0.5
5
1850
2050
4
1500
1.7
4210
-11.8
1126
-27.4
110
n.d.
729
-28.4
95
-28.4
06.03.2011
NG3
11.34
18.91
25.6
1.2
2.93
-156
6.9
110
1.4
136
77
4
700
-13.9
240
4.2
<1
7
1150
1500
1
1800
0.2
3609
-30.6
6254
-27
85
n.d.
165
n.d.
101
20.09.2011
NG3
11.4
18.88
26.1
1.1
1
-189
6.7
107
1.2
132
74
0.1
710
-12.6
226
4
<1
6
13300
1600
2
2000
0.05
5056
-30.4
4213
-27.5
42
n.d.
356
-28.4
256
n.d.
11.03.2012
NG3
10.59
18.89
24.6
0.4
1.4
-110
7.1
76
0.7
103
52
0.4
537
-12.3
137
1.4
<1
4
770
730
6
1450
1.5
11678
-30.8
513
-27.4
193
n.d.
478
-28.7
205
-29.5
10.03.2013
NG3
10.19
18.91
23.9
1.5
2.07
-135
6.7
69
1
125
53
3
609
-12.7
133
3.2
2.8
4
5500
1325
2
1600
0.4
4699
-16.7
1300
-27.2
52
n.d.
450
-28.3
25
n.d.
21.10.2013
NG3
10.05
18.87
25.5
1.6
4.7
-133
6.6
94
1
128
69
3
647
-13.3
204
1.4
4
2
2900
1230
6
1750
0.6
2058
-17.5
1984
-27.4
24
n.d.
450
-28.9
55
n.d.
06.03.2011
NG4
11.62
18.42
25.6
1.4
3.81
-4
6.7
167
1.7
184
50
110
660
-20.1
250
1.4
40
1
110
23
5
1700
4.2
11
n.d.
11
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
20.09.2011
NG4
11.71
18.4
26.2
1.2
0.91
-50
6.5
148
1.7
183
51
98
675
-19.6
234
1.4
24
<1
60
600
7
1750
3.6
12
n.d.
77
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
11.03.2012
NG4
10.98
18.35
26
0.5
2.2
15.8
6.9
150
1.8
187
48
101
715
-18.5
230
1.5
4
<1
<10
600
3
1700
4
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
10.03.2013
NG4
10.5
18.41
24.6
2
4.8
25
6.8
152
1.8
191
48
102
709
-14.2
210
1.4
3.9
<1
<10
430
2
1500
4.4
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
21.10.2013
NG4
10.4
18.4
25.5
1.9
6.58
61
6.5
144
1.8
174
49
98
656
-18.0
195
3.4
35
<1
<10
50
4
1500
3.6
29
n.d.
49
n.d.
43
n.d.
<5
n.d.
<5
n.d.
06.03.2011
NG5
11.19
17.33
21.7
1.2
2.4
-12
7.1
85
2.3
106
42
36
430
-17.8
170
1.5
13
1
30
127
3
1230
5.8
<5
n.d.
7
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
20.09.2011
NG5
11.22
14.32
26.1
0.9
0.42
-53
6.8
82
2.3
101
39
40
400
-16.5
164
1.5
19
<1
<10
80
4
1200
4.5
<5
n.d.
<10
n.d.
11
n.d.
<5
n.d.
<5
n.d.
11.03.2012
NG5
10.55
17.32
20.8
0.3
2
51.2
7.2
96
2.5
107
43
40
478
-15.8
171
1.7
9
<1
<10
165
3
1200
7
15
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
10.03.2013
NG5
10.03
17.31
23.5
1.5
5.58
143
6.7
104
2.7
112
46
44
456
-16.8
176
1.7
6.8
<1
<10
175
5
1300
7.8
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
21.10.2013
NG5
9.99
17.33
24.3
1.7
4.96
169
6.7
102
2.4
106
44
46
452
-17.4
165
1.5
8
<1
<10
170
10
1300
5.8
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
06.03.2011
NG6
11.15
16.73
24
1.3
3.4
-164
7.0
121
4
125
52
20
570
-21.0
225
2.7
0.7
1
2200
800
1
1430
5
239
-31
321
-27.2
<5
n.d.
14
n.d.
<5
n.d.
20.09.2011
NG6
11.2
16.74
26.2
1
1.5
-149
6.8
102
2.5
121
50
26
508
-19.2
210
2.4
7
<1
250
850
6
1400
4.8
348
-31.6
28
n.d.
23
n.d.
37
n.d.
100
n.d.
11.03.2012
NG6
10.53
16.74
23.4
0.4
1.2
-89.4
7.1
100
2.8
120
50
20
550
-18.6
192
2.4
3
<1
150
600
2
1320
7.1
102
-31.2
71
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
10.03.2013
NG6
10.01
16.72
22.5
2.5
2.7
-186
6.9
182
2.4
168
76
7
610
-17.0
452
6
2.7
2
250
2200
4
2000
6
41
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
<5
n.d.
21.10.2013
NG6
9.98
17.2
24.8
0.3
4.4
-123
6.4
158
2
147
69
4
609
-20.0
360
4.2
0.5
<1
4000
2200
9
1800
4.4
51
n.d.
35
n.d.
41
n.d.
79
n.d.
66
n.d.
n.d.-not determined
M- MTBE; B- benzene; T- toluene; ET- ethyl benzene; X-xylene
35
n.d.