Potential Occurrence of MTBE and BTEX in Groundwater Resources of Amman-Zarqa Basin, Jordan

Mustafa Al Kuisi1

Ghazi Saffarini1

Najal Yaseen1

Mahmoud Alawi2

1Department of Applied Geology and

Environment, The University of

Jordan, Amman, Jordan2Department of Chemistry, The

University of Jordan, Amman, Jordan

Research Article

Potential Occurrence of MTBE and BTEX inGroundwater Resources of Amman–Zarqa Basin,Jordan

This study investigates potential occurrence, distribution, and sources of the newly

added gasoline oxygenate, methyl-tert-butyl ether (MTBE) and the petroleum derivatives

benzene, toluene, ethylbenzene, and xylenes called collectively, BTEX, in Jordan’s

heavily populated Amman–Zarqa Basin (AZB). It presents the first data on the levels

of MTBE and BTEX in the aquifers of this basin. One hundred and seventy-nine (179)

groundwater wells were sampled near petrol service stations, oil refinery storage tanks,

car wrecks, bus stations, and chemical industries at different locations in the basin.

Headspace GC and purge and trap GC–MS were utilized to determine the target

substances in the samples. Concentrations of BTEX varied between no-detection (mini-

mum) for all of them to 6.6mg/L (maximum) for ethylbenzene. MTBE was found in few

samples but none has exceeded the regulated levels; its concentrations ranged between

no-detection to 4.1mg/L. However, though the contamination levels are very low they

should be considered alarming.

Keywords: Lead; Octane number; Oxygenate; Petroleum derivative

Received: September 1, 2011; revised: October 6, 2011; accepted: October 18, 2011

DOI: 10.1002/clen.201100473

1 Introduction

The intense search for an effective and economical octane boosting

alternative to lead as a gasoline additive is going on since the past

decades. Chemicals of oxygenates have come into view as alter-

natives for improving the octane number and the oxygen content

in gasoline [1]. The most important of these oxygenates has been

methyl tertiary butyl ether (MTBE). It has been considered as one of

the best agents for reducing automobile emissions that create ozone

and smog. The usage of MTBE has increased with the passage of time

since its first application in the USA late 1970s. This can be accounted

for as due to the amendments to clean Air Act (1990) which required

the use of cleaner burning fuels. The relatively high solubility of

MTBE in water, low soil adsorption and low biodegradability made

its environmental impact debatable and unproven, as it has the

potential for pervasive and persistent contamination

of groundwater [1]. In 1997, the United States Environmental

Protection Agency (U.S. EPA) considered MTBE as a possible carcogen

if present in potable water with concentrations ranging from 20 to

40mg/L or above [2]. The State of New Hampshire, for example, has

adopted a maximum contaminant level of 13mg/L for MTBE in

drinking water [1]. The states and the U.S. EPA have moved to ban

MTBE because of its propensity to contaminate ground and drinking

water supplies, as it has shown up in hundreds of underground fuel

links [1].

In Jordan, the only provider of oil products is Jordan Petroleum

Refinery Company (JPRC). During the concession agreement with the

refinery that was signed in 1957, three types of gasoline have been

used. They are as follows: ‘‘Regular Gasoline’’ containing lead with

Octane number of 87; ‘‘Unleaded Gasoline’’ with octane number of

92; and ‘‘Super Gasoline’’ which contain lead with octane number of

95 [3]. The production of unleaded gasoline, on the other hand,

began 1995 in limited quantities with high price because of the

small amounts produced by the Refinery. The Jordan Institute for

Standards and Metrology (JISM) specified the use of fourth tetraethyl

lead as an oxygenate up to 150 mg/L for regular and super gasoline

types, as a maximum, and 5 mg/L for unleaded gasoline. Based on the

repeated demands by the Ministry of Environment (MOEnv) and

the desire of the Ministry of Energy and Mineral Resources

(MEMR), a study was made to phase out lead in gasoline. The alterna-

tive to that was to use MTBE which is already used in different

European and Arab Countries [3]. The results of the study prompted

the formation of a joint committee with representatives from MEMR,

MOH, MOEnv, JPRC, Ministry of Finance, and the Association of

Owners of Gasoline Stations to assess the status of oil products’

tanks at gasoline stations, develop mechanisms to replace the faulty

tanks, and develop recommendations on the funding mechanism [3].

The committee has prepared a draft report concluded by a number of

recommendations, of which the most important ones relevant to

this study are listed below [3]:

� Holding the owners of gas stations responsible for any leakage that

would happen and requesting them to follow up on the status of

the tanks and to report any leakage which might occur.

Correspondence: Dr. M. Al Kuisi, Department of Applied Geology andEnvironment, The University of Jordan, P. O. Box 13437, 11942 Amman,JordanE-mail: [email protected]

Abbreviations: AZB, Amman–Zarqa Basin; BTEX, benzene, toluene,ethylbenzene, and xylenes; MTBE, methyl tertiary butyl ether; USRs,underground storage tanks

808 Clean – Soil, Air, Water 2012, 40 (8), 808–816

� 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com

� Requiring owners of the gas stations in the event of any leakage

from gasoline tanks in the future to either remove the tanks from

service (mechanical isolating) or replacing them with double wall

tanks.

� Appointing JISM to issue a Jordanian specification standard

regarding gasoline stations and their accessories, including gaso-

line tanks of the double wall types.

Ministry of Energy and Mineral Resources has committed itself to

implement the decision of the Cabinet to use MTBE to increase the

number of octane for gasoline instead of using lead. It has also

adopted recommendations suggesting removing faulty tanks and

giving a transition period to correct the situation. On February 8,

2008, the usage of lead with gasoline was stopped completely and

was replaced with MTBE. Consequently, two types of unleaded gas-

oline were introduced and still in use until the date of conducting

this study; the first type with an octane number of 90 and the other

with an octane number of 95 [3].

Because of its mobility, MTBE contamination can result from a

spill of as little as 10-gal of fuel and it can be the only contaminant

detected, as pointed out by some authors (www.cee.vt.edu/ewr/

environmental/teach/gwprimer/btex/btex.html) [4]. Even an over-

turned vehicle can result in an MTBE plume. The content of MTBE

in 10 gal of gasoline that is 11% by volume MTBE is about 3 kg. If such

an amount is to reach the water table, subsequent dissolution and

transport could lead to the contamination of millions of liters of

water [4].

The other substance of concern in this investigation is the famous

group of benzene, toluene, ethylbenzene, and xylenes (BTEX), it is

considered one of the major groups of soluble organic substances

which usually find their way into groundwater. BTEX compounds are

volatile organic compounds (VOCs) found in petroleum derivatives

such as gasoline. They find their way to groundwater if contami-

nation of petroleum derivatives occurs causing accordingly serious

pollution problems due to their polarity and very soluble character-

istics. Among the members of BTEX, and in addition to its toxicity,

benzene is known to be a carcinogen [4].

Since the date of introducing MTBE to fuel in Jordan, no special

monitoring activities or investigation studies, either governmental

or private, have addressed so far the issue of the potential incidence

of MTBE, as well as BTEX. The concerns over potential occurrence of

MTBE and BTEX in ground water of the heavily populated Amman–

Zarqa Basin (AZB) prompted the initiation of this study to assess the

existence, distribution, and concentrations of these substances in

water resources, to compare their concentrations to drinking-water

standards or advisories, and to determine whether there are factors

associated with any noticeable rates of MTBE and BTEX in ground-

water in AZB. The findings of this study may have implications for

groundwater protection plans and future water-resources manage-

ment policies in Jordan.

1.1 The study area

1.1.1 Hydrogeological characterization

The AZB is located in the central part of Jordan (Fig. 1) and extends

over two Governorates, namely Amman Governorate and Zarqa

Governorate. The catchment area of the Zarqa River, which is the

only single and major river running in the basin, measures

47 442 km2 and extends from Jabal Druz, east, to the Jordan River

in the Ghor, west. For a brief summary on AZB see reference [5]. Based

on to the water bearing potential, three aquifer systems are available

in AZB namely: the upper aquifer system (B2/A7), middle aquifer

system (A4 and A1/2) and lower aquifer system (K).

The shallow upper aquifer is unconfined and as such the water

level is free to rise and fall in response to seasonal fluctuations. The

lower aquifer is separated from the upper aquifer by a layer of

massive marl and marly limestone. This is a confined condition

in which the water level fluctuates in response to piezometric

Figure 1. The study area.

Clean – Soil, Air, Water 2012, 40 (8), 808–816 Occurrence of MTBE and BTEX in Groundwater 809


pressures. Recharge sources to this basin are natural and artificial.

Natural recharge sources include the lateral flow of groundwater

from the western highlands and percolation of surface and rain

water. Direct infiltration throughout the Zarqa–Ruseifa region takes

place where outcrops of the B1-2 and A7 formations commonly

occur. The depth of wells varies considerably from the shallow,

hand-dug wells along the Zarqa River to wells deeper than 500 m

which withdraw water from the lower aquifer [6].

Within the catchments area of AZB, various lithological units crop

out ranging from Jurassic to Quaternary in age. These deposits

mainly belong to the Ajlun and Belqa Groups according to

Jordanian classification. However, the Kurnub Group (Lower

Cretaceous) is usually found at certain depths except outcrops at

the western parts of the study area (Baq’a Valley) along the axis of

Suweileh anticline. In addition, the older Zarqa Group (Jurassic–

Triassic age) occurs at considerable depth [6].

2 Materials and methods

To determine the potential occurrence and distribution of MTBE and

BTEX in the groundwater resources of AZB, this study incorporated

both field investigations of existing conditions of gas stations especi-

ally observing installation of underground storage tanks (USTs)

were conducted as well as desk review of gas station census infor-

mation and specifications in addition to implementing well

sampling campaigns followed by laboratory analyses of collected

water samples.

Water samples for MTBE and BTEX measurements were collected

in two time intervals during May to June 2009 and February to

April 2010.

On each date, samples were typically taken from wells owned by

private and governmental sectors; most of these wells are used for

drinking purposes. In addition, some of the wells are used for

irrigation and industrial activities. The locations of the selected

wells are illustrated in Fig. 2. To avoid screen contamination

from the wells; samples were collected after a pumping time of

about 15 min. Temperature (Temp., 8C); pH; electrical conductivity

(EC, mS/cm); dissolved oxygen (DO, mg/L); and redox potential

(Eh, mV) were measured on site using portable instruments. The

collected samples mounted up to 179 and were stored in 100 mL

sample vials that were acidified by addition of concentrated (33%)

hydrochloric acid. The bottles were completely filled, with no head-

space (HS), cooled to 4 8C, and analyzed within 1 wk of collection [7].

The analysis was performed by a combination of headspace-solid-

phase microextraction (HS-SPME) and GC–MS. The MTBE signals

could be checked with respect to superimposition by other com-

pounds since the analyses were carried out in the full scan mode. The

detection limit was 1mg/L with a relative standard deviation of 10%.

In addition, MTBE was analyzed at Alpha Analytical, Inc. (Sparks,

Nevada), in 25-mL aliquots first, using purge and trap procedures for

concentration followed by GC/MS detection (GC-MSD) [7]. Laboratory

instrumentation consisted of a Tekmar autosampler, a Tekmar LSC

2000 liquid sample concentrator with a VOCARB 3000 trap, and a

ThermoQuest Trace 2000 Gas Chromatograph-Thermo Quest GCQ

plus Mass Spectrometer.

Figure 2. Location of selected wells for sampling and gas stations.

810 M. A. Kuisi et al. Clean – Soil, Air, Water 2012, 40 (8), 808–816


The calibration standards of MTBE and BTEX at concentrations of

at different concentrations were prepared in the sense of Edwards

et al. [7].

Two analytical methods were employed for determining the VOCs

MTBE and BTEX groups in the groundwater samples. The first

method was performed for the samples which were collected in

2009. These samples were analyzed at the laboratories of the

University of Jordan in Jordan using U.S. EPA Method 524.2. [7]

Whereas the second method which is called the German Method

[8] was used for samples collected in 2010. The latter samples were

analyzed at the laboratories of Heidelberg University in Germany.

U.S. EPA Method 524.2 [6] was utilized for the analysis of approxi-

mately 60 compounds, along with suitable internal standards and

surrogate compounds, in a drinking water matrix using GC–MS

electron impact full scan. A known volume (25 mL) of sample is

purged with an inert gas, typically helium, and the target analytes

are swept out of the water fraction as gases and moved onto a

sorbent bed (the ‘‘trap’’). After the purge event is completed, the

trap is placed in series with the chromatography column and the

analytes are thermally desorbed onto the column using a ballistic

heating program. This is followed by column, standard GC sepa-

ration detection, quantitation, and confirmation by MS. The German

Standard Method DIN 38407 group F9 [8] used in this study deals with

HS as sample preparation technique. The degree of uncertainty in

the instruments does not exceed 5% [8].

This norm concerns the analysis of the MTBE and the aromatic

compounds benzene, toluene, xylene as well as ethyl- and chloro-

benzene in water and waste water in a concentration range starting

up from 1mg/L (1 ppb). Other aromatic derivates and non-polar

compounds in the same boiling range can also be determined

according to this procedure [7]. Using HS techniques, a defined

volume of the unfiltered water sample is added into a gastight vial

which is then sealed with septa. The vial is conditioned at a given

time and temperature before sample injection. During the con-

ditioning time, an equilibrium state between the liquid phase

and the HS should be reached. The conditioning parameters are

determined by experiment and depend on the maximum concen-

tration of the compounds to be analyzed in the HS. After condition-

ing, an aliquot is taken from the HS, transferred to and analyzed in

gas chromatograph [7].

3 Results and discussion

From field observations and field interviews of people working in gas

stations it was found that the design of the underground tanks is not

fully suitable for gasoline containing MTBE. The recommended

design for these purposes, according to local specifications, must

be double-wall tanks. However, all old generation USTs and some of

the newly installed tanks are of single-wall. In general, the new gas

stations belonging to private investors use double-wall tanks to

comply with requirements of the new standards for USTs No. 599

of the year 2008 [9]. Similarly, at the time of installation, some

improper handling practices of USTs took place as shown in

Fig. 3, a practice that might increase the possibility of rapture of

the tanks the thing which may lead to possible leakages and cor-

rosion of the tanks. Reports indicate that the number of gas stations

in Jordan in 2007 reached 363 stations, 268 of these stations are

owned by JPR while 95 stations are owned by private sector [10]. This

number has increased and reached 409 stations in 2010. The total

number of gasoline tanks holding the three gasoline types

(unleaded, regular, and super gasoline) existing in gas stations

are around 1085 tanks, of which 750 are owned by JPR and 335

tanks are owned by private sector, as shown in Tab. 1. Moreover,

these tanks ranged between 1 and 40 years in age (Tab. 2). Finally, and

according to Tab. 3, it is clear that 55% of the whole USTs must be

replaced if using the MTBE to be continued as an additive.

Before this study, there were 183 gas stations in 2007 distributed

over the whole area of the basin as shown in Fig. 2 but nowadays the

number of gas stations has increased to 416 in 2011 (personal

communication with JPR); some of these gas stations are

owned by new private sector investors such as Al Manaseer

Group, Total, Gulf, etc. These newly constructed gas stations have

Figure 3. A real photo of an underground sto-rage tanks (USTs) before installation in a localgas station in Jordan (image taken by authors,2010).



more compliance with the new Jordanian Standard and Regulation

for USTs (No. 599) of the year 2008 [9].

The geochemical analysis and concentrations of the different

parameters of water samples from the upper, middle, and

lower aquifers in AZB are present in Tab. 4. However, there was

no difference between the results which obtains in 2009 comparing

to 2010.

Pollution indicators like sulfate, nitrate, and phosphate were also

measured and their average concentrations are also given in Tab. 4.

As shown in this table few samples exceeded the maximum permiss-

ible Jordanian limits for nitrate and sulfate. These samples were

collected from cultivated areas that apply natural and chemical

fertilizers for crop productions. Trace elements like lead and iron

were also measured. Lead ranged between 0.001 and 1.04 mg/L with

Table 1. Number of gas stations and tanks in Jordan [11]

Governorate No. of gas stations andtanks owned by JPR

No. of gas stations andtanks owned by private sector

Total number of gas stationsand tanks

No. of gas stations No. of tanks No. of gas stations No. of tanks No. of gas stations No. of tanks

Amman 88 328 51 200 139 528Irbid 54 111 3 11 57 122Zarqa 25 66 11 37 36 103Mafraq 17 37 7 19 24 56Ajlun 5 9 4 12 9 21Jerash 7 14 3 9 10 23Balqa 25 70 5 13 30 83Madaba 12 25 1 3 13 28Karak 14 33 4 12 18 45Tafeela 5 14 0 0 5 14Ma’an 10 25 2 4 12 29Aqaba 6 18 4 15 10 33Total 268 750 95 335 363 1085

Table 2. Ages of underground storage tanks [11]

Government Regular gasoline Super gasoline Unleaded gasoline Total

Until 13 years Exceeded 13 years Until 13 years Exceeded 13 years Until 13 years Exceeded 13 years

Amman 129 198 78 84 32 7 528Irbid 25 64 12 16 3 2 122Zarqa 38 31 18 11 4 1 103Mafraq 21 24 10 1 0 0 56Ajlun 10 3 6 0 2 0 21Jerash 8 9 4 2 0 0 23Balqa 18 42 8 14 0 1 83Madaba 9 13 5 1 0 0 28Karak 13 20 6 6 0 0 45Tafeela 4 7 2 1 0 0 14Ma’an 6 16 3 4 0 0 29Aqaba 9 11 6 5 2 0 33Total 290 438 158 145 43 11 1085

Table 3. Underground storage tanks situations [11]

Government Suitable tanks % Tanks need replacement % Total

Amman 239 45.27 289 54.73 528Irbid 40 32.79 82 67.21 122Zarqa 60 58.25 43 41.75 103Mafraq 31 55.36 25 44.64 56Ajlun 18 85.71 3 14.29 21Jerash 12 52.17 11 47.83 23Balqa’a 26 31.33 57 68.67 83Madaba 14 50.00 14 50.00 28Karak 19 42.22 26 57.78 45Tafeela 6 42.86 8 57.14 14Ma’an 9 31.03 20 68.97 29Aqaba 17 51.52 16 48.48 33Total 491 45.25 594 54.75 1085



an average value of about 0.02 mg/L. Few samples show concen-

trations exceeding the high permissible limit of the JISM [11] and

WHO [12]. Fe, on the other hand ranged from 0.001 to 5.33 mg/L with

an average value of 0.37 mg/L.

The concentrations of the MTBE and the BTEX group constituents

in the groundwater samples are presented in Tab. 4. Only 12 samples

from the investigated wells showed signs of MTBE and BTEX con-

tamination but none of which exceeded the maximum permissible

limits of JISM [11]. The concentrations of MTBE and BTEX in the rest

of the samples were below the detection limits of the GC/MS, which is

1mg/L. Aerial distribution of these contaminated samples occurs

mostly near the cities of Ruseifa, Zarqa, and Al Hashimyya (Fig. 4).

The compounds of the BTEX group were also evaluated. Maximum

concentrations of its individuals namely BTEX valued 5.6, 6.4, 6.6,

and 4.1mg/L, respectively. Benzene should be given more attention in

the evaluation of BTEX group results due to its toxicological nature

Table 4. Results of geochemical analysis and concentrations of parameters, MTBE and BTEX at the two periods were identical

Parameter Value (whole aquifers, 179) Number ofsamples

Regulatedlimits [12]

Water solubility (mg/L) at25 8C for MTBE and BTEX

Mean Min Max

EC (mS/cm) 1085 413 3150 179 1500pH 7.39 6.88 8.04 179 6.5–8.5Eh (mV) 388 �21 1050 179 –T (8C) 23.5 18.0 31.6 179 25SO4

2� (mg/L) 442.31 26.21 2876.26 179 500NO3

� (mg/L) 56.14 11.06 249.56 179 70PO4

3� (mg/L) 0.03 0.01 0.18 179 –Fe (mg/L) 0.37 0.001 5.33 179 1Pb (mg/L) 0.02 0.001 1.04 179 0.01MTBE (mg/L) 1.2 1.1 4.1 12 10 51 000 mg/LBenzene (mg/L) 1.7 1.2 5.6 12 10 1700Toluene (mg/L) 2.1 1.7 6.4 12 500 515Ethyl benzene (mg/L) 1.6 1.2 6.6 12 700 152Xylene (mg/L) 1.2 1.5 4.1 12 300 172

Figure 4. Distribution of contaminated wells.



and being carcinogenic to humans and has higher solubility in water

in comparison to the other three compounds. Detection limits of

all BTEX constituents are according to Clesceri et al. [13] 1mg/L.

However, this value was adopted also for all BTEX group [13].

Methyl-tert-butyl ether concentrations ranged from 1 to 4.1mg/L

with an average value of 1.2mg/L in the 12 contaminated samples

(Tab. 4). MTBE is characterized by higher solubility in water when

compared to other BTEX group constituents. Accordingly, it is

expected to undergo an increase in concentration over time if

any leakage from the underground tanks is taking place in the basin.

Since MTBE does not get sorbed to subsurface solids it can reach

the groundwater at almost the same velocity of recharge water.

Squillace et al. [14] pointed out that recharge velocity in its turn

varies in large areas and depend on many factors, among which

precipitation, evapotranspiration, hydraulic conductivity of

material present in the unsaturated zone and the thickness of the

unsaturated zone.

Based on Squillace et al. [14], in some parts of the United States,

where the depth to water is less than 3 m, recharge can reach the

underlying aquifer in a few days. Accordingly, pollutants such as

MTBE can reach the stations underlying aquifer in such a short

period of time. In the investigated area where the depth to water

is <9 m and the unsaturated zone is permeable as well, similar

recharge and transport conditions are likely to happen. Thus, as

Squillace et al. [14] mentioned, once MTBE reaches the ground water,

it can move at nearly the same velocity as the water. This will allow

MTBE plumes to occupy a large portion of groundwater as compared

to the BTEX compounds. This explains also why MTBE plumes can

move on the scale of kilometers away from the source of contami-

nation, while the BTEX plumes typically move <100 m from the

source.

In general, the contaminated wells in the study area abstract their

water from the shallow aquifer, which is mainly composed of gravels

and unconsolidated sediments and is also characterized by high

porosity and permeability. In addition, water level in these wells

was relatively shallow and ranged between 9 and 35 m below ground

surface. Thus, it is believed that these conditions might have facili-

tated the potential contamination from any leakage from the gas

stations located upstream of these wells, especially knowing that

these gas stations are very old (>25 years).

According to Zogorski [15] the ratio of the ground water velocity to

the velocity at which a compound is transported is referred to as the

retardation factor, R. This factor is dependent particularly on aquifer

properties, such as porosity and organic carbon content Koc. In case

of MTBE R is close to 1, whereas BTEX R values range from 1.1 to about

2.0 because they adsorb to soil or rock surfaces. Knowing that MTBE

contamination plumes are bigger than those of BTEX, one would

expect that in a certain period of time BTEX contamination will be

detected. Therefore, the detection of advancing MTBE plume should

be considered as a precursor to increasing BTEX contamination

overtime [16]. This is also to be expected along the groundwater

flow path as shown in Fig. 5.

Based on an earlier study [17], the causes of releases from storage

tanks are mainly due to corrosion of bare steel pipes connected to

Figure 5. Direction of groundwater movements for the upper aquifer (B2/A7) in the AZB.



these tanks. To a lesser extent, improper installation and accidents

might also be responsible for leaks. The most frequent types of leaks

are caused by spills and overfill. Nowadays, newly installed tanks

must be protected (cathodic protection) from corrosion and their

installation must follow a certain procedure. An alternative to the

steel tanks that corrode more easily is the use of fiberglass tanks

which are more resistant to corrosion. A disadvantage to the use of

fiberglass tanks is that they are very fragile and have a tendency to

crack, especially during installation. Because of this tendency to

break, steel tanks are most commonly used. It is worth mentioning

that all USTs used in Jordan are made of unprotected bare-steel

tanks, or steel, fiberglass or some combination of both [15].

US EPA [2] has not set a national standard for MTBE in drinking

water till now. However, in December 1997, it issued a Drinking

Water Advisory stating that the concentrations of MTBE in the range

of 20–40 ppb of water or below will probably not cause unpleasant

taste and odor for most people, recognizing that human sensitivity

to taste and odor varies widely. But the US EPA standards for BTEX

groups are less than the MTBE because BTEX tend to be more

carcinogenic than MTBE. WHO guidelines [12] are some of the most

important sources of advice on the safety and acceptability of drink-

ing water around the world. MTBE can be detected in water by taste

and odor at low concentrations. WHO considered that it was

unnecessary to set a health based guideline value for MTBE, since

any such value would be substantially above the concentration at

which MTBE could be detected by taste and odor. But in the case of

BTEX, they set standard limits. Finally, the Jordanian guidelines,

which are in reality based on WHO’s guidelines, require that for

drinking purposes, water should have MTBE concentrations below

10mg/L (ppb). Table 5 shows permissible limits according to the three

regulating agencies used in this study, namely, JISM [11]; US EPA [2];

and WHO [12]. Fortunately, all the collected samples were under the

maximum permissible limits of the three organizations.

4 Conclusions

This study is the first to assess the potential occurrence of MTBE and

BTEX in groundwater resources in Jordan namely in AZB area. Out of

179 analyzed water samples, only 12 showed BTEX and MTBE finding.

BTEX values ranged between 1 and 6.6mg/L (ppb) and are located in

areas near Ruseifa, Zarqa, and Al Hashimyya cities. The analyses

showed that the concentrations of the other analyzed samples were

below the detection limits of the GC/MS which is 1 ppb. This is most

probably due to many reasons. Most important of which is that BTEX

group tend to partition between sediments and soil rather than

leach into groundwater because of their low solubility and high

kow. They tend as well to volatize to atmosphere rather than stick to

soil particles. This could be a main reason for not detecting these

compounds in the groundwater resources in the study area in case

contamination is taking place. MTBE also was not found in water

samples except in 12 samples in an average value of 1.2mg/L. This low

concentration may be attributed to high vapor pressure which

predicts volatilization from moist and dry surfaces. In addition its

use as a gasoline additive in Jordan has just started since 2008 and it

might be still too early for ‘‘considerable’’ amounts of MTBE to reach

groundwater from USTs, an event that is not welcomed if happened.

Accordingly, drinking water quality management systems in the

country should be pro-active rather than being active in dealing

with such issue before it takes place.

Acknowledgments

Thanks are due to the anonymous reviewer of this journal for

highly improving the manuscript. Thanks and gratitude are also

due to the Deanship of Scientific Research at the University of Jordan

for supporting and sponsoring this research by grant no. 4100,

2/2009–2010. The senior author is extends great thank to

Dr. Lothar Erdinger from the Institute for Hygine and Mrs.

Franziska Forster from the Centre for Organismal Studies, Aquatic

Ecotoxicology Group, University of Heidelberg for analysing of the

samples at their institutes.

The authors have declared no conflict of interest.

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Table 5. Permissible limits for organic targeted contaminants/pollutants in drinking water according to JISM [12], US EPA [2], and WHO [13]

Chemicalsubstance

JISM-permissiblelevel (mg/L)

WHO-permissiblelevel (mg/L)

USEPA-permissiblelevel (mg/L)

MTBE 10 10 20–40Benzene 10 10 5Ethylbenzene 500 300 700Xylene 700 500 10Toluene 300 700 1



[8] DIN 38407, Teil 9, Deutsche Einheitsverfahren zur Wasser, Abwasser-und Schlammuntersuchung, Gemeinsam erfasste Stoffgruppe/GruppeF, Bestimmung von Benzol und einigen Derivaten mittelsGaschromatographie (F9); DIN Band III; 333. Lieferung, VerlagChemie und Beuth Verlag Weinheim/Berlin 1995.

[9] Jordan Institution for Standards and Metrology, JISM, StandardSpecifications for Tanks – Oil Storage Tanks, No. 599, JordanInstitution for Standards and Metrology, Amman, Jordan 2008.

[10] Ministry of Energy and Mineral Resources, MEMR, Assessment ofBenzene (Gasoline) Tanks in Jordanian Gas Stations, Ministry of Energyand Mineral Resources, Jordan 2007.

[11] Jordanian Institute of Standards and Metrology, JISM, DrinkingWater Standards No. 286/2008, Jordan Institution for Standards andMetrology, Amman, Jordan 2008, p. 13.

[12] World Health Organization, WHO, Guidelines for Drinking WaterQuality, World Health Organization, Geneva 2006.

[13] L. Clesceri, H. Greenberg, A. Eaton, Standards Methods for theExamination of Water and Wastewater, 20th Ed., American PublicHealth Association, Washington, DC 1998.

[14] P. J. Squillace, J. F. Pankow, N. E. Korte, J. S. Zogorski, EnvironmentalBehavior and Fate of Methyl tert-Butyl Ether (MTBE), US Departmentof the Interior, US Geological Survey National Water QualityAssessment Program (NAWQA), Washington, DC 1998.

[15] J. S. Zogorski, Fuel oxygenates and water quality, in InteragencyAssessment of Oxygenated Fuels, National Science and TechnologyCouncil, Washington, DC 1997.

[16] S. McAuley, MTBE Concentrations in Groundwater in Pennsylvania, USDepartment of the Interior, US Geological Survey, Water-ResourcesInvestigations, Washington, DC 2003.

[17] United State Environmental Protection Agency, US EPA, Proceedingsof the First National Workshop on Biological Criteria, US EPA,Lincolnwood, Illinois 1988.



Potential Occurrence of MTBE and BTEX in Groundwater Resources of Amman-Zarqa Basin, Jordan

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