Geochemical characterization and pollution ... - Springer Link

Original article

Geochemical characterization and pollution phenomena of aquifer waters in northern Israel U. Kafri Æ B. Lang Æ L. Halicz Æ O. Yoffe

logical regime and may improve the calculation of groundwater balances in northern Israel. The results also provide hints as to anthropogenic processes of groundwater pollution. Groundwaters in northern Israel show a wide variety of salinities and chemical compositions. Part of the water sources can be related to a definite aquifer, whereas others are indicative of a mixture of two or more sources. Brackish groundwater sources were found to be mixtures of fresh groundwaters with saline seawater or brine, end members. Attempts to group different water sources in Israel using major and trace elements content were performed by Arad and others (1986); Halicz and others (1992); Bein and others (1995) and recently by Yechieli and others (1997). Different aquifer waters were characterized by equivalent value (r) F/Cl ratios (Kafri and others 1989a, 1989b). At a first glimpse it seemed that some elements (e.g., Mo, Keywords Characterization Æ Geochemistry Æ U, B, Ba, F, Li, Sr) and their ratios to Cl are more Groundwater Æ Pollution significant and may serve as tagging tools. Also, the I content and the rI/rCl ratio were found in the literature to be a powerful tool for differentiation between aquifers and salinity sources (Lloyd and others 1982; Sukhija and others 1996). Introduction Some water sources issue from the alluvium, or along faults and seem to be fed laterally, or vertically by more The objective of the study was to characterize and than one aquifer. These are, herein, defined as mixed identify the different water sources in northern Israel using geochemical parameters. The resultant data enable sources. The necessity to accurately identify the different the identification of different end members when dealing aquifers that contribute to mixed sources arose, for example, in the course of the radon content study of with mixed water sources. The results of this study groundwater in Israel. The results of the present study contribute to a better understanding of the hydrogeowere detailed by Kafri and others (2001). Abstract Thirty-two springs, draining different aquifers in northern Israel, including fresh as well as brackish water sources, were seasonally sampled for two consecutive years and the water samples analyzed for major as well as trace elements. Based on these analyses, the geochemical parameters, the trace element to Cl ratios, as well as the anomalous concentration of different elements enable the characterization and differentiation of different aquifer waters. In addition, indications were obtained regarding the salinity sources of the brackish waters and the suspected sources of polluted water. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/ 10.1007/s00254-001-0502-y.

Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/ s00254-001-0502-y.

Received: 4 September 2001 / Accepted: 26 November 2001 Published online: 5 February 2002 ª Springer-Verlag 2002 U. Kafri (&) Æ B. Lang Æ L. Halicz Æ O. Yoffe Geological Survey of Israel, 30 Malkhe Yisrael St, Jerusalem 95501, Israel E-mail: [email protected] Tel.: +972-2-5314288 Fax: +972-2-5380688

370

Environmental Geology (2002) 42:370–386

Hydrological background Hydrogeological background of the study area can be summarized as follows: northern Israel is between the Mediterranean base level in the west and the Rift Valley base level in the east, with a water divide in between. The Golan Heights to the east of the Rift Valley also drains westward to the Rift Valley. Salinization of groundwater is related in the west to seawater encroachment, whereas, in the vicinity of the Rift Valley and the internal valleys, to mixture with a saline end member that occupies these regions.

DOI 10.1007/s00254-001-0502-y

Original article

The main hydrogeological units involved and discussed in the study area from bottom to top are described in Table 1. The karstic Arad Group aquifer is feeding the Dan and Banias springs, which are the sources of the Jordan River. It is exposed in Mount Hermon on the northern border of the country. The northeast directed Sion fault, which is part of the Jordan River Rift system, lies between the two springs dividing the intake area into two blocks. The western block feeds the Dan spring, whereas the eastern block feeds the Banias spring. The eastern block is known for its abundant basaltic volcanism, dolomitization, and mineralization within the aquifer, all of which are absent in the western block (Shimron 1989). The Judea Group aquifer constitutes the N–S-directed mountain crest of Israel. This sequence dips towards the west (Mediterranean Sea) and east (Rift Valley), where it is confined under the Mount Scopus Group. The Mount Scopus Group is an aquicludal sequence that includes, in places, aquiferous chert horizons. The most important, typical factors that effect the groundwater chemistry in contact with this group is the higher abundance of SiO2, phosphates, oil shales, and enrichment of associated elements (Nathan and others 1979; Kafri and others 1989a; Minster and others 1997; Minster 1998). The enrichment of all the above is one order of magnitude higher in the southern part of the country as compared with the area described in the north. An exception is the Yarmouk basin adjacent and east of the Jordan River Rift

Valley, which exhibits a ‘‘southern facies’’, which has been shifted some 110 km to the north by the Dead Sea Transform. The Avedat Group in northern Israel forms an aquitard in its chalky facies and an aquifer in the limestone facies. It is exposed mostly in synclines close to the Mediterranean Sea and the Rift Valley, overlying the Mount Scopus Group. The Cover Basalt aquifer is known from the eastern part of the study area on both sides of the Rift Valley. It is usually perched on top of Neogene aquicludal formations, but is sometimes in contact with the underlying aquifers.

Sampling considerations Sampling of the different aquifers in northern Israel was confined to spring waters to minimize contamination. This was done despite the fact that water wells are more abundant and available, but may, on the other hand, introduce contamination because of the water contact with metal casing, pumps, pipes, and oil. However, most of the springs are managed and the sampled water is partly in contact with metal pipes. Therefore, the sources were sampled with great caution to minimize the anthropogenic impact of pollution of the sampled waters. The following springs sampled are grouped according to the aquifers they drain (Fig. 1, Table 2):

Table 1 Description of the hydrogeological units


371

Original article

1. Major components (Na, K, Ca, Mg, Cl, NO3, HCO3, SO4, and SiO2) in new 330-ml polyethylene bottles after three times of washing with the sample water. 2. Trace elements: the samples were filtered on-line with a 0.45-lm filter and collected into 125 ml (pre-cleaned with 1:3 nitric acid) low density polyethylene bottles, containing 1 ml of supra-pure nitric acid (Baker – Instra grade). Analytical methods Major components – Na, K, Ca, Mg, SO4, and SiO2 were analyzed by an inductively coupled plasma atomic emission spectrometer (ICP-AES) – Perkin–Elmer Optima 3300 using Sc as an internal standard. Cl and NO3 were determined by ion-chromatography, bicarbonate by potentiometric titration, and Br by a flow injection ICP-mass spectrometer (ICP-MS; Sciex Perkin–Elmer Elan 6000). Trace elements – all trace elements (except for F) were determined by ICP-MS. The limit of detection for the majority of trace elements was better than 0.1 ppb, excluding Al, As, Fe, Ni, Se, and Zn with a limit of detection of about 1 ppb. Fluorine was analyzed by a specific electrode. The accuracy of the chemical analyses was confirmed using the standard reference materials – SLRS-3 (Canadian Riverine water reference material for trace elements), Fig. 1 SRM-1643d (National Institute of Standard and TechnolLocation map of the sampled springs. Numbers refer to springs listed ogy US reference material for trace elements), M-142–154 in Table 2 and GMW-2–5 (US Geological Survey; major constituents), T-145–161 and GWT-2–5 (USGS, trace constituents). 1. Arad Group Aquifer: Banias and Dan springs. 2. Judea Group Aquifer: Hardalit, Teo, Parod, Bezet, Ziv, Tsuf, Afeq, Sa’adia, and Taron springs. 3. Mt. Scopus Group horizons: Gush Halav, Zetim, and Results and discussion Qadesh springs. 4. Avedat Group Aquifer: Sahina, Harod, Aviv, Hashomer, Major components, contents and ratios (e-Table) Pina, and Amud springs. 5. Cover Basalt Aquifer: Shamir, Gonen, and Yardenon Groundwater chlorinity and water types springs. Most of the water sources in the study area, which drain 6. Mixed sources: Hanania, Amal, Zahav, Makle, Balzam, carbonate aquifers, are fresh, with chlorinities between a Nun, Doshna, Ayelet Hashahar, and Huga springs. few to several tens of ppm, typical for the proximity of the intake area and the flow through flushed aquifers. VariaSeasonal fluctuations in salinity and Cl content are known tions in chlorinity within this group (water of the Ca, Mgin Israel and elsewhere. When attempting to identify dif- HCO3 type) are caused by changes in lithology, residence ferent water types by other elements one should determine time of water, distance from the sea, and pollution. whether systematic seasonal changes occur and whether The Basalt aquifer water sources are also of the bicarthere are changes between consecutive years. Therefore, bonate type with expected higher amounts of Na as comfour seasonal sampling campaigns were carried out each of pared with the carbonate aquifers, derived from the the 2 years, between January 1998 and January 2000. basaltic host rocks. Unfortunately, only the first year was a ‘‘normal’’ average Brackish water sources with higher chlorinities between year, whereas the second one was extremely dry and some several hundreds to over a thousand ppm of the Judea of the springs completely dried up and had a late recovery. Group aquifer (Afeq, Sa’adia, Hanania, and Amal springs) Thus, the time series are incomplete. are considered, in general, as mixtures of a fresh water component with a saline end member. In this water subgroup, the water type tends to be a Na-chloride type. In Sampling and analytical procedure some cases (e.g., Makle spring), the slightly brackish waters (425–460 ppm Cl) exhibit a Na-chloride affinity in spite of the fact that no saline end member is evident. Sampling Water samples were collected from springs to determine Regarding the temporal change in chlorinity, in spite of the fact that the two consecutive years of sampling were not the content of: 372


Original article

Table 2 Location, altitude, and related aquifer of the sampled springs

Number

Water source

Coordinate X

Coordinate Y

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Banias Dan Bezet Hardalit Parod Taron Teo Tsuf Ziv Afeq Sa’adia Hanania Gush Halav Qadesh Zetim Amud Aviv Harod Hashomer Pina Sahina Gonen Shamir Yardenon Amal

21520 21120 17168 16751 19036 19382 20348 16445 17584 16110 15285 14416 19220 19850 19638 19730 19630 18367 20370 19940 21300 21102 21230 21320 19215

29490 29490 27582 27197 26042 26461 28196 26885 27141 25020 24380 21550 27050 27972 26502 25314 27536 21725 29540 26420 23280 27952 28690 28450 21245

390 200 240 100 480 530 70 78 320 5 5 10 690 440 705 –100 400 0 310 600 –120 155 220 300 –100

26 27

Ayelet Hashahar 20420 Balzam 21250

26938 23220

170 –150

28 29 30

Doshna Huga Makle

19670 20067 21260

25110 21348 23200

–172 –250 –160

31 32

Nun Zahav

19818 20363

24972 29143

–192 138

‘‘normal’’, it is evident that chlorinity is approximately stable in the fresh water sources, with no seasonal changes. On the other hand, the brackish water sources, which are mixtures between a fresh water component and a saline end member in depth, exhibit seasonal changes in chlorinity. In general, as noticed in the Hanania, Sa’adia, Afeq, and Amal springs, in previous years, the rainy (winter) season has been characterized by higher water yields accompanied by higher chlorinities (e-Table http://dx.doi.org/10.1007/ s00254-001-0502-y; Fig. 2). Moreover, in some cases (e.g., Hanania spring) the dry winter of 1999/2000 is also characterized by low chlorinity. This type of fluctuation supports the mechanism of salinities picked up from depth by ascending fresh water and, thus, higher heads and flows result in higher salinities, different from the conventional mixing mechanism (Kafri and Arad 1979). Cl/Br weight ratio All the fresh and non-thermal water sources, regardless of the aquifer they belong to, show a wide range of Cl/Br ratios between 110 and 450, but mostly around the normal rainfall and marine value of 300. Moreover, it seems that temporal anthropogenic Br is contributed in the proximity of agricultural areas, as well as by dust, solution of salts,

Altitude

Aquifer Arad Arad Judea Judea Judea Judea Judea Judea Judea Judea (saline) Judea (saline) Judea (saline) Mt. Scopus Mt Scopus Mt. Scopus Avedat Avedat Avedat Avedat Avedat Avedat Basalt Basalt Basalt Mixed (Judea + Avedat) Mixed Mixed (Judea + Mt. Scopus) Mixed Mixed Mixed (Judea + Mt. Scopus) Mixed Mixed (Basalt + Avedat)

and decomposition of organic matter in soils (Burg 1998), resulting in variations in the Cl/Br ratio. These large variations are mostly explained by the very low Cl (order of magnitude mostly 101 ppm) and Br (order of magnitude 101–102 ppb) contents. The brackish and saline sources are enriched in Cl and Br by a saline end member. These sources exhibit a narrower range of ratios (251–384) closer to the marine values and are far from a Ca-chloride brine signature (16) than, rCa/rMg ratio The rCa/rMg ratios of water seem, in general, to reflect the those of the Mt. Scopus Group sources. These springs are perched on top of, and their outlets partly incised into, the lithology of the relevant hosting aquifers as follows underlying Mt. Scopus Group. Thus, the above (Fig. 6):


375

Original article

waters adopt the rCa/rMg signature of the Mt. Scopus Group. The Basalt aquifer waters show, as expected, a rather low (0.9–1.5) ratio because of the low Ca and higher Mg content of the basalts involved. The Mixed group of water sources exhibit ratios, which sometimes enable it to relate them to a dominant end member. Thus, the Amal spring shows ratios (1.1–1.2) close to the Judea Group brackish waters. The Makle, Balzam, and Ayelet Hashahar springs exhibit ratios (2–2.9) indicative of a mixture between Judea and Mt. Scopus Group waters. The Zahav spring (2.2–2.5) indicates a mixture between Judea and Avedat Group waters. The Huga, Doshna, and Nun springs (0.9–1.3) exhibit a basalt water signature and the Hanania spring (0.8–0.9) the marine contribution. As expected, an increase in the rCa/rMg ratio is recognized from the more dolomitic units (Judea Group aquifer), through the more limestone units (Arad and Avedat Group aquifers), to the more chalky units (Mt. Scopus Group) accompanied by an increase in the Q ratio (Fig. 6). The fresh En Pina (Avedat Group aquifer) source with extremely high rCa/rMg ratio and Q values exceeding 1 Fig. 7 (with no Cachloride brine involved) is probably indicative rSiO2/rCl ratio versus Cl (ppm) of a base-exchange process emphasized in the more chalky units. SiO3 content and rSiO2 /rCl ratio The SiO2 content of the water depends on the availability of SiO2 in the hosting aquifer, as well as on its temperaNO3 content ture-dependent solubility. In the present study, most of the NO3 detected in the aquifer waters is either natural, by water sources, except for the thermal ones, exhibit roughly decomposition of organic matter found in the rock sethe same temperatures, and the differences in SiO2 content quence or overlying soil, or by anthropogenic pollution are mainly related to the SiO2 availability in the hosting from above (e-Table). The NO3 content in the fresh water sources of the study aquifer. The rSiO2/rCl ratio, in addition, is dependent on water chlorinity (Fig. 7). As salinity goes up this ratio area was found to be below 10 ppm in the Arad Group decreases because of limitations of SiO2 availability and aquifer water, and between 5 and 25 ppm in the Judea solubility. When SiO2 in normalized to Cl, the following is Group and Basalt aquifer sources. Usually, somewhat higher values (15–56 ppm) were detected in the Mt. Sco- recognized: pus and Avedat Group sources. All the above can be re- In the Arad Group aquifer sources, because of the low garded as natural ‘‘background’’ levels. Higher values in availability of SiO2 in the aquifer and the low water temperature, SiO2 content is low, between 4 and 9 ppm. the upper range, or that exceed the upper limit of each Because of the low chlorinity, the rSiO2/rCl ratios cluster group, can be thus suspected as a result of additional around 0.4–0.5. anthropogenic contribution, or pollution. In most of the fresh Judea and Avedat Group sources, SiO2 Soils covering the intake areas of the above aquifers in content varies between 7 and 15 ppm, with only a few Galilee reflect the same trend. Soils on natural uncultiattaining higher values (up to 33 ppm), and the rSiO2/rCl vated areas on top of the Judea Group aquifer show a rather low (0–3.5 ppm) NO3 content, whereas soils on top ratios cluster around 0.2–0.3. of Mt. Scopus and Avedat Group exposures, consisting of The Mt. Scopus water sources are more enriched in SiO2 (11–36 ppm) as a result of higher SiO2 availability in the chalks and limestones, yield higher (3–8.5 ppm) NO3 contents (Rabinovitch-Vin 1986). These soils are flushed hosting rock units. The respective rSiO2/rCl ratios are, down by recharge and the resultant waters in the respec- thus, between 0.4 and 0.6. tive aquifers reflect the NO3 content trend in the overlying The highest SiO2 content (28–36 ppm) and accordingly higher (1–1.3) rSiO2/rCl ratios are recognized in the Basalt soils. The Balzam and Makle springs in the Yarmouk basin are aquifer sources because of the higher SiO2 availability in exceptional by their very low (0.03–2 ppm) NO3 content, the basalts and the low water chlorinity. in spite of the fact that these ascending waters cross a thick Among the saline or brackish sources, those of the Judea Mt. Scopus Group organic-rich sequence (Minster 1998). Group aquifer exhibit a relatively low SiO2 content (13–15 ppm), and the mixed sources (e.g., Amal, Balzam, This is explained by the fact that, because of reducing Makle, and Hanania springs) show a higher SiO2 content conditions (oil shale, H2S), most of the nitrogen in the (15–29 ppm) contributed from the Mt. Scopus Group basin is in the form of NH4, and not as NO3. 376


Original article

Aviv, and Pina springs) show similar ratios to those of the Mt. Scopus Group sources because barite concretions are abundant in its chalky facies (Bogoch and others 1987). Some of the Avedat Group aquifer sources exhibit lower ratios because of either higher chlorinity (Sahina and Harod springs), or low Ba content (Hashomer spring). The Basalt water sources exhibit two clusters of ratios: a Trace element content and trace higher one, around 0.0015 of the Gonen spring with the element/equivalent Cl ratios An attempt is made to use the trace element content of the higher (36–53 ppb) Ba content, and a lower one, below various water sources as a tagging tool. To avoid differ- 0.0005, of the Shamir and Yardenon springs with the lower (2–17 ppb) Ba content. ences related to changes in salinity, the trace element contents were normalized to Cl and the trace elements to A general trend of decreasing rBa/rCl ratio with increasing chlorinity is recognized within most of the water groups. Cl equivalent ratio was employed (e-Table http:// dx.doi.org/10.1007/s00254-001-0502-y) and discussed. The F content and rF/rCl ratio trace elements chosen to be discussed were only those that A general trend of decreasing rF/rCl ratio with increasing their content was accurately determined above their detection limit. Some trace elements (B, I) though analyzed, chlorinity is recognized. This same trend is sometimes recognized within the different water groups, more emexhibit a random scatter of results and, thus, are not phasized in the Judea, Avedat, and Basalt aquifer sources. discussed herein. The Arad Group aquifer sources exhibit a relatively high rF/rCl ratio (0.14–0.26) because of the very low water Ba content and rBa/rCl ratio The Arad Group water sources exhibit a ratio of around chlorinity (Fig. 9). 0.0005. Among the two sources representing the aquifer, The Judea Group aquifer fresh water sources exhibit ratios the Ba content is similar, but the ratio of the Dan spring is between 0.004 and 0.012 and the saline ones ratios as low somewhat higher because of its lower chlorinity (Fig. 8). as 0.0004 because of the high water chlorinity. The fresh Judea Group aquifer sources exhibit ratios ap- The Mt. Scopus Group sources show an enrichment of F proximately between 0.0002 and 0.001. On the other hand, and, thus, a high rF/rCl ratio between 0.01 and 0.024 the brackish sources exhibit a very low ratio because of the because of the occurrence of phosphates and associated F-apatite in the hosting sequence (see also Kafri and high chlorinity contributed by the saline end member. The Mt. Scopus Group water sources exhibit higher ratios others 1989a). between 0.001 and 0.003, probably because of the known The Makle and Balzam brackish mixed sources, which occurrence of barite in the hosting sequence (Bogoch and contain a Mt. Scopus Group water component, indeed show, as expected, a somewhat higher rF/rCl ratio as Shirav 1978). compared with other sources with a similar chlorinity. The The Avedat Group aquifer sources, in contact with, or enrichment of F and the respective higher rF/rCl ratio were incised into, the underlying Mt. Scopus Group (Amud, sequence. The rSiO2/rCl ratios, on the other hand, of all the above are very low (10–2) because of the high chlorinity and the low SiO2 content (6.4 ppm) of the seawater end member. A general trend of decreasing rSiO2/rCl ratio with increasing chlorinity is recognized (Fig. 7).

Fig. 8 rBa/rCl ratio versus Cl (ppm)

Fig. 9 rF/rCl ratio versus Cl (ppm)


377

Original article

attributed, on the other hand, by Arad and Bein (1986) to the thermal nature of the above springs. The Avedat Group aquifer fresh sources exhibit ratios similar to, and even higher (up to 0.024) than those of the Judea Group aquifer sources, being in contact with the underlying Mt. Scopus Group. The Basalt aquifer sources exhibit ratios between 0.006 and 0.014. In general, the ratios described herein for most of the above aquifers resemble those obtained previously for the same aquifers (Kafri and others 1989a). Li content and rLi/rCl ratio Li content in the fresh water sources of the Judea and part of the Avedat Group and Basalt aquifers sources is very low, below 1 ppb. Thus, their rLi/rCl ratios cluster together with low ratios of around 10–4 and 10–5 (Fig. 10). The Arad Group aquifer exhibits somewhat higher ratios between 10–4 and 10–3 because of the very low chlorinity. The higher ratios are related to the Banias spring, possibly as a result of Li enrichment in its more mineralized catchment as compared with that of the Dan spring. Mt. Scopus Group sources and those of the Avedat Group aquifer in contact with the underlying Mt. Scopus Group are more enriched in Li, mostly above 2 ppb, thus clustering at higher ratios. Trace element enrichment in the Mt. Scopus Group, associated with phosphates, was described by Nathan and others (1979), a fact that might effect Li enrichment in groundwaters also in the study area. The Balzam and Makle mixed sources in the Yarmouk basin, with a Mt. Scopus Group water component, show a Li enrichment (85–286 ppb) and a respective high rLi/rCl ratio. This enrichment is compatible with the organic and Li enriched ‘‘southern’’ facies, described by Minster (1998) and Minster and others (1997).

Fig. 10 rLi/rCl ratio versus Cl (ppm)

378


Mo content and rMo/rCl ratio Mo content of the Arad and Judea aquifer sources shows a low content mostly below 0.5 ppb. Basalt aquifer sources yield content values between 1 and 1.5 ppb. Most of the Mt. Scopus Group sources already show a Mo enrichment (3–9 ppb), which presumably can be related to some Mo enrichment in phosphates in the same sequence (Nathan and others 1979), and a more emphasized enrichment in its organic part (Minster and others 1997). The Balzam and Makle springs, which include a Mt. Scopus Group water component, yield, despite the above, a rather low (mostly 0.2 ppb) Mo content, far below that of the Mt. Scopus Group sources, or the nearby Sahina (Avedat Group) spring. The Avedat Group aquifer sources exhibit a wide range of contents from very low (similar to those of the Judea Group aquifer sources), to higher ones (1–5.5 ppb) because of the contact with the underlying Mt. Scopus Group, and the extremely high contents (34–40 ppb) in the Sahina spring (see below). The respective rMo/rCl ratio values thus cluster and form, in general, separate fields (Kafri and others 2001). The brackish and saline sources exhibit very low ratios because of the high chlorinity. Rb content and rRb/rCl ratio The distribution of rRb/rCl is shown in Fig. 11. The Arad Group aquifer sources yield low contents (below 1 ppb) with somewhat higher ones (up to 1.3 ppb) in the Banias spring (Fig. 12) because of the occurrence of volcanics in the catchment feeding this spring as compared with the Dan spring catchment, which is devoid of volcanics. The fresh Judea Group aquifer sources yield low contents (below 1 ppb) and the saline ones up to 6.7 ppb. The Taron fresh water spring is an exception (0.9–2.2 ppb),

Fig. 11 rRb/rCl ratio versus Cl (ppm)

Original article

Fig. 12 rRb/rCl ratio versus Cl (ppm) – Arad Group aquifer

probably because of the Rb contribution from the nearby Dalton basalts, only a few kilometers up-gradient of the spring. Mt. Scopus Group sources are enriched in Rb, mostly between 1 and 14 ppb. The Avedat Group aquifer sources exhibit a wide range of values (0.1–5.4 ppb) according to the amount of contact of the sources with the underlying Mt. Scopus group. The Basalt aquifer sources yield contents between 3.5 and 5.7 ppb, as expected from the higher Rb content of the basalts. As a result of all the above, apart from the Judea and Avedat Group sources, all the rRb/rCl ratios of all other aquifers generally cluster in separate fields (Fig. 11). The Mixed group Balzam and Makle sources in the Yarmouk basin exhibit extremely high Rb content as well as high rRb/rCl ratios. This is probably caused by enrichment of the above and, similarly, with other trace elements in the Mt. Scopus Group of this basin. Sr content, rSr/rCl, and rSr/rCa ratios Sr content of the Arad Group aquifer sources is between 67 and 309 ppb. The Banias, as compared with the Dan spring, exhibits an enrichment in Sr because of the contribution of its more mineralized catchment. The Judea Group aquifer fresh sources basically yield the same range of values (51–216 ppb) as some of the Avedat Group aquifer sources. All the above values are in accordance with the limestone–dolomite aquifers. The saline Judea Group aquifer sources exhibit values exceeding 1,100 ppb. The Mt. Scopus Group and the Avedat Group aquifer sources in contact with the former are enriched in Sr, and, apart from the Qadesh spring, they yield Sr contents approximately between 350 and 700 ppb. The Mt. Scopus Group is known to contain phosphates

Fig. 13 rSr/rCl ratio versus Cl (ppm)

and Sr enrichment in association with phosphates has been previously documented (Nathan and others 1979). The Balzam and Makle springs, which contain a Mt. Scopus Group water component in the Yarmouk basin, exhibit even a more emphasized Sr enrichment (3,190–5,531 ppb) because of the higher phosphate content of this basin as compared with northern Israel. The Basalt aquifer sources yield Sr contents between 138 and 251 ppb. In accordance with all the above, the rSr/rCl ratios of the Mt. Scopus and Avedat Group sources cluster above those of the Judea Group aquifer sources as do the Basalt aquifer sources (Fig. 13). The Arad Group and the saline Judea Group sources exhibit high and low rSr/rCl ratios because of low and high chlorinity, respectively. The Balzam and Makle sources cluster at a high ratio regarding their chlorinity. The rSr/rCa ratio of a few springs in Galilee, as a function of water–rock interaction and external sources, was discussed by Burg (1998). The results of the present study (Fig. 14) show the following. The Arad and Judea Group aquifer sources yield similar rSr/rCa ratios of around 10–4. Higher rSr/rCl ratios, as well as rSr/rCa ratios, are found in the Banias spring as compared with the Dan spring because of the mineralized catchment. These ratios accord with those given for a limestone–dolomite aquifer by Burg (1998). The Sr enriched Mt. Scopus and Avedat Groups sources already show higher ratios between 0.002 and 0.003, similar to those attributed to chalk aquifers by Burg (1998). The Balzam and Makle sources, according to their Sr content, cluster at a very high rSr/rCa ratio. Basalt aquifer source ratios cluster separately (ratios between 0.0025– 0.0044).


379

Original article

Fig. 14 rSr/rCa ratio versus Cl (ppm)

A general trend of increasing rSr/rCa ratio with increasing chlorinity is recognized in all sources as well as within the different water groups (Fig. 14). The brackish Judea Group aquifer sources, which presumably contain a seawater component, exhibit a 0.002– 0.004 ratio as expected from a calculated proportional mixture between the fresh Judea Group aquifer and seawater. U content and rU/rCl ratio U content in the Arad Group aquifer sources was found to be around 0.2 ppb. The Basalt aquifer sources yield somewhat higher values between 0.1 and 0.3 ppb. The fresh Judea and most Avedat Group aquifer sources exhibit values approximately between 0.5 and 1.5 ppb. Mt. Scopus Group sources, except for the Qadesh spring, exhibit higher contents (1.8–4.4 ppb) as does the Avedat Group Sahina spring (4–4.6 ppb), perched on top of the Mt. Scopus Group. The relationship between U enrichment and phosphates is obvious and in the case of Mt. Scopus Group is well documented (Nathan and others 1979). Surprisingly, the Balzam and Makle sources exhibit a low U content (1.1–1.7 ppb), lower than expected from the associated phosphate-rich Mt. Scopus Group in the Yarmouk basin. This discrepancy can be explained by the extreme reducing conditions in the basin (Minster and others 1997), which results in a low U solubility (Hem 1970). In the Sahina spring, perched on top of the less organic and more oxidized upper sequence, U content is already ‘‘normal’’. Regarding rU/rCl ratios, it is evident that the Judea and most of the Avedat Group sources cluster together (Kafri and others 2001). The Basalt aquifer sources cluster separately at a low ratio, whereas most of Mt. Scopus Group

380


Fig. 15 rV/rCl ratio versus Cl (ppm)

sources and the Avedat Group Sahina spring cluster at higher ratios. The Arad and saline Judea Group aquifer sources exhibit relatively high and low ratios because of low and high chlorinity, respectively. V content and rV/rCl ratio The Arad Group aquifer sources show the lowest (0.1– 2 ppb) V content with higher values in the Banias spring and respective higher rV/rCl ratios because of the occurrence of volcanics in its catchment (Fig. 15). The Judea Group aquifer sources exhibit higher contents (1–4 ppb), both in fresh and brackish sources. The Mt. Scopus Group sources, or the Avedat Group aquifer sources in contact with the underlying Mt. Scopus Group, are enriched in V (1.7–14 ppb). This is because of the enrichment of V in this sequence related to phosphorites (Nathan and others 1979) or to organic matter (Minster and others 1997). The Sahina spring is enriched in V (27–33 ppb) as compared with other sources. The solubility of V in oxidized conditions, or in shallow sources, is relatively high whereas it decreases drastically in reducing conditions (Hem 1970). Thus, the Balzam and Makle springs, which ascend from deep reducing conditions, yield low (1 ppb) V contents whereas the shallow Sahina spring in oxidizing conditions is extremely enriched in V because of a higher solubility. Basalt aquifer sources also yield high V contents (6– 14 ppb) because of the abundance of V in the basalts. As a result, the rV/rCl ratio, in general, clusters at higher values from the Arad to the Judea, Mt. Scopus, Avedat Group, and Basalt aquifer sources. The saline sources exhibit very low ratios because of the higher chlorinity (Fig. 15).

Original article

Springs of the Yarmouk basin The Yarmouk basin requires special attention because it differs geochemically from the other (western) side of the Rift Valley. The geochemistry of the Hammat–Gader springs in the Yarmouk basin was discussed among others by Arad and Bein (1986), Arad and others (1986), Bajjali and others (1997), and Kafri and others (1989a). The hydrogeology of the Hammat–Gader springs and their Rn occurrence was summarized by Kafri and others (1997) as follows: The four springs of Sahina, Makle (Roman), Reah, and Balzam, exhibit respective chlorinites of 75, 480, 240, and 330 ppm, and temperatures of 29, 50, 37, and 42 C. A rough correlation between temperature and chlorinity is discerned. The springs’ waters are enriched in radon. The above springs are located in the Yarmouk Valley syncline. The hydrogeological setup, as given schematically in Fig. 16, supports the assumption that the springs emerge along a weakness (fault) zone along the Yarmouk gorge. This enables deep thermal waters, confined under a few to several hundred meters of the Mt. Scopus Group aquiclude, to ascend in a high velocity to the surface without losing its temperature to the surrounding rock sequence. This hydrogeological setup is also confirmed by a study on Jordanian boreholes and springs in this same region (Bajjali and others 1997).

The Judea Group regional aquifer is recharged in the nearby Ajlun-Irbid areas, but some contribution from the north is also plausible (Arad and Bein 1986). This is also supported by the fact that both Hammat Gader and the Jordanian water sources exhibit d18O values that lie on the local meteoric line, together with (tritium free) late Holocene recharge waters (Bajjali and others 1997). The Mt. Scopus Group is a thick aquiclude, except for its Mishash (chert) Formation, which acts here, as well as in other southern parts of Israel, as an aquifer. Jordanian boreholes, penetrating this aquifer, have proven it to be a productive aquifer under a considerable artesian pressure (Bajjali and others 1997). The Mt. Scopus sequence here, is different from the nearby western side of the Rift, by its very phosphorous character especially in the Mishash Formation (Al-Shereideh and others 1997; Bajjali and others 1997). The waters in contact with the Mt. Scopus Group, here and in central and southern Israel, were known to be enriched in P2O5, F, and Ba (Arad and others 1986; Kafri and others 1989a). This was explained by the fact that the Yarmouk basin represents a southern facies. The Roman (Makle), Reah, and Balzam springs seem to be fed, according to the water chemistry and temperature and due to their artesian pressure, by both Judea Group and Mishash Formation aquifers, through the fracture zone.

Fig. 16 Schematic hydrogeological cross-section in the Hammat Gader area (after Kafri and others 1997)


381

Original article

The Sahina spring, on the other hand, appears at the base of the Avedat Group aquitard/aquifer perched on the Mt. Scopus Group aquiclude, some 30–40 m higher than the other springs. The above head difference combined with low temperature and chlorinity of the Sahina waters indicate that the spring is perched and is not fed by the artesian aquifers underneath. The abundance of the different elements in the hosting sequence effects the water chemistry. In addition to P2O5, enrichment of Cd, Cu, Sr, Zn, and V were also described in the Irbid-Yarmouk basin (Al-Shereideh and others 1997). An important factor that controls the water geochemistry of the basin is the occurrence of a considerable organicrich oil-shale sequence (Minster and others 1997), in which reducing conditions at depth are evidenced among other things by considerable amounts of H2S in the water. The results of the present study exhibit the following in the Balzam and Makle springs:

Table 3 Comparison of the water chemistry between the Dan and Banias springs

Cl content rNa/rCl rSO4/rCl rCa/rMg Li, Rb, Sr, V content r(Li, Rb, Sr, V)/rCl rSr/rCa

Dan spring

Banias spring

Lower