Current research focuses on the study of salinization and contamination processes of water resources in Israel, the Middle East, and other aquifer systems in Italy, Turkey, Canada, and the USA. The research involves the development and utilization of novel geochemical and isotopic techniques in order to delineate the sources and mechanisms of water pollution. These studies characterize the fingerprints of various natural and man-made fluids, which enables discrimination between human (e.g., sewage contamination, waste-water irrigation) and natural (e.g.., salt-water intrusion) impacts on water resources. Several studies include the origin of saline plumes in the Mediterranean coastal aquifer, brines below and in deep basins in the eastern Mediterranean, boron contamination in aquifers in Tuscany, Italy, evolution of hydrothermal water in southwestern Turkey, fossil water along aquitard in central Canada, and mechanisms of pollution of coastal aquifers in Salinas Valley, California.
During the last year a major effort was given to establish research collaboration with Palestinian and Jordanian colleagues. A working team that includes scientists from Al Quds University, University of Amman, Technion, Geological Survey, and Ben Gurion University began constructing a framework for joint research projects. These studies include an evaluation of the sources of the salinity along the Jordan Valley (research proposal approved by the MERC program -- USAID) and mechanisms of groundwater salinization in the Jordan Valley. These studies aim to show that scientific cooperation can generate critical research and potential solutions for dealing with serious issues of water pollution in the Middle East in spite of political tension at the interstate level.
One of the most advanced stages in the utilization of boron isotope geochemistry occurs in the study of contaminated ground water and waste water. Following a German-Israeli cooperative research program (University of Regensburg, Germany), the unique geochemical characteristics of boron isotopes were used to trace the sources of groundwater contamination in Israel. The study showed that anthropogenic boron derived from detergents in sewage effluents has a distinguished isotopic composition relative to natural reservoirs (e.g. regional groundwater, sea water) and thus can be used to delineate the sources of ground water pollution. This study was the first to apply the boron isotope systematics for tracing anthropogenic contamination of natural aquatic systems by municipal sewage effluents. These new findings led to an improvement in tracing and elucidating the sources of contamination of groundwater.
2. The origin of brines in the Mediterranean
Hypersaline brines with salinity of up to 350 g/l occur at the bottom of and below (as pore waters or interstitial waters) the Mediterranean Sea. Re-examination of the chemical data revealed that these brines are not products of underlying evaporites dissolution as previously suggested, but rather, they are relics of fossil evaporate sea water entrapped in the sediments. The study of these brines showed that the Miocene evaporated sea water was entrapped in the sediments and modified by diagenetic reactions and advection-diffusion through the sedimentary column. This new interpretation offers a new prospective on the origin of the Mediterranean brines. The new theory suggests that 6 Ma old brines survived at the bottom and within the sediments of the modern Mediterranean Sea. This new concept has been confirmed recently through the utilization of boron isotopic ratios of hypersaline bottom brines and interstitial brines from the Mediterranean.
3. The geochemical signature of anthropogenic sources and their impact on the environment
The contribution of man-made components modifies the chemical composition of natural water resources. Different geochemical fingerprints can be used to trace the impact of the anthropogenic sources in the environment. Domestic waste water has a unique high Cl/Br ratio due to contribution of NaCl salts with low Br. The variations of Cl/Br ratios in sewage effluents and contaminated ground water from the Dan Region Reclamation project in Israel showed that the high Cl/Br signal can be used to trace contaminated ground water. The chemical modifications of domestic waste water due to water-rock interactions with the aquifer rocks were also evaluated for tracing the chemical signature of sewage-contaminated ground water. The sulfur isotopic composition of domestic waste water has also been evaluated as a potential tracer for tracing ground water contamination.
4. Origin of salinity in coastal aquifers
In order to have better constraints for the origin of salinity in coastal aquifers, several research projects were initiated in which different isotopic methodologies (boron, strontium, oxygen, hydrogen, sulfur) were integrated to trace the origin of salinity. The problem of ground water salinization is intensified in coastal aquifers where human activities (e.g., water exploitation, agriculture, reuse of waste water) accelerate water-quality deterioration. Monitoring and identifying the origin of the salinity are crucial for water management and remediation. Yet the variety of the possible salinization sources, particularly in phreatic aquifers which are sensitive to anthropogenic contamination, makes this task difficult. Ground-water salinization can be a result of both anthropogenic (e.g., agriculture return flows, irrigation with sewage effluent) or "natural processes" such as sea water intrusion and saline water flow from adjacent or underlying aquifers. By integrating the chemical, boron, strontium, and oxygen isotopes of contaminated ground water from the coastal aquifer of Israel, it is possible to distinguish between the different sources and to trace the sources of the salinity. In a parallel study in the coastal aquifer from Salinas Valley in central California, a large number of isotopic tracers (including, tritium-helium, and 14C dating) were also used to study the origin of salinity, nitrate pollution, and flow rates of ground water in the shallow 180-foot aquifer of the Salinas valley.
5. The origin of boron-enriched saline ground water in the coastal plain of the Cornia River, Italy
The quality of ground water from the coastal aquifer of Cornia River (Val di Cornia) in north-western Italy has been deteriorated with high concentrations of chloride and boron. The new drinking-water regulations of the EC makes the local high-boron groundwater unsuitable for domestic utilization. The project involves scientists from University of Pisa, CNR, and Ben Gurion University. The study investigates the chemical and boron isotopic compositions of selected ground water in an attempt to evaluate the sources and to establish the mechanisms for ground water contamination. Based on the geochemical and boron isotopic compositions we suggest that underlying hydrothermal fluids enter the shallow aquifer and affect its water quality.
6. Water Quality along the Jordan River: A Geochemical Perspective on the Sources of Salts
The joint project includes scientists from Al Quds University (PA), University of Amman (Jordan), Technion, Geological Survey, and Ben Gurion University (as a leading partner). The project aims to study the quality of water in the central and southern section of the Jordan River and to evaluate the sources of dissolved salts entering the river. The Jordan River receives fresh water and poor quality fluids from various sources including natural and man-made pollutants. These flows have directly led to the degradation of the water quality in the Jordan River. As the Jordan River reaches the Dead Sea, it becomes too saline to utilize for local irrigated agriculture. As a result, a valuable and significant (annual discharge of 150 to 250 MCM) water resource is lost and can not be used for relevant purpose.
The proposed project seeks to identify, assess, and quantify the impacts of these saline sources on the river salt budget and on the overall water quality. Since the different contamination sources may be distinguished by their chemical and isotopic compositions, we proposed to evaluate the impact of these sources by applying hydrogeochemical and isotopic indicators. The chemical and isotopic data, integrated with the regional hydrology and hydrogeology may provide the key to understanding the differential impact of the various sources. The project, thus, will integrate common and novel geochemical and isotopic techniques for the delineation of the sources and their impact on the quality of the river. We posit that managing the water systems in the Jordan Valley and identifying the major salt contributions might then help to reduce the salt load which, in turn, may provide additional water for utilization in the water-scarce area of the Jordan Valley.
7. Tracing Ground Water Salinization in the Lower Jordan Valley
The joint project includes scientists from Al Quds University (PA), University of Amman (Jordan), Technion, and Ben Gurion University. There are 150,000 people of Israeli, Jordanian, and Palestinian nationality who depend on an agriculturally-based economy in the Lower Jordan Valley. Irrigation with groundwater is a critical element to their livelihood. Furthermore, drinking water is currently derived from local groundwater, and with the anticipated increase in tourism in the near future, economic growth and viability depends on new and sustainable water sources for potable consumption.
Groundwater quality has been deteriorating in this area for some time. In the Jericho region, for example, dissolved chloride concentrations have increased from 100 milligrams per liter to over 2000 milligrams per liter during the last decade. Continuation of this groundwater deterioration threatens the water sources linked to the success of current and future agricultural and domestic economies. Currently there are no technologies available for assessing the causes and sources of this salinization or to prevent its further effect. Research tools that address the type, extent, and mechanisms of salinization are needed in order to begin protecting these vital resources. The general project objective is to improve the sustainability of groundwater resources in the lower Jordan Valley by understanding the current and future effects of groundwater salinization, a major cause of degrading potable water supplies. The ultimate goal will be to develop a numerical groundwater model to quantify the contributions of the different salinity sources to the salinization of the groundwater in this region.
We propose a joint, collaborative project to collectively gain improved understanding of the regional hydrology in the lower Jordan Valley. Our approach will couple state-of-the-art isotopic and geochemical fingerprinting methods with advanced numerical modeling techniques. Successful modeling requires comprehensive databases and tested conceptual models of groundwater flow. Existing data will be used to conceptualize groundwater flow and to form an initial framework for computerized groundwater modeling. Additional and newer types of data, such as isotopic and geochemical characteristics of the groundwater, as well as a series of “inverse” models, will be used to refine the conceptual and numerical models of the system so as to further delineate saline sources and predict their impact on future water quality in the area.
8. Tracing the Sources of fossil water in a thick clay-rich aquitard: Boron Isotope Geochemistry
Fossil water contains information on past geological environments which can be used to reconstruct the evolution of the hydrosphere. Clay-rich glacial tills and clay deposits in marine and continental settings provide the natural setting to examine such fossil fluids. This is due to low hydraulic conductivieties in which the velocity of advective transport is minimal (e.g. a few mm a year). In such aquitard systems the main salt and water transport is dominated by diffusion process. Thus, the history and basin evolution can also be reconstructed by the geochemical fingerprints of water that is entrapped in clay deposits
The chemical and boron isotopic compositions of pore water from an aquitard system in a test site in Saskatchewan, Canada was investigated. The aquitard system consists of 80 m of plastic clay-rich Battleford till disconformably overlying 77 m of late Cretaceous plastic marine clay (Snakebite Member). Chemical variations of pore water show conservative mixing relationships between four types of fluids entrapped along the section with distinguished chemical characteristics. The dD values and age-dating of the later (<-175‰, Hendry et al., in press) suggest that glacial meltwater was preserved in the till between 20 to 60 m . The chemical composition of these fluids represents the composition of pristine non-industrial atmosphere. The low Cl/Br ratio (~50) of the entrapped glacial meltwater is similar to that of modern inland precipitation which might suggest that bromide enrichment in the atmosphere can also be a natural process. The Na-Cl-HCO3 and the marine boron isotope composition of the saline water from the Cretaceous clay suggest that fossil seawater that was entrapped in the clay sediments was subsequently flushed by freshwater which modified the composition of the original seawater.
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Vengosh, A. and Starinsky, A. (1993). Relics of evaporated sea water in deep basins of the Eastern Mediterranean. Marine Geology, 115; 15-19.
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Vengosh, A., Starinsky, A. and Chivas, A.R., (1994). Boron isotopes in Heletz-Kokhav oilfield brines, the Coastal Plain, Israel. Israel Journal of Earth Sciences, 43; 231-237.
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Eisenhut S., Heumann, K.G. and Vengosh, A. (1996). Determination of boron isotopic variations in aquatic systems with negative thermal ionization mass spectrometry as a tracer for anthropogenic influences. Fresenius Journal of Analytical Chemistry , 354, 903-909.
Vengosh, A. and Keren R. (1996). Chemical modifications of groundwater contaminated by recharge of sewage effluent. Journal of Contaminant Hydrology , 23, 347-360.
Vengosh, A. and Pankratov I. (1998) Chloride/bromide and chloride fluoride ratios of domestic sewage effluents and associated contaminated ground water. Ground Water., 36, 815-824.
Vengosh, A., De Lange, G.J., Starinsky A. (1998). Boron isotope and geochemical evidence for the origin of Urania and Bannock brines at the eastern Mediterranean: Effect of water-rock interactions. Geochimica Cosmochimica Acta. 62, 3221-3228.