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Natural radioactivity in ground water in the Negev Desert and the Arava Valley, Israel

Natural radioactivity in ground water in the Negev Desert and the Arava Valley, Israel. Gustavo Haquin Soreq Nuclear Research Center, Yavne 81800 ISRAEL. Introduction.

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Natural radioactivity in ground water in the Negev Desert and the Arava Valley, Israel

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  1. Natural radioactivity in groundwater in the Negev Desert and the Arava Valley, Israel Gustavo Haquin Soreq Nuclear Research Center, Yavne 81800 ISRAEL

  2. Introduction In the last years high concentration of uranium and radium isotopes and radon were measured in groundwater from the Nubean sandstone (Kurnub) and the upper cretaceous limestone (Judea) aquifers in the Negev and the Arava valley. As most of the groundwater basins in the Middle East are being diminished or contaminated, exploitation of the deep aquifers units is increasing. Objectives of present work : • Mapping the natural radioactivity in groundwater in the south of Israel • Comparison of radium measurement methods • Understanding the physical and chemical processes of radium enrichment in groundwater • Assessment of the radiological consequences of consuming high radium groundwater

  3. Natural decay series

  4. Cyprus Dead Sea Negev Desert Arava valley Sinai Peninsula Red Sea

  5. Study area Kurnub aquifer Group 1: NE Negev - Craters Group 2: NE Negev – Dead Sea Group 3: South Arava Group 4: Ashalim Judea aquifer Group 5: South and central Arava Group 6: NE Negev Group 7 : NW Negev

  6. Processes for radium enrichment in ground water • Precipitation • Enrichment of SrSO4and PbSO4instead of BaSO4– atomic radius • Decrease in radium content in solid with increasing temperature • Adsorptionand ion exchange • Kd increase with time and decrease with T • Source for decay products flux into water • Linear correlation between radium concentration and salinity • Radium adsorption with MnOx depends on redox of water • Dissolution • Low PH and T increase dissolution Recoil • Recoil energy (daughter) following alpha disintegration of parent radionuclide • Change in decay product position in host rock

  7. Analytical methods (1) Soreq NRC, (2) BGU University, (3) Stanford University, (4) NRCN and GSI

  8. Radiological consequences The IL d.w. standard limit the overall dose from drinking water to 0.1 mSv/year. This limit is translated to activity concentration thresholds for each radium isotopes as presented in the table.

  9. Results of method comparison • Good correlation between different measurement methods. R=0.98

  10. R=0.97

  11. R=0.95

  12. Results of radium mapping • Radioactivity distribution: Dispersion of the phenomena along all the study area. • No hot-spots. • Anomalies of 222Rn in the region south to the Dead Sea.

  13. Mapping radium conc.

  14. Study area Kurnub aquifer Group 1: NE Negev - Craters Group 2: NE Negev – Dead Sea Group 3: South Arava Group 4: Ashalim Judea aquifer Group 5: South and central Arava Group 6: NE Negev Group 7 : NW Negev

  15. Mapping radium conc.

  16. Results of drinking water quality • The majority of the water in both aquifers are not suitable for consumption

  17. Water quality Kurnub aquifer 66% over old IL std. 96% over new IL std. Judea aquifer 34%over old IL std. 38% over new IL std.

  18. Results on geochemistry • Radium isotopes according to lithology (Judea 226Ra, Kurnub 228Ra and 226Ra). • Large daughter/parent disequilibrium: 222Rn/226Ra (0.2 - 225) 234U/238U (1.3 - 5.3) 224Ra/228Ra (0.1-5.4).

  19. Kurnub Judea Lithologic characterization

  20. Kurnub NE Negev - craters

  21. Total radium – salinity Craters • High salinity – low Ra: Adsorption of 226Ra in host rock. • Less precipitation of Ra with BaSO4. Total radium – salinity, DO. NE Negev (DS)

  22. South and central Arava

  23. כורנוב יהודה Increase in total Ra with T

  24. Judea NW Negev

  25. High salinity 1500 mg/L Low salinity 300 mg/L Ra related to chemistry Ra release in low DO water High salinity – adsorption sites Less Ra precipitates with BaSO4

  26. Conclusions • A systematic and comprehensive survey of natural radioactivity in the Kurnub and Judea aquifers was performed. • The natural radioactivity phenomena in groundwater is scattered along the south of Israel. • A comparison of five analytical methods for radium measurements was performed and an very good correlation was found between the different methods. • Isotopic radium characterization according to lithology. • 228Ra/226Ra < 1 as expected in carbonate aquifers (Judea) • Almost 40% of the wells do not fit IL and EU d.w. Standards.

  27. 228Ra/226Ra > 1 as expected in sandstone aquifers (kurnub). • Almost 96% do not fit new IL d.w. standard • The groundwater is supplied to the population after desalination which lower the radium concentration in the water. • Radium enrichment in groundwater is due to: adsorption, dissolution, precipitation and recoil. • The predominant geochemical process for radium enrichment are influenced in-situ by local characteristics (chemistry) of the water. • High U disequilibrium was found in both aquifers. • High excess of 222Rn was measured in both aquifers.

  28. In cooperation withA. Vengosh and N. Pery – Ben Gurion University.A. Paytan – Stanford UniversitySponsored by: Water quality Division at the Israel Water Commission

  29. ים המלח ירדן 2005 Thank you Gracie תודה Dead Sea

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