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| Titel |
Distribution of uranium and thorium in groundwater of arid climate region |
| VerfasserIn |
Ahmed Murad, Dalal Alshamsi, Ala Aldahan, Xiaolin Hou |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098097
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| Publikation (Nr.) |
 EGU/EGU2014-13737.pdf |
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| Zusammenfassung |
| Uranium, thorium and their decay products are the most common radionuclides in
groundwater in addition to potassium-40. Once groundwater is used for drinking, domestic
and irrigation purposes, the radionuclides will then pose environmental and health related
hazard originating from radioactivity and toxicity. In the investigation presented here,
assessment of 238U, 235U and 232Th concentrations in groundwater across of the United Arab
Emirates (UAE) is evaluated in terms of quality and sources. The region is dominated by arid
climate conditions and radioactivity assessment of groundwater is essential for safe use of
groundwater. Furthermore, the results were linked to data from other arid regions and
worldwide. Groundwater samples (total dissolved solids,TDS, 142.5 mg L-1 to
12770 mg L-1) from 67 different wells were collected across geomorphologically
different areas and most of the wells are actively used for agriculture. The aquifers are
recent sand dunes, Quaternary (3million years to present) sediments, and older
carbonate rocks (230-10 million years). The 235U, 238U and 232Th measurements
were carried out using ICP-MS system equipped with an Xt-skimmer cone and a
concentric nebulizer under hot plasma conditions. Concentrations of 235U, 238U and
232Th range at (0.125–508.4) ng L-1, (25.81–69237) ng L-1 and (0.236–2529)
ng L-1, respectively. Apparently, most 235U, 238U, 232Th concentrations in the
sampled groundwater are below the WHO proposed permissible level of 60000 ng/L
for total uranium (1 Bq L-1 for 235U and 10 Bq L-1 for 238U) and 5000 ng L-1
(1Bq L-1) for 232Th. A few samples show high concentrations of uranium that
are associated with high TDS values and occur within interbedded limestones and
shales aquifer. Comparison with worldwide groundwater data suggests that 238U
concentration is highest in the arid regions groundwater where the recharge to aquifers
is relatively low. The situation for 232Th concentrations seems less affected by
climatic conditions, most likely is related to its less solubility in water compared
to uranium. We calculated the accumulated TU and 232Th concentration in the
irrigation water annually to estimate the cumulative concentrations after twenty
years on specific agricultural areas. The TU and 232Th are expected not to reach
more than 1.14 x 10-3 g (1.14 mg) and 4.32 x 10-6 g (4.32 μg) respectively after
twenty years if the daily irrigation is at its maximum amount (10 m3). Despite
these obtained values of concentrations in irrigation water, the transfer of uranium
and thorium into crop is not readily and it is expected that only a tiny fraction of
the element end into the body. However, further research is needed to quantify
the dietary exposures in the UAE with detailed data from crops and consumers. |
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