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Vulnerability of groundwater resources to natural radiological hazards in the semi-arid terrains of North Africa and the Mediterranean Basin

Ziel

- The general objective of this project is to assess the effect of selective remobilisation of trace metals, including naturally occurring radionuclides (U, Th, Ra, etc.) on the quality of shallow groundwater in the semi-arid terrains of north Africa and the Mediterranean basin.

Sub-objectives are :
- To transfer and develop expertise in the counterpart's organisation to facilitate the assessment of the vulnerability of socially important, finite, aquatic resources to both man-made and natural hazards. Naturally occurring radionuclides will constitute the hazard under study;
- To determine the spatial and temporal distribution of naturally occurring radionuclides and associated major and trace elements in waters of the Amman-Zarka basin and Marconi region and interpret data to define the factors controlling the release and mobility of these contaminants;
- To quantify the degree of radiological and chemical hazard experienced by the local population through potable and agriculture use of water.
- In Jordan, the presence of elevated concentrations of U, Rn, Ra and other potentially toxic trace elements have been confirmed in the Hummar formation by both geophysical logging and the depthwise sampling of groundwater chemistry. The hypothesis that this contamination is due to present day remobilisation of a buried ore deposit rather than anthropogenic contamination from mine workings is consistent with dissolution of U and associated elements in a predominantly oxic hydrochemical environment and is therefore mainly due to natural processes. Although this remobilisation is not man-made, as originally thought, anthropogenic contamination of the aquifer by urban pollution increases the likelihood of exacerbating these processes. For example, by anthropogenic activity altering the water table, changes in the redox conditions prevailing within the borehole and the addition of complexing agents may enable remobilisation of currently insoluble radioactive elements.
- In Cyprus, the presence of Uranium enrichment within the Discopirina bed of the Upper Pakhna formation was confirmed by portable gamma ray spectrometry and quantitative x-ray fluorescence analysis. Similar enrichments were not observed in gypsums/shales from equivalent formations within the Polemi basin (Western Cyprus), despite enhanced Uranium concentrations in groundwaters derived from these formations (3 to 25 llgA). However, the gypsum/shale contact is poorly exposed in the West of the Polemi basin where U appears to be more enhanced in groundwaters.
- Review of existing regional data, preliminary site investigation and formulation of sampling framework for investigating the occurrence of radio-elements;
- Detailed review of hydrological and geological conditions in the selected study areas with particular emphasis on the identification of potential source terms and migration pathways;
- Chemical and radiochemical analysis of samples from the Amman-Zarka basin and the Marconi Cerestite formation;
- Chemical analysis of solid and liquid samples, incorporating a wide range of determinants to provide sufficient data for the computation of aqueous phase specification and capability of chemical species from the solid phase;
- Radiochemical analysis of samples collected during field excursions wil1 focus on the determination of U and Th series radionuclides;
- Computer modelling of aqueous phase specification will be used to model aqueous phase speciation of the dominant radiogenic species;
- Interpretation and identification of controlling factors;
- Hazard assessment based on the estimation of total chemical and radiogenic dose received, calculated from an environmental transfer pathway model and assuming three principal exposure pathways :
- external exposure from contaminated land,
- inhalation of soil gas/particulate contamination,
- ingestion of terrestrial and aquatic foods.
Results obtained from study sites will be placed into a regional context by reviewing regional data;
- Identification of management options.

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NERC British Geological Survey
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NG12 5GG Keyworth
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