Journals Proceedings

Abstract

Airborne radiometric surveys showed that Aja heights, of granitic composition, represent a radiometric anomaly area and should be of interest for detail study in a purpose of radiation protection. Ground surveys and radiometric analysis of rocks, surface soil, building materials and groundwater samples have been conducted. Radon-222 has been measured in groundwater and in the atmosphere (indoor and outdoor) of the inhabited area. Root uptake of natural uranium by vegetation grown in farms lie in the foot of the granitic massif has been investigated. Ground surveys showed an average effective dose rate, due to terrestrial γ-radiation, of 1.49 mSv/y. This level is about 3.3 times greater than the world average external effective dose rate (0.46 mSv/y) that estimated in normal background areas. The average concentrations (249 and 383 Bq/kg, respectively) of 238U and 232Th in the collected rock samples were higher than their worldwide average (about 61 Bq/kg for both radionuclides) in granites. The average concentrations of 238U and 232Th (156 and 187 Bq/kg, respectively) in the top-soil samples were greater than the normal soil-background of 40-50 Bq/kg for both radionuclides. Samples of building materials, collected from utilized quarries dispersed randomly in the area, indicated that the highest activity was found in the fragmented granites and the lowest activity was found in the black rock materials. The average activity concentrations of 238U, 234U, 226Ra and 228Ra in the groundwater were 0.40, 0.77, 0.29 and 0.46 Bq/L, respectively. These values exceeded the national guideline values set out for their concentration in drinking water. The average 222Rn concentrations in the groundwater and in the indoor and outdoor atmospheric air were 30.3 kBq/m3, 54.6 Bq/m3 and 10.5 Bq/m3, respectively. Root uptake of uranium by vegetation grown in the region showed demonstrable differences in uranium concentration between plant parts and types, which generally, followed the sequence: roots > leaves > stems or branches > fruits. Plant-soil transfer factors, based on the edible parts of the plant, for uranium isotopes were calculated. Some conclusions and recommendations are presented.