Constantin Papastefanou

Forty-nine samples from several plutons in northern Greece have been studied for their activity concentrations of 40K, 226Ra and 232Th by using gamma-ray spectroscopy. The activities of 40K, 226Ra and 232Th of the majority of the samples exceed the average level of these radionuclides in soil and building materials. Samples of basic composition have very low concentrations of radionuclides while intermediate and acid rocks are more enriched in 40K, 226Ra and 232Th and their decay products. In order to assess the radiological impact from the investigated rocks, absorbed gamma dose rate (Da), annual effective dose (HE), activity index (AI) and gamma-ray index (Iγ) were estimated. The activity concentrations and hazard indices were compared to those of plutonic rock samples from all over the world, as well as other building materials. The average of hazard indices of Greek granites is below ‘world’ average in all cases. Moreover, it is still bellow the criteria of UNSCEAR (2000). Therefore, at least from radiological point of view and for the investigated rocks, the use of granites from northern Greece as building materials is recommended.

The radioactivity in tobacco leaves collected from 15 different regions of Greece and before cigarette production was studied in order to find out any association between the root uptake of radionuclides from soil ground by the tobacco plants and the effective dose induced to smokers from cigarette tobacco due to the naturally occurring primordial radionuclides , such as ²²⁶Ra and ²¹⁰Pb of the uranium series and ²²⁸Ra of the thorium series and/or man-made radionuclides, such as ¹³⁷Cs of Chernobyl origin. Gamma-ray spectrometry was applied using Ge planar and coaxial type detectors of high resolution and high efficiency. It was concluded that the activities of the radioisotopes of radium, ²²⁶Ra and ²²⁸Ra in the tobacco leaves reflected their origin from the soil by root uptake rather than fertilizers used in the cultivation of tobacco plants. Lead-210 originated from the air and was deposited onto the tobacco leaves and trapped by the trichomes. Potassium-40 in the tobacco leaves was due to root uptake either from soil or from fertilizer. The cesium radioisotopes ¹³⁷Cs and ¹³⁴Cs in tobacco leaves were due to root uptake and not due to deposition onto the leaf foliage as they still remained in soil four years after the Chernobyl reactor accident, but were absent from the atmosphere because of the rain washout (precipitation) and gravitational settling. The annual effective dose due to inhalation for adults (smokers) for ²²⁶Ra varied from 42.5 to 178.6 μSv/y (average 79.7 μSv/y), while for ²²⁸Ra from 19.3 to 116.0 μSv/y (average 67.1 μSv/y) and for ²¹⁰Pb from 47.0 to 134.9 μSv/y (average 104.7 μSv/y), that is the same order of magnitude for each radionuclide. The sum of the effective doses of the three radionuclides varied from 151.9 to 401.3 μSv/y (average 251.5 μSv/y). The annual effective dose from ¹³⁷Cs of Chernobyl origin was three orders of magnitude lower as it varied from 70.4 to 410.4 nSv/y (average 199.3 nSv/y).

The radioactivity in tobacco leaves collected from 15 different regions of Greece before cigarette production was studied in order to estimate the effective dose from cigarette tobacco due to the naturally occurring primordial radionuclides, such as (226)Ra and (210)Pb of the uranium series and (228)Ra of the thorium series and or man-made radionuclides, such as (137)Cs of Chernobyl origin. Gamma-ray spectrometry was applied using Ge planar and coaxial type detectors of high resolution and high efficiency. It was concluded that the annual effective dose due to inhalation for adults (smokers) for (226)Ra varied from 42.5 to 178.6 microSv y(-1) (average 79.7 microSv y(-1)), while for (228)Ra from 19.3 to 116.0 microSv y(-1) (average 67.1 microSv y(-1)) and for (210)Pb from 47.0 to 134.9 microSv y(-1) (average 104.7 microSv y(-1)), that is the same order of magnitude for each radionuclide. The sum of the effective doses of the three natural radionuclides varied from 151.9 to 401.3 microSv y(-1) (average 251.5 microSv y(-1)). The annual effective dose from (137)Cs of Chernobyl origin was three orders of magnitude lower as it varied from 70.4 to 410.4 nSv y(-1) (average 199.3 nSv y(-1)).