Gamma-ray measurements of naturally occurring radioactive samples from Cyprus characteristic geological rocks

Abstract

Using high-resolution γ−ray spectroscopy, the terrestrial gamma radiation in all the predominant types of geological rock formations appearing in Cyprus was measured. Soil samples were collected from each rock type, sealed in 1-litre plastic Marinelli beakers, and measured in the laboratory for 24 hours each. From the measured γ−ray spectra, activity concentrations were determined for 232 Th (range from 1.3 to 52.8 Bq kg −1 ), 238 U (from 0.9 to 90.3 Bq kg −1 ) and 40 K (from 13 to 894 Bq kg −1 ). Elemental concentrations mean values of (2.8 ± 0.7) ppm, (1.3 ± 0.3) ppm and (0.6 ± 0.1) % were extracted, for thorium, uranium and potassium, respectively. Absorbed dose rates in air outdoors were calculated to be in the range of 0.1−50 nGy h −1 , depending on the geological features, with an overall mean value of (14.7 ± 7.3) nGy h −1 . The corresponding effective dose rates per person outdoors were estimated to be between 0.1 and 61.4 µSv y −1 , assuming a 20% occupancy factor.

Determination of thorium, uranium and potassium elemental concentrations in surface soils in Cyprus

“…The results obtained from the present wide-range investigations are in general agreement with the first studies on activity and elemental concentrations of naturally occurring radionuclides and on their associated dose rates in various rock types (Tzortzis et al, 2003a). They further confirm that the dose rates due to naturally occurring radiation in Cyprus are significantly lower (by a factor of five on an average) than the corresponding radioactivity levels reported from other areas worldwide.…”

“…The corresponding percentage contribution of samples of ophiolitic origin in the first study (Tzortzis et al, 2003a) was ∼39%, and this might explain why the results of the activity concentration and dose rates are slightly higher compared to the corresponding values of the present study.…”

“…The naturally occurring radionuclides considered in the present analysis of the measured γ−ray spectra are: 212 Pb (with a main gamma energy at ∼239 keV and a gamma yield of ∼43.1%), 214 Pb (∼352 keV, ∼37.1%), 214 Bi (∼609 keV, ∼46.1%), 228 Ac (∼911 keV, ∼29%), and 40 K (∼1461 keV, ∼10.7%). Under the assumption that secular equilibrium was reached between 232 Th and 238 U and their decay products, the concentration of 232 Th was determined from the average concentrations of 212 Pb and 228 Ac in the samples, and that of 238 U was determined from the average concentrations of the 214 Pb and 214 Bi decay products (Hamby and Tynybekov, 2000;Tzortzis et al, 2003a). Thus, an estimation of radionuclide concentration of 232 Th and 238 U was obtained, whereas a direct measurement of 40 K concentration was achieved.…”

“…Secondly, the analysis of selective elemental abundance (Th/U, K/U, and K/Th ratios) may also allow us to study the enrichment/depletion processes as a result of the complex metamorphic history, alteration and/or weathering that affected the investigating rocks (Chiozzi et al, 2002). Tzortzis et al (2003a) reported the first results of such measurements and the corresponding average annual effective dose rates equivalent to the population, using 28 soil samples collected from the main geological rock types appearing in the island.…”

Measurement of Indoor Terrestrial Gamma Radiation Dose and Evaluation of Annual Effective Dose at AECD Campus, Dhaka, Bangladesh

“…Both laboratory and in-situ gamma spectroscopy are often used for monitoring and assessment of radioactivity and radiation dose rates in the environment due to both natural and anthropogenic sources [15][16][17][18][19][20] . In-situ techniques for measuring the activity concentration resulting from the gamma radiation and characterizing its sources with gamma ray spectrometer have been used successfully in outdoor and indoor environment [12,[21][22][23] .…”