A Comprehensive Study of Natural Gamma Radioactivity Levels and Associated Dose Rates from Surface Soils in Cyprus

TL;DR

This study measured natural gamma radioactivity in soils across Cyprus, revealing low dose rates significantly below global averages, providing valuable data on environmental radioactivity levels and associated health risks.

Contribution

It offers a comprehensive survey of natural radionuclide levels in Cyprus soils using high-resolution gamma-ray spectrometry, filling data gaps for this region.

Findings

Radioactivity levels are below global averages.

Dose rates are among the lowest worldwide.

Data supports environmental and health risk assessments.

Abstract

A survey was carried out to determine activity concentration levels and associated dose rates from the naturally occurring radionuclides Th-232, U-238, and K-40, in the various geological formations appearing throughout the geographically accessible area of Cyprus, by means of high-resolution gamma-ray spectrometry. A total number of 115 representative soil samples were collected from all over the bedrock surface of the island, based on the different lithological units of the study area, sieved through a fine mesh, sealed in 1000-mL plastic Marinelli beakers, and measured in the laboratory with respect to their gamma radioactivity for a counting time of 18 hours each. From the measured spectra, activity concentrations were determined for Th-232 (range from 1.0x10^-2 to 39.8 Bq/kg), U-238 (from 1.0x10^-2 to 39.3 Bq/kg) and K-40 (from 4.0x10^-2 to 565.8 Bq/kg). Gamma absorbed dose rates in air outdoors were calculated to be in the range of 1.1x10^-2 - 51.3 nGy/h, depending on the geological features, with an overall mean value of 8.7 nGy/h and a standard deviation of 8.4 nGy/h. This value is by a factor of about 7 below the corresponding population-weighted world-averaged value of 60 nGy/h reported by UNSCEAR (2000), and one of the lowest that has been reported from similar investigations worldwide. Assuming a 20% occupancy factor, the corresponding effective dose rates outdoors equivalent to the population were calculated to be between 1.3x10^-2 and 62.9 micro Sv/y, with an arithmetic mean value of 10.7 micro Sv/y and a standard deviation of 10.3 micro Sv/y.