Radioactivity concentrations and risk assessment of Tekirdağ lignites (case study of Malkara coalfield)

Malkara coals are located in the Oligocene-aged Danişmen Formation in the Thrace Tertiary coal basin. The Danişmen Formation consists of limestone, sandstone, tuffite, siltstone, claystone and intercalated coal. Elemental and specific natural radionuclide concentrations of lignites collected from Tekirdağ–Malkara coalfield were determined, and the associated radiological risk was assessed. In order to examine the depth-dependent radionuclide concentration changes, samples were taken from top, middle and bottom parts of the boreholes. Gamma spectrometric measurements of radionuclide activities were performed with HPGe detector. The calculated mean 226 Ra, 232 Th and 40 K concentrations were 27.0 ± 3.57, 18.9 ± 3.28 and 155 ± 36.1 Bq kg −1 , and the measured U, Th, Pb and K concentrations were 4.04, 6.27, 10.6 ppm and 0.82%, respectively. Findings were comparable with the reported literature for Turkey and other countries from the world. The dose due to the radionuclide content of lignites was not very high to pose a serious health risk.