In the present work, naturally occurring radionuclides of Ra-226, Th-232 and K-40 were measured in soil samples collected from the Eastern Black Sea region of Turkey. It was found that the activity concentrations ranged from 12 to 120 Bq kg(-1) for Ra-226, from 13 to 121 Bq kg(-1) for Th-232 and from 204 to 1295 Bq kg(-1) for K-40. Besides naturally occurring radionuclides, Cs-137 activity concentration was measured in soil, lichen and moss samples and it was found that Cs-137 activity concentration ranged from 27 to 775 Bq kg(-1) with for soil, from 29 to 879 Bq kg(-1) for lichen and from 67 to 1396 Bq kg(-1) for moss samples. Annual effective doses due to the naturally occurring radionuclides and (CS)-C-137 were estimated. Ecological half-lives of (CS)-C-137 in lichen and moss species were estimated. The decrease of the activity concentrations in the present measurements (2007) relative to those in 1993 indicated ecological half-lives between 1.36 and 2.96 years for lichen and between 1.35 and 2.85 years for moss species. (C) 2008 Elsevier B.V. All rights reserved.