© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com Radiation Protection Dosimetry (2021), pp. 1–18 doi:10.1093/rpd/ncab035 DETERMINATION OF Ra-226, Th-232, K-40 and Cs-137 ACTIVITIES IN SOILS AND BEACH SANDS AND RELATED EXTERNAL GAMMA DOSES IN ARIKLI MINERALIZATION AREA (AYVACIK/TURKEY) Gülcan Top 1,2, *, Yüksel Örgün 3 , Ismail Ercüment Ayazlı 4 , Murat Belivermi¸ s 5 , Zekiye Karacık 3 and Györgyi Kampfl 2 1 Eurasia Institute of Earth Sciences, Solid Earth Sciences, Istanbul Technical University, Ayaza˘ ga Campus, Maslak, Istanbul 34469, Turkey 2 Faculty of Agricultural and Environmental Sciences, PhD School of Environmental Sciences, Szent István University (SZIU), Páter K. u. 1, Gödöll˝ o 2100, Hungary 3 Department of Geological Engineering, Faculty of Mines, Istanbul Technical University, Ayaza˘ ga Campus, Maslak, Istanbul 34469, Turkey 4 Department of Geomatics Engineering, Faculty of Engineering, Sivas Cumhuriyet University, Campus, Sivas 58140, Turkey 5 Department of Biology, Faculty of Science, Istanbul University, Vezneciler, Istanbul 34134, Turkey *Corresponding author: gulcantop@gmail.com Received 18 November 2020; revised 9 February 2021; editorial decision 15 February 2021; accepted 15 February 2021 Uranium mineralization areas may jeopardize public health and surrounding natural life. In the current study for radioactivity and geochemical analyses, 43 soil, 5 rock and 10 beach sand samples were collected in and around Arıklı (Ayvacık, Turkey) uranium mineralization area. Radioactivity levels in the soils (up to Ra-226: 629, Th-232: 240, K-40: 3669 Bq/kg) were found higher than the that of beach sands. Besides, radioactivity of the beach sand samples is found at normal levels (avg: Ra-226: 31, Th-232: 31, K-40: 542 Bq/kg) when compared to worldwide average soil. Dose values indicate that the region have ∼three times higher average gamma radioactivity than the corresponding world average although measured gamma doses ranged up to 687 nGy/h. The high measured values are related to uranium mineralization, alteration zones, faults and Arıklı tuff. INTRODUCTION It is an admitted fact that radioactive mineralization sites and related exploration activities may lead to a contamination problem and affect the living ecology of surrounding areas. ( 1 , 2 ) From these sites, radioac- tive elements can disperse by natural and artificial factors (wind, water, volcanic eruptions, biosphere, use of radioactive material-bearing rocks as build- ing material etc.). Over time, the accumulation and transport environments may act as a source even this process may lead to secondary mineralization fol- lowed by bed formation, and can threat for long-term wildlife, farming lands and settlements. ( 1 , 3 , 4) Outdoor absorbed gamma dose rate measure- ments are an important step for the determination of radioactive isotope distribution and related health hazard risks. The dose rate in the air at 1 m above the ground originate from natural and man-made radioactivity sources in the soil and air. While gamma radiation from natural gamma radiation originates from mainly terrestrial and partially cosmic sources, artificial sources originate from nuclear reactor fall-outs and nuclear weapon tests. ( 5) Terrestrial gamma rays fundamentally originate from the U-238 and Th-232 series and K-40 in the compositions of the soils and rocks. The worldwide average value of outdoor absorbed gamma dose rate in the air due to terrestrial sources is 51 nGy/h and the relative contributions of U-238, Th-232 and K-40 to this dose are about 35, 25 and 40%, respectively. ( 5 , 6 ) The cosmic-ray exposure rate at ground level is from gamma rays and muons that originate from interactions of high energy protons and neutrons in the upper atmosphere. Cosmic radiation level in a given outdoor area differs depending on the solar activity, the magnetic field of the earth, atmospheric pressure and altitude. The average gamma cosmic radiation dose at sea level is 32 nGy/h worldwide. ( 5 , 7 , 8) SiO 2 -saturated acidic magmatic rocks (e.g. granite, rhyolite, syenite and pegmatite) and soils derived from them contain a higher amount of natural radionuclides when compared with the other rock and Downloaded from https://academic.oup.com/rpd/advance-article/doi/10.1093/rpd/ncab035/6208113 by guest on 06 April 2021