Evaluation of Internal Exposure Caused by Ionizing Radiation of 226Ra, 232Th, 40K and 137Cs in Pine (Pinus Sylvestris L.) Timber

Abstract

Radionuclides after getting into the environment affect its components with ionizing radiation. One of the components of the environment is a tree. Radionuclides affect all live organisms. Radionuclides affect trees doubly, from outside as well as from inside. Trees receive outside exposure due to the passing of air masses polluted with radionuclides. When radionuclides get into the trees with nutrients through the root system, the tree receives internal exposure. The aim of the thesis is to evaluate the level of internal exposure the pine (Pinus sylvestris L.) receives due to the impact of ionizing radiation by radionuclides of natural (226Ra, 232Th, 40K) and artificial (137Cs) origin. Main objectives of the thesis capacitating the aim of the thesis are to evaluate specific activities of radionuclides 226Ra, 232Th, 40K and 137Cs in timber; to evaluate internal exposure caused by ionizing radiation of these radionuclides. When selecting the object of investigation (pine Pinus sylvestris L.) pollution of the soil of the place of growth of pine with radionuclides was also taken into account. Three pines (Pinus sylvestris L.) from different places in Lithuania (from Vilnius County, from Alytus County, and from the western part of Lithuania) were selected for the investigation. The investigations of specific activity of 226Ra, 232Th, 40K and 137Cs were performed according to the methodology indicated in LAND 36 – 2000. After the investigation of pine from Vilnius County there were the following mean specific activities of investigated radionuclides determined in timber by 1 m from floor: 15.9 ± 4.5 Bq/kg (137Cs), 245 ± 26 Bq/kg (40K), 5.6 ± 1.2 Bq/kg (226Ra), 12.2 ± 3.2 Bq/kg (232Th). The following mean specific activities of radionuclides were determined in pine timber from Alytus County: 2.4 ± 0.5 Bq/kg (137Cs), 162 ± 33 Bq/kg (40K), 0.9 ± 0.3 Bq/kg (226Ra), 1.1 ± 0.4 Bq/kg (232Th). In pine timber from Kairiai there were the following specific activities of investigated radionuclides determined: 3.7 ± 1.3 Bq/kg (137Cs), 9.6 ± 2.4 Bq/kg (40K), 3.8 ± 0.6 Bq/kg (226Ra), 19.4 ± 1.4 Bq/kg (232Th).