Ankara ili'nin radyoaktif kirliliğinin liken türleriyle biyoizlenmesi

Abstract

During the investigation of environmental radioactivity by using instantaneous instruments, detection limits are normally tend to be low. In order to measure activity reliably; lichens, which could also be called "biodisc" are used, since these instore a long period of time retrospectively and can give more reliable results for lower activities. In this context, in literature lichens are the most widely used bioindicators to determine environmental pollution levels. In this study, for measuring the specific activity of radionuclides; gamma-ray spectrometry method was used to ascertain radionuclides on lichens collected from Ankara province. During the radioactivity measurements, %78,5 n-type and %44,8 p-type HPGe (Germanium) detectors were used. In these measurements, maximum values for specific activities of radionuclides are found to be 28±2 Bq/kg (214Bi), 491±48 Bq/kg (210Pb), 29±2 Bq/kg (214Pb), 555±37 Bq/kg (226Ra) and 484±47 Bq/kg (234Th), from the decay products of 238U, 35±6 Bq/kg (228Ac); 14±1 Bq/kg (212Pb) and 46±4 Bq/kg (208Tl), from the decay products of element 232Th; the cosmogenic 7Be activity is 60±3 Bq/kg and natural potassium 40K activity is 817±27 Bq/kg, and the fission product 137Cs activity is 21±1 Bq/kg. Pseudevernia furfuracea, which is in our study has the highest 137Cs value of 4.0±0.3 Bq/kg, while for Xanthoria parietina lichen this value is 21±1 Bq/kg. X. parieatina lichen having higher 137Cs storage capacity compared to P. furfuracea lichen is the indication of that X. parieatina lichen is a much better type of bioindicator species. As a result of our studies in Ankara province, average 137Cs and 40K activity values were found to be respectively 3.3±0.4 Bq/kg and 182±9 Bq/kg, and below world or Turkey averages, while 226Ra activity were found to be higher than averages with the value of 121±11 Bq/kg. This thesis study, will be the first comprehensive research in which radioactive contamination levels for Ankara province is being investigated by the means of lichens. This study, will offer the most common bioindicator types amongst lichen species and give researchers a lead by contributing to the literature.