Yaşar Kobya

Evaluation of Outdoor Gamma Dose Rate and Cancer Risk in Artvin Province, Turkey

ABSTRACT In this study, we measured environmental outdoor gamma dose rates (terrestrial and cosmic) in 204 stations across the province of Artvin. The average outdoor gamma dose rate for the province of Artvin was found to be 174.81 nGy/h. The radiological map of Artvin was drawn with the help of measured outdoor gamma dose rates. Annual effective dose equivalent and lifetime cancer risk values were figured up for the adults in Artvin province by using measured outdoor gamma dose rates. The average annual dose equivalent and excess lifetime cancer risk were 214.5 μSv/y and 7.5 × 10−4, respectively. The values acquired were compared with the similar studies done around the world. The average annual effective dose equivalent and excess lifetime cancer risk were found to be approximately three times higher than the world average.

Investigation of Cs-137 and K-40 activities of natural spring waters of the Eastern Black Sea Region, Turkey

The activity concentrations of Cs-137 and K-40 radio nuclides in the natural spring waters of the Eastern Black Sea region of Turkey were measured using gamma-ray spectrometry. Annual effective dose equivalents of Cs-137 and K-40 in babies, children and adults were calculated from the obtained measurements. These results were compared with other studies and the limit values of World Health Organization. The activity concentrations were calculated and kriging-geostatistical method was used to plot the obtained data on the radioactive maps of Eastern Black Sea Region. Frequency distributions of the water samples for each province were determined. This study provides background values of investigated Cs-137 and K-40 in the water from the region, which could, also, be useful in forensic investigations to distinguish potential contributions from point pollution sources.

Spatial interpolation and radiological mapping of ambient gamma dose rate by using artificial neural networks and fuzzy logic methods

The aim of this study was to determine spatial risk dispersion of ambient gamma dose rate (AGDR) by using both artificial neural network (ANN) and fuzzy logic (FL) methods, compare the performances of methods, make dose estimations for intermediate stations with no previous measurements and create dose rate risk maps of the study area. In order to determine the dose distribution by using artificial neural networks, two main networks and five different network structures were used; feed forward ANN; Multi-layer perceptron (MLP), Radial basis functional neural network (RBFNN), Quantile regression neural network (QRNN) and recurrent ANN; Jordan networks (JN), Elman networks (EN). In the evaluation of estimation performance obtained for the test data, all models appear to give similar results. According to the cross-validation results obtained for explaining AGDR distribution, Pearsons r coefficients were calculated as 0.94, 0.91, 0.89, 0.91, 0.91 and 0.92 and RMSE values were calculated as 34.78, 43.28, 63.92, 44.86, 46.77 and 37.92 for MLP, RBFNN, QRNN, JN, EN and FL, respectively. In addition, spatial risk maps showing distributions of AGDR of the study area were created by all models and results were compared with geological, topological and soil structure.

Doğu Karadeniz Bölgesinin Doğal Kaynak Sularındaki Toplam Alfa ve Toplam Beta Aktivite Dağılımlarının Bulanık Mantık Yöntemi ile Değerlendirilmesi ve Haritalandırılması

Ozet: Bu calismada bulanik mantik yaklasimi kullanarak, Dogu karadeniz bolgesindeki dogal kaynak sularindan olculen toplam alfa ve toplam beta aktivite konsantrasyonlarinin genel dagilimi belirlenmis ve olcum alinmayan noktalar icin tahmin degerleri hesaplanarak, haritalandirilmasi gerceklestirilmistir. Olcumler Artvin, Rize, Trabzon, Giresun, Ordu, Gumushane ve Bayburt olmak uzere toplam 7 ilde belirlenen 40 istasyondan elde edilmistir. Bu istasyonlarin tamamindan olculen toplam alfa ve toplam beta aktivite degerleri bulgularindan yararlanarak calisma alaninin genel yapisi icin bulanik kumeler ve kural tabanlari olusturulmustur. Bu calismada Dogu-Bati X koordinati, Guney-Kuzey Y koordinati ve yukseklik verileri ile birlikte toplam alfa ve toplam beta konsantrasyonlari bulanik kumeler ile gosterilmis ve bulanik kurallar ile tahminlerde bulunulmustur. Bulanik modelin performans degerlendirmesi ise capraz dogrulama diyagramlari ile degerlendirilmistir. Bu diyagramlardan toplam alfa ve toplam beta icin pearson’s r katsayilari sirasiyla 0.74 ve 0.80 olarak bulunmustur.Calismanin sonucunda olcum alinmayan tum noktalar icin bulanik mantik modellemesi tahminlerinde bulunulmus ve sonuclar radyolojik dagilim haritalari olarak gosterilmistir. Bu calisma ile radyolojik dagilimin bulanik mantik yaklasimlari kullanilarak tespit edilebilecegi ve olcum alinmayan noktalar icin tahmin degerlerinin belirli guven araliginda hesaplanabilecegi gosterilmistir. Anahtar Sozcukler : Bulanik Mantik Modellemesi, Cevresel Radyoaktivite, Dogal kaynak suyu, Dogu Karadeniz bolgesi Abstract: In the study, drawing upon the fuzzy logic approach, the general distribution of gross alpha and gross beta concentrations measured from the natural spring waters in the Eastern Black Sea region was identified, and the predicted values were mapped calculating for the unmeasured points. The measurements were obtained from 40 stations in designated 7 cities which are Artvin, Rize, Trabzon, Giresun, Ordu, Gumushane and Bayburt. Fuzzy sets and rule bases were generated for the general structure of the study area benefiting from the findings of gross alpha and gross beta activity values measured in all these stations. In this study, East-West X coordinate, South-North Y coordinate and height data were indicated in fuzzy sets with gross alpha and gross beta concentrations, and predictions were done using fuzzy rules. The performance evaluation of fuzzy model was assessed by means of cross validation diagrams. Pearsons r coefficient are found as 0.74 and 0.80 respectively for gross alpha and gross beta from these diagrams. In the conclusion of study, fuzzy logic model predictions were represented and the results were indicated as radiological distribution maps. This study demonstrates that the radiological distribution is able to be detected using fuzzy logic approach, and that the predicted values for unmeasured points are able to be calculated in a specific confidence interval. Keywords : Fuzzy Logic Modelling, Environmental radioactivity, Natural spring water, Eastern Blacksea region