Nijerya'nın Güneybatı Temel Kompleks Bölgesinde Yüzeye Çıkan Granit Kayaların Doğal Radyoaktivite ve Radyolojik Tehlikelerinin Yerinde Değerlendirilmesi
Kaya materyallerinden kaynaklanan radyoaktif emisyon (gama ışını) insanlara ve çevresine tehdit oluşturur. Bu nedenle, Nijerya'nın Güneybatı Temel Kompleksi'nde iki farklı bölgeden yüzeye çıkan granit kayalar ile bunların kalıntısı olan toprakların doğal radyoaktivite ve radyolojik tehlike endeksleri Gamma-ray spektrofotometre kullanılarak değerlendirilmiştir. Bu çalışmada, granit yapıdaki kayaların doğal radyasyon düzeylerinin ve bağlantılı radyolojik tehlikelerin çalışma alanında yaşayan ve gama ışınına maruz kalan insanlar üzerindeki etkilerinin belirlenmesi amaçlanmıştır. Veriler, taşınabilir Gamma-ray Spektrometresi kullanılarak her biri 200 m’lik altı jeofizik travers boyunca 5 m’lik istasyon aralığı ile toplanmıştır. 40K, 238U ve 232Th için temel ve aktivite konsantrasyonlarının ağırlıklı ortalama değerlerinin sonuçları sırasıyla %2.00 ± 1.43, 3.13 ± 0.90 ppm, 12.32 ± 4.99 ppm ve 629.28 ± 447.29, 38.58 ± 11.02, 49.96 ± 20.23 ?? ??−1 dir. Elde edilen U/Th (1.32) ve Th/U (2.14) ortalama konsantrasyon oranları, sırasıyla, genel standart oranları olan 0.26’dan yüksek ve 3.5’tan düşüktür. Aktivite konsantrasyonları ve konsantrasyon oranlarındaki artış, yüzeye çıkan granit kayalarda radyoaktif minerallerin zenginleştiği anlamına gelebilir. Çalışma alanında yaşayan insanlar için gamma ışını maruziyetinde uygulanan yıllık dış ve iç etkili dozları dünyanın izin verilen 1 ??? ? −1 standardının altında olduğundan, alan radyolojik olarak güvenlidir. Bununla birlikte, AGDE ve ELCR'nin tahmini ortalamaları olan 525.620 ??? ? −1 ve 1.273 x10-3 değerlerindeki artışın, izin verilen 300 ??? ? −1 ve 0.29 x10-3 standart miktarların üzerinde olması da ciddi radyolojik tehditler anlamına gelmemelidir. Bu nedenle, alanın ve kayaların radyoaktivite seviyesinin sürekli izlendiği kontrol önlemleri tatbik edilmelidir.
In situ natural radioactivity and radiological hazard assessments of granite gneiss outcrops in parts of the Southwestern Basement Complex of Nigeria
Radioactive emission (gamma ray) emanating from rock materials constitutes threats to humans and their environment. Hence, thenatural radioactivity and radiological hazard indices of some granite gneiss outcrops with their residual soils from two differentlocalities within the Southwestern Basement Complex of Nigeria were assessed using Gamma-ray spectrometry. The study aimedat determining the natural radiation levels of granite gneissic rocks and associated radiological threats to people living in thestudy area from gamma ray exposure. Data were collected along six geophysical traverses of 200 m each with station spacing of5 m using the portable hand-held Gamma-ray Spectrometer. The results of weighted mean values of the elemental and activityconcentrations for 40K, 238U, and 232Th are 2.00 ± 1.43%, 3.13 ± 0.90 ppm, 12.32 ± 4.99 ppm and 629.28 ± 447.29, 38.58 ± 11.02,49.96 ± 20.23 ?? ??−1respectively. The obtained mean concentration ratios of 1.32 for U/Th and 2.14 for Th/U were higher than0.26 and lower than 3.5 global standard ratios respectively. The increase in activity concentrations and concentration ratio mayhave suggested the enrichment of radioactive minerals in the granite gneissic rocks. The annual outdoor and indoor effective dosesof gamma ray exposure for people living in the study area were below the world permissible standard of 1 ??? ?−1, thus, the areais radiologically safe. However, increase in estimated mean of AGDE and ELCR; 525.620 ??? ?−1 and 1.273 ?10−3 above theworld permissible standards of 300 ??? ?−1 and 0.29?10−3respectively does not translate to significant radiological threats.Therefore, control measure by constant monitoring of the radioactivity levels of the area and rocks should be practiced.
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