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      Sedimentlerde radyoizotopik yöntemlerle yaş tayini

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      Author(s)
      Erten, Hasan N.
      Date
      2001
      Source Title
      Turkish Journal of Engineering and Environmental Sciences
      Print ISSN
      1300-0160
      Publisher
      Scientific and Technical Research Council of Turkey - TUBITAK
      Volume
      25
      Issue
      2
      Pages
      237 - 242
      Language
      Turkish
      Type
      Article
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      Abstract
      Sedimentlerde yaş tayini, sediment boyunca kimyasal element dağılımı ile birlikte ele alınınca doğal ve kültürel olayların çevresel etkilerinin belirlenmesinde çok önemli rol oynamaktadır. Doğal 238U radyoaktif serisinin bir ürünü olan 210Pb (t1/2= 22.3y) kullanılarak sedimentlerde son 200 yılı kapsayan bir süre içinde yaş tayini yapmak mümkün olmaktadır. Diğer yandan çevrede yapay olarak bulunan 137Cs (t1/2= 30.1y) izotopunun sediment boyunca dağılımı incelemelerinden 1954-1963 yıllarındaki yeryüzünde yapılan nükleer silah denemelerinin sonucunda ve 1986 yılındaki Çernobil kazasında çevreye yayılan 137Cs’nin dağılım profillerinden söz konusu tarihleri belirlemek mümkün olmaktadır. Bu yöntem 210Pb ile birlikte kullanıldığı zaman güvenilir sediment çökelme hızı tayinleri yapılabilmektedir. Diğer yandan bir kozmik ışın ürünü olan 7Be(t1/2=53.3g) izotopunun incelenmesi ise sediment örneklerinin kayıpsız elde edilişlerini belirlemektedir. Radyoizotopik yöntemler klasik yöntem olarak kullanılan katman sayma yöntemi ile karşılaştırılabilir. ˙
       
      Dating of lake sediments together with the determination of the distribution of trace elements throughout the depth of sediments, gives us valuable information in the study of the impact of natural and cultural events on the environment. Using 210Pb(t1/2=22.3y) a member of the natural radioactive 238U series, it is possible to date sediments within the last 200 years. The fallout nuclide 137Cs(t1/2=30.1y) with its known deposition pattern resulting from extensive tesying of nuclear weapons in the atmosphere between 1954-1963 and from the nuclear accident in Chernobyl in 1986 provides a complimentary method of sediment dating. The maxima in fall-out corresponding to the 1963 and 1986 are usually well preserved in sediment horizons and they can be used as time markers. 7Be(t1/2=53.3d), a cosmic ray produced nuclide is expected to be present only in the uppermost sediment layers. The presence of 7Be in the sediments ensures complete core recovery. Sediment cores from Lakes Zurich and Constance from the Sea of Marmara, southern Turkey and northern Cyprus were dated using natural 210Pb, fallout 137Cs and cosmic-ray produced 7Be radionuclides.
      Keywords
      Cosmic rays
      Geochronology
      Lakes
      Lead
      Trace elements
      Uranium
      Nuclear weapons
      Sediments
      Anthropogenic effect
      Atmospheric deposition
      Dating method
      Geochronology
      Lacustrine deposit
      Radionuclide
      Aves
      Marmara
      Meleagris gallopavo
      Permalink
      http://hdl.handle.net/11693/24716
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