İstanbul'un Avrupa yakasındaki sularda radon ölçümü ve yıllık etkin dozların belirlenmesi = Measurement of radon in the waters of the European side of Istanbul and determination of annual effective doses

Abstract

Bu tezin ana amacı çalışma alanında bulunan su örneklerinin ölçülen radon konsantrasyonlarının kullanım amaçlarına göre bölge halkı üzerinde doğurabileceği radyolojik etkilerin ve risklerin değerlendirilmesidir. İstanbul'un nüfusuyla, endüstriyel faaliyetleriyle ve her açıdan ülkemizin lokomotifi olduğu düşünüldüğünde çevresel radyasyon analizlerinin yapılması ve takibinin düzenli olması da bir gereklilik olmuştur. Bu tez çalışmasında su örneklerinde radon ölçümleriyle literatüre önemli bir katkı sunulması da amaçlanmaktadır. Bu bahsedilen araştırmaların tüm İstanbul'da yapılması uzun bir süreç ve maliyet gerektirdiğinden bu tez çalışması İstanbul'un Avrupa yakasıyla sınırlandırılmıştır. İstanbul ili Avrupa yakasındaki farklı ilçelerden toplanan su örneklerinin analiz edilip bünyelerinde radon gazı barındırıp barındırmadığının tespit edilmesi, sonuçların ulusal ve uluslararası düzeyde yapılmış benzer çalışmalarla karşılaştırılması ve insan sağlığı için radyolojik açıdan bu suların güvenli olup olmadığının belirlenmesi çalışmanın motivasyonunu oluşturmaktadır. Bu tez çalışmasında İstanbul'un Avrupa yakasında tespit edilen elli farklı noktadan, farklı zamanlarda toplanan su numunelerinin (doğal kaynak suları, çeşme suları, dere yatakları, bentler, barajlar, göletler…gibi) içerisinde çözünmüş halde olan radon (Rn-222) gazı konsantrasyonları RAD-7 elektronik radon ölçüm dedektörü kullanılarak Sakarya Üniversitesi Nükleer Fizik Laboratuvarında ölçülmüştür. Ölçüm sonuçları Dünya Sağlık Örgütü (DSÖ) ve literatürdeki benzer çalışmaların verileriyle karşılaştırılmıştır. Ölçülen ortalama radon konsantrasyonlarına bağlı olarak bu suların kullanımından kaynaklı her bir numune için insan vücuduna etki eden yıllık efektif dozlar hesaplanarak, ulusal ve uluslararası çalışmalarla karşılaştırılmıştır. Ölçümü yapılan numunelerdeki maksimum radon aktivitesi 48,986 Bq/L, minimum radon aktivitesi 0,144 Bq/L ve ortalama radon aktivitesi 11,035 Bq/L olarak tespit edilmiştir. Bu suların kullanımı ve içilmesinden kaynaklı hesaplanan efektif dozların yetişkinler için; 0,25 μSv/y ile 85,72 μSv/y aralığında, çocuklar için; 0,262 μSv/y ile 89,15 μSv/y aralığında, bebekler için ise; 0,50 μSv/y ile 169 μSv/y aralığında değiştiği bulunmuştur. Elde edilen tüm doz sonuçlarına göre, bebeklerde doz alımı yetişkin ve çocuklardan daha yüksek çıkmıştır. Yetişkin ve çocuklar için hesaplanan tüm yıllık etkin doz sonuçları, DSÖ tarafından önerilen yıllık efektif doz 100 μSv/y değerinin altında iken birkaç numunede bebekler için hesaplanan dozların bu limit değeri aştığı gözlenmiştir. Sonuç olarak, içme suyu olarak kullanılan farklı türdeki sularda (yeraltı suları, baraj, gölet, doğal kaynak suları) radon kaynaklı radyolojik risk düzeyinin düşük olduğu tespit edilmiştir.

The main purpose of this thesis is to evaluate the radiological effects and risks that the measured radon concentrations of the water samples in the study area may cause on the people of the region according to their intended use. Considering that Istanbul is the locomotive of our country with its population, industrial activities and every aspect, it has been a necessity to carry out environmental radiation analyzes and follow up regularly. In this thesis study, it is also aimed to make an important contribution to the literature with radon measurements in water samples. Since it requires a long process and cost to carry out these researches in all of Istanbul, this thesis study is limited to the European side of Istanbul. The motivation of the study is to analyze the water samples collected from different districts on the European side of Istanbul and to determine whether they contain radon gas, to compare the results with similar studies conducted at national and international level and to determine whether these waters are safe for human health in terms of radiology. As a result of the existence of the universe and the world, which is our planet, there are a number of elements that they contain within their bodies. Some of these elements have radioactive properties. These radioactive elements transfer the radiation in their bodies to the environment by radiating after a certain period of time. Radioactive elements on Earth emit radiation into the soil, subsurface waters and the earth's surface. The radioactive effect emitted by the universe due to the cosmic elements it possesses is the water resources on the earth and on the surface with the air and the rains; they reach open waters such as lakes, streams, dams, seas, etc. The radionuclides and radioactive potassium in the natural radioactive series of uranium and thorium are the main source of natural radioactivity in waters, especially groundwater. When the concentrations of activity of these radionuclides are above the normal value, drinking and utility water distributed from sources fed from groundwater can increase the radiation dose to which humans are exposed. When soil and rocks containing even small amounts of uranium interact with surface and groundwater, it is not surprising that we encounter radon in the water we drink or use. Radon gas is a radioactive element that has no color, smell or taste, is included in the noble gases class of the periodic table with the atomic number 86, and is formed as a result of the radioactive decay of natural uranium in rock, soil and water. Uranium and its decay products can be found in nature in different concentrations. For this reason, radon can pass through all surfaces, rocks, water, soil fragments and building materials containing uranium or radium (226Ra), which is a decay product, into the environment. In this thesis study, water samples collected at different times from fifty different points identified on the European side of Istanbul (natural spring waters, tap waters, stream beds, embankments, dams, ponds... The concentrations of radon (Rn-222) gas dissolved in it were measured at Sakarya University Nuclear Physics Laboratory using RAD-7 electronic radon measurement detector. The measurement results were compared with the data of similar studies in the World Health Organization (WHO) and the literature. Depending on the measured average radon concentrations, the annual effective doses affecting the human body for each sample resulting from the use of these waters were calculated and compared with national and international studies. The maximum radon activity in the measured samples was 48.986 Bq/L, the minimum radon activity was 0.144 Bq/L and the mean radon activity was 11.035 Bq/L. Radon is an element with a low reactivity value. Therefore, it cannot bind chemically to the tissues by inhalation. In addition, its resolution in textures is also very low. Only radon and its decay products can be transported to the lungs by respiration by attaching to dust and other particles and forming radioactive aerosols. The decay products continue to decay, releasing radiation, until they become stable. With the formation of decay in the respiratory tube, the dose of radiation in the bronchial epithelium increases. The biological effects of alpha radioactivity are important because some of the decay products are alpha emitters. To put it another way, radon gas molecules in soil and water emit into the air as time goes on. These radon gas molecules that enter the air combine with statically charged particles suspended in the air and are taken into the body by respiration. These particles, which are taken into the body through the air, adhere to the inner surface of the lung and disrupt the DNA chain in the lung tissue and cause damage to the lungs and various organs and therefore cancer over time. Within the scope of our thesis, it was found that the effective doses calculated from the use and drinking of the measured waters ranged from 0.25 μSv/y to 85.72 μSv/y for adults, in the range of 0.262 μSv/y to 89.15 μSv/y for children, and from 0.50 μSv/y to 169 μSv/y for infants. According to all the dose results obtained, dose intake in infants was higher than in adults and children. All annual effective dose results calculated for adults and children were below the WHO recommended annual effective dose value of 100 μSv/y, while in a few samples the calculated doses for infants exceeded this limit value. As a result, it was determined that the level of radiological risk due to radon was low in different types of water used as drinking water (groundwater, dam, pond, natural spring water). As a result of drinking water containing radon and inhaling radon gas released into the air from these waters, various organs of the body are also affected by this situation. Inhaled radons interact with the lungs and used radons interact with the stomach, large intestine, gonads (ovaries), liver, kidneys and skin, causing damage. The doses to which the stomach and large intestine are exposed due to drinking the measured waters range from 0.004 μSv/y to 1.234 μSv/y, with average doses of 0.278 μSv/y. The doses to which the liver is exposed due to the consumption of measured waters range from 0.006 μSv/y to 2.057 μSv/y, with an average dose of 0.463 μSv/y, the doses to which the ovaries (gonads) are exposed vary between 0.002 μSv/y and 0.512 μSv/y, and the average dose is calculated as 0.116 μSv/y. The doses to which the kidneys are exposed as a result of the inhalation of the measured water into the air and the inhalation of this radon air vary between 0.018 μSv/y and 6.172 μSv/y and the average dose is calculated as 1.390 μSv/y. When the annual effective doses to which the organs are exposed are compared, respectively, from high dose to down; lungs-kidneys-gonads-stomach and colon-skin. The total dose received by all organs has an average value of 5.886 μSvy‐1 and ranges from 0.077 μSv/y to 26.129 μSv/y. Therefore, the total dose amounts affecting the body organs calculated for the samples taken were lower than the threshold value recommended by the WHO World Health Organization (100 μSv/y).