Türkiye’de Üretilen Tütün Ürünlerinde 210pb Ve 210po Radyoaktivite Seviyelerinin ve Maruz Kalınan Radyasyon Dozunun Araştırılması - 210pb Uzaklaştırılması İçin Adsorbent Geliştirilmesi

Abstract

Lead-210 (210Pb) and polonium-210 (210Po) are the natural radioisotopes of the uranium-238 (238U) decay chain. They are released into air by the emanation of radon-222 (222Rn), a radioactive nobel gas in 238U decay chain, from soil through fissures. Since 210Pb and 210Po have very long half lifes, they maintain in water, soil, plant and other environmental samples. The major sources of enhanced natural radioactivity are mining activities, combustion of coal and fossil fuels and other energy production such as geothermal energy, and the use of phosphate rock. The enhancement of the natural radioactivity means the enhancement of the 210Pb and 210Po amounts in the environment which increases the radioation dose the people are exposed to. In this study, the activity values of 210Pb and 210Po in the tobacco samples have been measured. The radiation dose to which a smoking person is exposed to originating from 210Pb and 210Po activities have been calculated in a defined scenario. The tobacco samples were subjected to a series of complicated radiochemical processes to become ready to measure the 210Pb and 210Po activities in the measurement systems. These processes are mainly solving the sample and the radiochemical separation of the radioisotopes. In this study, two different methods have been applied to dissolve the tobacco samples. The first method was dissolving of the samples by acid mixture, and the second was dissolving of the samples by leaching. After the dissolving procedures of samples were completed the radiochemical separation of 210Pb and 210Po radioisotopes were performed by using Sr-resin. The adsorption of 210Po obtained at the end of radiochemical separation onto the silver disc was performed during 4 hours at 90 °C. The silver disc then was washed with distilled water and put in the alpha spectrometer to measure the 210Po activity. The adsorbed 210Pb on the Sr-resin at the end of the radiochemical separation was poured off from the column by various chemical processes. By adding sulphuric acid (H2SO4 (aq)) solution and then heating on a magnetic mixer lead (II) sulphate (PbSO4(k)) residue was gained. After a series of chemical processes applied, the (PbSO4(k)) residue was completely dried and the amount of the residue was weighted to determine the chemical efficiency for 210Pb. The prepared sample was waited for during about one month in a desiccator for the 210Pb/(Bismuth-210) 210Bi radioactive equilibrium and then measured by proportional counter to determine the 210Pb activity. In the tobacco samples collected from the 11 different regions of Turkey, the 210Po activity concentrations were determined between 10.54 ± 1.01 Becquerel (Bq) kg-1 and 31.05 ± 1.71 Bq kg-1, and the 210Pb activity concentrations were determined between 12.60 ± 1.01Bq kg-1 and 31.30 ± 1.71 Bq kg-1. The radiation dose to which a cigarette smoker in one package (20 cigarettes) per day was exposed to radioisotopes 210Pb and 210Po was calculated. By considering the stored percentage of 210Po and 210Pb in lung, it is estimated that a person smoking 20 cigarettes in a day will expose to 68.19 μ(Sievert)Sv year -1 and 24.45 μSv year-1 average dose caused by 210Po and 210Pb, respectively. Two adsorbents have been synthesized as an alternative to Sr-resin to be used to determine 210Pb activity. Sodium alginate, which is a cheap and easily available was used to prepare two different adsorbents. Sodium alginate (NaAlg)/Acrylamide (AAm) and NaAlg / Calcium chloride (CaCl2) materials have been prepared by using gamma -radiation. The usability of the prepared adsorbents to adsorb and analyze 210Pb was investigated. The optimum adsorption conditions of the lead ions by CaAlg were determined as 60 mg L-1 initial concentration, 100 mg adsorbent amount, 6 pH value at 60 °C for 120 minutes agitation time. The optimum adsorption conditions of the lead ions by (NaAlg/AAm)IPN were determined as 75 mg L-1 initial concentration, 300 mg adsorbent amount, 7 pH value at 40 °C and 240 minutes agitation time. The desorption efficiencies of lead from CaAlg ve (NaAlg/AAm)IPN by using 1.0 M (HNO3 (aq)) for 25 mL solution volume and at 30 °C at the end of 2 hours were determined as 96% and 85%, respectively. In the desorption studies, the adsorbed lead amounts were 72 mg mL-1 in 100 mg CaAlg and 58,6 mg mL-1 in 300 mg (NaAlg/AAm)IPN. The spectroskopic and thermal characterizations of CaAlg and (NaAlg/AAm)IPN were also performed by using FTIR and TGA technigues. The thermodynamical parameters of (ΔG°, ΔH° and ΔS°) the processes of Pb2+ ion adsorption by CaAlg and (NaAlg/AAm)IPN polymers have been calculated. The applications to the Langmuir and Freundlich adsorption isoterms at 25 °C (for CaAlg) and at 30 °C (for (NaAlg/AAm)IPN) have been analyzed.