اندازه‌گيري عنصر سزيم-137 در نمونه‌هاي طبيعي خاكي جهت بررسي فرسايش خاك

چكيده انگليسي :

Measurement of the element Cesium 137 in natural soil samples for investigating soil erosion Mehdi Moghni mehdi nucl@gmail com Date of Submission March 03 2018 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiAbstractSoil is one of the main national wealth of each country which the serious planning must be taken topreserve it Growing populations and foods demand in the recent years have led farmers to exploitmarginalized lands such as forests and pastures in different countries This is while marginal lands withhigh erosion potential have low production potential Over the past few decades surface erosion hascaused many obvious and hidden problems that need research and scientific planning in order to preventthis destructive process Researchers from all over the world have been seeking from past times tocalculate erosion rates in different lands by using different methods The use of radioactive materials is aquick and economical tool for describing soil erosion Cesium 137 is a synthetic radioactive element witha half life of 30 2 years which wasreleasedto the earth atmosphere due to nuclear tests and explosionswith rainfall in the 1950s 1970s Fallen cesium 137 is highly adsorbed on clay and organic matter and isconcentrated in surface horizons Physical processes such as erosion and tillage are the main reason forthe redistribution of cesium 137 in the soil Therefore by measuring the amount of cesium 137 in soilsamples annual soil erosion can be calculated This research was carried out with the main purpose ofmeasuring the activity of cesium 137 and soil erosion in soil samples collected from two hill slopes withpasture and agricultural application in Semirom south of Isfahan province Each hill has five differentpositioning slopes including summit shoulder back slope foot slope andtoe slope and in each position two depths of 0 15 and 15 30 cm were sampled by 20 to 20 cm cross sectional sampling High puritygermanium detector HPGe a multichannel analyzer and gamma vision software were used to determinethe radioactive elements of 20soil samples By using the cesium 137 method the average rate of soilerosion in agricultural application samples was found to be 105 62 ton per hectare per year and 63 33 tonper hectare per year in pasture application samples both of which are higher than the mean rate of naturalsoil erosion 20 tons per hectare per year due to wind rain and flood Therefore it is necessary to considermeasures such preventing of further agricultural use and grazing livestock in these areas Also in thisstudy the concentrations of natural radionuclides such as uranium 238 thorium 232 potassium 40 andradium 226 in soil samples were measured According to the measurements it was found that theconcentration of the above mentioned radioactive elements were in the range of 13 63 to 29 29 14 11 to28 68 255 14 to 639 22 and 44 92 to 79 49 Becquerel per kilogram respectively that all of these values are withinnatural limits

مقني، مهدي

اندازه‌گيري عنصر سزيم-137 در نمونه‌هاي طبيعي خاكي جهت بررسي فرسايش خاك

عنصر سزيم , پرتوهاي گاما و ايكس , پرتوزايي , واپاشي پرتوزا , مدل بيلان