برآورد نرخ فرسايش بادي با استفاده از تكنيك سزيم- 137 در منطقه شرق اصفهان

چكيده انگليسي :

87 Using the 137Cs Technique to Estimate Wind Erosion Rate in the East of Isfahan Fateme Ghaysari f ghisari65@yahoo com December 9 2013 Department of Soil Science IsfahanUniversity of Technology Isfahan 84156 83111 Iran Language Farsi Degree M Sc S Ayoubi Assoc Prof Supervisor Ayoubi@cc iut ac ir Abstract Wind erosion is one of the most basic processes of land degradation and one of the most seriously environmental concents in the arid and semi arid regions The ratio of surface area affected by wind erosion in Iran is more than 6 times the global average Thus it is crucial to control wind erosion in the arid regions of Iran as the most serious environmental problem In this study 137Cs technique has been used to estimate the rates of soil wind erosion 137Cs is an artificial radionuclide with a high gamma radiation and half life of 30 2 years which was released into the environment as a result of nuclear weapons tests primarily during the 1950 1970 137Cs fallout reaches the earth s surface mostly as a result of precipitation and is strongly and rapidly adsorbed by fine soil colloidal particles such as clay minerals and organic matter in the topsoil Chemical or biological removal of 137Cs from soil particles is limited and it is assumed that only physical processes moving soil particles such as soil erosion and tillage particle are involved in the 137Cs transport In the Segzi region in the East of Isfahan soil erosion rate have increased as a result of improper gypsum and clay mining operations Therefore the objective of this study to estimate wind erosion rates with 137Cs technique and also explore the correlation between physicochemical and magnetic susceptibility properties with 137Cs as an indicator of wind erosion along northeast southwest transect across the Segzi district east of Isfahan In this study Sixteen sites were selected along a northeast southwest transect with 42 km length and eighty soil samples were analyzed in for five depths 0 5 5 10 10 20 20 30 30 50 cm Additional 20 soil samples were collected from the reference site for soil loss and deposition calculations Soil samples were air dried in the laboratory and thoroughly sieved using a 2 mm sieve Sample weighing 500 g was then placed in Marinelli beakers and Sealed for 137Cs analysis by gamma ray spectroscopy Magnetic susceptibility at low frequency and magnetic susceptibility at high frequency were measured Magnetic susceptibility was measured at low frequency 0 46 kHz and high frequency 4 6 kHz using a Bartington MS2 dual frequency sensor The results of correlation analysis showed that among of all physic chemical and magnetic properties there were significant positive correlations between soil clay content r 0 63 silt content soil r 0 5 soil organic matter r 0 63 total N r 0 83 the magnetic susceptibility at high frequency r 0 55 magnetic susceptibility at low frequency r 0 6 and magnetic susceptibility at dependent frequency r 0 5 with 137Cs inventory There were significant negative correlations between Sand content r 0 55 pH r 0 7 and 137Cs inventory The results of 137Cs calculations showed that the often studied sites mainly in the northern part of transect showed erosion rates ranging from 12 90 46 86 t ha 1yr The major affecting soil erosion process in north of the studied transect is associated dominantly with occurrence of improper gypsum mining operations and human activities In the southern part of transect deposition rates of 7 21 7 64 t ha 1yr was observed presumably influenced by increasing plant cover The results of the present study derived from 137Cs for the first time in Iran for wind erosion assessments had significant implications for further researches in arid region of Iran Keywords Wind erosion deposition Cesium 137 and Magnetic Susceptibility

قيصري، فاطمه

برآورد نرخ فرسايش بادي با استفاده از تكنيك سزيم- 137 در منطقه شرق اصفهان

رسوب , 137 و پذير رفتاري مغناطيسي