تخمين نرخ مكاني فرسايش و رسوب با تكنيك سزيم-137 با استفاده از روش زمين آمار روي يك شيب تپه مركب در منطقه اردل استان چهارمحال بختياري

چكيده انگليسي :

Spatial Prediction of Soil Loss and Deposition on a Complex Hillslope Using 137Cs Inventory and Geostatistic in Ardel District Chaharmahal Bakhtiari Province Farideh Abbaszadeh Afshar aafshar farideh@yahoo com 2009 2 28 Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiDr A Jalilian jalalian@cc iut ac irDr H Khalafi hkalafi@aeoi org irAbstractSoil erosion and sediment deposition represent serious problems in the world Several quantitative andqualitative techniques have been developed and used to measure soil erosion and deposition throughout theworld However most of them do not produce the spatial patterns of soil redistribution within the fields tounderstand soil loss Understanding of the spatial distribution of soil erosion and deposition within acatchment is important for designing soil and water conservation measures Use of nuclear techniques inerosion monitoring and especially for qualification of soil loss has offered a fast and economical tool toestimate erosion rate 137Cs is an artificial radionuclide with a half life of 30 12 years which released into theenvironment as a result of nuclear weapons test primarily during the period of 1950s 1970s with themaximum rate of 137Cs fallout from atmosphere in 1963 137Cs fallout is strongly and rapidly adsorbed by fineparticles as by clay minerals and organic mater in the topsoil Chemical or biological removal of 137Cs fromsoil particles is negligible and it is assumed that only physical processes soil redistribution soil erosion andtillage practice are involved in 137Cs transport In the study area soil erosion rates have increased greatly overnatural rates as a result of human activities Deforestation over grazing changes in land use and non sustainable farming practices are main concerns of land degradation by human activity in the study Thereforeresearch objectives were to establish the spatial variability of cesium and to map the pattern of 137Csredistribution using geostatistics and variography and to establish soil redistribution rate at the complex hillslope in the west of Iran Chahar Mahal Bakhtieari province 90 soil sample sites were surveyed with aTheodolite and in a grid pattern with 20 m distances The dried soil samples sieved to pass through a 2 mmscreen and were placed in Marinelli beakers and sealed for 137Cs analyses The 137Cs activity Bq kg 1 wasmeasured by gamma spectroscopy with a high resolution germanium detector Spatial correlation analyses of137 Cs redistribution were performed with version 5 1 of GS software and the different geostatisticalparameters and the fitted model were introduced in the SURFER8 Software to produce a map of the spatialdistribution of 137Cs and soil redistribution The results of study showed that the mean erosion rate in thestudied field estimated about 20 9 t ha 1 year 1 by applying the proportional model Whereas the simplifiedmass balance model calculated soil erosion rate approximately 29 8 t ha 1 year 1 The estimates of net soil lossobtained for proportional and mass balance 6 3 t ha 1 year 1 and 8 t ha 1 year 1 respectively Geostatisticalanalytical according to soil properties and 137Cs contents within the firld showed that spherical model wasfitted to OM total N 137Cs content K EC and pH Moreover exponential model was fitted to CCE and Bd 137 Cs distribution within the field prepared using block kriging using prepared 137Cs map Map of soilredistribution based on mass balance analysis was constructed Visual incorporation of soil redistribution mapindicated that footslope and toeslope position showing soil deposition At some downslope parts of the fieldobserved the soil erosion due to tillage practices The highest soil erosion rate was observed in shoulderposition Since the selected hillslope is a complex hillslope soil erosion and soil deposition are occurred inupslope and midslope synchronously Soil loss has been declined in same parts of the upslope because ofhawing

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تخمين نرخ مكاني فرسايش و رسوب با تكنيك سزيم-137 با استفاده از روش زمين آمار روي يك شيب تپه مركب در منطقه اردل استان چهارمحال بختياري

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