ارزيابي توزيع مجدد خاك در اراضي تپه ماهوري كشت شده با استفاده از تكنيك هاي سزيم-137 و پذيرفتاري مغناطيسي در منطقه چلگرد استان چهارمحال و بختياري

چكيده انگليسي :

Soil Redistribution Assessment in Cultivated Hilly Regions Using Magnetic Susceptibility and 137Cs Techniques in Chehlgerd Region Chahrmahal Bakhtiari Province Mohammad Ahmadi Mohamadahmady46@yahoo com 2011 3 7 Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiDr S Ayoubi ayoubi@cc iut ac irDr H Khalafi khalafi@aeoi org irAbstractAccelerated soil erosion on cultivated lands is a serious global problem especially in hilly regions with undulatingtopography Soil erosion not only results in on site soil degradation but also leads to off site problems related to downstreamsedimentation as well as surface and ground water pollution It reduces soil productivity as result of loss of soil organic carbonand plant nutrients There are two general approaches for assessing the spatial characteristics of sediment flux on hill slopes The first is the use of soil morphology information such as observations of buried A horizons or profile truncation todetermine net gain or loss at a point The second general approach is the use of radionuclide tracer inventories relative toknown fallout which may be used to quantify the accumulation or loss of soil to which the radionuclide is adsorbed 137Cs half life of 30 2 years deposited on land became tightly adsorbed to soil fine particles as by clay minerals and organic matterand was concentrated in the surface layer Its subsequent vertical and lateral redistribution are controlled by the erosion transport and deposition of soil and sediment particles Magnetic techniques provide a rapid sensitive way to characterizesediments in aquatic environments and have also been used to study soil erosion and trace topsoil movement on a hill slope In the Chehlgerd region of Chahrmahal Bakhtiari Province soil erosion rates have increased greatly over natural rates as aresult of human activities Therefore the objective of this study was to evaluate the efficacy of magnetic measurements forassessing soil redistribution by comparing with Cs 137 technique results Also comparison of simple mass balance andproportional models was the other goal of this research The selected study area was located at hilly region of Chelgerd Charmahal Bakhtiari province in west of Iran At first the digital elevation model DEM was derived from theinterpolation of topographic map Then primary and secondary topographic attributes were extracted from the DEM byTopographic analysis system TAS software Based upon the landform features ten transects were established and in fiftypoints from two depths 0 30 and 30 50 cm one hundred samples were collected in an area of 50 cm2 Also in the sevenpoints in reference site the sampling was done with 5 cm increments to 40 cm soil depth The dried soil sample were sievedto pass through a 2 mm screen after 2mm fine earth was weighed about 500 g for 137Cs analyses by gamma ray spectroscopy In this study a set of environmental magnetic parameters including magnetic susceptibility at low frequency lf saturationisothermal remanent magnetization SIRM isothermal remanent magnetization IRM 100mT were measured Magneticsusceptibility was measured at low frequency 0 47 kHz lf and high frequency 4 7 kHz using a Bartington MS2 dualfrequency sensor The results of study showed that among of all physicochemical and magnetic properties the availablepotassium and magnetic susceptibility at low frequency r 0 58 had the highest correlation with 137Cs inventory withcoefficient of 0 58 for both In multivariate regression analysis the available potassium and magnetic susceptibility at lowfrequency were introduced as independent variables for regression model r 0 78 The results emphasized that in order toestimation of soil erosion and redistribution the use magnetic susceptibility solely could not explain all the variability Using137 Cs technique maximum average soil loss 57 6 t ha 1 year 1 and deposition 75t ha 1 year 1 were observed in the shouldersand toe slopes positio

احمدي، محمد

ارزيابي توزيع مجدد خاك در اراضي تپه ماهوري كشت شده با استفاده از تكنيك هاي سزيم-137 و پذيرفتاري مغناطيسي در منطقه چلگرد استان چهارمحال و بختياري

فرسايش خاك , نانو ذرات مگنتيت و مگهميت