Penilaian tabur-semula tanih di tanah pertanian menggunakan isotop sekitaran caesium-137

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Date
2002-10
Authors
Othman, Zainudin
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Abstract
Environmental radionuclides have the potential to be used to trace sediment movements. Caesium-131 ( 131 Cs), a radionuclide released during nuclear weapon tests from I 950 's to 1960's is strongly adsorbed on to clay. It enters the Jvfalaysian environment through cold continental polar (cPk) air mass circulation and Hadley cell effects from the higher latitude regions, converged during Inter-tropical Convergence Zones (ITCZ) oscillation and deposited through precipitation on to the soil as fallouts. Its content in the soil profile has been used to estimate soil loss due to water erosion in agricultural/and. Two soil sampling methods, incremental and bulk sampling. were adopted to collect samples from the erosion plot and reference sites to a depth of 40cm for the determination of 137 Cs inventories. The soil depthprofile of 137 Cs inventory at an undisturbed site exhibits an exponential function with most of the contents are accumulated l'r"ithin the upper I 2 em portion of the soil profile ll:lzereas in the disturbed sites the 137 Cs content were partially mixed within the plough layer. The average 137 Cs reference inventory from two different locations was 580.7 Bq/m2 while loca/ 131Cs reference inventory was 55I.9 Bqlm2 . The USLE, Ritchie's equation and three mathematical models were used to estimate the rate of soil loss. The Proportional Model was found suitable to be used in this environment. Net soil/ass from the study slope was estimated at 7.9 tonlhalyr and is in good agreement with the value estimated by the USLE of 4.34 tonlhalyr. The soil redistribution patterns show that the upper and middle slopes had been eroded while deposition was observed at the foot slope. The maximum landform evolutions of the eroded areas was 4.5mm/yr and 0.5mmlyr for the depositional areas. The long-term erosion rate of the study area was considered low.
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Tabur-semula tanih , Isotop sekitaran caesium-137
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