Using of cesium - 137 for the soil erosion and sedimentation process assessment

Soil erosion and the sedimentation of the eroded material in flood plain and water body represent a major problem in many parts of the world. Classical methods for erosion assessment have a lot of disadvantages that can be avoided by measurement of soil radionuclide content. Cs-137 monitoring for erosion and sedimentation assessment has the advantage of giving data about this phenomena mediated on a long time period. Cs-137 is a radioactive isotope with special chemical and physical characteristics that permit its use in long term investigation of the environment problems, especially in erosion and sedimentation process assessment. Cesium is strongly adsorbed on clay fraction of soil and for this reason the soil movement involves the cesium content too. Due to the nuclear tests in atmosphere done especially in the years '50 and the beginning of '60, but mainly due to the nuclear accident from Chernobyl in 1986, a great amount of Cs-137 was deposited on the Romanian territory. The deposition from nuclear test could be considered uniform over Romania, but the deposition of Cs-137 originating from Chernobyl accident was extremely non-uniform because of meteorological conditions from the spring of 1996, when many local rains were registered. In Romania there are several areas strongly affected by erosion especially in the central part of Moldavian Table Land, where many conservation actions were implemented to prevent the environment degradation. To characterize the inventory of Cs-137, samples of soil, sediment and water were taken. The investigated area is located in Moldavia; samples were collected from Tutovei Hill, Moldavian Central Table Land and Moldavian Plain. The erosion rates on the investigated agricultural terraces (located far away from the top of the slope) are high, up to 2 cm/year. The sedimentation has also high values in these areas ranging from 2 to 4 cm/year. (authors)