Volume 31, N. 3, September-December 2008 | PDF(2 downloads)
Erosion is the most harmful form of soil degradation, it affects plants’ productivity and causes severe environmental damage, such as sediment accumulation and pollution of water sources. With the purpose of obtaining significant information about losses and soil deposition on the Rio das Ondas basin, a study of the losses caused by erosion by means of cesium 137 (137Cs) concentration in the soil was conducted. Soil samples were collected for reference in four places, in vertexes and in the center of a triangle with five meters edges in a soil under native vegetation. Thus, samples in two perpendicular transects to the pendant were collected, one (transect A) under soy crops and another (transect B) under corn crops. The samples of the triangle’s vertexes and of the transects were collected at a depth varying from 0.00 m to 0.60 m, with intermission of 0.10 m between them and the samples collected in the triangle’s center varied between 0.00 m to a 1.00 m depth, distributed between layers from 0.05 m to 0.50 m and, from this value on, a sample at a 1.00 m depth was collected. After being air-dried, these samples were reduced to bran and passed through a 2 mm sieve, they were bagged and sent to Nuclear Physics Applied Laboratory (LFNA) of the State University of Londrina (UEL)” so as to analyze the 137Cs concentration in soil. The results obtained from the activity of 137Cs in the three places of the transects A and B varied between 0.14 e 0.42 Bq.kg-1 (soy crop) and between 0.12 and 0.24 Bq.kg-1 (corn crop), showing a variation of 137Cs according to the position of the place on the downgrade. It was observed in the results 22.52 t.ha-1.year-1 soil losses on the transect located in the soy crop (A) and 38.13 and 21.18 t.ha-1 .year-1 in the transect B located in the corn crop. These results indicate great deposition of sediments in the valley, mainly in the soil under soy crop.