Mabit,L., Klik,A., Benmansour,M., Toloza,A., Geisler,A. and Gerstmann,U.C.(2009): Assessment of erosion and deposition rates within an Austrian agricultural watershed by combining 137Cs, 210Pbex and conventional measurements. Geoderma, 150, 231-239.

『オーストリアの農業流域での137Csと210Pbeと従来測定法を併用した浸食と堆積速度の評価』


Abstract
 To control soil erosion and associated land degradation worldwide there is a need to assess the impact of major land use and the effectiveness of specific soil conservation technologies using various approaches. This study was conducted in an agricultural field at Mistelbach, Austria to assess the magnitude of deposition rates using Fallout Radio Nuclides ‘FRNs’ (137Cs and 210Pbex) and the mid-term (13 years) erosion rates using conventional runoff plot measurements in a small agricultural watershed under conventional and conservation tillage/cropping practices.
 Long-term erosion measurements (1994-2006) from runoff plots located in the upper part of an agricultural field just up-slope from a deposition area reached 29.4 t ha-1 yr-1 from the conventional tilled plot, 4.2 t ha-1 yr-1 from the conservation tillage plot and 2.7 t ha-1 yr-1 from the direct seeding treatment. Soil losses were reduced significantly by a factor of 10 using no tillage, direct seeding treatment.
 Using 137Cs data that integrate the 1954-2007 period, the sedimentation rates down slope of the field containing the runoff plots were estimated to be 26.1 t ha-1 yr-1 using the 137Cs depth distribution profile and at 20.3 t ha-1 yr-1 using the Mass Balance Model 2 (MBM 2). The erosion rates under conventional tillage are in agreement with the sedimentation rates estimated down slope of the field by the 137Cs depth distribution profile and MBM 2. In the lowest part of the watershed sedimentation rates of up to 50.5 t ha-1 yr-1 were estimated through the 137Cs depth distribution profile. These rates were greater than the average erosion rates measured by the erosion plots because this area is more representative of sedimentation processes occurring in the study area due to its topographical position and the basin geomorphology. The 210Pb data obtained did not fulfill the requirements for the successful application of the methodology under the experimental conditions.
 This study demonstrates the complementarities of both methodologies (137Cs and runoff plots) to assessing erosion and sedimentation processes in an agricultural landscape.

Keywords: Soil erosion; 137Cs; 210Pb; Erosion plots; Sedimentation rates; Erosion rates』

1. Introduction
2. Materials and methods
 2.1. Study area
 2.2. Runoff and erosion measurements using conventional erosion plots
 2.3. Soil sampling design in the reference site
 2.4. Laboratory analyses
  2.4.1. Samples pre-treatment, gamma spectrometry measurements
  2.4.2. Physiochemical analysis of the reference site soil
 2.5. Estimates of the 137Cs areal activity and conversion into soil redistribution
3. Results and discussion
 3.1. Erosion rates obtained with the conventional erosion plots
 3.2. Physiochemical characterization of the reference site and evaluation of the 137Cs baseline level
 3.3. 210Pb baseline level and test of the 210Pb methodology
 3.4. Assessment of soil deposition rates using 137Cs data
4. Conclusions
Acknowledgements
References


戻る