Skip navigation
SuUB logo
DSpace logo

  • Home
  • Institutions
    • University of Bremen
    • City University of Applied Sciences
    • Bremerhaven University of Applied Sciences
  • Sign on to:
    • My Media
    • Receive email
      updates
    • Edit Account details

Citation link: https://nbn-resolving.de/urn:nbn:de:gbv:46-00103198-10
00103198-1.pdf
OpenAccess
 
copyright

Quantification of short-term erosion rates using the cosmogenic radionuclide Be-7


File Description SizeFormat
00103198-1.pdf21.66 MBAdobe PDFView/Open
Other Titles: Bodenerosions-Quantifizierung durch kosmogenisches Radionuklid Be-7
Authors: Jha, Abhinand 
Supervisor: Kirchner, Gerald 
1. Expert: Kirchner, Gerald 
Experts: Fischer, Helmut  
Abstract: 
ABSTRACT The fallout radionuclides 137Cs, 210Pbex are used widely for obtaining quantitative information on soil erosion and sediment redistribution rates within agricultural landscapes, over several spatial and temporal scales, and they are frequently seen to represent a valuable complement to conventional soil erosion measurement techniques. However, measurements of these radionuclides provide estimates of medium term (i.e. 40-100 years) soil erosion rates. The shorter-term perspective provided by the 7Be method has the potential to estimate soil erosion rates associated with individual events or short periods. The 7Be method has become increasingly relevant in an environment impacted by climate change, changing land use and other human activities. The present work establishes a mathematical model based on the physical processes of molecular diffusion and radioactive decay, to study the vertical behaviour of 7Be in soils. This model was further used to quantify erosion rates for 12 individual erosional events over a period of two years at our study site in Müncheberg, Germany. The scope of the model was explored analytically as well as numerically for Pulse-like fallout initial condition, zero concentration initial condition and exponential distribution initial condition. The model was fitted to more than 15 depth distributions and the resulting model parameter, effective diffusion coefficient D, is evaluated. In general diffusion coefficients estimated were of the order of 10-12 10-13 m2 s-1 for loamy to sandy soil types. Diffusion coefficients estimated for our study site were about 10-13 m2 s-1. The soil analyses indicate that the diffusion coefficient D is not merely a fitting parameter, but is related to the physico-chemical properties of radionuclide transport in soils. The erosion rates estimated at tilled and no-till plots at our study site were between < 0.001 - 4.7 ± 0.4 kg m-2 and 0.3 ± 0.5 kg m-2 - 2.0 ± 1.4 kg m-2 respectively. The magnitude of erosion rates estimated at the no-till plots was less than that at the tilled plots. The main conclusions of this work are: - The mathematical model developed during this study describes the transport of 7Be in soils. It is the first extensive model proposed so far that despite of its many simplifications, adequately represents the exponential distribution of 7Be profiles at disturbed and undisturbed or reference sites. - Main physical processes, which transport of 7Be in soil are, diffusion and radioactive decay. Migration parameters and measurements confirm that sorption is the main physical process, which confines 7Be concentration to soil surface. - Current erosion estimation methods with 7Be available in the literature for estimating erosion rates for single rainfall event was successfully modified to quantify erosion rates for multiple rainfall events. - Erosion rates estimated with 7Be technique were successfully used to differentiate between the rill-interrill, splash and surface erosion at the study plot. - The Diffusion model proposed in this study does not take into account the vegetation cover and thus overestimates the erosion rates or in some cases shows the occurrence of deposition on the plot.
Keywords: Soil erosion; Radionuclides in soil; Cosmogenic radionuclides; Beryllium-7; diffusion model
Issue Date: 4-Dec-2012
Type: Dissertation
Secondary publication: no
URN: urn:nbn:de:gbv:46-00103198-10
Institution: Universität Bremen 
Faculty: Fachbereich 01: Physik/Elektrotechnik (FB 01) 
Appears in Collections:Dissertationen

  

Page view(s)

257
checked on May 8, 2025

Download(s)

58
checked on May 8, 2025

Google ScholarTM

Check


Items in Media are protected by copyright, with all rights reserved, unless otherwise indicated.

Legal notice -Feedback -Data privacy
Media - Extension maintained and optimized by Logo 4SCIENCE