Inhaltszusammenfassung

1H NMR relaxometry is used in earth science as a non-destructive and time-saving method to determine pore size distributions in porous media. For its successful application in soil science, the comparison of pore size distribution determined from conventional methods is necessary. Pore size distributions of six disturbed soil samples with various textures and SOM content were determined by conventional soil water retention methods with matric potentials between -3 ...1H NMR relaxometry is used in earth science as a non-destructive and time-saving method to determine pore size distributions in porous media. For its successful application in soil science, the comparison of pore size distribution determined from conventional methods is necessary. Pore size distributions of six disturbed soil samples with various textures and SOM content were determined by conventional soil water retention methods with matric potentials between -3 and -390 kPa (pF 1.5 and 3.6, respectively). The results were used for the evaluation of 1H NMR relaxometry for the assessment of pore size distributions in soil samples. A new approach has been developed to transform transverse relaxation time (T2) distributions of water protons in soil samples at pF 1.5 into pore size distributions by estimating the transformation parameters (e.g. surface relaxivity) from T2 - distributions of soil samples at different matric potentials. The results show that the shape of T2 - distributions is strongly affected by soil texture, SOM content and soil matric potential. For the transformation of the relaxation time distributions, two surface relaxivities for relaxation time domains representing macropores and micro-/mesopores were needed for each soil sample. A good agreement between pore size distributions determined via conventional soil water retention and 1H NMR relaxometry was found. Therefore, 1H NMR relaxometry can now be used to determine pore size distributions in soil samples and further to study soil - water interaction like swelling of SOM and clay and its effects on the pore size distribution.» weiterlesen» einklappen

Autoren