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| Titel |
Multiscale characterization of pore size distributions using mercury porosimetry and nitrogen adsorption |
| VerfasserIn |
J. Paz-Ferreiro, A. M. Tarquis, J. G. V. Miranda, E. Vidal Vázquez |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030396
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| Zusammenfassung |
| The soil pore space is a continuum extremely variable in size, including structures smaller
than nanometres and as large as macropores or cracks with millimetres or even centimetres
size. Pore size distributions (PSDs) affects important soil functions, such as those related with
transmission and storage of water, and root growth. Direct and indirect measurements
of PSDs are becoming increasingly used to characterize soil structure. Mercury
injection porosimetry and nitrogen adsorption isotherms are techniques commonly
employed for assessing equivalent pore size diameters in the range from about 50 nm to
100 μm and 2 to 500 nm, respectively. The multifractal formalism was used to
describe Hg injection curves and N2 adsorption isotherms from two series of a
Mollisol cultivated under no tillage and minimum tillage. Soil samples were taken
from 0-10, 10-20 and 20-30 cm depths in two experimental fields located in the
north of Buenos Aires and South of Santa Fe provinces, Argentina. All the data
sets analyzed from the two studied soil attributes showed remarkably good scaling
trends as assessed by singularity spectrum and generalized dimension spectrum.
Both, experimental Hg injection curves and N2 adsorption isotherms could be fitted
reasonably well with multifractal models. A wide variety of singularity and generalized
dimension spectra was found for the variables. The capacity dimensions, D0, for
both Hg injection and N2 adsorption data were not significantly different from
the Euclidean dimension. However, the entropy dimension, D1, and correlation
dimension, D2, obtained from mercury injection and nitrogen adsorption data showed
significant differences. So, D1 values were on average 0.868 and varied from 0.787 to
0.925 for Hg intrusion curves. Entropy dimension, D1, values for N2 adsorption
isotherms were on average 0.582 significantly lower than those obtained when
using the former technique. Twenty-three out of twenty-four N2 isotherms had D1
values in a relatively narrow range, from 0.518 to 0.666, but the remaining one
exhibit a rather large D1 value of 0,992. The entropy dimension, D1, is a measure of
diversity, so that it gauges the concentration degree of the pore size distribution
on a specific pore size range. Therefore, Hg injection curves indicate a relatively
homogeneous pore size distribution in the diameter range from 50 nm to 100 μm. In
contrast, except for one of the studied samples, D1 values for N2 adsorption isotherms
reflected clustering and indicated that most of the measure concentrates in a small size
domain. The significance of multifractal indices for assessing differences in pore size
distributions of the two study soil series under no tillage and minimum tillage was
discussed.
Acknowledgements. This work was financed by MEC (Spain) under project
CGL2005-08219-C02-01. |
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