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| Titel |
Testing the ISP method with the PARIO device: Accuracy of results and influence of homogenization technique |
| VerfasserIn |
Wolfgang Durner, Magdalena Huber, Li Yangxu, Andi Steins, Thomas Pertassek, Axel Göttlein, Sascha C. Iden, Georg von Unold |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145477
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| Publikation (Nr.) |
 EGU/EGU2017-9422.pdf |
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| Zusammenfassung |
| The particle-size distribution (PSD) is one of the main properties of soils. To determine the
proportions of the fine fractions silt and clay, sedimentation experiments are used. Most
common are the Pipette and Hydrometer method. Both need manual sampling at specific
times. Both are thus time-demanding and rely on experienced operators. Durner et al.
(Durner, W., S.C. Iden, and G. von Unold (2017): The integral suspension pressure
method (ISP) for precise particle-size analysis by gravitational sedimentation, Water
Resources Research, doi:10.1002/2016WR019830) recently developed the integral
suspension method (ISP) method, which is implemented in the METER Group
device PARIOTM. This new method estimates continuous PSD’s from sedimentation
experiments by recording the temporal evolution of the suspension pressure at a certain
measurement depth in a sedimentation cylinder. It requires no manual interaction after start
and thus no specialized training of the lab personnel. The aim of this study was
to test the precision and accuracy of new method with a variety of materials, to
answer the following research questions: (1) Are the results obtained by PARIO
reliable and stable? (2) Are the results affected by the initial mixing technique to
homogenize the suspension, or by the presence of sand in the experiment? (3) Are the
results identical to the one that are obtained with the Pipette method as reference
method?
The experiments were performed with a pure quartz silt material and four real soil
materials. PARIO measurements were done repetitively on the same samples in a
temperature-controlled lab to characterize the repeatability of the measurements.
Subsequently, the samples were investigated by the pipette method to validate the results. We
found that the statistical error for silt fraction from replicate and repetitive measurements was
in the range of 1% for the quartz material to 3% for soil materials. Since the sand fractions, as
in any sedimentation method, must be measured explicitly and are used as fixed parameters in
the PARIO evaluation, the error of the clay fraction is determined by error propagation from
the sand and silt fraction. Homogenization of the suspension by overhead shaking gave lower
reproducibility and smaller silt fractions than vertical stirring. However, it turned
out that vertical stirring must be performed with sufficient rigour to obtain a fully
homogeneous initial distribution. Analysis of material sieved to < 2000 μm and to < 200
μm gave equal results, i.e., there was no hint towards dragging effects of large
particles. Complete removal of the sand fraction, i.e. sieving to < 63 μm lead to
less silt, probably due to a loss of fine material by the sieving process. The PSD’s
obtained with the PARIO corresponded very well with the results of the Pipette
method. |
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