Articles
WATER CONTENT DETERMINATION WITH TDR IN PEAT SUBSTRATES
Article number
644_42
Pages
313 – 317
Language
English
Abstract
With Time Domain Reflectometry (TDR) equipment it is possible to determine the water content in substrates and soils.
In contrast to gravimetrical water content measurement, TDR represents a non-destructive way for water content determination appropriate for both substrates and soils.
This method is based on the fact that the dielectric constant is directly proportional to the water content in a material.
For transferring dielectric constant values to water content values, calibration equations are used.
Results from two of our equations as well as one developed in Finland and one in Poland were evaluated using gravimetrically determined water content.
Using PVC ring cylinders with high humified sphagnum peat at normal and hard compaction, the equations were evaluated at the container capacity for different layers.
For the normal compacted cylinder, we overestimated with the Polish equation for the different layers and slightly underestimated with our equation.
At hard compaction, the Polish equation gave an overestimation and our equation an underestimation for the water content.
The relevance for use of TDR-equipment in a wide water content interval was studied in two evaporation experiments with normal compacted low humified sphagnum peat in pots.
The equations showed with one exception an underestimation for water content values over 20% and an overestimation for water content under 20%.
In contrast to gravimetrical water content measurement, TDR represents a non-destructive way for water content determination appropriate for both substrates and soils.
This method is based on the fact that the dielectric constant is directly proportional to the water content in a material.
For transferring dielectric constant values to water content values, calibration equations are used.
Results from two of our equations as well as one developed in Finland and one in Poland were evaluated using gravimetrically determined water content.
Using PVC ring cylinders with high humified sphagnum peat at normal and hard compaction, the equations were evaluated at the container capacity for different layers.
For the normal compacted cylinder, we overestimated with the Polish equation for the different layers and slightly underestimated with our equation.
At hard compaction, the Polish equation gave an overestimation and our equation an underestimation for the water content.
The relevance for use of TDR-equipment in a wide water content interval was studied in two evaporation experiments with normal compacted low humified sphagnum peat in pots.
The equations showed with one exception an underestimation for water content values over 20% and an overestimation for water content under 20%.
Authors
G. Kritz, T. Khaled
Keywords
evaporation, compaction, calibration equation
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