Outline of an Automated System for the Quasi-Continuous Measurement of the Particle-Size Distribution.

Attila NEMES1, Imre CZINKOTA2, György CZINKOTA3, László TOLNER2 and Balázs KOVÁCS4

1 Research Institute for Soil Science and Agricultural Chemistry of the Hungarian Academy of Sciences, Herman Ottó u. 15., H-1525 Budapest, Hungary

2 Szent István University, Dept. of Soil Science and Agricultural Chemistry, Páter Károly u. 1., H-2103 Gödöllő, Hungary

3 ALTAIR Bt., Hegyalja u. 13, H-2151 Fót, Hungary

4 University of Miskolc, Dept. of Hydrogeology and Engineering Geology, H-3515 Miskolc-Egyetemváros, Hungary

Summary

Soil texture is an important input parameter for many soil hydraulic pedotransfer functions (PTFs) of the day. Common soil particle-size classes are required to be able to uniformly determine the texture of the soils. However, it is not always possible – due to different national classification systems – and much valuable information is disregarded while either deriving or applying PTFs.

One way to get common particle-size class information is to interpolate the particle-size distribution (PSD) curve. Advanced interpolation solutions are becoming available, but there is always uncertainty associated with these techniques. Another possibility is to measure all PSD curves in such a way that it is compatible to the commonly used classification systems.

A new automated measurement technique is introduced, that can easily provide PSD data compatible to any (and all) of the existing national and international classification systems at the same time, without the burden of extra labor. A computerized measurement system has been developed to record density changes in a settling-tube system in any discretional (small) time steps, which in turn allows the derivation of a quasi-continuous PSD curve. The measurement is based on areometry (Stokes-law), thus the system is compatible to the most commonly applied settling-tube measurements. The new evaluation method of measured values takes into consideration the density changes along the areometer–body so it avoids the problem of reference point determination. The theory and setup of the system are explained and measurement examples are given. The presented comparative measurements show excellent correspondence with conventional settling-tube results for various soil materials, and the reproducibility of the measurement shows to be very high.

Using this technique does not require more sample preparation than past methods. The automated reading requires less manpower to perform the measurement - which also reduces human error sources - but provides very detailed PSD data that has advantages like revealing multi-modality in the particle-size distribution – among others.