No abstract

The Hungarian Detailed Soil Hydrophysical Database, called MARTHA ver2.0 has been developed to collect information on measured soil hydraulic and physical characteristics in Hungary. Recently this is the largest detailed national hydrophysical database, containing controlled information from a total of 15,005 soil horizons. Two commonly used pedotransfer functions were tested to evaluate the accuracy of the predictions on the MARTHA data set, representative for Hungarian soils. In general, the application of both examined pedotransfer functions (Rajkai, 1988; Wösten et al., 1999) was not very successful, because these PTFs are representative for other soil groups. The classification tree method was used to evaluate the effect of soil structure on the goodness of estimations. It was found that using the soil structure data the inaccuracies of soil water retention predictions are more explainable and the structure may serve as a grouping variable for the development of class PTFs.

There are global aspirations to harmonize soil particle-size distribution data measured by the laser diffraction method and by traditional sedimentation techniques, e.g. sieve-pipette methods. The need has arisen therefore to build up a database, containing particle-size distribution values measured by the sieving and pipette method according to the Hungarian standard (sieve-pipette methods-MSZ) and the laser diffraction method according to a widespread and widely used procedure. In our current publication, 155 soil samples measured with sieve-pipette methods-MSZ and laser diffraction method (Malvern Mastersizer 2000, HydroG dispersion unit) were compared. Through the application of the usual size limits at the laser diffraction method, the clay fraction was under-and the silt fraction was overestimated compared to the sieve-pipette methods-MSZ results, and subsequently the soil texture classes were determined according to the results of both methods also differed significantly from each other. Based on our previous experience, the extension of the upper size limit of the clay fraction from 2 to 7 µm increases the comparability of sievepipette methods-MSZ and laser diffraction method, in this way the texture classes derived from the particle-size distributions were also more in accordance with each other. The difference between the results of the two kinds of particle-size distribution measurement methods could be further reduced with the pedotransfer functions presented. K e y w o r d s: laser diffraction, particle-size distribution, pedotransfer function, soil texture triangle

Results of the performed preliminary particle size determination (PSD) experiments of soils show the importance of the preparation details of the laser diffractometer method (LDM). The analysis of the effect of each preparation factor on soil PSD data calls attention to the need for working out standard instructions defining the pre-treatments and settings for the LDM instrument. Further laboratory experiments involving larger soil datasets are required for the better understanding of the effects of soil pre-treatments and settings on PSD data. There is a practical reason of substituting the time-consuming pipette method with the LDM. In case of this substitution, linkages of the LDM PSD data and other soil properties are to be established. Correlation study of the LDM and conventional PSD data could make the harmonization of newly built and historical databases possible. Finally, the introduction of the LDM technique to soil physical methodology could generate the reevaluation of existing soil physical interrelations.

Water storage and flow in soils are highly dependent on soil structure, which strongly determines soil porosity. However pore size distribution can be derived from soil water retention curve (SWRC). Structural characteristics of cultivated arable fields (693 soil profiles, 1773 samples) and soils covered by treated forest stands (137 soil profiles, 405 samples) were selected from the MARTHA Hungarian soil physical database, and evaluated for expressing organic matter effects on soil structure and water retention. For this purpose the normalized pore size distribution curves were determined for the selected soils, plus the modal suction (MS) corresponding to the most frequent pore size class of the soil. Skewness of soils’ pore size distribution curves are found different. The quasi-normal distribution of sandy soils are transformed into distorted in clayey soils. A general growing trend of MS with the ever finer soil texture was shown. Sandy soils have the lowest average MS values, i.e. the highest most frequent equivalent pore diameter. Silty clay and clay soil textures are characterized by the highest MS values. A slight effect of land use and organic matter content is also observable in different MS values of soils under forest vegetation (’forest’) and cultivated arable land (‘plough fields’). MS values of the two land uses were compared statistically. The results of the analyses show that certain soil group’s MS are significantly different under forest vegetation and cultivation. However this difference can be explained only partly and indirectly by the organic matter of different plant coverage in the land use types.

It was recently shown that estimated transport parameters for nonaqueous phase liquids (NAPLs) could differ significantly from measured parameters because of poor estimates for fluid conductivity. Most of the estimation procedures of the different multiphase flow simulators assume that porous media are rigid and noninteracting (ideal porous medium). This assumption is not valid in aggregated soil systems consisting in part of clay minerals. Inadequate conductivity estimates may be a direct result of desaggregation or clay volume changes (pore-size distribution changes) when contact with different fluids occurs. To expand the experimental data set of models describing the movement of organic liquids polluting the soils and possibly to discover new relationships between the NAPL conductivity and the other soil parameters, a series of experiments was set up in which the air permeability was measured with a PL 300 permeameter (UGT) and the fluid (NAPL and water) conductivity was measured using the falling head method. The measurements were carried out on artificial soil columns. The soils originated from different horizons of characteristic Hungarian soils. The relationships between the NAPL conductivity and the various other soil parameters were examined statistically. To give a better prediction for the NAPL conductivity, a new estimation method that is based on the easily measurable soil parameters was suggested.

A talaj szilárd fázisa által közrezárt pórustér nagysága és a pórusok méret szerinti eloszlása meghatározza a talajok fontosabb fizikai (pl. mechanikai sajátságok, légáteresztő-, vízvezető-és víztartó-képesség), kémiai (pl. diffúziós anyagáramlá-sok, szén-és tápanyagdinamika) és biológiai tulajdonságait (pl. mikrobiológiai aktivitás, gyökérfejlődés) (pl. HORN, 2004;HAJNOS et al., 2006;SMUCKER et al., 2007; BEN-HUR et al., 2009;ALAOUI et al., 2011;AKBARI & GHOSHAL, 2015). A pórusrendszer ismerete nélkül nem érthetők meg a talajfunkciók és nem számszerű-síthetőek a talajban lejátszódó folyamatok. A víz áramlása telítetlen porózus közeg-ben a Richards-egyenlet alapján modellezhető, melynek két legfontosabb tényezője a víztartó-és a vízvezető-képesség. A víz és a szerves folyadékfázisú szennyező anyagok terjedésének, transzportjának szimulációjához elengedhetetlen a közeg porozitása, folyadékvezető-és visszatartó képessége közötti összefüggés lehetőség szerint minél pontosabb számszerűsítése. A matematikai, statisztikai módszerek és a modellezés technikai hátterét biztosító számítástechnikai fejlesztések hatására a porózus közegben történő vízmozgás szimulációs modellezése jelentős fejlődésen ment keresztül az elmúlt 70 évben. A víztől eltérő polaritású folyadékokra vonatkozóan e hidrológiai jellemzők számítása azonban mind a mai napig a porózus közeg jelentős leegyszerűsítését, ún. ideálisan porózus közeget feltételezve lehetséges. Tanulmányunkban áttekintést kívánunk nyújtani azokról a fontosabb kutatásokról, melyek a "normál" (természetes állapotú) és a szerves folyadékokkal szennyezett talajok pórusrendszerét jellemző folyadék-visszatartó és a folyadékvezető képessé-get, illetve e két fontos, a vízforgalmat vagy a szennyezés-terjedést szimuláló modellek számára nélkülözhetetlen talajtulajdonság kapcsolatát vizsgálták.

The pollution of soils with nonaqueous-phase liquids (NAPL) may endanger the quality of soils, their utilization, and the groundwater reservoir. To develop NAPL transport models, the most important soil parameters are the hydrophysical properties of the solid phase such as the retention capacity. Because the measurement of these soil properties is time-consuming and costly, in most cases they are estimated. However, the commonly used estimation methods are mostly validated with laboratory measurements using soil columns made from sand, quartz, or glass-bead samples, with negligible contents of clay and organic matter. These estimation methods consider the soil as ideal porous media and thus may not provide appropriate results for soils with variably physical and chemical properties. In the 1990s a research program commenced at this university to create an appropriate estimation method for predicting the NAPL retention capacity of soils. Two estimation methods, the Leverett equation and the prediction with pedotransfer functions (PTF), were compared. We assumed that the oil retention of soil is sufficiently predictable from basic soil properties, but we later discovered that these models needed to be refined further because NAPL retention in soils may be influenced by different properties at a higher pressure level than at lower pressure. Moreover, the quantity and the quality of clay minerals in soils may also influence the retention capacity of soils. The aim of this study was to determine the effect of different investigated soil parameters on NAPL retention measured at different pressure values. A series of mineral mixtures containing different clay minerals were used, the PTFs were established, and the role of the main soil properties in NAPL retention was investigated with statistical analysis.