Analysis of correlations between BET-specific surface area, humus materials and other soil properties on typical Hungarian soil types

Abstract

In our study, we examined 27 different Hungarian soil profiles to reveal the relationship between N2-BET specific surface area (N2-BET SSA) and other soil physical properties. According to the univariate statistical analysis, it can be stated that the soil particle size distribution shows the closest correlation to the SSA. The clay content has a strong positive correlation with it, on the contrary the increasing sand content causes decreasing specific surface area. It can be proved that the calcium carbonate and humus content have a not too strong negative correlation, but Hargitai's humic stability index has a weak positive correlation with the N2-BET values. We could not verify the relationship between soil pH and specific surface area. We also examined the combined effect of different soil properties on the N2-BET SSA and the role of the soil class and soil types. Based on the entire database, the most important factors of the N2-BET SSA are the clay content, the humus content, and eventually the carbonate content. If we also have information about the quality of humic matter,then the clay content, the humus content, the humus quality and the pH are those soil properties that primarily affect the size of the N2-BET SSA. It has been found that the accuracy of the specific surface area estimation models can be improved by taking into consideration the taxonomic classification of the soils (soil main type, soil type) as a category variable. In some cases, we do not have direct measurement results, however, the knowledge of the soil taxonomy provides a lot of indirect information of the soils' parameters and their combined effects.