Characterization of Soil Organic Substances by UV-Vis Spectrophotometry in Some Soils of Hungary

Abstract

UV-Vis spectrometry methods are widely used to characterize soil organic matter, especially humic substances from different extracts of soils. Our aims were to investigate organic characteristics of soils, as part of a project focusing on relationships between solute mineral components and organic matter quality. The study was performed using UV-Vis spectrophotometry on six Hungarian soils. For the characterization of humic substances we used several visible and UV methods. Humic materials were extracted from soils using a variety of extractants. We found that a decrease in pH and an increase in dissolved electrolyte concentration supported coagulation in preferance to dissolution in almost every case. The highest absorbance values was given by extractants which contained sodium-pyrophosphate. In our experience double extraction methods (ENaF/ENaOH according to Hargitai, A talaj szerves anyagának meghatározása és jellemzése. In: Buzás I (ed) Talaj- és agrokémiai vizsgálati módszerkönyv II. Mezőgazdasági Kiadó, Budapest, 1988, E400NaOH+Na4P2O7/E400PBS) and E4/E6 are suitable for analysing humic substances. Comparing these three visible methods there are only slight differences between them. The results do not show strong correlation between visible and UV methods as these techniques analyse different properties of soil humic substances.