Michal HUDEC, Zita JENISOVÁ & Jana BRANIŠA
Constantine the Philosopher University in Nitra, Faculty of Natural Sciences, Department of Chemistry, Tr. A. Hlinku 1, 949 74 Nitra, Slovak Republic, michal.hudec@ukf.sk, zjenisova@ukf.sk, jbranisa@ukf.sk

SPECTROSCOPIC CHARACTERISTICS OF HUMIC SUBSTANCES IN RELATION TO LEAD AND CADMIUM LEVELS IN CONTAMINATED SOILS FROM WESTERN CARPATHIANS

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The paper deals with the study of the sorption properties of humic substances by using UV-VIS and fluorescence spectroscopy in different soil types on the Slovak Neovulcanites. We observed main spectral peaks by synchronous scan excitation fluorescence spectra of humic substances in soil at λex/λem: 340/360, 404/424, 423/443, 468/488, 490/510, 507/527 with a constant difference Δλ = 20 nm. Fluorescence indexes (F) were calculated from SFS spectra at Δλ = 20 nm (as a ratio RFI404/RFI423). Also, the classical method of humic substances fractionation to assess their quality was applied, because the humic substances can help to improve unfavourable soil properties, plant productivity and nutrient uptake. The comparison is given of the calculated parameters from different spectral regions and humic substances fractionation. The results showed correlation between total organic carbon and fluorescence indexes (r=-0.590, p<0.05), between humic substances content in soil and fluorescence indexes (r=0.983, p<0.01), as well as between colour indexes (QHS) (r=-0.716, p<0.01). Content of humic substances was in the positive correlation with the bioavailable forms of lead (r=0.709, p<0.01) and cadmium (r=0.692, p<0.01), which plants are able to take. On the total content of cadmium and the bioavailable forms lead and cadmium has an impact also the spectral peak at 468/488 nm, which is associated with the presence of five or more fused aromatic rings.