engleski

SPECTROSCOPIC CHARACTERIZATION OF HUMIC SUBSTANCES OF ANTHROPOGENIC SOILS DERIVED FROM TERRA ROSSA

The aim of the study was spectroscopic characterization of humic substances and evaluation of humus quality of anthropogenic soils derived from Terra Rossa. The study was conducted on 15 soil samples collected from top-soil horizon of olive groves in Middle Dalmatia (Croatia). Total organic carbon was determined according to Walkley-Black method (1934) and humic substances isolation following procedure given by Schnitzer (1982). Spectroscopic characterization of isolated humic substances was carried out by measuring absorbance in VIS spectral range 400-700 nm and optical indices (Q4/6, E4/6) were calculated. SOC content in top-soil samples varied from 1.45% to 4.21% with mean value of 2.98%. The absorption spectrum showed monotonous decrease of absorbance from 400 to 700 nm for all samples. The optical indices E4/6 and Q4/6 varied from 3.58 to 5.05 and from 3.91 to 5.04, respectively and indicated differences of humus quality. The optical index below 4, which implies a high quality of humus, was determined in six samples. The low humus quality (optical index above 4) was determined in other nine samples. The SOC content has significant positive correlation with optical indices Q4/6 and E4/6. Soils with higher organic carbon content have lower humus quality.

VIS spectrum, E4/6, humus quality, Dalmatia

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