Determination of elements by atomic absorption spectrometry and energy dispersive X-ray spectroscopy in humic acids and soil samples

Determination of various elements in humic acids and soil samples is important with regard to their biological availability. This work was focused on the identification of trace elements presented in soil samples and humic acids preparates. The object of our study was the samples of grassland soil classified according to FAO as Eutric Cambisol (locality Vatín, Czech-Moravian Upland). Labile and total several element contents in the studied samples were determined. The labile forms were measured in the 0.01 M CaCl2 extract by using high resolution continuum source atomic absorption spectrometer. Total element contents were determined after extraction in aqua regia. Basic soil properties were measured by commonly used methods - soil reaction and conductivity by potentiometric method, texture by pipette method, CEC according to Kappen method and Cox by titrimetric oxidation. Soil humic acids (HA) were isolated according to standard IHSS method. Elemental composition of HA was determined by CHSN/O analyzer. Energy dispersive X-ray spectroscopy allowed us to detect elements in situ in HA molecule and following elements were found: Fe, Cu, Zn, Ti, Ca, K, S, P, Si and Br. The presence of mentioned elements in humic acids preparates was compared with the determined amounts of labile forms and total contents in the soil samples.