METAL CONTENTS OF HUMIC SUBSTANCES ISOLATED FROM SOIL, BROWN WATER AND LANDFILL LEACHATES

Humic substances isolated from soil, bog lake water and landfill leachates by the XAD-method (adsorption at pH = 2.0; desorption at pH greater-than-or-equal-to 13) contain significant amounts of metals. Data from atomic absorption and atomic emission measurements for the initial aqueous solutions (Cr, Fe, Co, Ni, Cu, Zn, and Cd) are compared with the data for isolated humic samples. The well complexed metals like Cr3+, Fe3+ and Cu2+ are found in relatively large amounts in the isolated humic material. The values are up to some per cent of the metal concentration originally present in the aqueous samples. Most bivalent metals (Co2+, Ni2+, Cd2+) are present in residual amounts of the order of 10(-3) of the dissolved metal concentrations in the original solutions. The complexation capacities (CC) for the isolated HS decrease according to their origin: soil > bog lake water > leachates from dumping areas. The systematic error for the determination of CC due to the strongly bound residual metal content is, in general, smaller than 1 %.