Trace metals in humic acids and their hydrolysis products

The role of humic acids in the transport of trace elements in the Sava river biocycle (near Zagreb, Yugloslavia) has been investigated by means of neutron activation analysis. Humic acids can accumulate certain trace elements, but little is known about their selectivity under certain physicochemical conditions. Humic acids isolated from Sava river sediments were hydrolized to their main components, namely to amino acids (proteins), phenols (and phenolic acids), carbohydrates, polycyclic aromatics, and metals. Degradation of humic acids in the environment occurs by the action of microorganisms, and during this step, certain trace metals become available to Sava river animals through standard physiological processes. In this work neutron activation analysis was applied to the quantitative and qualitative determination of trace metals in humic acids of Sava river origin, and in their hydrolysis products. The trace metals measured were Ag, Fe, Co, Cs, Eu, Sb, Sc, Se, and Sr. The concentrations obtained ranged from 0.05 to 2730 micrograms of a certain microconstituent per gram of sample. The experimental data are compared with the laboratory experiments on the determination of stability constants for metal complexes of humic acids and their hydrolysis product. From these data it is possible to suggest the ecological importance of trace metals bonded to humic acids in a certain region. The results concerning the role of humic acids in the cycle of trace elements in Sava river biocycle are discussed.