MOBILITY OF SOME HEAVY-METALS IN SOIL-PLANT SYSTEMS STUDIED ON SOIL MONOLITHS

The soil can act as a natural buffer by retaining toxic materials pres ent in municipal and industrial wastes and sewage sludges. Countries o f Eastern Europe currently have a limited industrial infrastructure fo r recycling wastes. One of the most rational and economic ways for the se countries to dispose of their waste waters and sludges is to apply them to agricultural fields, thereby utilizing also their nutrient con tent. A U.S.-Hungarian research project was recently started with the aim of studying the fate and transport of selected heavy metals in the soil profile of cropped undisturbed soil monoliths. Preliminary exper iments were carried out to study the adsorption-desorption processes o f these chemicals on disturbed soil samples, and to investigate the pl ant-availability of different metal forms. Concentrations of Zn, Pb, C r and Cd in the soil solution were found to decrease with increasing s oil moisture content and length of the adsorption period, both showing hyperbolic relationships. Lower soil moisture contents increased both the solution concentrations and the adsorbed concentrations of the el ements. Release of adsorbed Zn and Cd was higher than that of Pb and C r. Higher plant-availability of inorganic forms of Ni correlated with a higher phytotoxicity as compared to Ni applied in sewage sludge.