TRACE-METALS UPTAKE AND DISTRIBUTION IN CORN PLANTS GROWN ON A 6-YEARURBAN WASTE COMPOST AMENDED SOIL

A 6-year field study was performed to evaluate heavy metal accumulatio n in the top 20 cm of a clay-loam calcareous soil (Fluventic Xerochrep t) amended with urban waste compost and to determine heavy metal uptak e and distribution in corn plants grown in this soil. Compared with un treated soils, amended soils showed a significant increase only in Cu, Zn, Pb and, in the last 2 years, Cr concentrations. The corn plants g rown on the amended soil showed a general increase in metal uptake, wh ich was about three times greater for Pb and two times greater for the other heavy metals than in plants grown on untreated soil. At times, the diluting effect resulting from enhanced growth rates of the plants with compost application resulted in lower concentrations in the plan ts grown on treated plots. Cr and Pb were less mobile in the corn plan t and were accumulated only in root tissues. Only in the last 3 years of the experiment were traces of Pb found also in the stalks. The limi ted mobility of Pb was confirmed in a contemporary hydroponic greenhou se experiment. The values of the plant/soil transfer coefficients were within the lower range reported in the literature, indicating that in the soil studied (which contained 14% CaCO3) there was limited transf er of heavy metal ions from the soil to the corn plants. It is conclud ed that the long-term application of large amounts of urban waste comp ost to CaCO3-containing soils does not necessarily cause medium-term p roblems to plant, animal or human health.