Content of heavy metals and their fractions in soil in result of residual effect of waste materials

Analysed was the effect of various material supplements, ie municipal sewage sludge and various doses of ash-sludge and ash-peat mixtures on total content of heavy metals (Cr, Zn, Pb, Cu, Cd and Ni) and their fractions. Five fractions of heavy metals were determined in soil by means of Tessier’s method after competed three-year pot experiment on maize as the test plant. Application of ash-sludge and ash-peat mixtures to the soil influenced the increase in heavy metal content in soil but the amount of these metals did not exceed the standards established for arable soils. The pot experiment with maize revealed that the residual fraction played the main role in Cr, Zn and Pb accumulation, fraction bound to organic matter in Cu and Ni accumulation, whereas exchangeable and residual fraction in Cd accumulation. Heavy metal mobility (the sum of two first fractions) in the analysed ash-sludge and ash-peat mixtures supplied to the soil, irrespectively of applied extractant, was diversified and did not exceed the following values of total content: Cr – 0.39 %; Zn – 20 %, Pb – 13 %, Cu 10 %, Cd – 69 % and Ni – 4 %. The investigations have shown that cadmium was the best available to maize whereas chromium the least.