Mobility of selected heavy metals in municipal sewage sludge

The research was aimed at determining the interaction of municipal sewage sludge with the environment in the aspect of its potential for land applications in agriculture, land reclamation and land adaptation to different uses. Sequential extraction of heavy metals according to Briimmer's method was used in the study. A detailed interpretation of the data allowed to state that the highest content of copper was found in one of the most mobile bindings (fraction I). For other heavy metals only trace amounts were found in the bindings considered as the most mobile (fraction I-III) which proved less risk posed to the environment. The highest percentage share of heavy metals in the investigated sludge was determined in fractions IV to VII (i.e. in bindings rather unavailable to the ecosystem). It should be highlighted that three out of the seven determined metals were bound in the highest amounts with the organic matter (fraction IV): i.e. Zn 49.97%, Pb 66.58%, Mn 41.91%.; three with silicates (fraction VII): i.e.: Cu 40.60%, Ni 88.58%, Cr 34.33%; and only cadmium was found to be bound (30.29%) with crystalline iron oxides (fraction VI).