Zinc speciation in soil under various rates of sewage sludge and liming

The influence of sewage sludge doses and liming on the speciation of zinc in the soil has been investigated. For the highest dose of sludge, 15 wt. %, more than twofold increase in zinc content compared with the control has been observed. Based on sequential analysis of zinc content in sewage sludge, it was found that its concentration in the easily soluble and exchangeable fractions was low while it was the highest in the organic fraction. The concentration of zinc in selected soil fractions was dependent on the sludge dose and liming. In the first year of the experiment, zinc was mainly bound to organic matter and residual, while in the second year – to organic matter. In limed soil, much more zinc was bound to the residual fraction compared with the soil without liming.