The Effect of Liming and Sewage Sludge Application on Heavy Metal Speciation in Soil

The aim of this paper is to assess the effect of liming and low doses of municipal sewage sludge (5%, 10%, 15% of the soil mass) on lead, chromium and nickel speciation in soil. The 420-day experiment was carried out in laboratory conditions. In all the samples lead, chromium and nickel concentration was determined with the ICP-AES method, while the content of those metals in different fractions was measured with the seven-step Zeien and Brummer method, on the 30th and 420th days of the experiment. Sewage sludge doses significantly diversified lead, chromium and nickel amounts in the soil. The highest dose of sludge caused a significant increase, compared to the control, in the content of those metals. In the sludge the dominant forms of metals tested in the experiment were lead and chromium bound to organic matter (F4) as well as nickel bound to amorphous iron oxides (F5). Liming decreased the mobility of the metals in the soil.