Fractions of heavy metals in the soil after the application of municipal sewage sludge, peat and furnace ash

Abstract

The aim of the study was to evaluate the effect of the addition of various materials, i.e. municipal sewage sludge, furnace ash and peat, as well as various doses of ash-sludge and ash-peat mixtures, on some physico-chemical properties of the soil: pH, hydrolytic acidity, sorption complex capacity, organic C content, the content of P, K and Mg available forms, total content of heavy metals and their forms soluble in 1 mol · dm-3 HCl solution, and their speciation as well. Municipal sewage sludge and of ashsludge and ash-peat mixtures use in the experiment caused the greatest increase in sorption capacity, in content of phosphorus, potassium and magnesium and resulted in a gradual increase in the content of studied heavy metals. The addition of ash and applied mixtures to the soil caused a change in soil reaction (the pH increase). The ash was characterized by a low content of heavy metals. After peat and its mixtures with ash application decreased content of heavy metals was observed, and when the peat was used alone could be seen the greatest increase in the organic C content in the substrate. Distribution of heavy metals in the fractions separated in different combinations show large variations, depending on the tested metal and the studied variant. Chromium, zinc, lead and cadmium have been stored mainly in the residual fraction (FV), and most of the copper and nickel have been specifically bound with organic matter (FIV). It has been found that the alkaline materials application to the soil decreased the solubility of most heavy metals, which results in a limitation of their uptake by plants. Chromium and copper were an exception, which solubility increased with the alkalinity of the substrate. An exception was chromium and copper, which solubility increased with the alkalinity of the substrate.