Application of Sequential Extraction Procedure to Evaluation of Influence of Sewage Sludge Amendment on Cd and Zn Mobility in Soil

Abstract

The modified SM&T EUR 14763 EN sequential extraction procedure was applied to evaluation of water-soluble, exchangeable, Fe/Mn oxide-bound, organic-bound, and residual cadmium and zinc in three soils differing in physicochemical properties. The soil parameters were altered by an addition of sewage sludge pre-incubated under aerobic and/or anaerobic conditions. The addition led to significant changes in Cd and Zn separation into the main fractions. While cadmium distribution tended to lower mobility accompanied by increasing residual fraction, potentially mobilizable zinc fractions increased with decreasing residual fraction. The water-soluble (plant-available) fraction correlated with pH of the soil and/or sewage sludge added to the soil. The amount and composition of the soil and the organic matter in sludge were the dominant factors affecting the distribution of potentially mobilizable fractions of elements. The sequential extraction procedure can reasonably elucidate the changes in element distribution in soil fractions by changing physicochemical properties of the soil.