Fractionation, Characterization, and Speciation of Heavy Metals in Sewage Sludge and Sludge‐Amended Soils: A Review

Abstract

AbstractThe speciation of heavy metals in soils determines the availability of metals for plant uptake and the potential for contamination of groundwater following the application of municipal sewage sludge to agricultural land. Methods used to characterize heavy metals in the solid phase of sludges and sludge‐amended soils include chemical extractions, elutriation, and filtration, while chromatographic techniques and computer calculations are frequently applied to the solution phase. Such studies have shown metals to be predominantly associated with the solid phase; soluble and exchangeable species generally represent < 10% of total metals. Speciation in sludge‐amended soils initially reflects that of the sludge itself, although changes with time have been observed. It is apparent, however, that more refined interpretation of analytical data obtained by current speciation techniques is required to further characterize heavy metals. In addition, certain techniques used to speciate metals in other matrices may have applications for sludges and sludge‐amended soils.