Metal-rich sewage sludge

In China and other countries, the application of C-rich organic materials to heavy metal-contaminated soils is a common practice. However, the potential risk of metal mobilization should not be overlooked when metal dissolution facilitated by DOM released from organic wastes exceeds metal immobilization caused by particular organic matter. Figure 10.8 demonstrates that addition of DOM derived from green manure, pig manure, peat, rice litter, and sewage sludge to a Cu-contaminated soil caused an increase in soil water-soluble Cu contents. Compared to the control (no... 

Toxicity of natural origin is found in soils formed from Cu sulfide-rich parent rocks, especially when the soil is acid. Bioaccumulation of Cu in humus followed by episodes of reduction can concentrate the element in sulfide form in natural wetlands. Because copper is not only phytotoxic but also a commonly abundant metal pollutant in waste materials, Cu in wastes such as sewage sludges is often the first element to limit land application. 

---